BIODEGRADABLE POLYMERIC MATERIALS AND ARTICLES FABRICATED THEREFROM

Abstract: A composition comprising one or more polymers and a filler which comprises one or more degradation enhancing materials which enhance the biodegradation of the polymers in association with one or more biodegradable safening materials which inhibit the enhancing activity of the enhancing materials whereby on biodegradation of the safening materials the activity is completely or partially restored.

Description: BIODEGRADABLE POLYMERIC MATERIALS AND ARTICLES FABRICATED THEREFROM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to biodegradable polymeric compositions and to articles fabricated therefrom. More par icularly, this invention relates to such compositions which exhibit improved biodegradability when exposed to environmental effects such as sunlight, heat, water, oxygen, pollutants, microorganisms, insects, animals and mechanical forces such as wind and rain. 2. Prior Art Many discardable packaging items such as bags and containers are destined, after a relatively short functional life to arrive as a significant component of urban garbage. Because of the increased use of plastics in the fabrication of these discardable packing materials, it has been proposed to make throwaway materials from biodegradable plastics to ameliorate waste disposal problems. However, the low cost high volumne packaging materials such as polyethylene, polypropylene, polystyrene and poly(ethylene terephthalate) are not naturally biodegradable. Several methods have been proposed to enhance the biodegradability of such polymeric materials and/or to develop other useful buodegradable polymeric materials. For example, U.S. Patent No. 4,016,111 discloses that compositions of ethylene acrylic acid copolymer and a starchy material are biodegradable. U.S. Patent No. 4,337,181 describes a biodegradable composition containing up to about 60% gelatinized starch and various levels of ethylene acrylic acid copolymer and optionally polyethylene. U.S. Patent No. 4,016,117 describes a biodegradable composition which comprises a synthetic resin, a biodegradable granular filler such as natural starch, and a substance which is autooxidizable to yield a peroxide which attacks the carbon to carbon linkages of the resin. PCT Appln. WO 88/09354 describes a degradable polymer composition which is a blend of a normally stable chemically saturated polymer such as polyethylene, a less stable chemically unsaturated polymer or copolymer such as a styrene/butadiene block copolymer, or natural rubber, an anti-oxidant active over a limited period and a latent pro-oxidant such as an organic salt of a transition metal, e.g. cobalt naphthenate, which may optionally include filler particles of a directly biologically sensitive material such as a natural starch, a derivative of natural starch, a natural protein, a natural cellulose or a sugar. Previous efforts to make non-biodegradable polymers biodegradable by blending them with biodegradable fillers and other additives have not been successful. Existing biodegradable plastics are deficient in properties required in most packaging applications and are more expensive than commonly used packaging plastics. Furthermore, such materials often fail to degrade in a reasonable period of time to the point where they lose their structural integrity and fall apart. This loss in physical properties, embrittlement and disintegration are required in order to lessen the volume of such articles in landfills, or to allow release of the contents of the plastic package (such as in the case of yard waste) or cause the fragmentation and disappearance of litter and so forth. SUMMARY OF THE INVENTION The present invention is directed to biodegradable polymer composition which obviates one or more of the defects of conventional biodegradable resins. The composition of this invention comprises and intimate mixture of: (a) one or more polymers; and (b) an effective amount of one or more particulate fillers which comprise one or more degradation enhancing materials which enhance the biodegradation of the polymers, which materials are associated with one or more biodegradable and degradable safening materials which inhibit the activity of said degradation enhancing materials during said association whereby on biodegradation or degradation of said safening material the activity of said enhancing materials is completely or partially restored. Another aspect of this invention relates to an article of manufacture fabricated totally or in part from the biodegradable composition of this invention. Several beneficial effects are provided by the invention. For example, low concen rations of the particulate filler are required in order to provide an acceptable level of disintegration of the composition within a reasonable period of time. The degradation enhancing material is released when the composition is exposed to environmental (biodegradation) conditions, and is not time dependent. Thus, there is no danger or substantially reduced danger of premature degradation and associated shelf life problems. A wide variety of degradation enhancing materials and safening materials having a wide /ariety of properties can be used, which facilitates the use of the invention with a wide variety of polymers and environmental conditions. Some useful degradation enhancing materials not only cause failure of the polymer due to their own