Chewing gum manufacture using pin and blade extruders

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 08/362,254, filed on Dec. 22, 1994, now U.S. Pat. No. 5,543,160, which is a continuation-in-part of U.S. application Ser. No. 08/305,363, filed on Sep. 13, 1994, now abandoned.

FIELD OF THE INVENTION

This invention is a process for the total manufacture of chewing gum base and chewing gum using a modified high efficiency continuous mixer.

BACKGROUND OF THE INVENTION

Conventionally, chewing gum base and chewing gum product have been manufactured using separate mixers, different mixing technologies and, often, at different factories. One reason for this is that the optimum conditions for manufacturing gum base, and for manufacturing chewing gum from gum base and other ingredients such as sweeteners and flavors, are so different that it has been impractical to integrate both tasks. Chewing gum base manufacture, on the one hand, involves the dispersive (often high shear) mixing of difficult-to-blend ingredients such as elastomer, filler, elastomer plasticizer, base softeners/emulsifiers and, sometimes wax, and typically requires long mixing times. Chewing gum product manufacture, on the other hand, involves combining the gum base with more delicate ingredients such as product softeners, bulk sweeteners, high intensity sweeteners and flavoring agents using distributive (generally lower shear) mixing, for shorter periods.

In order to improve the efficiency of gum base and gum product manufacture, there has been a trend toward the continuous manufacture of chewing gum bases and products. U.S. Pat. No. 3,995,064, issued to Ehrgott et al., discloses the continuous manufacture of gum base using a sequence of mixers or a single variable mixer. U.S. Pat. No. 4,459,311, issued to DeTora et al., also discloses the continuous manufacture of gum base using a sequence of mixers. Other continuous gum base manufacturing processes are disclosed in European Publication No. 0,273,809 (General Foods France) and in French Publication No. 2,635,441 (General Foods France).

U.S. Pat. No. 5,045,325, issued to Lesko et al., and U.S. Pat. No. 4,555,407, issued to Kramer et al., disclose processes for the continuous production of chewing gum products. In each case, however, the gum base is initially prepared separately and is simply added into the process. U.S. Pat. No. 4,968,511, issued to D'Amelia et al., discloses a chewing gum product containing certain vinyl polymers which can be produced in a direct one-step process not requiring separate manufacture of gum base. However, the disclosure focuses on batch mixing processes not having the efficiency and product consistency achieved with continuous mixing. Also, the single-step processes are limited to chewing gums containing unconventional bases which lack elastomers and other critical ingredients.

In order to simplify and minimize the cost of chewing gum manufacture, there is need or desire in the chewing gum industry for an integrated continuous manufacturing process having the ability to combine chewing gum base ingredients and other chewing gum ingredients in a single mixer, which can be used to manufacture a wide variety of chewing gums.

SUMMARY OF THE INVENTION

The present invention provides methods for the continuous manufacture of a wide variety of chewing gum products using a modified high efficiency mixer which does not require the separate manufacture of chewing gum base. It has been found that by shortening, or backing out, one or more hollow feed pins that are typically used in a blade and pin type extruder, greater feed of ingredients can be achieved. Additionally, clogging of feed orifices can be avoided. However, it has also been determined that certain pins cannot be shortened or backed out.

In an embodiment, the present invention provides a method for manufacturing chewing gum comprising the steps of adding chewing gum ingredients to an extruder that includes pins that circumscribe a shaft having blades. Pursuant to the present invention, the extruder includes at least one hollow pin that has a clearance from the shaft of at least 2.7% of the barrel diameter.

In another embodiment, a method for modifying a blade and pin extruder so as to allow it to manufacture chewing gum is provided comprising the steps of increasing the distance between at least one hollow pin and a shaft of the extruder so that the distance is equal to at least 2.7% of the barrel diameter.

In another embodiment, a method of continuously manufacturing chewing gum in a blade and pin extruder is provided, comprising the steps of: a) adding at least an elastomer and filler into a high efficiency continuous mixer; b) adding a least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticizers into the continuous mixer, and mixing said ingredient with the elastomer and filler; c) adding at least one sweetener and at least one flavor into the continuous mixer, and mixing said sweetener and flavor with the remaining ingredients to form a chewing gum product; and d) wherein at least one ingredient is added through a hollow pin that is located at a greater distance from a shaft of the extruder then at least one other pin of the extruder.

In still another embodiment, a method of continuously manufacturing chewing gum without requiring the separate manufacture of a chewing gum base is provided, comprising the steps of: a) adding at least an elastomer and filler into a blade and pin continuous mixer; b) subjecting at least the elastomer and filler to mixing in the continuous mixer; c) adding at least one sweetener and at least one flavoring agent into the elastomer and filler in the continuous mixer; d) subjecting at least the sweetener, flavoring agent, elastomer and filler to distributive mixing in the continuous mixer, to form a chewing gum product; e) continuously discharging the chewing gum product from the mixer; and f) wherein at least one ingredient is added to the continuous mixer through a hollow pin located at a distance from the shaft of at least 3% of the diameter of the barrel.

