Environmentally friendly chewing gum bases including polyhydroxyalkanoates

Chewing gum bases, and resultant chewing gums, that are environmentally friendly are provided. The chewing gum base comprising approximately 1 to about 99% by weight polyhydroxyalkanoates having side chain lengths of C.sub.4 to C.sub.30.

BACKGROUND OF THE INVENTION
 The present invention relates generally to chewing gum compositions and
 methods for making same. More specifically, the present invention relates
 to chewing gum compositions that are more environmentally acceptable than
 typical compositions.
 For hundreds of years, people have enjoyed chewing gum like substances. In
 the late 1800's, the predecessor to today's chewing gum compositions were
 developed. Today chewing gum is enjoyed daily by millions of people
 worldwide.
 Chewed gum is usually disposed of in the wrapper that initially houses the
 chewing gum. Likewise, chewed gum can be disposed of in other substrates
 by wrapping the substrate around the chewed gum.
 Although chewed gum can be easily disposed of without creating any
 problems, chewed gum when improperly disposed can create environmental
 issues. In this regard, the improper disposal of chewed gum, e.g.,
 expectorating the chewed gum on a sidewalk, floor, or like area can create
 a nuisance. Typically, these gum cuds are mainly composed of a water
 insoluble masticatory part which is represented by the gum base. Due to
 their formulations, these gum cuds have an adhesive like characteristic.
 Therefore, the chewed gum cuds can stick to surfaces on to which they are
 placed. This can create environmental sanitation issues if the chewed gum
 cuds are improperly discarded.
 SUMMARY OF THE INVENTION
 The present invention provides a chewing gum base, and resultant chewing
 gum, that is environmentally friendly. As used herein the term
 "environmentally friendly" refers to a chewing gum composition that: will
 degrade; and can be easily removed from indoor or outdoor surfaces.
 Pursuant to the present invention environmentally friendly gum bases are
 provided that include polyhydroxyalkanoates.
 To this end, the present invention provides a chewing gum base comprising
 approximately 1 to about 99% by weight polyhydroxyalkanoates having side
 chain lengths of C.sub.4 to C.sub.30.
 The polyhydroxyalkanoates can be either homopolymers or copolymers of
 monomers with different side chains.
 In an embodiment, the gum base does not include non-biodegradable rubbers
 and resins.
 In an embodiment, the polyhydroxyalkanoates have side chain lengths of
 C.sub.6 to C.sub.22.
 In an embodiment, the polyhydroxyalkanoates comprise approximately 10% to
 about 99% by weight of the gum base.
 In an embodiment, the polyhydroxyalkanoate is derived from natural
 occurring plants.
 In an embodiment, the polyhydroxyalkanoate is derived from a fermentation
 process.
 In an embodiment, the polyhydroxyalkanoate is derived from a transgenic
 plants.
 In an embodiment, the polyhydroxyalkanoates include low molecular weight
 biodegradable resins.
 In an embodiment, the low molecular weight biodegradable resins are chosen
 from the group consisting of polyterpenes and wood rosin esters.
 In another embodiment of the present invention, a chewing gum base free of
 non-biodegradable rubbers and resins is provided comprising approximately
 3% to about 99% by weight polyhydroxyalkanoates having side chain lengths
 of C.sub.4 to C.sub.30 and a filler.
 In an embodiment, the filler is chosen from the group comprising of zein,
 oat fiber, gluten, casein, cellulose, as well as calcium carbonate, talc,
 magnesium silicate, and other inorganic fillers.
 In an embodiment, the polyhydroxyalkanoates have side chain lengths of
 C.sub.6 to C.sub.20.
 In an embodiment, the polyhydroxyalkanoates comprise approximately 10% to
 about 80% by weight of the gum base.
 In an embodiment, the polyhydroxyalkanoate is derived from natural
 occurring plants.
 In an embodiment, the polyhydroxyalkanoate is derived from a fermentation
 process.
 In still another embodiment, a chewing gum is provided comprising a water
 soluble portion and a water insoluble base that includes at least one
 polyhydroxyalkanoate having a chain length of C.sub.4 to C.sub.30.
