WO2021091371A1 - Enhanced biodegradable nitrile rubber glove - Google Patents

Abstract

An enhanced biodegradable multilayer nitril rubber glove is disclosed, wherein the glove inner layer comprises a larger amount, more preferably a significant larger amount, of a biodegradable agent than an amount of a biodegradable agent present in the glove outer layer. After glove use such as in a hospital, disposal of the disclosed biodegradable glove is in particular intended, after shredding, for a fast thermophilic anaerobic digestion process.

Description

Enhanced biodeqradafofe nitrile rubber clove

Technicai field and background:

[001] The present disclosure relates to enhanced biodegradable gloves and methods for the manufacture thereof. In the recent years, users more and more demand disposable products, such as hospitai gloves, to be in a certain extent biodegradable, in order to reduce the problems the disposable waste creates for the environment. Biodegradable gloves are known in the prior art, such as disclosed in US2014/0065311 , the contents of which disclosure are for ease of reading fully incorporated here within, [002] The definitions and all technical and scientific terms in the fo!Sowing description are identical as to those defined in US2014/0065311 (D1 = for example known as Showa Best Gloves with Eco Best Technology), this applies to terms such as for example "biodegradable”, "ranges", "polymer", "glove former” etc. etc..

[003] However, to a certain extent, the in US2014/0065311 (D1 ) disclosed gloves are intended for dumping on ordinary landfills, and do not match the requirements as nowadays posed by European end-users such as hospitals, since most hospital waste is not ending in a landfill but finally fed into waste incinerators. As the cost for waste incineration is growing fast, up to and above 2000 Euro per ton of waste, a need has arisen for enhanced biodegradable hospital products, in particular for enhanced biodegradable gloves.

[004] Recently, in some hospitals the waste including solids and liquids is centrally collected and shredded in a so called Pharmafiiter shredder, the iiquids/solids are than separated, followed by a water treatment for the liquids and for the solids followed by an anaerobic high temperature treatment (at around 60 degrees Celcius ) for a few months, after which the solids, significantly reduced in mass, are incinerated.

[005] Another disposable glove design is disclosed in US2010/0257657 (D2 = SmartHealth), wherein polylactic acid biodegradable gloves are the subject of disclosure. This document, in disclosing only PLA based gloves, is dearly leading away from the use of nitril rubber as a base material for the gloves. However it might be of some interest for the skilled person because of the disclosed multi layered approach (see tig. 3 in US2010/0257657, and fig. 7 for the production method), and because of the notion that document in paragraph 29 that each layer of the poiyiactic acid (PLA) glove is being designed to comply with specific requirements for a given end-use application. [006] Yet another biodegradable multi layer based glove is disclosed in

US2013/0067635 (D3 = inteplast Group), for ethylene based gloves only. Again this disclosure is leading away from the commonly known nitril (butyl) rubber based gloves, but this publication is still of interest for the shown multi layer approach in general. The PLA (as in D2 = US2010/0257657) and ethylene (as in D3 = US2Q13/0067635) based gloves are deemed inferior to nitril rubber gloves, in particular in medical environments. For those reasons a skilled person is unlikely to consider the contents of these publications when trying to further improve the biodegradability of nitril rubber based gloves.

[007] The term nitrile rubber in this application also includes so called soft nitrile rubber formulations, such as disclosed in EP0925329 (D4 = North Safety Products), wherein it is explained in more detail how crosslinking increases the strength and elasticity of the rubber.

[008] Carboxylated nitrile rubbers can be chemically crosslinked in at least two ways: the butadiene subunits can be covalently crosslinked with sulfur/accelerator systems; and the carboxylated (organic acid) sites can be ionically crosslinked with metal oxides or salts. Sulfur crosslinks often result in large improvements in oil and chemical resistance. Ionic crosslinks, resulting from, for example, the addition of zinc oxide to the rubber, result in a rubber having high tensile strength, puncture resistance, and abrasion resistance, as well as high elastic modulus (a measure of the force required to stretch a film of the rubber), but poor oil and chemical resistance.