In a further embodiment, a method of continuously manufacturing chewing gum without requiring separate manufacture of a chewing gum base, comprising the steps of: a) adding at least an elastomer and filler into a blade-and-pin mixer that includes hollow pins that are located at different distances from a shaft of the extruder, and mixing the elastomer and filler together using blades and pins; b) adding-at least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticizers into the blade-and-pin mixer, and mixing said at least one ingredient with the elastomer and filler using blades and pins; and c) adding at least one sweetener and at least one flavor into the blade-and-pin mixer, and mixing said sweetener and flavor with the remaining ingredients to form a chewing gum product.

A high efficiency continuous mixer is one which is capable of providing thorough mixing over a relatively short distance or length of the mixer. This distance is 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. In an embodiment, the method of the invention comprises performing the following mixing 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 that the ingredients exist as a substantially homogeneous chewing gum mass, using a total L/D of not more than about 40.

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 remaining ingredients, and/or wherein a portion of the remaining (non-base) ingredients are added upstream with or before some of the base ingredients. An important feature is that a substantially homogenous chewing gum product mass be formed in a single continuous mixer, using an L/D of not more than about 40, without requiring a separate mixer to manufacture the chewing gum base.

With the foregoing in mind, it is an advantage of the invention to provide a continuous method for manufacturing chewing gum which does not require a separate manufacture of chewing gum base.

It is also an advantage of the invention to provide an improved blade and pin extruder for manufacturing chewing gum.

It is also an advantage of the invention to provide a method of reducing, or preventing, clogging of the ingredient addition orifices in an extruder.

It is also an advantage of the present invention to provide a method of injecting increased volumes of liquid ingredients into the extruder.

It is also an advantage of the invention to provide a continuous method for making chewing gum which accomplishes every essential mixing step using a single mixer.

It is also an advantage of the invention to provide a continuous method for making chewing gum which requires less equipment, less capital investment, and less labor than conventional manufacturing methods.

It is also an advantage of the invention to provide a continuous manufacturing method that produces chewing gum having greater product consistency, less thermal degradation, less thermal history, and less contamination than chewing gum produced using conventional processes that require longer manufacturing times and more manufacturing steps.

The foregoing and other features and advantages of the invention will become further 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 perspective view of a Buss high efficiency mixer in an opened state 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 a 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 high efficiency mixer configuration.

FIG. 2C

is a perspective view of a restriction ring assembly used in the high efficiency mixer configuration.

FIG. 3

is a perspective view showing the relative positioning of the elements of

FIGS. 2A

,

2

B and

2

C in the high efficiency mixer configuration.

FIG. 4

is a perspective view of a low-shear mixing screw element used in the high efficiency mixer configuration.

FIG. 5

is a perspective view of a high-shear mixing screw element used in the high efficiency mixer configuration.

FIG. 6

is a perspective view of a barrel pin element used in the high efficiency mixer configuration.

FIG. 7

is a schematic diagram of an arrangement of mixing barrel pins and ingredient feed ports.

FIG. 8

is a schematic diagram of a mixing screw configuration.

FIG. 9

is a schematic diagram of another mixing screw configuration.

FIG. 10

is a schematic diagram of a process for making chewing gum of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention provides methods and extruders for the total manufacture of chewing gum, using a continuous high-efficiency mixer, without requiring the separate manufacture of chewing gum base. This method can be advantageously performed using a continuous mixer whose mixing screw is composed primarily of precisely arranged mixing elements with only a minor fraction of simple conveying elements. A presently preferred mixer is a blade-and-pin mixer exemplified in

FIG. 1. A

blade-and-pin mixer 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, Ill.

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 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 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 1-5 mm, 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 ⅓, and the downstream on-screw element

21

has an L/D of about ⅔, 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 coincides with the L/D of the 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.

1

. 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 at least certain of the stationary pins

144

as the screw

120

rotates and reciprocates axially (FIG.

1

). 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

145

which permits attachment at selected locations along the inner barrel shaft

142

. Some of the pins

144

are configured as liquid injection ports by providing them with hollow center openings.

Hollow pins allow one to inject liquid ingredients into the mixer

100

at various points along the barrel

140

. Since the primary purpose of the pins

144

(both hollow and solid) is to interact with the blades

124

to enhance mixing, the pins

144

are designed to have very little clearance with the blades and with the screw shaft

122

. But, due to the close tolerance with the screw shaft

122

, the injection of liquid is often impeded. This is especially true with high volume and/or high viscosity liquid ingredients. On the other hand, in the case of low volume and/or low viscosity ingredients, the pin orifice may be partially or completely clogged by material moving through the extruder body. This problem can be especially exacerbated in view of the ingredients necessary to make chewing gum.

