Note: Descriptions are shown in the official language in which they were submitted.
-21 99704
WO 96/0816.~ PCT/US95/11027
REDUCED ANTIOXIDANT GUM BASE AND METHOD OF PREPARATION
FIELD OF l~IE lN V~ lON
This invention is directed to a gum base
having reduced initial antioxidant levels, a method of
making gum base which requires less initial antioxidant
than conventional methods, and a finished gum base and
chewing gum which have normal antioxidant levels but
reduced levels of degraded antioxidant by-products.
BACRGROllND OF THE lNV~':N LlON
Gum bases, for use in chewing gum, are
typically manufactured using antioxidants. The
antioxidants must be added at sufficient levels into
the gum base to provide stability of a) the gum base
ingredients, during manufacture of the gum base; b) the
gum base and other chewing gum ingredients, during
manufacture of the chewing gum; and c) the finished
chewing gum product, during shelf storage.
The most severe conditions requiring
antioxidant generally occur during manufacture of the
gum base, as a result of the relatively high shear,
high temperature an;d long mixing times required to
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95111027
-- 2
disperse the elastomer, filler, and other gum base
ingredients. For instance, a two hour total mixing
time at 280~F is common for a conventional batch
process used to make gum base. Even though the
antioxidant is often added late, along with fats and
oils, a half hour or more is often required to
incorporate the stabilized fats and oils into the base.
During this time, much of the antioxidant initially
added is often lost due to degradation and
volatilization from the heat. This loss may exceed 40
of the initial antioxidant.
Compared to the gum base manufacturing
process, the preparation of chewing gum product from
gum base and other chewing gum ingredients is much more
gentle. Any loss of antioxidant during the later
manufacture of chewing gum is generally much less
significant, or even negligible, compared to the loss
of antioxidant during the initial manufacture of
chewing gum base.
The synthetic antioxidants butylated
hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)
are effective stabilizers for finished chewing gum
products at levels of about 10-100 parts per million
(ppm). Because the gum base generally constitutes
about 10-50~ by weight of the chewing gum product,
these antioxidants are added at higher concentrations
during manufacture of the gum base. During the mixing
of the gum base ingredients, these antioxidants
partially volatilize or degrade into complex furans,
biphenyl compounds, and other unwanted chemicals. The
initial addition of antioxidant into the gum base must
be sufficiently high to permit these losses as well as
the dilution of antioxidant occurring when the gum base
is combined with other chewing gum ingredients.
Other synthetic antioxidants, and natural
antioxidants, volatilize or degrade to some extent
during gum base manufacture. These other antioxidants
W096/0816~ 2 1 9 9 7 0 4 PCT~S95/11027
-- 3
include, for example, tert-butyl hydroquinone (TBHQ)
and tocopherols. In order to minimize the degradation
of antioxidant, and reduce the amount of unwanted
chemical by-products, there is a demand for a process
which efficiently combines the gum base ingredients
using less severe conditions.
SUMMARY OF THE lNv~NllON
The present invention includes a stabilized
chewing gum base made using lower initial antioxidant
levels than conventional gum bases, and a method of
making gum base which causes less volatilization and
degradation of antioxidants. The results are a
finished gum base which includes a normal level of
remaining antioxidant, and less unwanted degradation
by-products, compared to conventional finished gum
bases, and a corresponding stabilized chewing gum which
contains less chemical by-products.
A gum base is prepared initially using an
antioxidant in the range of about l0 to about 2000 ppm
based on the weight of the gum base. The level used
will depend on the particular antioxidant being used,
local regulations, shelf life expectations and other
factors. The antioxidant may be synthetic or natural,
and is preferably selected from BHT, BHA, TBHQ, propyl
gallate, or combinations thereof. After the gum base
ingredients have been mixed with each other, and
combined with other chewing gum ingredients to form a
finished product, at least about two-thirds of the
initial antioxidant will remain, and will be present in
the chewing gum product at about 7 to about l000 ppm
based on the weight of the chewing gum.
The level of the antioxidant present in the
finished chewing gum is conventional. The differences
are that the starting level of antioxidant added during
manufacture of the gum base is lower than in a
conventional method, and the percentage of the initial
WO96/0816~ rcT~s95lllo27
21 99704
-- 4
antioxidant remaining in the finished gum base and
chewing gum product is higher. Because less
antioxidant is lost during processing, especially due
to degradation, there is less quantity of unwanted
reaction products of the antioxidant. The result is a
cleaner, better tasting chewing gum product.
In order to accomplish these objectives, the
chewing gum base is prepared using a process which is
gentler than conventional batch processes. By
"gentler", it is meant that the gum base is made using
less mixing time, less temperature, less shear, or some
combination of the foregoing. Preferably, the gum base
is prepared using a continuous mixer having an average
residence time for gum base manufacture of not more
than about 20 minutes, and an average gum base mixing
temperature of not more than about 140~C (with a peak
mixing temperature of not more than about 160~C).
Preferably, the manufacture of the gum base and chewing
gum are integrated into a single efficient continuous
mixer.
With the foregoing in mind, it is a feature
and advantage of the invention to provide a method of
making gum base during which a higher percentage of
antioxidant initially added is retained, compared to
conventional gum base manufacturing methods.
It is also a feature and advantage of the
invention to provide a gum base and corresponding
chewing gum in which higher percentages of antioxidant
initially added are retained, compared to conventional
products.
It is also a feature and advantage of the
invention to provide a gum base and chewing gum having
normal levels of antioxidant in the finished products,
and lower levels of degraded antioxidant chemicals,
compared to conventional products.