[009] Many currently available rubber formulations generally employ a combination of the two curing mechanisms. For example, in combination with sulfur and accelerators, carboxylated nitrile rubber manufacturers frequently recommend addition of 1 -10 parts of zinc oxide per 100 parts of rubber (as is also disclosed in par. 129 and 130 in US2014/0065311 (= D1) . [0010] When zinc oxide is not employed, the curing time required to reach an optimum state ot cure can be much longer and the curing may be less efficient. This means that the crosslinks are longer (more sulfur atoms per crosslink) and there may be a higher amount of sulfur that does not crosslink po!ymer chains. The result can be a less- effectively cured rubber that has lowered heat resistance and less chemical resistance. [0011] However, ionic crosslinking often increases the stiffness of an article made from the rubber. This is a disadvantage for applications in which a softer rubber is needed.

For example, surgical gloves made of soft rubbers can provide greater tactile sensitivity for the wearer, which is desirable to improve the surgeon’s "fee!" during operations and to prevent fatigue of the hands.

[0012] A more comfortable nitrite glove that is easier to stretch, i.e. has lower elastic modulus, can be made using a polymer which contains less acrylonitrile or by crosslinking the polymer to a iesser degree. These changes, however, often compromise strength, chemical resistance, or both, resulting in articies that are unsuitable for many applications. Accordingly, a soft rubber having strength and chemical resistance similar to stiffer rubbers is highly desirable.

[0013] US-A-2, 868,754 discloses the formation and use of carboxyl-containing elastomers. The problems associated within the use of zinc oxide curing agents are overcome in this document by using alkali metal aluminates. Another method includes the steps of combining a nitriie latex base with a stabilizing agent, such as ammonium caseinate, and adjusting the pH of the nitrile latex to about 8.5 - 10.0 to yield a basic nitrile rubber. The basic nitriie rubber is contacted with a substantially metallic-oxide-free sulphur crosslinking agent and with at least one accelerator, to form a nitriie rubber composition. That composition is substantially free of metallic oxide. [0014] Another known biodegradable nitrii rubber giove is known under the brand name

Powerform S6 Ecotek. These gloves use a single layered glove design made of nitrii rubber mixed with a naturally occurring microorganism, which makes them suitable for industrial app!ications.

[0015] One the latest relevant disclosures on biodegradable elastomeric compositions, including nitrii rubber, is given in WO2019/074354. The therein stated disclosure for elastomers in general does form some relevant prior art but also indicates the rather large step the present inventors had to take in order to arrive at the nitril rubber gioves forming the subject matter as disclosed in the present ciaims.

[0016] The objective of this invention is to prepare nitril rubber based gloves, such as for exampie disciosed in US2014/0065311 (= D1), in particular also including the soft nitril rubber gloves such as those disclosed in EP0925329 D4), with a strongly enhanced biodegradable functionality, complying to ail up to date generally known norms and standards, such as the norms and standards listed in US2014/0065311 , for hospital or medical examination gloves such as for strength and chemical resistance, but as well as for the latest biodegradation norms and standards. [0017] It is to be understood, that the foregoing general and following detailed description are exemplary and explanatory only and are in no way not restrictive to the invention, as defined in the claims.

Description: [0018] After own extensive testing of the biodegradable gloves produced following the US2014/0065311 disclosure, it appeared most functionalities could be met within norms and standards, however in particular not for the aspect that these gioves shall degrade much faster as is required by modern hospital use. A normal solution would be, to add a bit more biodegrading agent, however was shown only possible to a very limited extent for strength and other required functional requirements.

[0019] While on a norma! landfill the outside of the glove remains outside forever, the difference with the recent practice in especially designed hospital waste treatment systems (based on for exampie EP2859952 and EP3015750 Pharmafilter B.V.) can be used to a common advantage to create an improved biodegradability of the nitril rubber glove. This insight is key to the present invention.