Surprisingly it has been determined that the above problems can be eliminated by backing out or shortening certain hollow pins. It has been found that pins in certain locations can be shortened or backed out, with little or no effect on mixing efficiency. By so shortening or backing out the pins, however, this allows greater feed rates through the pins especially with high volume and/or high viscosity liquids. In the case of low volume, low viscosity ingredients, increasing the clearance between the pin

144

and the screw shaft

122

prevents clogging of the orifice.

In this regard, it should be noted that in a typical blade and pin extruder, pins, including the hollow pins, normally have a specified clearance between the pin

144

and the surface of the screw shaft

122

. The standard clearance from the pin to the shaft is about 2.0 to 2.5% of the barrel diameter. In the case of the 100 mm BUSS extruder, this clearance is about 2.5 mm. In an extruder having a 200 mm barrel diameter, the clearance is 4.5 mm, in a 400 mm diameter barrel, the clearance is 8.5 mm, etc.

Pursuant to the present invention, at least one of the hollow pins is backed out or shortened so that the clearance is at least 2.7% of the barrel diameter. In a preferred embodiment, the pin is backed out or shortened so that the clearance is approximately 4% to 7% of the barrel diameter. For example, in a 100 mm BUSS extruder, at least one hollow pin is located approximately 4.5 to about 6.5 mm from the shaft.

Although, in most cases, the shortening of the pins does not have an adverse effect on the mixing performance of the mixer, it has been surprisingly found that in certain locations a major degregation of mixing performance will be observed if the pins

144

are shortened. In particular, if pins

144

that are located adjacent or in close proximity to ports where large quantities of dry ingredients are added are shortened or backed out, this can cause serious problems.

In this regard, it has been found that if these pins are shortened, problems can occur with conveying efficiency. Additionally, reducing the length of these pins can cause a build-up of material on the screw. In addition to other problems, this build-up can result in a lack of free volume for ingredient addition.

Accordingly, the pins that are located in close proximity to ports where large quantities of dry ingredients are added must be inserted to their full depth. On the other hand, in such cases, it may be necessary to move the ingredient injection point away from the port.

The present invention overcomes numerous problems that can be encountered in an extruder or mixer, especially a high efficiency continuous mixer. Excessive back pressure and/or insufficient or erratic flow rates are observed in liquid ingredient feed systems that use gravimetric feeds or volumetric pumps to inject ingredients through hollow pins. Clogging with low volume injection may also be remedied by the present invention.

The present invention can be used in conjunction with, or as a substitute for, the optimalization of pin orifice sizes. In certain instances, it may be desirable to bore out an orifice. This concept is disclosed in U.S. patent application entitled: “METHOD FOR MANUFACTURING CHEWING GUM USING MIXER WITH MODIFIED INJECTION OPENINGS,” Ser. No. 08/526,887, being filed on even date herewith, the disclosed of which is hereby incorporated herein by reference. In cases were the orifice has been bored out, the present invention will insure that the full benefits of that modification are gained.

Although there are numerous ways to shorten the pins

144

, one method for the 100 mm extruder is to install one or more additional washers onto the pin before the pin is screwed into the barrel. The standard washer used in the 100 mm extruder is approximately 2 mm thick. Accordingly, by adding an extra washer, one can increase the clearance from 2.5 mm to 4.5 mm. A third washer can increase the clearance to 6.5 mm. It may be desirable to have a clearance of 6.5 mm to accommodate high volume, high viscosity ingredient addition.

Another way to practice the present invention which is applicable to all extruders is to cut or grind 0.5% to about 5% of the barrel diameter from the terminal end of the pin

144

. Of course, it is also possible to have pins

144

custom manufactured at a desired length.

FIG. 7

is a schematic view showing a preferred barrel configuration, including an arrangement of barrel pins

144

. Barrel pins

144

are present in most or all of the available locations, in all three rows as shown. Pins

145

,

147

,

149

, and

151

are hollow pins. Hollow pins

145

and

147

are shortened. In this regard, pin

145

is located 4.5 mm from the shaft and pin

147

is located 6.5 mm from the shaft. Pins

149

and

151

are not shortened and are inserted to full depth. Pin

145

is used for flavor injection, pin

147

for syrup and glycerin injection, and pins

149

and

151

for fat blend injection.

It should also be noted on

FIG. 7

that the group of pins identified at

153

cannot be shortened without adversely effecting performance. It should be noted further that not all of the identical pin locations may be fitted with pins due to screw clearance considerations.

FIG. 8

is a schematic view illustrating a mixing screw configuration. The mixer

200

whose configuration is illustrated in

FIG. 8

has an overall active mixing L/D of about 19.