activity, but also promote further biodegradation of the safening material and/or other biodegradable additives that may be in the composition, causing a cascading effect. BRIEF DESCRIPTION OF THE DRAWINGS This invention can be better understood from a consideration of the specification in conjunction with the drawings in which: Figure 1 is a graph indicating the degree to which high density polyethylene is protected by beta- cyclodextrin. Figure 2 is a graph indicating the conductance of the formation and degradation of a beta-cyclodextrin sodium dodecyl sulfate complex. Figure 3 is a graph indicating the conductance of the formation of a beta-cyclodextrin cetyl pyrdinium chloride complex and of a starch/cetyl pyridinium chloride complex. Figure 4 is a graph indicating the conductance of the formation and degradation of a corn starch/sodium dodecyl sulfate complex. DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of this invention comprises two essential ingredient. One essential ingredient is a polymeric resin. The type of polymeric resin used may vary widely. Illustrative of useful resins are aromatic, aliphatic and cycloalipha ic polyamides such as poly(m-xylylene adipa ide) , poly(p-xylylene sebacamide), poly 2,2,2-trimethyl-hexamethylene terephthalamide), poly (piperazine sebacamide), poly (metaphenylene isophthalamide) (Nomex), poly (p-phenylene terephthalamide) (Kevlar); the copolyamide of 30% hexamethylene diammonium isophthalate and 70% hexamethylene diammonium adipate, the copolyamide of up to 30% bis-(-amidocyclo-hexyl)methylene, terephthalic acid and caprolactam, polyhexamethylene adipamide (nylon 66), poly(butyrolactam) (nylon 4), poly (9-aminonoanoic acid) (nylon 9), poly(enantholactam) (nylon 7), poly(capryllactam) (nylon 8), polycaprolactam (nylon 6), poly (p-phenylene terephthalamide), polyhexamethylene sebacamide (nylon 6,10), polyaminoundecana ide (nylon 11), polydodecono-lactam (nylon 12), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polycaproamide, poly(nonamethylene azelamide) (nylon 9,9), poly(decamethylene azelamide) (nylon 10,9), poly(decamethylene sebacamide) (nylon 10,10), poly[bis-(4-aminocyclothexyl) methane 1,10- decanedicarboxamide] (Qiana) (trans), or combination thereof; and aliphatic, cycloaliphatic and aromatic polyesters such as poly( 1,4-cyclohexlidene dimethyl eneterephathalate) cis and trans, poly(ethylene-l, 5-naphthalate) , poly(ethylene-2,6-naphthalate) , poly(l, 4-cyclohexane dimethylene terephthalate) (trans), poly(decamethylene terephthalate), poly(ethylene terephthalate), poly(ethylene isophthalate) , poly(ethylene oxybenozoate) , poly(para-hydroxy benzoate), poly(dimethylpropiolactone) , poly(decamethylene adipate), poly(ethylene succinate), poly(ethylene azelate), poly(decamethylene sebacate) , poly( 6, -dimethyl- propiolactone) , and the like. Also illustrative of useful polymeric resins are polymers copolymers formed by polymerization of α,β -unsaturated monomers of the formula: R. R 2 -C = CH. wherein: R and R are the same or different and are hydrogen,hydroxy, halogen, alkylcarbonyl, carboxy, alkoxycarbonyl, heterocycle or alkyl or aryl either unsubs ituted or substituted with one or more substituents selected from the group consisting of alkoxy, cyano, hydroxy, alkyl and aryl. Illustrative of such polymers of L.B-unsaturated monomers are polymers including polystyrene, polyethylene, plypropylene, poly( 1-octadence) , polyisobutylene, poly(1-pentene) , poly(2-methylstyrene) , poly(4-methylstyrene) , poly(1-hexene) , poly( 1-pentene) , poly(4-methoxystrene), poly(5-methyl-l-hexene) , poly(4-methylpentene) , poly (1-butene), polyvinyl chloride, polybutylene, polyacrylonitrile, ρoly(methyl pentene-1), poly(vinyl alcohol), poly(vinylacetate) , poly(vinyl butyral), poly(vinyl chloride), poly(vinylidene chloride), vinyl chloride-vinyl acetate chloride copolymer, poly(vinylidene fluoride), poly(methyl acrylate, poly(methyl methacrylate), poly(methacrylo-nitrile), poly(acrylamide) , poly( inyl fluoride), poly(vinyl formal), poly(3-methyl- 1-butene), poly(1-pentene), poly(4-methyl-l-butene) , poly(1-pentene) , poly(4-methyl-l-pentence, poly( 1-hexane) , poly(5-methyl-l-hexene) , poly(1-octadence) , poly(vinyl- cyclopentane) , poly(vinylcyclothexane) , poly(a-vinyl- naphthalene) , poly(vinyl methyl ether), poly(vinyl- ethylether), poly(vinyl propylether) , poly(vinyl carbazole), poly(vinyl pyrolidone), poly(2-chlorostyrene) , poly(4-chlorostyrene) , poly(vinyl formate), poly(vinyl butyl ether), poly(vinyl octyl ether), poly(vinyl methyl ketone), poly(methylisopropenyl ketone), poly(4-phenylstyrene) and the like. Preferred resins for use in the composition of this invention are resins which are commonly used in the fabrication of packaging materials such as polyethylene, polyethylene terephthalate, polystyrene, polyurethane, polyvinyl chloride, polypropylene, polycarbonate and blends of such materials. The above list of preferred is merely intended to be representa ive of useful and preferred resins, and other resins which are used as packaging materials may also be used. In the most referred embodiments of this invention, the resins of choice are polyethylene (high density, low density and linear low density), polyethylene terephthalate, polyvinyl chloride, polyurethane and blends of such polymers. The second essential ingredient of the composition of this invention is an effective amount of a particulate