[0020] Because in modern hospital waste disposal systems a shredder will shred the complete glove in pieces, with these pieces sized in the cm range (so pieces with dimensions of around 0.5 to 5 cm large), an inside and outside of the glove will not exist anymore once anaerobic digestion (storage) at around 60 degrees Celsius begins to activate the biodegradable agent and the NBR nitri! rubber starts to degrade, under emission of gasses sucked away (which might be used as biogas for heating purposes). [0021] By adding relatively much more biodegrading agent into a glove inner layer, where initially it does not have too much a detrimental effects on the glove functional requirements, and keeping the outer layer filled with less biodegrading agent as an additive, overall glove biodegradation is significantly enhanced under modern hospital waste treatment condition, while keeping a fully functional nitrii rubber glove, displaying an uncompromised quality performance when in use.

[0022] Against common wisdom, this invention adds much more biodegradable agent to the nitrii rubber polymer as is conventionally known and disclosed, such as in US2014/0065311 (= D1 , Showa), wherein 2 % of a biodegradable agent as additive is clearly regarded as upper limit.

[0024] A nitrii rubber glove has been prepared, wherein first an inner nitrif rubber layer comprising 5 % (by weight) of a biodegradable agent (in this case: ECM Biofiims Masterbatch pelieis, comprising Low Density Polyethylene pellets with additive ingredients of Organoleptic-Organic chemical names / cultured colloids, Harmonized system based Schedule B code EGM6.0404 is 3901 .10.5020) is first produced around a glove former, followed by a second outer layer on the glove former applying a nitrii rubber comprising only 2 % (by dry parts) of the same biodegradable agent composition. [0025] The effect on the biodegradation, as per ASTM D5511 "Standard test method for determining anaerobic biodegradation of plastic materials under high-solids anaerobic digestion conditions", of an, as in example 1 , produced glove has been tested in a real life hospital environment, using a "Pharmafilter B.V." shredding first, followed by a 6 week anaerobic digester storage at 60 degrees Celsius. The effects were surprisingly convincing, as was furthermore proven by a more than 100 % larger C02 production in the resulting off-gassing.

[0026] Biodegradability in the ASTM D5511 test came at least 40 % higher as compared to the percentage biodegradation of the corresponding reference materia! (using for example gloves known in the market place as Showa Best Gloves with Eco Best Technology, apparently based on US2014/0065311 technology). Bui what was even more important was the strongly improved digester biodegradation at temperatures of 60 degrees Celsius, after 60 days (compared to the Showa Best Gloves) an Improva! rate of over 100 % in biodegradation effect was measured.

[0027] Wherein after 60 days in the digester (after shredding) the Showa Best gloves with Eco Best Technology showed a biodegradation in the range of 4 to 5 %, the gloves according to the invention were at least 9 to 10 % biodegraded, with potentially a much further degradation after 300 or 900 days in the range of 30 up to 90 % overall biodegradation.

[0028] Other components such as a swelling agents, or other chemo attractant agents, can/may be added in small amounts for enhancing the biodegradation effects, but were regarded not yet necessary for this comparative example. Other chemistries, such as alkali stabilizers, as indicated in US2014/0065311 , as included in its entirety for reference again, can be included in minor quantities in any of the glove layers for the usual and obvious functional reasons (this also includes, if required, curing agents). Any of the biodegradable components mentioned in US2014/0065311 can be mixed into another blend of a suitable biodegradable agent, and mixed into one the glove layers as per claim 1 and dependent claims.