The foregoing and other features and
advantages of the invention will become further
WO96/0816l 2 1 9 9 7 0 4 PCT~SsS/11027
-- 5
apparent from the following detailed description of the
presently preferred embodiments, read in conjunction
with the accompanying examples and drawings. The
detailed description, examples and drawings are
intended to be merely illustrative rather than
limiting, the scope of the invention being defined by
the appended claims and equivalents thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partial exploded perspective view
of a preferred Buss high efficiency continuous mixer
used to practice the method of the invention,
illustrating a mixing barrel and mixing screw
arrangement.
Fig. 2A is a perspective view of an on-screw
element used on the upstream side of a restriction ring
assembly, in the presently preferred high efficiency
mixer configuration.
Fig. 2B is a perspective view of an on-screw
element used on the downstream side of the restriction
ring assembly in the presently preferred high
efficiency mixer configuration.
Fig. 2C is a perspective view of a
restriction ring assembly used in the presently
preferred high efficiency mixer configuration.
Fig. 3 is a perspective view showing the
relative positioning of the elements of Figs. 2A, 2B
and 2C in the presently preferred high efficiency mixer
configuration.
Fig. 4 is a perspective view of a low-shear
mixing screw element used in the presently preferred
high efficiency mixer configuration.
Fig. 5 is a perspective view of a high-shear
mixing screw element used in the presently preferred
high efficiency mixer configuration.
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95/11027
-- 6
Fig. 6 is a perspective view of a barrel pin
element used in the presently preferred high efficiency
mixer configuration.
Fig. 7 is a schematic diagram of a presently
preferred arrangement of mixing barrel pins and
ingredient feed ports used to practice the method of
the invention.
Fig. 8 is a schematic diagram of a presently
preferred mixing screw configuration used to practice
the method of the invention.
DET~TT-~n DESCRIPTION OF T~E
PRESENTLY PREFERRED l~MBODIMENTS
In accordance with the invention, a gum base
and chewing gum are manufactured using one or more
antioxidants added during manufacture of the gum base,
in such a way that at least about two-thirds of the
total antioxidant initially added to the gum base is
still present after the chewing gum manufacture has
been completed. Preferably, at least about three-
fourths of the antioxidant initially added to the gum
base is still present in the final chewing gum product.
This means that no more than about one-third, and
preferably no more than about one-fourth, of the total
antioxidant added to the gum base, is volatilized,
degraded, or otherwise lost during the manufacture of
gum base and chewing gum. This represents a
significant improvement over the prior art, in which
more than 40~ of the antioxidant initially added to the
gum base was lost during manufacture of the gum base
alone.
The level of antioxidant present in the
finished chewing gum made according to the invention is
comparable to the levels of antioxidant present in
conventional finished chewing gums. Because less
antioxidant is lost during manufacture of the gum base,
the level of antioxidant initially added to the gum
base may be lower for the gum base and chewing gum made
WO96/0816~ 21 99704 PCT~S95/11027
-- 7
according to the invention. Also, the finished chewing
gum of the invention has less degraded antioxidant by-
products (for example, complex furans and biphenyl
compounds) than prior art chewing gums containing the
same antioxidant levels. Generally, the level of
antioxidant in the finished chewing gum will be about
l-lO00 ppm, depending primarily on which antioxidant is
used. Preferably, the chewing gum will include about
27-300 ppm antioxidant.
The level of antioxidant initially added to
the gum base may be determined based on the level of
the particular antioxidant desired in the chewing gum
product, the level of gum base to be used in the
chewing gum, and the amount of antioxidant lost during
manufacture of the gum base and chewing gum. The
antioxidant level initially added to the gum base
should be about l-lO00 ppm based on the weight of the
chewing gum, preferably about 8-300 ppm based on the
weight of the chewing gum, to be produced from the gum
base. This requires a starting level of about 10-2000
ppm based on the weight of the gum base, preferably
about 40-lO00 ppm.
It is expected that the amount of antioxidant
lost during manufacture of the chewing gum will be
small or negligible compared to the amount lost during
manufacture of the gum base. Put another way, at least
about two-thirds, and preferably at least about three-
fourths, of the antioxidant initially added to the gum
base will remain after the gum base manufacture has
been completed, and will still remain (with only minor
variation) after the chewing gum manufacture has been
completed. When gum base is prepared separately from
chewing gum, the finished gum base should contain about
7 to about 2000 ppm antioxidant, preferably about 27 to
about lO00 ppm antioxidant.
The present invention contemplates the use of
any commercially acceptable synthetic or natural
WO96/0816~ 2 1 9 9 7 0 4 PCT~SsS/11027
-- 8
antioxidant in the chewing gum base. Preferred
antioxidants include one or more of BHT, BHA, TBHQ, and
propyl gallate. Of these, BHT, BHA and combinations
thereof are especially suitable for use with the
invention, because there is a desire to reduce the
amount of conventional synthetic antioxidants added in
chewing gum and, particularly, to reduce their
degradation by-products.
In addition to the antioxidant, the gum base
includes elastomers, elastomer plasticizers (resins),
fats, oils, waxes, softeners and inorganic fillers.
The elastomers constitute about 5 to about 95 per cent
by weight of the base, preferably between lO and 70 per
cent by weight and most preferably between 15 and 45
per cent by weight. Elastomers may include synthetic
elastomers such as polyisobutylene, polybutadiene,
isobutylene-isoprene copolymer, styrene-butadiene
copolymer, polyvinyl acetate, vinyl acetate-vinyl
laureate copolymer, polyethylene, ethylene vinyl
acetate, polyvinyl alcohol or mixtures thereof.