 It is an advantage of the present invention to provide an environmentally
 friendly chewing gum base.
 Still further, it is an advantage of the present invention to provide a
 chewing gum composition made from an environmentally friendly chewing gum
 base.
 Another advantage of the present invention is to provide a degradable
 chewing gum containing an environmentally friendly chewing gum base.
 Moreover, an advantage of the present invention is to provide a chewing gum
 composition that when chewed, if improperly discarded will degrade
 naturally.
 An additional advantage of the present invention is to provide a gum base
 that includes environmentally friendly polyesters derived from either
 fermentation of carbohydrates or extraction of natural plants.
 Still, an advantage of the present invention is to provide a source of
 polyesters for the gum base that are from renewable resources.
 Additional features and advantages of the present invention are described
 in, and will be apparent from the detailed description of the presently
 preferred embodiments and from the drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
 The present invention provides improved chewing gum base. Specifically, the
 present invention provides chewing gum bases that are environmentally
 friendly. In this regard, the chewing gum base includes
 polyhydroxyalkanoates. Additionally, improved chewing gums as well as
 ingredients used for chewing gum bases are described.
 The chewing gum base of the present invention includes
 polyhydroxyalkanoates. It has been surprisingly found that gum bases
 formed with polyhydroxyalkanoates can be constructed so that they are
 biodegradable. Additionally, the chewing gums made from such gum bases
 possess similar characteristics to conventional chewing gums.
 Polyhydroxyalkanoates are a class of polymers that have rapid
 biodegradability. Polyhydroxyalkanoates exist in some natural plants and
 also can be synthesized by a fermentation process. Thus,
 polyhydroxyalkanoates are renewable polyesters that can be used to
 construct chewing gum. FIG. 1 illustrates schematically the cycle of
 polyhydroxyalkanoates.
 Polyhydroxyalkanoates have the following general structure:
 ##STR1##
 where R=H--C.sub.11, and m=0-3
 Depending on the length of the side chain "R", the polymers can either be
 plastics (short side chains) or elastomers (long side chains). Short side
 chain polyhydroxyalkanoates tend to be highly crystalline and lack
 elasticity. They do not therefore offer certain of the desirable chewing
 characteristics required by chewing gums.
 Polyhydroxyalkanoates with long side chains, such as those having at least
 four carbon lengths, e.g. C.sub.4 -C.sub.30, have very little
 crystallinity and possess high elasticity. This is due to an increase in
 free volume. These long side chain polyhydroxyalkanoates can thereby be
 used to replace rubbers and resins that are used in conventional gum
 bases. This results in a gum base that is not only readily biodegradable,
 but, additionally the ingredients are from renewable resources. Moreover,
 the resultant gums possess similar chewing characteristics to conventional
 chewing gums.
 The present invention can be used to construct a variety of chewing gums.
 In general, a chewing gum composition typically comprises a water-soluble
 bulk portion, a water-insoluble chewable gum base portion and flavoring
 agents. The water-soluble portion dissipates with a portion of the
 flavoring agent over a period of time during chewing. The gum base portion
 is retained in the mouth throughout the chew. The term chewing gum refers
 to both a chewing and a bubble gum type gum in its general sense.
 The insoluble portion of the gum, usually referred to as the gum cud,
 typically may contain any combination of elastomers, vinyl polymers,
 elastomer plasticizers, fillers, softeners, waxes and other optional
 ingredients such as colorants and antioxidants.
 The variety of gum base ingredients typically used provide the ability to
 modify the chewing characteristics of gums made from the gum base.
 Elastomers provide the rubbery, cohesive nature to the gum which varies
 depending on this ingredient's chemical structure, level in the gum base,
 and how it may be compounded with other ingredients.
 Elastomers suitable for use in the gum base and gum of the present
 invention include polyhydroxyalkanoates having linear or branched
 saturated or unsaturated side chains of C.sub.4 -C.sub.30. Preferably, the
 polyhydroxyalkanoates have normal or iso-side chains of C.sub.4 -C.sub.20,
 and most preferably C.sub.8 -C.sub.18. The polyhydroxyalkanoates
 elastomers can have only one-size side chains, or any combination of
 different side chains throughout the polymer main chains.