filler. The filler is a material which is designed to be inactive during the use of the composition and which enhances the degradation of the polymer on exposure of the composition of this invention to a suitable environment,as for example a garbage dump or landfill. The filler is comprised of a degradation enhancing material which is effective to enhance the degradation of the polymeric material and a biodegradable safening agent which inhibits the act. ? ity of the enhancing material. In operation, the safening material associates with the degradation enhancing agent, thereby completely or partially inhibiting its activity during the association. On exposure of the composition to a suitable environment containing agent(s) effective to biodegrade the biodegradable safening material, the activity of the enhancing material is competely or partially restored, which results in an enhancement of degradation of the polymer. As used herein, "associa ion" is any chemical, physical or like interaction between the biodegradable safening material and the degradation enhancing material which completely or partially inhibits the biodegradation enhancing characteristics of the degradation enhancing material, and which allows a complete or partial restoration of such characteristics on the biodegradation of the biodegradable safening material. The nature of the association between the biodegradable safening material and the degradation enhancing material may vary widely and essentially depends on the properties of these two materials. The only requirement is that this association inhibits the activity of the enhancing material during the association, and that this activity is totally or partially restored on biodegradation of the safening material. Certain representative associations include ionic and covalent bonding as for example in the case of the ionic bonding of a metal with cellulose as in sodium cellulose, the ionic bonding of metal salts and ionic species such as metal salts of fatty acids as for example sodium stearate and various covalent fatty acid derivatives such as fatty acid derivatives of proteins or carbohydrates. Other forms of association include non covalent associations such as intercalation, inclusion complexation, chelation and non-specific adsorption as for example the inclusion of a hydrophobic surfactant or stress cracking agent within the cavity of a cyclodextrin molecule. Still other forms of association includes incapsulation where the enhancing material is physically encapsulated and surrounded by the safening material. Suitable safening agents may vary widely. Any material which is degradable and which is capable of inhibiting the biodegradation enhancing activity of the enhancing material can be used. As used herein, a material is "degradable" where it degrades as a result of exposure to the environmental effects of sunlight, heat, water, oxygen, pollutants, microorganisms, insects and/or animals. Usually such materials are naturally occurring and are usually "biodegradable". As used herein, "biodegradable" materials are those which are degraded by microorganisms or by enzymes and the like produced by such microorganisms. Illustrative of suitable safening materials are starches and starch derivatives such as rice and maize starch, dextrin, cyclodextrin, a ylose, amylopec in, defatted or solvent extracted starch, and the like. Other useful safening materials include sugars and derivatives thereof, such as sucrose, dextrose, maltose, mannose, galactose, lactose, fructose, glucose, glyamic acid, gluconic acid, maltobionic acid, lactobionic acid, lactosazone, glucosazone, and the like. Still other useful safening materials are cellulose and derivatives thereof such as esters of cellulose as for example, triacetate cellulose, acetate cellulose, acetate- butyrate cellulose, nitrate cellulose and sulfate cellulose, ethers of cellulose as for example, ethyl ether cellulose, hydroxymethyl ether cellulose, hydroxypropyl ether cellulose, carboxymethyl ether cellulose, ethylhydroxy ether cellulose, and cyanoethylether ether cellulose, ether-esters of cellulose as for example, acetoxyethyl ether cellulose, propionoxypropyl cellulose, and benzoyloxypropyl cellulose and urethane cellulose as for example, phenyl urethane cellulose. Other useful safening agents include proteins such as zein, soy protein or protein hydrolysates, casein, collagen, elastin, albumins and the like and lignins. Useful biodegradable safening materials also include fats and fatty acids such as mono-, di- and tri-glycerides derived from animal or plant material and the common derivatives of these fats such as fats obtained from peanut oil, corn oil, coconut oil, cottonseed oil, palm oil and tallow, and fatty acids such as oleic acid, stearic acid, lauric acid, myristic acid and palmitic acid; biodegradable anti-oxidants such as tocophenols, rosemary (rosemari-quinone) and mustard seed extracts, ascorbic acid and compounds closely related to vitamin C such as ascorbic acid-2-phosphates and ascorbic acid-6-fatty acid esters propionic acid; and biodegradable polymers such as poly(glycolide) , poly(tetramethylene carbonate), poly(lactide) , ρoly(glycolide-co-lactide) , poly(caprolactone) , poly(tartaric acid), poly(ethylene-co-ketone acetal), ρoly(hexamethylene azelate), poly(decamethylene succinate), poly(decamethylene azelate), poly(ethylene succinate), poly(hexamethylene sebacate), poly(ethylene