Elastomers may also include natural elastomers,
including natural rubber such as smoked or liquid latex
and guayule as well as natural gums such as jelutong,
lechi caspi, perillo, massaranduba balata, massaranduba
chocolate, nispero, rosindinha, chicle, gutta hang kang
or mixtures thereof. Elastomers provide the rubbery,
cohesive nature to the gum which varies depending on
the elastomer's chemical and physical properties, and
how the elastomer is blended with other ingredients.
Synthetic elastomers are preferred for use with the
present invention.
Elastomer plasticizers modify the finished
gum firmness when used in the gum base. Elastomer
plasticizers typically constitute from about 0 to about
75 per cent by weight of the gum base, preferably 5 to
45 per cent by weight and most preferably lO to 30 per
cent by weight. Elastomer plasticizers include natural
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95111027
g
rosin esters such as glycerol ester of partially
hydrogenated rosin, glycerol ester of polymerized
rosin, glycerol ester of partially dimerized rosin,
glycerol ester of-rosin, glycerol ester of tall oil
rosin, pentaerythritol esters of partially hydrogenated
rosin, methyl and partially hydrogenated methyl esters
of rosin, pentaerythritol ester of rosin or mixtures.
Elastomer plasticizers also include synthetics such as
terpene resins derived from alpha-pinene, beta-pinene,
dipentene or di-limonene, and combinations thereof.
Waxes include synthetic (e.g. polyethylene
and Fischer-Tropsch waxes) and natural (candelilla
carnauba, beeswax, rice bran or mixtures thereof) and
petroleum (e.g. microcrystalline and paraffin). Waxes,
when used, generally constitute up to 30 weight per
cent of the gum base. When used, waxes aid in the
curing of finished gum made from the gum base and also
help improve the release of flavor, increase the shelf
life and improve the chewing texture.
Fillers modify the texture of the gum base
and aid processing. Fillers/texturizers include
magnesium and calcium carbonate, ground limestone and
silicate types such as magnesium and aluminum silicate,
clay, alumina, talc as well as titanium oxide, mono-,
di- and tricalcium phosphate, cellulose polymers such
as ethylcellulose and methylceltulose, wood, or
mixtures thereof. The filler typically comprises about
1 to about 60 per cent by weight of the gum base. Gum
bases which utilize acidic ingredients preferably
contain a filler that is inert to acids, most
preferably talc.
Softeners and emulsifiers modify the texture
and cause the hydrophobic and hydrophilic components of
the gum base and chewing gum to become more miscible.
Softeners/emulsifiers include tallow, hydrogenated
tallow, lard, hydrogenated and partially hydrogenated
vegetable oils, cocoa butter, glycerol monostearate,
~ 7 n A PCT~S95111027
WO96/0816~ /1 U~
! _
- 10 -
glycerol triacetate, lecithin, mono-, di- and
triglycerides, acetylated mono-, di- and triglycerides,
distilled mono-, di- and triglycerides, and fatty acids
(e.g. stearic, palmitic, oleic, linoleic and linolenic
acids) or mixtures thereof. Softeners/emulsifiers
generally constitute between 0.5 and 40 weight per cent
of the gum base.
Colorants and whiteners impart desired color
or remove undesired color by whitening the base and/or
the chewing gum. Colorants and whiteners include FD&C
type lakes, plant extracts, titanium dioxide or
mixtures thereof.
The gum base constitutes about 5-95~ by
weight of the chewing gum, preferably about 10-50~ by
weight of the chewing gum, most preferably about 20-30
by weight of the chewing gum. In addition to the gum
base, which is generally water-insoluble, the chewing
gum includes a water-soluble bulk portion and one or
more flavoring agents. The water-soluble portion
dissipates over a period of time during chewing. The
gum base remains in the mouth throughout the chewing
process.
The water soluble portion of the chewing gum
may include softeners, bulk sweeteners, high intensity
sweeteners, flavoring agents and combinations thereof.
Softeners are added to the chewing gum in order to
optimize the chewability and mouth feel of the gum.
The softeners, which are also known as plasticizers or
plasticizing agents, generally constitute between about
0.5-15~ by weight of the chewing gum. The softeners
may include glycerin, lecithin, and combinations
thereof. Aqueous sweetener solutions such as those
containing sorbitol, hydrogenated starch hydrolysates,
corn syrup and combinations thereof, may also be used
as softeners and binding agents in chewing gum.
Bulk sweeteners constitute between 5-95~ by
weight of the chewing gum, more typically 20-80~ by
WO96/0816~ 21 99704 PCT~S95/11027
-- 11 --
weight of the chewing gum and most commonly 30-60~ by
weight of the chewing gum. Bulk sweeteners may include
both sugar and sugarless sweeteners and components.
Sugar sweeteners may include saccharide containing
components including but not limited to sucrose,
dextrose, maltose, dextrin, dried invert sugar,
fructose, le w lose, galactose, corn syrup solids, and
the like, alone or in combination. Sugarless
sweeteners include components with sweetening
characteristics but are devoid of the commonly known
sugars. Sugarless sweeteners include but are not
limited to sugar alcohols such as sorbitol, mannitol,
xylitol, hydrogenated starch hydrolysates, maltitol,
and the like, alone or in combination.
High intensity sweeteners may also be present
and are commonly used with sugarless sweeteners. When
used, high intensity sweeteners typically constitute
between 0.001-5~ by weight of the chewing gum,
preferably between 0.01-1~ by weight of the chewing
gum. Typically, high intensity sweeteners are at least
20 times sweeter than sucrose. These may include but
are not limited to sucralose, aspartame, salts of
acesulfame, alitame, saccharin and its salts, cyclamic
acid and its salts, glycyrrhizin, dihydrochalcones,
thaumatin, monellin, and the like, alone or in
combination.