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 are 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. 8

, the configuration of the mixing screw

120

is schematically illustrated as follows. Zone

210

, which is the initial feed zone, is configured with about 1⅓ 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 1⅓ L/D of mixing, and the two high shear mixing elements contribute about 1⅓ L/D of mixing. Zone

220

has a total mixing L/D of about 3.0, including the end part covered by a 57 mm restriction ring assembly

30

with cooperating on-screw elements

20

and

21

(not separately designated in FIG.

8

).

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 1.0, 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 4.0.

Straddling the end of the second mixing zone

230

and the start of the third mixing zone

240

is a 60 mm restriction ring assembly

30

with cooperating on-screw elements

20

and

21

having an L/D of about 1.0. Then, zone

240

is configured, from left to right, with 4.5 high shear mixing elements

50

contributing a mixing L/D of about 3.0. Zone

240

also has a total mixing L/D of about 4.0.

Straddling the end of the third mixing zone

240

and the start of the fourth mixing zone

250

is another 60 mm restriction ring assembly

30

with cooperating on-screw elements having an L/D of about 1.0. 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 7⅓. Zone

250

has a total mixing L/D of about 4.0, and zone

260

has a total mixing L/D of about 4.0.

FIG. 9

illustrates schematically another configuration of the mixing screw

271

. The configuration is preferably used with the barrel configuration of FIG.

7

. With respect to the legend of

FIG. 9

, please note: A indicates a conveying element; B indicates a low shear kneading element; C indicates a restriction ring; D indicates a high shear kneading element; and E indicates a stellite tipped kneading element.

Before explaining where the various chewing gum ingredients are added to the continuous mixer

200

, and how they are mixed, it is helpful to discuss the composition of typical chewing gums that can be made using the method of the invention. A chewing gum generally includes a water soluble bulk portion, a water insoluble chewing gum base portion, and one or more flavoring agents. The water soluble portion dissipates over a period of time during chewing. The gum base portion is retained in the mouth throughout the chewing process.

The insoluble gum base generally includes elastomers, elastomer plasticizers (resins), fats, oils, waxes, softeners and inorganic fillers. The elastomers may include polyisobutylene, isobutylene-isoprene copolymer, styrene butadiene copolymer and natural latexes such as chicle. The resins may include polyvinyl acetate and terpene resins. Low molecular weight polyvinyl acetate is a preferred resin. Fats and oils may include animal fats such as lard and tallow, vegetable oils such as soybean and cottonseed oils, hydrogenated and partially hydrogenated vegetable oils, and cocoa butter. Commonly used waxes include petroleum waxes such as paraffin and microcrystalline wax, natural waxes such as beeswax, candellia, carnauba and polyethylene wax.

The gum base typically also includes a filler component such as calcium carbonate, magnesium carbonate, talc, dicalcium phosphate and the like; softeners, including glycerol monostearate and glycerol triacetate; and optional ingredients such as antioxidants, color and emulsifiers. The gum base constitutes between 5-95% by weight of the chewing gum composition, more typically 10-50% by weight of the chewing gum, and most commonly 20-30% by weight of the chewing gum.

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 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, levulose, 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 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 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 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 different 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 above, 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 accomplish the total chewing gum manufacture 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 at 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 highly 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 polyvinylacetate 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 and, optionally, 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.

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 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. It may be desirable to employ a simple shaping extruder to form an intermediate shape prior to final shaping into sticks, pellets, etc. 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.

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 and chewing gum product are accomplished in a single continuous mixer using a mixing L/D of not more than about 40.

EXAMPLE 1

Testing the Suitability of a Continuous Mixer

The following preliminary test can be employed to determine whether a particular continuous mixer with a particular configuration meets the requirements of a high efficiency mixer suitable for practicing the method of the invention.

A dry blend of 35.7% butyl rubber (98.5% isobutylene −1.5% isoprene copolymer, with a molecular weight of 120,000-150,000, manufactured by Polysar, Ltd. of Sarnia, Ontario, Canada as POLYSAR Butyl 101-3); 35.7% calcium carbonate (VICRON 15-15 from Pfizer, Inc., New York, N.Y.); 14.3% polyterpene resin (ZONAREZ 90 from Arizona Chemical Company of Panama City, Fla.) and 14.3% of a second polyterpene resin (ZONAREZ 7125 from Arizona Chemical Company) is fed into the continuous mixer in question equipped with the mixer configuration to be tested. The temperature profile is optimized for the best mixing, subject to the restriction that the exit temperature of the mixture does not exceed 170° C. (and preferably remains below 160° C.) to prevent thermal degradation. In order to qualify as a suitable high efficiency mixer, the mixer should produce a substantially homogeneous, lump-free compound with a uniform milky color in not more than about 10 L/D, preferably not more than about 7 L/D, most preferably not more than about 5 L/D.