 Natural elastomers used in conventional gum bases may include natural
 rubber such as smoked or liquid latex and guayule, natural gums such as
 jelutong, lechi caspi perillo, massaranduba balata, massaranduba
 chocolate, nispero, rosidinha, chicle, gutta percha, gutta kataiu, niger
 gutta, tunu, chilte, chiquibul, gutta hang kang. Synthetic elastomers used
 in conventional gum bases may include high molecular weight elastomers
 such as butadiene-styrene copolymers and isobutylene-isoprene copolymers,
 low to high molecular weight elastomers such as polybutadiene and
 polyisobutylene, vinyl polymeric elastomers such as polyvinyl acetate,
 polyethylene, vinyl copolymeric elastomers such as vinyl acetate/vinyl
 laurate, vinyl acetate/vinyl stearate, ethylene/vinyl acetate, polyvinyl
 alcohol or mixtures thereof.
 The elastomers for use in a gum base or gum of the present invention are
 the polyhydroxyalkanoates alone or in combination with other typical gum
 base ingredients. However, the gum base and gum of the present invention
 are free of non-degradable elastomers such as butadiene-styrene
 copolymers, isobutylene-isoprene copolymers, polybutadiene,
 polyisobutylene, and vinyl polymeric elastomers (polyvinyl acetate,
 polyethylene, vinyl acetate/vinyl laurate, vinyl acetate/vinyl stearate,
 ethylene/vinyl acetate) or mixtures thereof.
 More preferably, the polymers used are polyhydroxyalkanoates alone, as
 better illustrated in the pending Examples below.
 Other optional ingredients such as antioxidants may also be used in the gum
 base. Antioxidants prolong shelf-life and storage of gum base, finished
 gum or their respective components including fats and flavor oils.
 Antioxidants suitable for use in gum base or gum of the present invention
 include butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT),
 beta-carotenes, tocopherols, acidulants such as Vitamin C, ascorbic acid,
 propyl gallate, other synthetic and natural types of mixtures thereof.
 Preferably, the antioxidants used in the gum base are butylated
 hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tocopherols, or
 mixtures thereof.
 Waxes aid in the curing of the gum made from the gum base as well as
 improve shelf-life and texture. Wax crystal also improves the release of
 flavor. The smaller crystal size allows slower release of flavor since
 there is more hindrance of the flavor's escape from this wax versus a wax
 having larger crystal sizes.
 Elastomer plasticizers vary the firmness of the gum base. Their specificity
 on elastomer inter-molecular chain breaking (plasticizing) along with
 their varying softening points cause varying degrees of finished gum
 firmness and compatibility when used in base. This may be important when
 one wishes to provide more elastomeric chain exposure to the alkanic
 chains of the waxes.
 Elastomer plasticizers optionally suitable for use in the present invention
 include natural 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,
 partially hydrogenated methyl esters of rosin, pentaerythritol ester of
 rosin, synthetic elastomer plasticizers such as terpene resins derived
 from alpha-pinene, beta-pinene and/or d-limonene and mixtures thereof.
 Occasionally, both terpene and rosin ester resins may be used in the
 present invention. The terpene rosin ester ratios may range from about
 1:15 to about 15:1.
 Softeners modify the texture of the base and introduce sharp melting
 transitions during chewing. Softeners suitable for use in the gum base and
 gum of the present invention include triglycerides of non-hydrogenated,
 partially hydrogenated and fully hydrogenated cottonseed, soybean, palm,
 palm kernel, coconut, safflower, tallow, cocoa butter, medium chain
 triglycerides and the like.
 The preferred softeners include unsaturated, partially saturated or fully
 saturated oils that contain, as one or more of their constituent groups,
 fatty acids of carbon chain length of from 6 to 18.
 Monoglycerides, diglycerides, acetylated monoglycerides, distilled mono-
 and diglycerides and lecithin may, from their manufacturing processing,
 contain triglyceride levels less than 2 percent by weight. Though these
 ingredients are softeners, they would not be considered as being of the
 same family as the above mentioned softeners oils and would be in a family
 of their own, namely emulsifiers.