azelate), poly(3-methoxy-4-hydroxy styrene), poly(amino triazole), poly(hydroxy butyrate), poly(hydroxyvalerate) , poly(hydroxy butiyrate-co-hydroxy valerate), poly(dihydropyran) , ρoly(spiro ortho carbonate) and poly(1-phenylalanine/ethylene glycol/l,6-diisocyanato hexane) . Preferred biodegradable safening materials are starch and starch derivatives such as cyclodextrins, fats, fatty acids and biodegradable polymers such as poly(carbonates) , and homopolymers and copolymers derived from the polymerization of hydroxy alkanoic acids and their derivatives such as poly(B -hydroxy butyrate), poly(lactide) , polyglycolic acid and copolymers thereof, and particularly preferred biodegradable safening materials are starches and starch derivatives and biodegradable polymers derived from the polymerization of hydroxyalkanoic acids and their derivatives. Most preferred biodegradable safening agents are cyclodextrins, poly(beta-hydroxybutyrate) , poly(lactides) , poly(glycolide) and block copolymers containing g -hydroxybutyrate glycolide and/or lactide recurring monomeric units. Useful degradation enhancing materials include any material which in an unassociated form is capable of directly or indirectly enhancing the degradation of a polymeric material to some extent and which is capable of association with a biodegradable safening material which inhibits the activity of the enhancing material, such activity being restored on biodegradation of the biodegradable safening material. Useful enhancing materials may vary widely. Illustrative of useful materials are stress cracking agents as for example, surfactants. Useful surfactants include, anionic, cationic, zwitterionic and nonionic surfactants. Useful anionic surfactants include alkali metal, ammonium and amine soaps and alkali metal salts of alkyl-aryl sulfonic acids, sodium dialkyl sulfosuccinate, sulfated or sulfonated oils such as glycocholic acid sodium salt, glycodeoxycholic acid sodium salt, sodium dioxychalate, cholic acid sodium salt, 1-deconesulfonic acid sodium salt, caprylic acid sodium salt, sodium dodecyl sulfate, taurocholic acid sodium salt, taurodeoxycholic acid sodium salt, sodium decyl sulfate, sodium octyl sulfate, sodium hexyl carboxylate, sodium heptyl carboxylate, sodium octyl carboxylate, sodium nonyl carboxylate, sodium decyl carboxylate and sodium dodecyl carboxylate, disodium dodcyl phosphate, disodium 4-alkyl 3-sulfonatosuccinates and sodium dodecyl benzenesulfonate. Useful cationic surfactants include salts of long chain primary, secondary and tertiary amines such as oleylamine acetate, cetylamine acetate, didodecylamine lactate, the acetate of aminoethyl-amino ethyl stearamide, dilauroyl triethylene tetramine diacetate, and l-aminoethyl-2-heptadecenyl imidazoline acetate; quaternary salts such as cetylpyridinium bromide, hexodecyl ethyl morpholinium chloride, didodecyl ammonium chloride, cetylpyridinium chloride, dodecyltrimethyl- ammonium bromide, hexadecyl trimethylammonium bromide, te radecyl tri ethylammonium bromide, dodecyl ammonium chloride, cetyl tri ethyl ammonium bromide, benzalkonium chloride, decomethonium bromide, methylbenzethonium chloride, 4-picoline dodecyl sulfate, sodium perfluorooctanoate, sodium hexyl sulfosuccinate, sodium octyl sulfosuccinate, sodium cyclohexyl acetate, sodium cyclohexyl propionate, sodium cyclohexyl butanoate and sodium cyclohexyl sulfamate. Useful zwitterionic surfactants include N-alkyl-N,N- dimethyl-3-ammonio-l-propane sulfonates such as N-decyl- N,N-dimethyl-3-ammonio-l-propane, N-dodecyl-N,N-dimethyl-3- ammonio-l-propane, N-hexadecyl-N,N-dimethyl-3-ammonio-l- propane, N-octyl-N,N-dimethyl-3-ammonio-l-propane, and N-dodecyl-N,N-dimethyl-3-ammonio-l-propane, D,L-alpha- phosphatidyl choline and dipalma ioyl. Useful nonionic surfactants include n-alkyl-D- glucopyranosides and n-alkyl-D-maltosides such as decyl-D-glucopyranoside, dodecyl-D-glucopyranoside, heptyl-D-glucopyranoside, octyl-D-glucopyranoside, nonyl-D-glucopyranoside, decyl-D-maltoside, dodecyl-D- maltoside, heptyl-D-maltoside, octyl-D-maltoside, and nonyl-D-maltoside, condensation products of higher fatty alcohols with alkylene oxides, such as the reaction product of oleyl alcohol with 10 ethylene oxide units; condenstation products of alkylphenols with alkylene oxides, such as the reaction products of isooctylphenol, octylphenol and nonylphenol with from abut 12 to about 30 ethylene oxide units; condensation products of higher fatty acid amides with 5 or more alkylene oxide units such as ethylene oxide units; polyethyl glycol esters of long chain fatty acids, such as tetraethylene glycol monopalmitate, hexaethyleneglycol monolaurate, nonaethyleneglycol dioleate, tridecaethyleneglycol monoarachidate, triosaethylene glycol monobehenate, tricosaethyleneglycoldibehanate, polyhydric alcohol partial higher fatty acid esters such as sorbitan trisearate, ethylene oxide condensation products of polyhydric alcohol parital higher fatty esters, and their inner anhydrides (mannitol-anhydride, called Mannitan, and sorbitol-anhydride, called Sorbitan), such as glycerol monopalmitate reacted with 10 molecules ofethylene oxide, pentaerythritol monooleate reacted with 12 molecules of ethylene oxide, sorbitan monostearate reacted with 10 to 15 molecules of ethylene oxide; long chain polyglycols in which one hydroxyl group is esterified with a higher fatty acid and the other hdroxy group is etherified