[0029] From document US2014/0065311 , for being clear about what is regarded a biodegradable agent as defined in this application, a non-exhaustive listing of possible biodegradable agents is hereby listed, suitable to be used as components in order to enhance the degradation of the nitrii rubber glove after use: Biodegradation is generally considered as consisting of either enzyme-catalyzed hydrolysis, non-enzymatic hydrolysis, metabolic action, or both. The enzymes may be either endoenzymes which cleave the internal chain linkages within the chain or exoenzymes which cleave terminal monomer units sequentially. [0030] Biodegradation is a functional decay of material, e.g. loss of strength, substance, transparency, or good dielectric properties where it is known to be identifiable with exposure of the materia! to a living environment, which may itself be very complex, and the property loss may be attributable to physical or chemical actions as first steps in an elaborate chain of processes. [0031] A biodegradable polymer is a high molecular weight polymer that, owing to the action of micro- and/or macroorganisms or enzymes, degrades to lower molecular weight compounds. Natural polymers are by definition those which are biosynthesized by various routes in the biosphere. Proteins, polysaccharides, nucleic acids, lipids, natural rubber, and lignin, among others, are all biodegradable polymers, but the rate of this biodegradation may vary from hours to years depending on the nature of the functional group and degree of complexity. Biopolymers are organized in different ways at different scales. This hierarchical architecture of natural polymers allows the use of relatively few starting molecules (i.e. monomers), which are varied in sequences and conformations at molecular-, nano-, micro-, and macroscale, forming truly environmentally adaptable polymers. [0032] On the other hand, the repetitive units of synthetic polymers are hydrolyzable, oxidizable, thermally degradable, or degradable by other means, Nature also uses these degradation modes, e.g,, oxidation or hydrolysis, so in that sense there is no distinction between natural or synthetic polymers. The catalysts promoting the degradations in nature (catabolisms) are the enzymes, which are grouped in six different classes according to the reaction catalyzed. These classes include oxidoreductase for catalyzing redox reactions, transferase for catalyzing transfer of functional group reactions, hydrolase for catalyzing hydrolysis, lyase for catalyzing addition to double bond reactions, isomerase for catalyzing isomerization and iigase for catalyzing formation of new bonds using ATP. [0033] Biodegradation of oxidizable polymers is generally slower than biodegradation of hydrolyzable ones. Even polyethylene, which is rather inert to direct biodegradation, has been shown to biodegrade after initial photo-oxidation. An oxidized polymer is more brittle and hydrophilic than a non-oxidized polymer, which also usually results in a material with increased biodegradability. [0034] For example, by combining a nickel dithiocarbamate (photo antioxidant) with an iron dithiocarbamate (photo proxidant). a wide range of embrittlement times may be obtained.

[0035] The g!oves disclosed herein provides for increased susceptibi!ity to biodegradation of nitril rubber by means of additives including a biopoiymer. In this way a nitril rubber polymer blend is obtained that is more susceptible to biodegradation. [0036] A filler might he added to a composition to be added to a polymer thereby increasing the biodegradability. For relevant fillers, reference is also made to claims 8, 9 and 10 as stated in WO2019/074354. Starch is of course one of the more popular fillers (as in Starch-graft-acrylonitrile ANS), however also collagen is a known filler in combination with nitril rubber, as well as Is keratine.

[0037] Microbial or enzymatic attack of pure aromatic polyester is increased by exposure to certain microbes, for example Trichosporum, afhrobacteria and Asperyillus negs. [0038] Aliphatic polyester degradation is seen as a two-step process: the first is depolymerization, or surface erosion. The second is enzymatic hydrolysis which produces water-insoluble intermediates that can be assimilated by microbial cells.

[0039] Polyurethane degradation may occur by fungal degradation, bacterial degradation and degradation by polyurethane enzymes.

[0040] In one aspect, the biodegradation agent can be a polymer, such as a biodegradable polymer. The polymers can be homo- or co-polymers. In one aspect, the polymer is a homopolymer, !n another aspect, the polymer is a co-poiymer. Co-polymers include AB and ABA type co-polymers. In one aspect, the polymer comprises poiy!actic acid, poiy(lactic-co-glycolic acid), poiypoiypropy!ene carbonate, poiycaproiacione, poiyhydroxyaikanoate, chitosan, giuten, and one or more a!iphatic/aromatic polyesters such as polybutylene succinate, polybutylene succinate-adipate, polybutyiene succinate- sebacate, or polybutyiene terephthalate-coadipate, or a mixture thereof.