 Optional fillers used in gum base modify the texture of the gum base and
 aid in processing. Fillers suitable for use in the gum base and gum of the
 present invention include carbonate or precipitated carbonated types such
 as 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 ethyl, methyl and wood or mixtures thereof.
 The fillers can also be organic powders such as polystyrene, polyethylene,
 oat fiber, wood fiber, apple fiber, zein, gluten, gliadin, casein, etc.
 For the present invention, natural organic fillers such as zein, oat
 fiber, gluten, casein, and cellulose are preferred since they will aid in
 faster biodegradation.
 Particle size has an effect on cohesiveness, density and processing
 characteristics of the gum base and its compounding. The smaller the
 particle size, the more dense and cohesive the final gum base. Also, by
 selecting fillers based on their particle size distribution, initial mass
 compounding may be varied, thus allowing alteration of the compounding
 characteristics of the initial mass during gum base processing and
 ultimately the final chew characteristics of gums made from these gum
 bases.
 Talc filler may be used in the gum base and gum of the present invention
 that may come in contact with or employ acid flavors or provide an acidic
 environment needed to prevent degradation of an artificial sweetener by
 reacting with calcium carbonate type fillers. Mean particle size for
 calcium carbonate and talc fillers typically range from about 0.1 micron
 to about 15 microns.
 More preferably, the optional fillers used have a mean particle size range
 from about 0.4 to about 14 microns and are calcium carbonate and talc.
 The starting mass preferably may comprise one or more of filler,
 polyhydroxyalkanoates, and elastomer plasticizer. Preferably, the starting
 mass is comprised of some or all of the polyhydroxyalkanoates elastomer,
 some or all of the filler, and some or all of the elastomer plasticizer.
 The levels of gum base ingredients present in the starting mass may range
 from about 0 percent to about 40 percent elastomer plasticiser, 0-15
 percent vinyl polymer, 0 to 40 percent fillers, and from about 10 percent
 to about 40 percent elastomer, all by weight of the gum base ingredient.
 Flavorants and colorants impart characteristics or remove or mask undesired
 characteristics. Colorants may typically include FD&C type lakes, plant
 extracts, fruit and vegetable extracts and titanium dioxide. Flavorants
 may typically include cocoa powder, heat-modified amino acids and other
 vegetable extracts.
 Preferably, the optional colorants and flavorants are FD&C lakes and cocoa
 powder respectively and are present at levels from about 0 percent to
 about 15 percent by weight.
 Gum bases are typically prepared by adding an amount of the elastomer,
 elastomer plasticizer and filler, and on occasion a vinyl polymer, to a
 heated (50-240.degree. F.) sigma blade mixer with a front to rear speed
 ratio of from about 1.2:1 to about 2:1, the higher ratio typically being
 used for chewing gum base which requires more rigorous compounding of its
 elastomers.
 The initial amounts of ingredients comprising the initial mass may be
 determined by the working capacity of the mixing kettle in order to attain
 a proper consistency and by the degree of compounding desired to break
 down the elastomer and increase chain branching. The higher the level of
 filler at the start or selection of a filler having a certain particle
 size distribution, the higher the degree of compounding and thus more of
 the elastomeric chain cross linking are broken, causing more branching of
 the elastomer thus lower viscosity bases and thus softer final gum base
 and gum made from such a base. The longer the time of compounding, the use
 of lower molecular weight or softening point gum base ingredients, the
 lower the viscosity and firmness of the final gum base.
 Compounding typically begins to be effective once the ingredients have
 massed together. Anywhere from 15 minutes to 90 minutes may be the length
 of compounding time.
 Preferably, the time of compounding is from 20 minutes to about 60 minutes.
 The amount of added elastomer plasticizer depends on the level of
 elastomer and filler present. If too much elastomer plasticizer is added,
 the initial mass becomes over plasticized and not homogenous.
 After the initial ingredients have mass homogeneously and compounded for
 the time desired, the balance of the base ingredients are added in a
 sequential manner until a completely homogenous molten mass is attained.