with a low molecular alcohol, such as methoxypolyethylene glycol 550 monostearate (550 meaning the average molecular weight of the polyglycol ether). A combination of two or more of these surfactants may be used. For example, a cationic surfactant may be blended with a nonionic surfactant, or an anionic surfactant with a nonionic surfactant. Other useful degradation enhancing material include olefins especially mono, di and tri unsaturated fatty acids, triglycerides and derivatives such as lipoproteins and lipopolysacharides; agents capable of a change in physical properties upon exposure to environmental conditions such as moisture, for example, bentonite clay; oxidizing agents such as halogens and heterosubs ituted anions, especially tri iodide (I ); strong acids, strong bases and certain salts such as trifluoroacitic acid, dichloroacetic acid, hydrochloric acid, lithium bromide, zinc cloride, sodium cyanide, phosphoric acid, nitric acid, sulfuric acid, sodium hydroxide, lithium hydroxide, and sodium alkoxide; and transition metal salts (cobalt, copper, nickel, zinc, manganese, cadmium, iron) alone or in combination with organic compounds such as fatty acids (e.g. stearate or naphthenate, and the like) as salt complexes. Still other useful degradation enhancing materials include solvents and other materials which enhance the degradation of specific polymers as for example n-hexane/n heptane (1:1), isobutyl acetate, 5-methyl-2-hexanone, 2-pentanone, 3-pentanone, toluene, cyclohexane, and tetrahydrofuran which are detrimental to ρoly(butadienes) ; xylene, p-xylene, tetralin, decalin, tetrachloroethylene, n-butyl acetate, diphenyl ether, butyl sterate, squalene, glycol dipalmitate, tripalmitin which are detrimental to polyethylene, poly(propylene) and poly(tetrafluoro- ethylene); N,N-dimethylformamide, N,N-dimethylacetamide, Y-butyrolactone, nitric acid, hydroxyacetonitrile, dimethylformamide, ethylene carbonate, propylene carbonate, malonitrile, succinonitrile, sulfuric acid, which are detrimental to polyacrylonitrile; cyclohexanone, cyclopentanone, and tetrahydrofuran which are detrimental to poly(vinyl chloride); acetonitrile, heptanone-4, isoamyl acetate, n-butyl chloride, heptanone-3, n-propanol, acetone, benzene, n-butyl acetate, n-butyl chloride, and chloroform which are detrimental to poly(methylmethacrylate) ; benzene, toluene, butanone, and cyclohexanone which are detrimental to poly(styrene) ; phenol, o-chlorophenol, aniline, cyclopentanone, ethylene carbonate, cyclohexanone, benzyl alcohol, acetic anhydride, and dimethyl formamide which are detrimental to poly(oxymethylene) ; o-chlorophenol, phenol, trifluoroacetic acid, and dichloroacetic acid which are detrimental to poly(ethylene terephthalate, nylon 6 and nylon 66 and mineral acids such as HC1, HBr, H SO , and H PO,, trifluoroacetic acid, inorganic salts such as Ca(SCN) 2 , LiSCN, NaSCN, Lil, Nal, KI, and K 2 [HgI.]), strong bases such as LiOH, and NaOH, tetraalkyl bases, metal complex solutions such as ( [Cu(NH 3 ) (OH)-, dimethyl sulfoxide, and dimethylformamide which are detrimental to cellulosic materials. Preferred degradation enhancing materials are stress cracking agents which are materials which cause the polymer composition to crack, and particularly preferred degradation enhancing materials are surfactants. More preferred surfactants are capable of not only degrading the plastic but also exhibit a beneficial effect by enhancing the biodegradation of any biodegradable component incorporated into the plastic. Most preferred for use in the practice of this invention as degradation enhancing materials are nonionic surfactants, or mixtures of nonionic surfactants and other types of surfactants. Particularly preferred for use in the practice of this invention are nonionic surfactants such surfactants are capable of not only degrading the polymers but also exhibit a beneficial effect by enhancing the biodegradation of any biodegradable component in the polymer. Preferred nonionic surfactants for use in the practice of this invention are alkylarylpolyethers, such as the condensation products of alkylphenols, such as octylphenol, nonylphenol and isooctyphenol, and alkylene oxides, such as ethylene oxide; fatty acid alkanol amides; poly-alkoxylated alcohols, such as polyethoxylated tridecanol, idotridecyl alcohol adduct with ethylene oxide; and fatty alcohol polyethers. The particularly biodegradation safening materials and degradation enhancing material selected in any particular situation will depend on a number of factors including the capability of the biodegradation safening material for inhibiting the activity of the degradation enhancing material, the level and nature of the activity of the degradation enhancing material, the polymeric material stability of the complex, especially as it pertains to processing conditions for the polymeric mateial and the effect that the degradation enhancing material has upon the biodegradation of incorporated components of the polymer, the proposed use of the composition and article fabricated therefrom, the cost of the composition and article fabricated therefrom, the usable lifetime of the composition and article fabricated therefrom, the time after exposure to biodegradation (environental) conditions which degradation is desired to take place. For example, when the degradation enhancing material is a surfactant, the biodegradation safening material is