Combinations of sugar and/or sugarless
sweeteners may be used in chewing gum. The sweetener
may also function in the chewing gum in whole or in
part as a water soluble bulking agent. Additionally,
the softener may provide additional sweetness such as
with aqueous sugar or alditol solutions.
Flavor should generally be present in the
chewing gum in an amount within the range of about 0.1-
15~ by weight of the chewing gum, preferably between
about 0.2-5~ by weight of the chewing gum, most
preferably between about 0.5-3~ by weight of the
WO9610816~ 2 1 9 9 7 0 4 PCT~S95/11027
- 12 -
chewing gum. Flavoring agents may include essential
oils, synthetic flavors or mixtures thereof including
but not limited to oils derived from plants and fruits
such as citrus oils, fruit essences, peppermint oil,
spearmint oil, other mint oils, clove oil, oil of
wintergreen, anise and the like. Artificial flavoring
agents and components may also be used in the flavor
ingredient of the invention. Natural and artificial
flavoring agents may be combined in any sensorially
acceptable fashion.
Optional ingredients such as colors,
emulsifiers, pharmaceutical agents and additional
flavoring agents may also be included in chewing gum.
In accordance with the invention, the gum
base should be made using a continuous mixer. The
average mixer residence time used to complete the
manufacture of the gum base should be no more than
about 45 minutes, preferably no more than about 30
minutes, most preferably about 20 minutes or less.
Also, the average mixer temperature used to manufacture
the gum base should be no more than about 140~C,
preferably no more than about 125~C. By so limiting
the average residence time and temperature, the
volatilization and degradation of antioxidants added
during manufacture of the gum base can be minimized.
In order to minimize the residence time, the
continuous mixer should be capable of providing
thorough mixing of the gum base ingredients, to form a
homogeneous gum base, using a relatively short distance
or length of the mixer. This distance can be expressed
as a ratio of the length of a particular active region
of the mixer screw, which is composed of mixing
elements, divided by the maximum diameter of the mixer
barrel in this active region. This ratio is
abbreviated as L/D.
The method of the invention contemplates that
the gum base manufacture should be performed using an
WO96/08161 21 99704 PCT~S95/11027
- 13 -
L/D of not more than about 40. This means that the gum
base ingredients are added to the continuous mixer and
blended to a homogeneous mass using an L/D of not more
than about 40. Preferably, the gum base should be made
using a mixing L/D of not more than about 30, most
~ preferably not more than about 20.
A variety of continuous mixers can be
properly configured to manufacture the gum base in
accordance with the invention. The continuous mixer
may be a properly configured twin screw extruder (with
corotating or counterrotating screws), a single screw
extruder, a blade-and-pin mixer, or another continuous
mixing apparatus. One particularly suitable continuous
mixer is a high efficiency blade-and-pin mixer as
described further herein. Another very suitable mixer
for making the gum base is a ZSK58 corotating twin-
screw extruder available from Werner-Pfleiderer Corp.
in Ramsey, N.J.
In a preferred embodiment, the manufacture of
the gum base, and the combining of the gum base with
the remaining chewing gum ingredients, are both
performed in a single integrated high efficiency
continuous mixing process. When the manufacture of gum
base and chewing gum are so integrated, the method of
the invention comprises performing the following steps
in a single continuous mixer:
a) adding and thoroughly mixing at least a
portion of the chewing gum base ingredients (elastomer,
elastomer plasticizer, filler, etc.) in a continuous
mixer, using an L/D of not more than about 25;
b) adding at least a portion of the
remaining (non-base) chewing gum ingredients
(sweeteners, flavors, softeners, etc.), and thoroughly
mixing these ingredients with the gum base in the same
mixer, using an L/D of not more than about 15; and
c) sufficiently completing the entire
addition and mixing operation in the same mixer, so
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95111027
- 14 -
that the ingredients exist as a substantially
homogeneous chewing gum mass, using a total ~/D of not
more than about 40.
When performing the above integrated method,
it is preferred that the gum base ingredients be
completely added and mixed upstream from the remaining
chewing gum ingredients, and that the remaining
ingredients be completely added downstream for mixing
with the already blended gum base. However, the
invention also includes those variations wherein a
portion of the gum base ingredients may be added
downstream with or after some of the rem~;n;ng
ingredients, and/or wherein a portion of the rem~;n;ng
(non-base) ingredients are added upstream with or
before some of the base ingredients. The important
feature is that a substantially homogeneous chewing gum
product mass be formed in a single continuous mixer,
using an L/D of not more than about 40.
When performing the integrated method to make
gum base and chewing gum in a single mixer, a blade-
and-pin mixer can be used. A blade-and-pin mixer,
exemplified in Fig. 1, uses a combination of
selectively configured rotating mixer blades and
stationary barrel pins to provide efficient mixing over
a relatively short distance. A commercially available
blade-and-pin mixer is the Buss kneader, manufactured
by Buss AG in Switzerland, and available from Buss
America, located in Bloomingdale, Illinois.
Referring to Fig. 1, a presently preferred
blade-and-pin mixer 100 includes a single mixing screw
120 turning inside a barrel 140 which, during use, is
generally closed and completely surrounds the mixing
screw 120. The mixing screw 120 includes a generally
cylindrical shaft 122 and three rows of mixing blades
124 arranged at evenly spaced locations around the
screw shaft 122 (with only two of the rows being
visible in Fig. 1). The mixing blades 124 protrude
2 1 9 9 7 0 4 PCT/US95111027
WO96/08161
- 15 -
radially outward from the shaft 122, with each one
resembling the blade of an axe.