To thoroughly check for lumps, the finished rubber compound may be stretched and observed visually, or compressed in a hydraulic press and observed, or melted on a hot plate, or made into a finished gum base which is then tested for lumps using conventional methods.

Also, the mixer must have sufficient length to complete the manufacture of the gum base, and of the chewing gum product, in a single mixer, using a total mixing L/D of not more than about 40. Any mixer which meets these requirements falls within the definition of a high-efficiency mixer suitable for practicing the method of the invention.

EXAMPLES 2-13

Continuous Chewing Gum Manufacture

The following examples were run using a Buss kneader with a 100 mm mixer screw diameter, configured in the manner described above (unless indicated otherwise), with five mixing zones, a total mixing L/D of 19, and an initial conveying L/D of 1⅓. No die was used at the end of the mixer, unless indicated otherwise, and the product mixture exited as a continuous rope. Each example was designed with feed rates to yield chewing gum product at the rate of 300 pounds per hour.

Unless indicated otherwise, the conditions and method for each example was as follows:

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 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 200° F., and oil cooling was used at higher temperatures. Where water cooling was desired, tap water (typically at about 57° 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 Z

1

, Z

2

, Z

3

, Z

4

and Z

5

, respectively. Fluid temperatures were also set for the mixing screw

120

, and are reported below as S

1

.

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 T

1

, T

2

, T

3

, T

4

, T

5

and T

6

, 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 temperature (about 77° F.) unless otherwise noted.

EXAMPLE 2

This example illustrates the preparation of a spearmint flavored non-tack sugar chewing gum. A mixture of 24.2% terpene resin, 29.7% dusted ground butyl rubber (75% rubber with 25% fine ground calcium carbonate as an anti-blocking aid) and 46.1% fine ground calcium carbonate was fed at 25 lb/hr into the first large feed port (port

212

in FIGS.

7

and

8

). Low molecular weight polyisobutylene (mol. wt.=12,000), preheated to 100° C., was also added at 6.3 lb/hr into this port.

Ground low molecular weight polyvinyl acetate was added at 13.3 lb/hr into the second large feed port (port

232

in FIGS.

7

and

8

).

A fat mixture, preheated to 83° C., was injected into the liquid injection ports in the third mixing zone (ports

241

and

243

in FIG.

7

), at a total rate of 18.4 lb/hr, with 50% of the mixture being fed through each port. The fat mixture included 30.4% hydrogenated soybean oil, 35.4% hydrogenated cottonseed oil, 13.6% partially hydrogenated soybean oil, 18.6% glycerol monostearate, 1.7% cocoa powder, and 0.2% BHT.

Glycerin was injected into the first liquid injection port in the fifth mixing zone (port

261

in

FIG. 7

) at 3.9 lb/hr. A mixture of 1.1% sorbitol and 98.9% sugar was added into the large feed port in the fifth mixing zone (port

262

in

FIG. 7

) at 185.7 lb/hr. Corn syrup, preheated to 44° C., was added into the second liquid injection port in the fifth mixing zone (port

263

in

FIG. 7

) at 44.4 lb/hr. Spearmint flavor was added into the third liquid injection port in the fifth mixing zone (port

264

in

FIG. 7

) at 3.0 lb/hr.

The zone temperatures Z

1

-Z

5

were set (in ° F.) at 350, 350, 150, 57 and 57, respectively. The mixing screw temperature S

1

was set at 120° F. The mixture temperatures T

1

-T

6

were measured at steady state (in ° F.) as 235, 209, 177, 101 and 100, and fluctuated slightly during the trial. The screw rotation was 80 rpm.

The chewing gum product exited the mixer at 120° F. The product was comparable to that produced by conventional pilot scale batch processing. The chew was slightly rubbery but no base lumps were visible.

EXAMPLE 3

This example illustrates the preparation of a peppermint flavored non-tack sugar chewing gum. A dry mixture of 57% dusted ground butyl rubber (75% rubber, 25% calcium carbonate) and 43% fine ground calcium carbonate was added at the first large feed port

212

(FIG.

7

), at 13.9 lb/hr. Molten polyisobutylene (preheated to 100° C.) was also added to port

212

at 9.5 lb/hr.

Ground low molecular weight polyvinyl acetate was added to port

232

at 13.0 lb/hr.

A fat mixture (preheated to 82° C.) was pumped 50/50 into ports

241

and

243

at a total rate of 23.6 lb/hr. The fat mixture included 33.6% hydrogenated cottonseed oil, 33.6% hydrogenated soybean oil, 24.9% partially hydrogenated soybean oil, 6.6% glycerol monostearate, 1.3% cocoa powder and 0.1% BHT. Glycerin was added to port

261

at 2.1 lb/hr. A mixture of 98.6% sugar and 1.4% sorbitol was added to port

262

at 196 lb/hr. Corn syrup (preheated to 40° C.) was added to port

263

at 39.9 lb/hr. Peppermint flavor was added to port

264

at 2.1 lb/hr.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 350, 350, 300, 60 and 60, respectively. The screw temperature (S

1

) was set at 200° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 297, 228, 258, 122, 98 and 106, respectively. The screw rotation was 85 rpm.