preferably a carbohydrate such as starch or a starch derivative including a ylose, linear polysaccharides and cyclic polysaccarides such as cyclodextrins which function to form an inclusion complex and encapsulate the surfactant and protect the polymeric material from the deteriorating effects of the surfactant. Biodegradation of the carbohydrate releases the surfactnat which can enhance the degradation of the polymeric material. Similarly when the biodegradation enhancing material is potassium triiodide, the biodegradable safening material is preferably a polysaccharide such as a starch which is capable of complexing the salt which functions to prevent or retard the formation of the halogen, I_ which adversely affects the polymeric material. Here again, on biodegradation of the starch, the I is released to enhance the degradation of the polymeric material. The composition of the invention includes an "effective amount" of the particulate filler. As used herein, an "effective amount" is an amount which when activated is sufficient to enhance the biodegradation of the polymeric material to any extent. This amount may vary widely and depends on a number of factors such as the amount and activity of the degradation enhancing material in the filler and the like. In general, the amount of filler employed is at least about 0.001 weight percent based on the total weight of the composition. In the preferred embodiments of the invention, the amount of the filler is from about 0.05 to about 40 weight percent based on the total weight of the composition, and in the particularly preferred embodiments of the invention is from about 0.01 to about 20 weight percent on the aforementioned basis. Amongst these particularly preferred embodiments, most preferred are those embodiments in which the amount of the filler is from about 1 to about 10 weight percent based on the total weight of the composition. The filler is in particulate form to allow dispersion of the filler in the polymeric material. In the preferred embodiments of the invention, the particle size is equal to or less than about 1000 υm. The lower limit in particle size is not critical, and in the preferred embodiments of the invention, the size of the particles is as small as possible which facilitates the dispersion of the filler in the polymeric material. In the more preferred embodiments of the invention, the particle size is from about 0.1 to about 500 um, and in the most preferred embodiments of the invention, particle size is from about 1 to about 300 μm. Amongst the most preferred embodiments of the invention, those in which the particle size is from about 2 to about 200 ym are the embodiments of choice. In addition to the above-described essential components, the composition of this invention can include various optional components which are additives commonly employed with polymers. Optional components include fillers, nucleating agents, plasticizers, impact modifiers, chain extenders, pigments, colorants, mold release agents, antioxidants, ultra violet light stabilizers, lubricants, antistatic agents, fire retardants, and the like. These optional components are well known to those of skill in the art, and accordingly, will not be described herein in detail. The composition may further comprise .additional particulate biodegradable fillers which further enhance the rate of biodegradation of the composition. Illustrative of useful and preferred fillers are those materials described as useful for biodegradable safening materials. Preferred fillers are starches. The amount of biodegradable filler may vary widely and amounts normally used in the art may be used. However, in the preferred embodimets of the invention, the amount of such biodegradable filler is not more than about 30 weight percent based on the total weight of the composition and more preferably not more than about 20 weight percent and most preferably not more than about 10 weight percent. The composition of this invention can be prepared by blending or mixing the essential ingredients, and other optional components, as uniformly as possible employing any conventional blending means. Appropriate blending means, such as melt extrusion, batch melting and the like, are well known in the art and will not be described herein in greater detail. In one useful procedure, the blending procedure can be carried out at elevated temperatures above the melting point of the polymer and the nucleating agent either preformed, or as individual components of the agent separately or as a combination of the components in a suitable form as for example, granules, pellets and preferably powders is added to the melt with vigorous stirring. Alternatively, all or a portion of the var . us components of the filler can be masterbatched or preblended with the polymer in the melt and this premixed or masterbatch added to the polymer in the melt in amounts sufficient to provide the desired amount of the filler in the polymer product. Stirring is continued until a homogeneous composition is formed. Blending temperatures and blending pressures, and the order of addition of the various components are not critical and may be varied as desired provided that a substantially homogeneous composition results. The blending procedure can be carried out at elevated temperatures, in which case the polymer component is melted and the filler and other optional ingredients are admixed therewith by