The mixing barrel 140 includes an inner
barrel housing 142 which is generally cylindrical when
the barrel 140 is closed around the screw 120 during
operation of the mixer 100. Three rows of stationary
pins 144 are arranged at evenly spaced locations around
the screw shaft 142, and protrude radially inward from
the barrel housing 142. The pins 144 are generally
cylindrical in shape, and may have rounded or bevelled
ends 146.
The mixing screw 120 with blades 124 rotates
inside the barrel 140 and is driven by a variable speed
motor (not shown). During rotation, the mixing screw
120 also moves back and forth in an axial direction,
creating a combination of rotational and axial mixing
which is highly efficient. During mixing, the mixing
blades 124 continually pass between the stationary pins
144, yet the blades and the pins never touch each
other. Also, the radial edges 126 of the blades 124
never touch the barrel inner surface 142, and the ends
146 of the pins 144 never touch the mixing screw shaft
122.
Figs. 2-6 illustrate various screw elements
which can be used to configure the mixing screw 120 for
optimum use. Figs. 2A and 2B illustrate on-screw
elements 20 and 21 which are used in conjunction with a
restriction ring assembly. The on-screw elements 20
and 21 each include a cylindrical outer surface 22, a
plurality of blades 24 projecting outward from the
surface 22, and an inner opening 26 with a keyway 28
for receiving and engaging a mixing screw shaft (not
shown). The second on-screw element 21 is about twice
as long as the first on-screw element 20.
Fig. 2C illustrates a restriction ring
assembly 30 used to build back pressure at selected
locations along the mixing screw 120. The restriction
WO96/0816~ ~ 2 1 9 9 7 0 4 PCT~S95/11027
- 16 -
ring assembly 30 includes two halves 37 and 39 mounted
to the barrel housing 142, which halves engage during
use to form a closed ring. The restriction ring
assembly 30 includes a circular outer rim 32, an inner
ring 34 angled as shown, and an opening 36 in the inner
ring which receives, but does not touch, the on-screw
elements 20 and 21 mounted to the screw shaft.
Mounting openings 35 in the surface 32 of both halves
of the restriction ring assembly 30 are used to mount
the halves to the barrel housing 142.
Fig. 3 illustrates the relationship between
the restriction ring assembly 30 and the on-screw
elements 20 and 21 during operation. When the mixing
screw 120 is turning inside the barrel 140, and
reciprocating axially, the clearances between the on-
screw elements 20 and 21 and the inner ring 34 provide
the primary means of passage of material from one side
of the restriction ring assembly 30 to the other. The
on-screw element 20 on the upstream side of the
restriction ring assembly includes a modified blade 27
permitting clearance of the inner ring 34. The other
on-screw element 21 is placed generally downstream of
the restriction ring assembly 30, and has an end blade
(not visible) which moves close to and wipes the
opposite surface of the inner ring 34.
The clearances between outer surfaces 22 of
the on-screw elements 20 and 21 and the inner ring 34
of the restriction ring assembly 30, which can vary and
preferably are on the order of 1-5mm, determine to a
large extent how much pressure build-up will occur in
the upstream region of the restriction ring assembly 30
during operation of the mixer 100. It should be noted
that the upstream on-screw element 20 has an L/D of
about 1/3, and the downstream on-screw element 21 has
an L/D of about 2/3, resulting in a total L/D of about
1.0 for the on-screw elements. The restriction ring
assembly 30 has a smaller L/D of about 0.45 which
2 1 9 9 7 0 4 pCT~S9S/11027
WO96/0816~
- 17 -
coincides with the L/D of on-screw elements 20 and 21,
which engage each other but do not touch the
restriction ring assembly.
Figs. 4 and 5 illustrate the mixing or
"kneading" elements which perform most of the mixing
work. The primary difference between the lower shear
mixing element 40 of Fig. 4 and the higher shear mixing
element 50 of Fig. 5 is the size of the mixing blades
which project outward on the mixing elements. In Fig.
5, the higher shear mixing blades 54 which project
outward from the surface 52 are larger and thicker than
the lower shear mixing blades 44 projecting outward
from the surface 42 in Fig. 4. For each of the mixing
elements 40 and 50, the mixing blades are arranged in
three circumferentially-spaced rows, as explained above
with respect to Fig. l. The use of thicker mixing
blades 54 in Fig. 5 means that there is less axial
distance between the blades and also less clearance
between the blades 54 and the stationary pins 144 as
the screw 120 rotates and reciprocates axially (Fig.
l). This reduction in clearance causes inherently
higher shear in the vicinity of the mixing elements 50.
Fig. 6 illustrates a single stationary pin
144 detached from the barrel 140. The pin 144 includes
a threaded base 14 5 which permits attachment at
selected locations along the inner barrel shaft 142.
It is also possible to configure some of the pins 144
as liquid injection ports by providing them with hollow
center openings.
Fig. 7 is a schematic view showing the
presently preferred barrel configuration, including the
presently preferred arrangement of barrel pins 144.
Fig. 8 is a corresponding schematic view illustrating
the presently preferred mixing screw configuration.
The mixer 200 whose preferred configuration is
illustrated in Figs. 7 and 8 has an overall active
mixing L/D of about l9.
W096/0816~ 2 1 9 9 7 0 4 PCT~S9StllO27
- 18 -
The mixer 200 includes an initial feed zone
210 and five mixing zones 220, 230, 240, 250 and 260.
The zones 210, 230, 240, 250 and 260 include five
possible large feed ports 212, 232, 242, 252 and 262,
respectively, which can be used to add major (e.g.
solid) ingredients to the mixer 200. The zones 240 and
260 are also configured with five smaller liquid
injection ports 241, 243, 261, 263 and 264 which can be
used to add liquid ingredients. The liquid injection
ports 241, 243, 261, 263 and 264 include special barrel
pins 144 formed with hollow centers, as explained
above.