[0041] In one aspect the polymer is polybutyiene succinate, in one aspect, the polybutyiene succinate can have a number average molecular mass (Mn) from 1 ,000 g/moie to 100,000 g/mo!e.

[0042] The biodegradation agent may comprise a carboxylic acid compound. The biodegradation agent may comprise a chemo attractant compound; a giutaric acid or its derivative; a carboxylic acid compound with chain length from 5-18 carbons; a polymer; and a swelling agent.

[0043] The biodegradation agent may further comprise a microbe capable of digesting the acrylonitrile butadiene based (nitril) rubber. [0044] The polymer that may be comprised in the biodegradation agent can be selected from the group consisting of: poiydivinyl benzene, ethylene vinyl acetate copolymers, polyethylene, polypropylene, polystyrene, po!yterephtha!ate, polyesters, polyvinyl chloride, methacrylate, nylon 6, polycarbonate, polyamide, polychloroprene, acrylonitrile butadiene based rubber, and any copolymers of said polymers, or a combination thereof. [0045] The biodegradation agent may further comprise a compatibiiizing additive.

[0046] The biodegradation agent may further comprise a carrier resin. Suitable carrier resins include, but are not limited to, po!ydivinyl benzene, ethylene vinyl acetate copolymers, maleic anhydride, and acrylic acid with polyolefins, or a combination thereof. [0047] The biodegradation agent may further comprise a ehemotaxis agent to attract microbes. Suitable ehemotaxis agents comprise, but are not limited to, a sugar or a furanone. It can be selected from 3,5 dimethylyentenyl dihydro 2(3H)furanone isomer mixtures, emoxyfurane and N-acyihomoserine lactones. The ehemotaxis agent may comprise coumarin and/or coumarin derivatives, [0048] Without being bound by theory, it is believed that the biodegradation agent enhances the biodegradability of otherwise non-biodegradab!e plastic products through a series of chemical and biological processes when disposed of in a microbe-rich environment, such as a biologically active landfill or a digester tank held at elevated temperatures in between 50 to 70 deg C. The biodegradation agent causes the plastic to be an attractive food source to certain soil microbes, encouraging the plastic to be consumed more quickly than plastics without the biodegradation agent.

[0049] The biodegradation agent requires the action of certain enzymes for the biodegradation process to begin, so plastics containing the biodegradation agent will not start to biodegrade during the intended use of the materials and gloves described herein. For example, the microbes can secrete enzymes that break down the polymers into components that are easily consumed by microbes. Typically, when an organic material biodegrades in an anaerobic environment, the by-products are: humus, methane and carbon dioxide. It Is believed that when plastics containing the biodegradation agent are biodegraded to the same by-products as an organic material, [0050] Biodegradation processes can affect polymers in a number of ways. Microbial processes that can affect polymers include mechanical damage caused by growing cells, direct enzymatic effects leading to breakdown of the poiymer structure, and secondary biochemical effects caused by excretion of substances other than enzymes that may directly affect the polymer or change environmental conditions, such as pH or redox conditions. Although microorganisms such as bacteria generally are very specific with respect to the substrate utilized for growth, many are capable of adapting to other substrates over time. Microorganisms produce enzymes that catalyze reactions by combining with a specific substrate or combination of substrates. The conformation of these enzymes determines their catalytic reactivity towards poiymers. Conformational changes in these enzymes may be induced by the changes in pH, temperature, and other chemica! additives.