The chewing gum product exited the mixer at 119° F. The finished product was free of lumps but was dry and lacked tensile strength. These defects were attributed to the formula rather than the processing.

EXAMPLE 4

This example illustrates the preparation of a spearmint flavored gum for pellet coating. A blend of 27.4% high molecular weight terpene resin, 26.9% low molecular weight terpene resin, 28.6% dusted ground butyl rubber (75% rubber, 25% calcium carbonate) and 17.1% fine ground calcium carbonate was fed into the first large port

212

(FIG.

7

), at 33.5 lb/hr. Molten polyisobutylene (100° C.) was pumped into the same port at 1.3 lb/hr.

Low molecular weight polyvinyl acetate was fed to port

232

at 19.8 lb/hr.

A fat mixture (82° C.) was added 50/50 into ports

241

and

243

, at a total rate of 17.4 lb/hr. The fat mixture included 22.6% hydrogenated cottonseed oil, 21.0% partially hydrogenated soybean oil, 21.0% hydrogenated soybean oil, 19.9% glycerol monostearate, 15.4% lecithin and 0.2% BHT.

Sugar was fed into port

262

at 157.8 lb/hr. Corn syrup (40° C.) was added to port

263

at 68.4 lb/hr. Spearmint flavor was added to port

264

at 1.8 lb/hr.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 160, 160, 110, 60 and 60, respectively. The screw temperature (S

1

) was set at 68° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 230, 215, 166, 105, 109 and 111, respectively. The screw rotation was 80 rpm.

The chewing gum product exited the mixer at 121° F. The product was firm and cohesive when chewed (normal for a pellet center). No base lumps were visible.

EXAMPLE 5

This example illustrates the preparation of a peppermint flavored sugar chewing gum. A blend of 24.4% dusted ground butyl rubber (75% rubber, 25% calcium carbonate), 18.0% low molecular weight terpene resin, 18.3% high molecular weight terpene resin and 39.4% fine ground calcium carbonate was added to the first large port

212

(

FIG. 7

) at 27.6 lb/hr.

A blend of 11.1% high molecular weight polyvinyl acetate and 88.9% low molecular weight polyvinyl acetate was added into the second large feed port

232

at 14.4 lb/hr. Polyisobutylene (preheated to 100° C.) was also added to this port at 3.5 lb/hr.

A fat mixture (83° C.) was added 50/50 into ports

241

and

243

, at a total rate of 14.5 lb/hr. This fat mixture included 31.9% hydrogenated cottonseed oil, 18.7% hydrogenated soybean oil, 13.2% partially hydrogenated cottonseed oil, 19.8% glycerol monostearate, 13.7% soy lecithin, 2.5% cocoa powder and 0.2% BHT.

Glycerin was injected into port

261

at 3.9 lb/hr. A mixture of 84.6% sucrose and 15.4% dextrose monohydrate was added to port

262

at 203.1 lb/hr. Corn syrup (40° C.) was injected into port

263

at 30.0 lb/hr. A mixture of 90% peppermint flavor and 10% soy lecithin was injected into port

264

at 3.0 lb/hr.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 350, 350, 100, 60 and 60, respectively, and the screw temperature (S

1

) was set at 100° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 308, 261, 154, 95, 94 and 105, respectively. The screw rotation was set at 55 rpm.

The product exited the mixer at 127° F. The finished product had good chew characteristics and there was no evidence of rubber lumps.

EXAMPLE 6

This example illustrates the preparation of a fruit-flavored sugar gum. A mixture of 39.3% dusted ground butyl rubber (75% rubber, 25% calcium carbonate), 39.1% low molecular weight terpene resin and 21.6% fine ground calcium carbonate was added to the first large feed port

212

(

FIG. 7

) at 20.6 lb/hr.

A mixture of 33.0% low molecular weight terpene resin and 67.0% low molecular weight polyvinyl acetate was added at 24.4 lb/hr into the second large feed port

232

. Polyisobutylene (preheated to 100° C.) was also added at 1.0 lb/hr into the port

232

.

A fat/wax composition (82° C.) was injected 50/50 into the liquid injection ports

241

and

243

, at a total rate of 14.0 lb/hr. The composition included 29.7% paraffin wax, 21.7% microcrystalline wax (m.p.=170° F.), 5.7% microcrystalline wax (m.p.=180° F.), 20.5% glycerol monostearate, 8.6% hydrogenated cottonseed oil, 11.4% soy lecithin, 2.1% cocoa powder, and 0.3% BHT.