Referring to Fig. 7, barrel pins 144 are
preferably present in most or all of the available
locations, in all three rows as shown.
Referring to Fig. 8, the presently preferred
configuration of the mixing screw 120 for most chewing
gum products is schematically illustrated as follows.
Zone 210, which is the initial feed zone, is configured
with about 1-1/3 L/D of low shear elements, such as the
element 40 shown in Fig. 4. The L/D of the initial
feed zone 210 is not counted as part of the overall
active mixing L/D of 19, discussed above, because its
purpose is merely to convey ingredients into the mixing
zones.
The first mixing zone 220 is configured, from
left to right (Fig. 8), with two low shear mixing
elements 40 (Fig. 4) followed by two high shear
elements 50 (Fig. 5). The two low shear mixing
elements contribute about 1-1/3 L/D of mixing, and the
two high shear mixing elements contribute about 1-1/3
L/D of mixing. Zone 220 has a total mixing L/D of
about 3.0, including the end part covered by a 57mm
restriction ring assembly 30 with cooperating on-screw
elements 20 and 21 (not separately designated in Fig.
8).
21 99704
rcrrusssnlo27
WO96/0816~
- 19 -
The restriction ring assembly 30 with
cooperating on-screw elements 20 and 21, straddling the
end of the first mixing zone 220 and the start of the
second mixing zone 230, have a combined L/D of about
l.o, part of which is in the second mixing zone 230.
Then, zone 230 is configured, from left to right, with
three low shear mixing elements 40 and 1.5 high shear
mixing elements 50. The three low shear mixing
elements contribute about 2.0 L/D of mixing, and the
1.5 high shear mixing elements contribute about 1.0 L/D
of mixing. Zone 230 has a total mixing L/D of about
4Ø
Straddling the end of the second mixing zone
230 and the start of the third mixing zone 240 is a
60mm restriction ring assembly 30 with cooperating on-
screw elements 20 and 21, contributing a combined L/D
of about 1Ø Then, zone 240 is configured, from left
to right, with 4.5 high shear mixing elements 50
contributing a mixing L/D of about 3Ø Zone 240 also
has a total mixing L/D of about 4Ø
Straddling the end of the third mixing zone
240 and the start of the fourth mixing zone 250 is
another 60mm restriction ring assembly 30 with
cooperating on-screw elements 20 and 21, contributing a
combined L/D of about 1Ø Then, the remainder of the
fourth mixing zone 250 and the fifth mixing zone 260
are configured with eleven low shear mixing elements 40
contributing a mixing L/D of about 7 1/3. Zone 250 has
a total mixing L/D of about 4.0, and zone 260 has a
total mixing L/D of about 4Ø
As stated above, it is generally preferred
that the gum base and ultimate chewing gum product are
made continuously in the same mixer. Generally, the
gum base portion is made using a mixing L/D of about 25
or less, preferably about 20 or less, most preferably
about 15 or less. Then, the remaining chewing gum
ingredients are combined with the gum base to make a
2 1 9 9 7 0 4 PCT~S95/11027
WO 96/0816~
- 20 -
chewing gum product using a mixing L/D of about 15 or
less, preferably about 10 or less, most preferably
about 5 or less. The mixing of the gum base
ingredients and the remaining chewing gum ingredients
may occur in distinct parts of the same mixer or may
overlap, so long as the total mixing is achieved using
an L/D of about 40 or less, preferably about 30 or
less, most preferably about 20 or less.
When the preferred blade-and-pin mixer is
used, having the preferred configuration described
about, the total chewing gum can be made using a mixing
L/D of about 19. The gum base can be made using an L/D
of about 15 or less, and the remaining gum ingredients
can be combined with the gum base using a further L/D
of about 5 or less.
In order to minimize the shear and, thus,
minimize the volatilization and degradation of an
antioxidant using the preferred blade-and-pin mixer
200, it is advantageous to maintain the rpm of the
mixing screw 120 at less than about 150, preferably
less than about 100. Also, the mixer temperature is
preferably optimized so that the gum base is at about
130~F or lower when it initially meets the other
chewing gum ingredients, and the chewing gum product is
about 130~F or lower (preferably 125~F or lower) when
it exits the mixer. This temperature optimization can
be accomplished, in part, by selectively heating and/or
water cooling the barrel sections surrounding the
mixing zones 220, 230, 240, 250 and 260.
In order to manufacture the gum base, the
following preferred procedure can be followed. The
elastomer, filler, and at least some of the elastomer
solvent are added to the first large feed port 212 in
the feed zone 210 of the mixer 200, and are subjected
to efficient dispersive mixing in the first mixing zone
220 while being conveyed in the direction of the arrow
122. The remaining elastomer solvent (if any) and
21 99704
W096/0816~ PCTtUS9StllO27
- 21 -
polyvinyl acetate are added to the second large feed
port 232 in the second mixing zone 230, and the
ingredients are subjected to a more distributive mixing
in the remainder of the mixing zone 230.
Fats, oils, waxes (if used), emulsifiers,
colors and antioxidants are added to the liquid
injection ports 241 and 243 in the third mixing zone
240, and the ingredients are subjected to distributive
mixing in the mixing zone 240 while being conveyed in
the direction of the arrow 122. At this point, the gum
base manufacture should be complete, and the gum base
should leave the third mixing zone 240 as a
substantially homogeneous, lump-free compound with a
uniform color. At this point, at least about two-
thirds and, preferably, at least about three-fourths of
the-antioxidant initially added, should still remain in
the base.