vigorously stirring the melt. Similarly, the various solid components can be granulated, and the granulated components mixed dry in a suitable blender, or for example, a Banbury mixer, as uniformly as possible, then melted in an extruder and extruded with cooling. The compositions according to the invention are thermoplastic biodegradable materials from which molded articles of manufacture can be produced by te conventional shaping processes, such as melt spinning, casting, injection molding and extruding. The compositions of this invention are especially useful for fabrication of extruded films, as for example, films for use in food packaging. Such films can be fabricated using conventional fil extrusion techniques. Such films formed from the composition of this inven ion are biodegradable such as being buried or composted with other garbage, the film degraded by evironmental effects such as sunlight, heat, water, oxygen, pollutants, microorganisms, and the like. The following examples are presented to more fully illustrate the invention and are not to be construed as limitations thereon. EXAMPLE I A) Preparation of the β-Cyclodextrin (CD) Complex With Igepal. The molecular complex of CD with Igepal was prepared by combining the individual soluble components and recovrerng the precipitated complex. In 100 ml of water 15 grams of CD was dissolved by heating. A 5 ml solution of 32% Igepal (Igepal CO630), a non-ionic surfactant obtained from GAF Corporation was warmed to reduce its viscosity and then added dropwise into the hot CD solution over a period of about 15 minutes with constant stirring. The solution was next alowed to cool slowly to room temperature and then maintained at 4 C for approximately 15 hours. The resultant precipitated complex was recovered by filtration and then air dried. To estimate the ratio of CD to Igepal in the complex a known weight of complex was subjected to extensive acid hydrolysis so as to fully degrade the cyclodextrin to its component glucose units, which could then be measured using a glucose analyzer (Beck an Instruments) . The amount of cyclodextrin in the complex can thus be determined (7 glucose molecules per 1 β-cyclodextrin molecule) with the remainder of the weight of the complex due to the Igepal. In one example, 150 mg of the complex was hydrolyzed by refluxing for 1.5 hours at 100°C in 100 ml of 1 M HC1. The glucose produced was measured and accounted for 115.3 mg of the sample wtih 38 mg representing the contribution of the Igepal. Using the molecular weights of the cyclodextrin and Igepal the ratio of cyclodextrin to Igepal in the complex was determined to be approximately 1.6 to 1. B) Testing of the Complex. To test the ability of the complex to function as a biologically released destructive agent a method was developed to measure the destructive effect of the release of the stress cracking agent, Igepal. The assay method developed for this purpose uses small pieces of polyethylene which are stressed by gentle bending in the middle of a 1 cm by 3 cm sample. The ends of the pieces are held together to maintain the gentle stress and thus provide a point of failure for the plastic and reduce the time for the assay and the samples are immersed in the test solution. Normal crazing and stress cracking will occur without the introducton of an external stress, but in a longer time fram. This assay method was first used to determine the appropriate concentration of Igepal to be used for for stress cracking. The results are set forth in Figure 1. As shown in Figure 1, a concentration of greater than 0.05 mM was found to completely, or nearly completely, break the plastic samples in the stress cracking assay within 24 hours at 60 β C. The protective effect of the cyclodextrin encapsulant was demonstrated in a similar experiment in which cyclodextrin was added to the aforementioned testing mixture (0.05 mM Igepal). The Igepal no longer broke the plastic samples and stress cracking was either low or not measurable. To demonstrate the biodegradability of such a complex and the results of the release of the Igepal, the same test was run, except that the enzyme alpha amylase which is known to degrade cyclodextrins was added to the mixture. The result of this experiment is also depicted in Figure 1 and shows that a normal microbial enzyme is capable of releasing the a detrimental agent (Igepal) from the complex (with CD) and that the free agent can destroy the plastic. C) Incorporation of the complex into high density polyethylene (HDPE). β-Cyclodextrin and the complex of CD with Igepal were incorporated into HDPE to produce a plastic product of ten mil thickness containing the appropriate additives at a level of 10% by weight. The physical properties of the final products (and a control plastic containing no additive) are shown in the following Table 1. TA3LE 1 Tensile Strength Sample Wt% @ yield @ break ID filler psi psi (1) Control 0 4020 1741 (2) Igepal Complex in beta-Cyclodextrin 10 3803 1636 (3) beta-Cyclodextrin 10 3703 3309 TABLE 1 (cont'd) Elongation Tensile @ yield @ break Impact % % ft-lb/in 84.6 37.9 21.2 To determine if the complex in the plastic was susceptible to biodegradation, the samples were placed in an enzyme solution containing alpha amylase and glucoamylase which make possible the degradation of the cyclodextrin and its conversion to glucose. Glucose is readily measured using an instrument such as a glucose