[0051] Microbes that may assist in biodegradation are psychrophiles, mesophiies, thermophi!es, actinomycetes, saprophytes, absidia, acremonium, alternaria, amerospore, arthhnium, ascospore, aspergiiius, aspergiilus caesiei!us, aspergi!lus Candidas, aspergiiius carneus, aspergiilus ciavatus, aspergiilus defiectus, aspergiiius fiavus, aspergiilus fumigatus, aspergiiius glaucus, aspergiilus niduians, aspergiilus ochraceus, aspergiiius oryzae, aspergiiius parasiticus, aspergiilus penici!ioides, aspergiiius restrictus, aspergiiius sydowi, aspergiiius terreus, aspergiilus ustus, aspergiilus versicolor, aspergiilus/penicillium-like, aureobasidium, basidsomycetes, basidiospore, bipoiaris, biastomyces, B. borsteiensis, botrytis, Candida, cepha!osporium, chaetomium, cladosporium, ciadosporium fuivum, e!adosporium herbarum, ciadosporium macrocarpum, ciadosporium sphaerospermum, conidia, conidium, conidoboius, Cryptococcus neoformans, cryptostroma eorticale, cunninghame!ia, curvuSaria, dreschlera, epiooccum, epidermophytcn, fungus, fusanum, fusarium solans, geotrichum, g!iociadium, heiicomyces, heiminthosponum, histoplasma, humicu!a, hyaline myceisa, memnonieiia, microsporum, mold, monilia, mucor, myceiium, myxomycetes, nigrospora, oidium, paeciiomyces, papulospora, penicii!ium, periconia, perithecium, peronospora, phaeohyphomycosis, phoma, pithomyces, rhizomucor, rhizopus, rhodococcus, rhodotoruia, rusts, saccharomyces, scopuiariopsis, sepedonium, serpuia lacrymans, smuts, spegazzinia, spore, sporoschisma, sporothrix, sporotrichum, stachybotrys, stemphyiium, syncephalastrum, Thermononespore fusca DSM43793, toruia, trichocladium, trichoderma, trichophyton, trichothecium, tritirachium, ulociadium, verticilium, waiiemia and yeast.

[0052] One or several furanone compounds combined can act as chemo attractants for bacteria and or as odorants for the decomposing or degrading polymer. Some furanones, particularly certain ha!ogenated furanones are quorum sensing inhibitors. Quorum sensing inhibitors are typically low-molecular-mass molecules that cause significant reduction in quorum sensing microbes, fn other words, halogenated furanones kiii certain microbes. Halogenated furanones prevent bacteria! colonization in bacteria such as V. fischeri, Vibrio harveyi, Serratia ficaria and other bacteria. However, the natural furanones are ineffective against P. aeruginosa, but synthetic furanones can be effective against P. aeruginosa.

[0053] Some furanones, inc!uding but not limited to those listed beiow, can be chemo attractant agents for bacteria. Suitable furanones include but are not limited to: 3,5 dimethylyentenyl dihydro 2{3H)furanone isomer mixtures, emoxyfurane and N- acyihomoserine lactones, or a combination thereof.

[0054] Bacteria that have shown to attract to the furanone compounds listed above inciude, but are not limited to C. vioiaceum.

[0055] Other chemo attractant agents include sugars that are not metabolized by the bacteria. Examples of these chemo attractant agents may include but are not limited to: galactose, galactonate, glucose, succinate, ma!ate, aspartate, serine, fumarate, ribose, pyruvate, oxaiacetate and other L-sugar structures and D-sugar structures but not limited thereto. Examples of bacteria attracted to these sugars inciude, but are not limited to Escherichia coli, and Salmonella, in a preferred embodiment the sugar is a non-estererfied starch.