The fourth mixing zone 250 is used primarily
to cool the gum base, although minor ingredient
addition may be accomplished. Then, to manufacture the
final chewing gum product, glycerin, corn syrup, other
bulk sugar sweeteners, high intensity sweeteners, and
flavors can be added to the fifth mixing zone 260, and
the ingredients are subjected to distributive mixing.
If the gum product is to be sugarless, hydrogenated
starch hydrolyzate or sorbitol solution can be
substituted for the corn syrup and powdered alditols
can be substituted for the sugars.
Preferably, glycerin is added to the first
liquid injection port 261 in the fifth mixing zone 260.
Solid ingredients (bulk sweeteners, encapsulated high
intensity sweeteners, etc.) are added to the large feed
port 262. Syrups (corn syrup, hydrogenated starch
hydrolyzate, sorbitol solution, etc.) are added to the
next liquid injection port 263, and flavors are added
to the final liquid injection port 264. Flavors can
alternatively be added at ports 261 and 263 in order to
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95/11027
- 22 -
help plasticize the gum base, thereby reducing the
temperature and torque on the screw. This may permit
running of the mixer at higher rpm and throughput.
The gum ingredients are compounded to a
homogeneous mass which is discharged from the mixer as
a continuous stream or "rope". The continuous stream
or rope can be deposited onto a moving conveyor and
carried to a forming station, where the gum is shaped
into the desired form such as by pressing it into
sheets, scoring, and cutting into sticks. Because the
entire gum manufacturing process is integrated into a
single continuous mixer, there is less variation in the
product, and the product is cleaner and more stable due
to its simplified mechanical and thermal histories.
Because there is very little antioxidant loss during
the chewing gum manufacturing stage, the final product
should still contain at least about two-thirds and,
preferably, at least about three-fourths of the
antioxidant added during manufacture of the gum base.
A wide range of changes and modifications to
the preferred embodiments of the invention will be
apparent to persons skilled in the art. The above
preferred embodiments, and the examples which follow,
are merely illustrative of the invention and should not
be construed as imposing limitations on the invention.
For instance, different continuous mixing equipment and
different mixer configurations can be used without
departing from the invention as long as the preparation
of a chewing gum base is accomplished in an efficient
continuous mixer using a mixing L/D of not more than
about 40.
E~MPLE 1 ( COMPAR~TIVE )
The following gum base composition was
prepared using a conventional batch process:
W O96/0816~ - 23 - PCTrUS95/11027
Inqredient ~ BY Weiqht
Butyl Rubber (shredded) 9.89
Calclum Carbonate 13.19
- Polyvinyl Acetate (Mol. Wt. = 25,000) 21.77
Polyisobutylene 15.83
Cocoa Powder 0.50
Glycerol Monostearate 2.64
Hydrogenated Cottonseed Oil13.19
HydLog~lated Soybean Oil 13.19
Partially Hydrogenated Soybean L Palm Oil 9.76
BHT 0.04
TOTAL 100.O
The foregoing composition was made using a
Werner-Pfleiderer dual sigma blade mixer having a 757-
pound batch size. The mixer was run using front and
rear blade speeds of 48.8 and 33.8 rpm and was heated
with 45 psi steam. The total mixing time for making
the batch was 135 minutes.
The butyl rubber, calcium carbonate,
polyvinyl acetate, polyisobutylene and cocoa powder
were added to the batch mixer and blended during the
first 75 minutes. The hydrogenated soybean oil was
added at 75 minutes and blended with the above
ingredients. As mixing continued, the hydrogenated
cottonseed oil was added at 90 minutes. The BHT,
glycerol monostearate and partially hydrogenated
soybean and palm oil were all added at 105 minutes,
after which all the ingredients were blended for an
additional 30 minutes.
Analytical testing of the finished gum base
showed BHT present at a level of 232 ppm. This
represented a 42~ loss from the 400 ppm BHT initially
added. One month later, the gum base was tested again,
and the BHT was detected at 223 ppm.
The following chewing gum composition was
made from the above gum base using a laboratory batch
mixing process.
2 i 9 9 7 0 4 pCTrUS9S/11027
W 096/0816~
- 24 -
Inqredient ~ Bv Weiqht
Sugar 64.4
Gum Base 20.0
Corn Syrup 13.3
Sorbitol o.g
Glycerin 0.7
Peppermint Flavor 0.7
TOTAL 100.O
Analytical testing of the finished chewing
gum showed BHT present at 43.7 ppm, possibly indicating
a slight additional loss during the mixing of chewing
gum. The total BHT loss for both phases of production
was 45~.
EXAMPLE 2
The same chewing gum product composition of
Example 1 was manufactured using a Buss kneader with a
lOOmm screw diameter, configured in the preferred
manner described above for integrated manufacture of
the gum base and chewing gum in a single continuous
mixer. As described above, the mixer was configured
with five mixing zones, a total mixing L/D of 19, and
an initial conveying L/D of 1 1/3. No die was used at
the end of the mixer, and the chewing gum product
exited as a continuous rope. The example was designed
to yield a production rate of about 300.1 pounds per
hour finished gum.
Liquid ingredients were fed using volumetric
pumps into the large feed ports and/or smaller liquid
injection ports generally positioned as described
above, unless otherwise indicated. The pumps were
appropriately sized and adjusted to achieve the desired
feed rates.
Dry ingredients were added using gravimetric
screw feeders into the-large addition ports positioned
as described above. Again, the feeders were
WO96/0816~ 2 1 9 9 7 0 4 PCT~S95/11027
- 25 -
appropriately sized and adjusted to achieve the desired
feed rates.