Glycerin was injected into the liquid injection port

261

at 3.3 lb/hr. A mixture of 88.5% sucrose and 11.5% dextrose monohydrate was added at 201.0 lb/hr into the large port

262

. Corn syrup (40° C.) was injected at 3.0 lb/hr into the liquid injection port

263

, and a mixture of 88.9% fruit flavor and 11.1% soy lecithin was injected at 2.7 lb/hr into the liquid injection port

264

.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 425, 425, 200, 61 and 61, respectively. The screw temperature (S

1

) was set at 66° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 359, 278, 185, 105, 100 and 109, respectively. The screw rotation was set at 70 rpm.

The chewing gum product exited the mixer at 122° F. The product was very soft while warm and fell apart during chewing. However, this was not atypical for this product. After aging for two months, the product was again chewed and found to have excellent texture and flavor. No rubber lumps were visible.

EXAMPLE 7

This example illustrates the preparation of a sugar chunk bubble gum. For this example, the mixer configuration was varied slightly from the preferred configuration described above and used for Examples 2-6. Specifically, a round-hole 30 mm die was installed at the exit end of the mixer.

A blend of 68.9% high molecular weight polyvinyl acetate and 31.1% ground talc was added into the first large feed port

212

(FIG.

7

), at 35.4 lb/hr. Polyisobutylene (preheated to 100° C.) was also added to port

212

at 3.95 lb/hr. Further downstream, in the first mixing zone

220

, acetylated monoglyceride was injected at 2.6 lb/hr, using a liquid injection (hollow barrel pin) port not shown in FIG.

7

.

Additional polyisobutylene (100° C.) at 3.95 lb/hr, and glycerol ester of partially hydrogenated wood rosin at 13.4 lb/hr, were added into the second large port

232

. A mixture of 43.6% glycerol monostearate, 55.9% triacetin and 0.5% BHT was added at 6.7 lb/hr into the liquid injection port

241

.

Glycerin was injected at 2.1 lb/hr into the, liquid injection port

261

. A mixture of 98.4% sucrose and 1.6% citric acid was added at 170.4 lb/hr into the large port

262

. Corn syrup (40° C.) was injected at 58.5 lb/hr into liquid injection port

263

, and a mixture of 60% lemon-lime flavor and 40% soy lecithin was added at 3.0 lb/hr into the liquid injection port

264

.

The zone temperatures (Z

1

-Z

5

, ° F.) were ultimately set at 440, 440, 160, 61 and 61, respectively. The screw temperature (S

1

) was ultimately set at 80° F. The mixture temperatures (T

1

-T

6

, ° F.) were ultimately measured as 189, 176, 161, 97, 108 and 112, respectively. The screw rotation was 55 rpm.

At first, the product exited the extruder at 140° F. and exhibited signs of heat stress. The zone temperatures Z

1

and Z

2

were then reduced by 10° F. each, and the screw temperature S

1

was raised by 20° F., to the values shown above. This caused the chewing gum exit temperature to drop to 122° F., and the product quality improved markedly.

During chewing, the product exhibited excellent texture, flavor, and bubble blowing characteristics. No rubber lumps were visible.

EXAMPLE 8

This example illustrates the preparation of a spearmint flavored sugarless gum. A mixture of 42.1% fine ground calcium carbonate, 18.9% glycerol ester of wood rosin, 16.7% glycerol ester of partially hydrogenated wood rosin, 17.0% ground butyl rubber, and 5.3% dusted ground (25:75) styrene butadiene rubber (75% rubber, 25% calcium carbonate) was added into port 212 (

FIG. 7

) at 38.4 lb/hr.

Low molecular weight polyvinyl acetate at 12.7 lb/hr, and polyisobutylene (preheated to 100° C.) at 7.6 lb/hr, were added into port

232

.

A fat mixture (82° C.) was injected 50/50 into ports

241

and

243

, at a total rate of 20.9 lb/hr. The fat mixture included 35.7% hydrogenated cottonseed oil, 30.7% hydrogenated soybean oil, 20.6% partially hydrogenated soybean oil, 12.8% glycerol monostearate and 0.2% BHT.

Unlike the previous examples, glycerin was injected at 25.5 lb/hr into the fourth mixing zone

250

(

FIG. 7

) through a liquid injection port (not shown). A coevaporated blend of hydrogenated starch hydrolysate and glycerin (at 40° C.) was injected further downstream in the fourth mixing zone

250

through another liquid injection port (not shown). The coevaporated blend included 67.5% hydrogenated starch hydrolysate solids, 25% glycerin and 7.5% water.

A mixture of 84.8% sorbitol, 14.8% mannitol and 0.4% encapsulated aspartame was added into port

262

in the fifth mixing zone

260

, at 162.3 lb/hr. A mixture of 94.1% spearmint flavor and 5.9% lecithin was injected at 5.1 lb/hr into the port

264

located further downstream.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 400, 400, 150, 62 and 62, respectively. The screw temperature (S

1

) was set at 66° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 307, 271, 202, 118, 103 and 116. The mixing screw rotation was 69 rpm.