analyzer (Bechman Instruments) . The results of this experiment are shown in the following Table 2. TABLE 2 % degradation of cyclodextrin control: Time (h) HDPE + complex HDPE + cyclodextrin no enzyme only 0 0 .92 0 .94 0 2.3 0 The production of glucose during the time period of the test shows that the cyclodextrin within the plastic can be degraded by microbial enzymes. As shown in the tests described above, the degradation of the cyclodextrin portion of the cyclodextrin/Igepal complex will liberate the Igepal. The Igepal will in turn cause stress cracking of the plastic. With the samples chosen for the testing of the incorporation of the complex into the plastic (10% loading) it was not possible to show the result of stress cracking in our standard test within a short period of time. In part, this is due to the difference in the low temperatures used to accelerate and test the stress cracking. Furthermore, in order to demonstrate cyclodextrin degradation (glucose production) the 10% loading was appropriate, however, this relatively high level of complex addition caused a sufficient change in the physical properties so as to affect the response of the plastic to stress cracking failure. EXAMPLE II Complexation and Degradation of a β -Cyclodextrin With Sodium Dodecyl Sulfate (SDS) and of β -Cyclodextrin and Corn Starch With Cetyl Pyridinium Chloride (CPC). Using the procedure of Example I, the complexation of cyclodextrin with destructive agents other than Igepal was demonstrated using positively and negatively charged surfactants. In both cases the formation and degradation of the complex were monitored by changes in the conductance of the solution. As the low molecular weight, charged surfactant was immobilized by the formation of a complex with cyclodextrin and conductivity decreased. Upon addition of an appropriate enzyme to degrade the cyclodextrin, the conductivity again rose indicating the release of the destructive agent in solution. An example of this effect is shown in Figures 2 and 3 in which the formation and degradation (by the addition of the enzyme alpha-amylase) of a beta-cyclodextrin complex with SDS and and the formation of a beta-cyclodextrin complex and a corn starch complex with CPS are measured by conductivity changes. EXAMPLE III Starch Complexes with Sodium Dodecyl Sulfate. Using the procedure of Example I, the complexation and degradation of corn starch (Pearl Starch) was demonstrated with sodium dodecyl sulfate. As shown by monitoring conductivity changes (Figure 4) starch can complex a stress-cracking surfactant (SDS), and release it upon enzymatic degradation. Since starch has been widely used as an additive to plastics, it follows that the starch/surfactant complex could be added then the surfactant released upon exposure to conditions which promote biodegradation.

Claims: WHAT IS CLAIMED IS: 1. A biodegradable composition comprising a mixture of: a) one or more polymers; and 5 b) an effective amount of one or more particulate fillers which comprise one or more degradation enhancing materials which enhances the biodegradation of said polymers associated with one or more biodegradable safening materials which inhibit the 0 activity of said degradation enhancing materials during said association, and on biodegradation of said safening materials the activity of said enhancing materials is restored. 2. A composition according to claim 1 wherein 5 said polymers are selected from the group consisting of polyethylene, polyethylene terephthalate, polystyrene, polyurethane, polyvinyl chloride, polypropylene and polycarbonate. 3. A composition according to claim 1 wherein 0 said biodegradable safening materials are selected from the group consisting of starch and starch derivatives, fats, fatty acids, biodegradable polymers and combinations thereof. 4. A composition according to claim 3 wherein 5 said biodegradable safening materials are selected from the group consisting of starches and starch derivatives, polymers derived from the polymerization of hydroxy alkanoic acids and mixtures thereof. 5. A composition according to claim 4 wherein 3 Q said safening materials are selected from the group consisting of cyclodextrins, poly(beta-hydroxy butyrate), poly(hydroxy valerate) , poly(lactides) , ρoly(glycolide) , block copolymers containing beta-hydroxy butyrate, glycolide and/or lactide -.c recurring monomeric units and mixtures thereof. 6. A composition according to claim 1 wherein said degradation enhancing materials are selected from the group consisting of stress cracking agents. 7. A composition according to claim 6 wherein said degradation enhancing materials are selected from the group consisting of surfactants. 8. A composition according to claim 7 wherein at least one or said surfactants is a non-ionic surfactant. 9. A composition according to claim 1 wherein the amount of the particulate filler is at least about 0.001 weight percent based on the total weight of the composition. 10. A composition according to claim 1 wherein the particle size of the filler is equal to or less than about 100 μm.

Inventors: ALLENZA PAUL, OLTMANN HAROLD D, ROHRBACH RONALD P, SCHOLLMEYER JULIE, ALLENZA, PAUL, OLTMANN, HAROLD, D., ROHRBACH, RONALD, P., SCHOLLMEYER, JULIE
Applicants: ALLIED SIGNAL INC, ALLIED-SIGNAL INC.
Application year: 1990
Main classification: C08L23
IPC codes: A62D3, C08B37, C08K5, C08L1, C08L23, C08L25, C08L27, C08L69, C08L75, C08L101