Temperature control was accomplished by
circulating fluids through jackets surrounding each
mixing barrel zone and inside the mixing screw. Water
cooling was used where temperatures did not exceed
100~C, and oil cooling was used at higher temperatures.
Where water cooling was desired, tap water (typically
at about 55~F) was used without additional chilling.
Temperatures were recorded for both the fluid
and the ingredient mixture. Fluid temperatures were
set for each barrel mixing zone (corresponding to zones
220, 230, 240, 250 and 260 in Figs. 7 and 8), and are
reported below as Zl, Z2, Z3, Z4 and Z5, respectively.
Fluid temperatures were also set for the mixing screw
120, and are reported below as S1.
Actual mixture temperatures were recorded
near the downstream end of mixing zones 220, 230, 240
and 250; near the middle of mixing zone 260; and near
the end of mixing zone 260. These mixture temperatures
are reported below as T1, T2, T3, T4, T5 and T6,
respectively. Actual mixture temperatures are
influenced by the temperatures of the circulating
fluid, the heat exchange properties of the mixture and
surrounding barrel, and the mechanical heating from the
mixing process, and often differ from the set
temperatures due to the additional factors.
All ingredients were added to the continuous
mixer at ambient temperatures (about 77~F) unless
otherwise noted.
For this run, the zone temperatures Z1-Z5
were set (in ~F) at 350, 350, 300, 78 and 78,
respectively. The screw temperature S1 was set at
150~F. Actual mixture temperatures (Tl-T6, ~F) were
measured, at steady state, as 325, 293, 256, 127, 114
and 115, respectively. The screw rotation was 90 rpm.
2 1 9 ~ 7 n 4 PCT~S95/11027
WO96/0816~ /l U
- 26 -
A dry mixture of 57~ butyl rubber and 43~
calcium carbonate was added, at 13.9 pounds per hour,
into the first large feed port (port 212 in Figs. 7 and
8). Polyisobutylene, preheated to 100~C, was also
added at 9.5 pounds per hour into this port.
Low molecular weight polyvinyl acetate
(weight average Mol. Wt. = 25,000) was added at 13.0
pounds per hour into the second large feed port 232.
Cocoa powder was also added at 0.3 pounds per hour into
this port.
A mixture of 0.1~ BHT, 34.0~ hydrogenated
cottonseed oil, 34.0~ hydrogenated soybean oil, 6.7~
glycerol monostearate and 25.2~ partially hydrogenated
soybean and palm oil was preheated to about 80-90~C for
about 1.5 hours before the start of the run. During
the run, this mixture was injected into two liquid
injection ports 241 and 243 in the third mixing zone
240, at a total rate of 23.3 pounds per hour. This
resulted in an initial BHT concentration of 77.6 ppm
based on the weight of the chewing gum, comparable to
the 80 ppm used for Example 1.
Glycerin was injected at 2.1 pounds per hour
into liquid injection port 261 in the fifth mixing zone
260.
A mixture of 98.6~ sugar and 1.4~ sorbitol
was added at 196 pounds per hour into the feed port 262
in the mixing zone 260.
Corn syrup (at about 40~C) was injected at
39.9 pounds per hour into liquid injection port 263 in
zone 260. Peppermint flavor was injected at 2.1 pounds
per hour into liquid injection port 264 in zone 260.
The chewing gum product, which exited at a
temperature of about 50~C, was judged to be of
acceptable quality. Analytical testing showed the
final product to contain BHT at a level of 59.6 ppm,
versus the 77.6 ppm that was initially added. This
represented only a 23~ loss in BHT during the
21 99704
PCT~S95/11027
WO96/0816~
- 27 -
integrated manufacture of the gum base and chewing gum,
far less than the 45~ loss experienced in Example 1,
when the gum base and chewing gum were prepared using
conventional techniques.
EXAMPLE 3
As explained above, Example 2 was performed
using the same starting level of BHT as Example 1.
Because the BHT loss during production of the gum base
and chewing gum was substantially less for Example 2
than for Example 1, the finished product of Example 2
had a higher BHT content than the finished product of
Example 1. In order to provide a product using the
method of Example 2 which has a BHT content of only
43.7 ppm (to match the product of Example 1), it would
be necessary to perform the method of Example 2 using a
lower starting quantity of BHT.
Given that the method of Example 2 resulted
in a 23~ loss of BHT, the desired starting quantity can
be determined by dividing the target end quantity by
the fraction of initial BHT expected to remain after
manufacture:
43.7 ppm = 56.8 ppm
(1.00-.23)
Thus, the starting quantity of BHT should be
56.8 ppm based on the production rate of the chewing
gum. At a production rate of 300.1 pounds per hour,
the BHT should be initially added to the mixer at
0.0170 pounds per hour. Instead of combining 0.1~ BHT
into the preheated mixture of BHT and oils which is
added via injection ports 241 and 243, the preheated
mixture need only contain about 0.073~ BHT.
It should be appreciated that the method of
the present invention is capable of being incorporated
in the form of a variety of embodiments, only a few of
which have been illustrated and described above. The
invention may be embodied in other forms without
WO96/0816l 2 1 9 9 7 0 4 PCT~S95/11027
- 28 -
departing from its spirit or essential characteristics.
It will be appreciated that the addition of certain
other ingredients, process steps, materials or
components not specifically included will have an
adverse impact on the present invention. The best mode
of the invention may therefore exclude ingredients,
process steps, materials or components other than those
listed above for inclusion or use in the invention.
However, the described embodiments are to be considered
in all respects only as illustrative and not
restrictive, and the scope of the invention is,
therefore, indicated by the appended claims rather than
by the foregoing description. All changes which come
within the meaning and range of equivalency of the
claims are to be embraced within their scope.