 Typically, any remainder of elastomer, elastomer plasticizer, vinyl
 polymer and filler, are added within 60 minutes after the initial
 compounding time. The filler and the elastomer plasticizer would typically
 be individually weighed and added in portions during this time. The
 optional waxes and the oils are typically added after the elastomer and
 elastomer plasticizers and during the next 60 minutes. Then the mass is
 allowed to become homogenous before discharge.
 Typical base processing times may vary from about one to about three hours,
 preferably from about 11/2 to 21/2 hours, depending on the formulation.
 The final mass temperature when dumped may be between 70.degree. C. and
 130.degree. C. and preferably between 100.degree. C. and 120.degree. C.
 The completed molten mass is emptied from the mixing kettle into coated or
 lined pans, extruded or cast into any desirable shape and allowed to cool
 and solidify. Those skilled in the art will recognize that many variations
 of the above described procedure may be followed.
 Examples of the process to make the inventive gum base may differ from the
 typical process and are detailed in the pending Examples below. These are
 presented to exemplify embodiments of the present invention and in no way
 are presented to limit the scope of the present invention.
 Gum formulas may comprise from about 10 to about 95 weight percent a gum
 base made in accordance with the present invention in a gum formula
 typically known to those in the art.
 The water-soluble portion of the chewing gum may comprise softeners,
 sweeteners, flavoring agents and combinations thereof. The sweeteners
 often fill the role of bulking agents in the gum. The bulking agents
 generally comprise from about 5 percent to about 90 percent, preferably
 from about 20 percent to about 80 percent.
 Softeners are added to the chewing gum in order to optimize the chewability
 and mouth feel of the gum. Softeners typically constitute from about 0.5
 percent to about 25.0 percent by weight of the chewing gum. Softeners
 contemplated for use in the gum include glycerin, lecithin and
 combinations thereof. Further, aqueous sweetener solutions such as those
 containing sorbitol, hydrogenated starch hydrolysates, corn syrup and
 combinations thereof may be used as softeners and bulking agents in gum.
 Sugar-free formulations are also typical.
 Sugar sweeteners generally include saccharide-containing components
 commonly known in the chewing gum art which comprise, but are not limited
 to, sucrose, dextrose, maltose, dextrin, dried invert sugar, fructose,
 levulose, galactose, corn syrup solids and the like, alone or in any
 combination.
 The sweetener for use in the present invention can also be used in
 combination with sugarless sweeteners. Generally, sugarless sweeteners
 include components with sweetening characteristics but which are devoid of
 the commonly known sugars and comprise, but are not limited to, sugar
 alcohols such as sorbitol, mannitol, xylitol, hydrogenated starch
 hydrolysates, maltitol and the like, alone or in any combination.
 Depending on the particular sweetness release profile and shelf-life
 stability needed, bulk sweeteners of the present invention can also be
 used in combination with coated or uncoated high-intensity sweeteners or
 with high-intensity sweeteners coated with other materials and by other
 techniques.
 High-intensity sweeteners, or artificial sweeteners and peptide sweeteners
 as they may be referred to, typically may include, but are not limited to,
 alitame, thaumatin, aspartame, sucralose, acesulfame, saccharin and
 dihydrochalcones. The range of these sweetener types in gum typically may
 range from about 0.02 to 0.10 weight percent for sweeteners such as
 alitame, thaumatin and dihydrochalcones, and from about 0.1 to about 0.3
 weight percent for sweeteners like aspartame, sucralose, acesulfame and
 saccharin.
 A flavoring agent may be present in the chewing gum in an amount within the
 range from about 0.1 to about 10.0 weight percent and preferably from
 about 0.5 to about 3.0 weight percent of the gum. The flavoring agents may
 comprise 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, clove oil, oil of
 wintergreen, anise and the like. Artificial flavoring components are also
 contemplated for use in gums of the present invention. Those skilled in
 the art will recognize that natural and artificial flavoring agents may be
 combined in any sensory acceptable blend. All such flavors and flavor
 blends are contemplated for use in gums of the present invention.