The chewing gum product exited the mixer at 117° F. The gum had good appearance with no sorbitol spots or rubber lumps. The gum was slightly wet to the touch, sticky and fluffy (low density), but was acceptable. During chewing, the gum was considered soft initially but firmed up with continued chewing.

EXAMPLE 9

This example illustrates the preparation of a sugarless spearmint gum for use in coated pellets. A mixture of 28.6% dusted ground butyl rubber (75% rubber, 25% calcium carbonate), 27.4% high molecular weight terpene resin, 26.9% low molecular weight terpene resin and 17.1% calcium carbonate was added into port

212

(

FIG. 7

) at 41.9 lb/hr.

Low molecular weight polyvinyl acetate at 24.7 lb/hr, and polyisobutylene (preheated to 100° C.) at 1.7 lb/hr, were added into port

232

.

A fat composition (82° C. ) was injected 50/50 into ports

241

and

243

at a total rate of 21.7 lb/hr. The fat composition included 22.6% hydrogenated cottonseed oil, 21.0% hydrogenated soybean oil, 21.0% partially hydrogenated soybean oil, 19.9% glycerol monostearate, 15.4% glycerin and 0.2% BHT.

A 70% sorbitol solution was injected into the fourth mixing zone

250

(

FIG. 7

) at 17.4 lb/hr, using a hollow barrel pin liquid injection port (not shown).

A mixture of 65.8% sorbitol, 17.9% precipitated calcium carbonate and 16.3% mannitol was added at 184.2 lb/hr into the final large port

262

. A mixture of 71.4% spearmint flavor and 28.6% soy lecithin was added at 8.4 lb/hr into the final liquid injection port

264

.

The zone temperatures (Z

1

-Z

5

, ° F.) were set at 400, 400, 150, 61 and 61, respectively. The screw temperature (S

1

) was set at 65° F. The mixture temperatures (T

1

-T

6

, ° F.) were measured as 315, 280, 183, 104, 109 and 116, respectively. The screw rotation was set at 61 rpm.

The chewing gum exited the mixer at 127° F. The product appearance was good with no sorbitol spots or rubber lumps. However, the initial chew was reported as being rough and grainy.

EXAMPLE 10

This example illustrates the preparation of a peppermint flavored sugar chewing gum. A mixture of 27.4% dusted ground butyl rubber (75% butyl rubber dusted with 25% calcium carbonate), 14.1% lower softening terpene resin (softening point=85° C.), 14.4% higher softening terpene resin (softening point 125° C.) and 44.1% calcium carbonate was fed at 24.6 lb/hr into the first large feed port (port

212

in FIGS.

7

and

8

).

A mixture of 73.5% low molecular weight polyvinyl acetate, 9.2% high molecular weight polyvinyl acetate, 8.6 lower softening terpene resin and 8.7% higher softening terpene resin was fed at 17.4 lb/hr into the second large feed port

232

. Polyisobutylene was also added at 3.5 lb/hr into this port.

A fat mixture, preheated to 83° C., was injected into the liquid injection ports in the third mixing zone (ports

241

and

243

in FIG.

7

), at a total rate of 14.5 lb/hr, with 50% of the mixture being fed through each port. The fat mixture included 0.2% BHT, 2.5% cocoa powder, 31.9% hydrogenated cottonseed oil, 19.8% glycerol monostearate, 18.7% hydrogenated soybean oil, 13.7% lecithin, and 13.2% partially hydrogenated cottonseed oil.

A mixture of 84.6% sugar and 15.4% dextrose monohydrate was injected at 203.1 lb/hr into the large feed port

262

in the fifth mixing zone. Glycerin was added at 3.9 lb/hr into the first liquid injection port 261 in the fifth mixing zone. Corn syrup, preheated to 44° C., was added at 30.0 lb/hr into the second liquid injection port

263

in the fifth mixing zone. A mixture of 90.0% peppermint flavor and 10.0% lecithin was injected into the third liquid injection port

264

in the fifth mixing zone at 3.0 lb/hr.

The zone temperatures Z

1

-Z

5

were set (in ° F.) at 350, 350, 110, 25 and 25, respectively. The mixing screw temperature S

1

was set at 101° F. The mixer temperatures T

1

-T

6

were measured at steady state (in ° F.) as 320, 280, 164, 122, 105 and 103, respectively. The screw rotation was 63 rpm, and the product exited the mixer at 52-53° C.

The peppermint sugar gum product was desirably soft, and acceptable in quality.

EXAMPLE 11

This example illustrates the preparation of a sugarless stick bubble gum. For this example, the screw configuration shown in

FIG. 8

, and used for the previous examples, was varied as follows. The conveying section

210

and mixing sections

220

,