 Optional ingredients such as colourants, emulsifiers and pharmaceutical
 agents may be added to the chewing gum.
 In general, chewing gum is manufactured by sequentially adding the various
 chewing gum ingredients to a commercially available mixer known in the
 art. After the initial ingredients have been thoroughly mixed, the gum
 mass is discharged from the mixer and shaped into the desired form such as
 by rolling into sheets and cutting into sticks, extruded into chunks or
 casting into pellets.
 Generally, the ingredients are mixed by first melting the gum base and
 adding s it to the running mixer. The base may also be melted in the mixer
 itself. Colourants or emulsifiers may also be added at this time. A
 softener such as glycerin may also be added at this time, along with syrup
 and a portion of the bulking agent/sweetener. Further portions of the
 bulking agent/sweetener may then be added to the mixer. A flavoring agent
 is typically added with the final portion of the bulking agent/sweetener.
 A high-intensity sweetener is preferably added after the final portion of
 bulking agent and flavor have been added.
 The entire mixing procedure typically takes from five to fifteen minutes,
 but longer mixing times may sometimes be required. Those skilled in the
 art will recognize that many variations of the above described procedure
 may be followed.
 By way of example, and not limitation, examples of the present invention
 will now be given:
 EXAMPLE 1
 To a laboratory gum base mixer (Plastograph from Brabender Corp., Rochelle
 Park, N.J.) set at 90.degree. C., 35 grams of polyhydroxyalkanoate (PHA-1)
 was added, then 20 grams of calcium carbonate powder (mean particle=4.5-5.
 0 micron) was slowly added while the mixer compounded the polymer. After
 20 minute mixing, 2.5 grams of fully hydrogenated cotton seed oil and 2
 grams of partially hydrogenated soya oil were added. The gum base was
 homogeneous and smooth.
 The PHA-1 elastomer that was added was a copolymer of 3-hydroxctanote and
 3-hydroxynhexanote (about 91:9 ratio). It possess a Tg of -35.degree. C. A
 Tm of 61.degree. C., and heat of fusion .DELTA.H=15.0 J/g as revealed by
 differential scanning calorimetry (DSC). Gel permation chromatography
 (GPC) showed Mn=75,000 and Mw=127,000 relative to polystyrene standards.
 X-ray crystallinity is less than 25%.
 EXAMPLE 2
 Same as Example 1, but PHA-2 was used in place of PHA-1. PHA-2 is a
 copolymer of units with side chains C.sub.8 and C.sub.10. It was much
 softer than PHA-1. GPC analysis showed Mn=65,000 g/mol and Mw=106,700
 g/mol relative to polystyrene standards. DSC showed Tg=-30.degree. C.,
 Tm=61.degree. C., and .DELTA.H=15.0 J/g.
 EXAMPLE 3
 Same as Example 1, but oat fiber (200 mesh through) was used to replace
 calcium carbonate.
 EXAMPLE 4
 Same as Example 1, but talc was used to replace calcium carbonate.
 EXAMPLE 5
 To a laboratory gum mixer set at 50.degree. C. was added 25 grams of gum
 base Example 1, 77 grams of 6x sugar, 25.5 grams of 45Be corn syrup and
 mix them for 20 minutes. Then 0.6 g 96% glycerol and 0.8 grams of
 peppermint flavor was added. Additional 5 minutes was continued before
 discharging.
 EXAMPLE 6
 To the gum mixer set at 50.degree. C. was added 20.0 grams of PHA-2, 5
 grams of C.sub.a CO.sub.3 powder, 59.4 grams of 6.times. sugar powder, and
 20 grams of 45 Be corn syrup.
 After mixing for 20 minutes, 0.6 grams of peppermint oil were added.
 Additional 5 minutes mixing was extended before discharging the gum.
 It should be understood that various changes and modifications to the
 presently preferred embodiments described herein will be apparent to those
 skilled in the art. Such changes and modifications can be made without
 departing from the spirit and scope of the present invention and without
 diminishing its attendant advantages. It is therefore intended that such
 changes and modifications be covered by the attendant claims.