[0056] The biodegradation agents are combined with an acrylonitrile butadiene based rubber. When combined in small quantities with any of acryionitriie butadiene based rubber, the resulting gloves become biodegradable while maintaining their desired characteristics. The resulting materials and products (i.e. gloves) made therefrom exhibit the same desired mechanical properties, and have effectively similar shelf-lives as products without the additive, and yet, when disposed of, are able to at least partially metabolize into inert biomass by the communities of anaerobic and aerobic microorganisms commonly found almost everywhere on Earth,

[0057] This biodegradation process can take place aerobically or anerobicaliy. It can take place with or without the presence of light. Traditional poiymers and products therefrom are now able to biodegrade in land fill and compost environments within a reasonable amount of time as defined by the ERA to be 30 to 50 years on average. [0058] The biodegradation agents increase, when added, the biodegradation rate of the disclosed gloves. The gloves can be degraded into an inert humus-like form that is harmless to the environment. An example of attracting microorganisms through chemotaxis is to use a positive chemotaxis, such as a scented polyethylene terephthalate pellet, starch D-sugars not metabolized by the microbes or furanone that attracts microbes or any combination thereof.

[0059] The biodegradation process might begin with one or more proprietary swelling agents that, when combined with heat and moisture, expands the plastics' molecular structure. After the one or more swelling agents create space within the plastic’s molecular structure, the combination of bio -active compounds discovered after significant laboratory trials attracts a colony of microorganisms that break down the chemical bonds and metabolize the plastic through natural microbial processes.

[0060] The biodegradation agent might comprise a furanone compound, a glutaric acid, a hexadecanoic acid compound, a polycaprolactone poiymer, a carrier resin to assist with placing the additive materia! into the polymeric material in an even fashion to assure proper biodegradation. The biodegradation agent can also comprise organoleptic organic chemicals as swelling agents i.e. natural fibers, cultured colloids, cyclo-dextrin, poiyiactic acid, etc.

[0061] The carrier resin may be selected from, but is not limited to the group of: ethylene vinyi acetate, poly vinyl acetate, maieic anhydride, and acrylic acid with polyolefins. The biodegradation agent may further comprise dipropylene glycol.

[0062] The biodegradation agent may be Incorporated in the polymers described herein by, for example, granulation, powdering, making an emulsion, suspension, or other medium of similar even consistency. The biodegradation agent may be blended into the polymeric material just before sending the nitril rubber material to the forming machinery for making the gioves.

[0063] Any carrier resin may be used (such as poly-vinyl acetate, ethyi vinyl acetate, etc,) where poiy olefins or any plastic material that these carrier resins are compatible with can be combined chemicaily and allow for the dispersion of the additive.

[0064] The biodegradation agent may comprise one or more antioxidants that are used to controi the biodegradation rate. Antioxidants can be enzymatically coupied to biodegradable monomers such that the resulting biodegradable polymer retains antioxidant function. Antioxidant-couple biodegradabie polymers can be produced to result in the antioxidant coupied polymer degrading at a rate consistent with an effective administration rate of the antioxidant. Antioxidants are chosen based upon the specific application, and the biodegradable monomers may be either synthetic or nature! .

[0065] An exemplary biodegradation agent may comprise the organic lipid based SR5300 product available from ENSO Plastics of Mesa, Ariz. [0066] Those skilled in the art wifi recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific gioves described herein. Such equivalents are considered to be within the scope of this invention and are covered by the following claims.

Claims

What is c!aimed:

Claim 1 ; An enhanced biodegradable multilayer nitril rubber glove, in particular suitable for medical use, comprising an inner layer intended for contacting a hand, at least further comprising an outer iayer suitable for contacting objects, characterized in that the inner Iayer comprises a relative larger amount, more preferably a relative significant larger amount, of a biodegradable agent than an relative amount of a biodegradable agent present in the outer iayer.

Claim 2: A glove as per claim 1 , characterized in that the inner Iayer is thicker as the outer iayer, preferably with an inner Iayer more than 50 % thicker as the outer layer, more preferably with an inner iayer more than 100 % thicker as the outer Iayer.

Claim 3: A g!ove as per any of the previous claims, wherein the giove materia! comprises more than 50 % nitrii rubber, preferably wherein the giove materia! comprises more than 70 % nitril rubber, more preferably wherein the glove materiai comprises more than 90 % nitril rubber, all based on dry parts.

Claim 4: A glove as per any of the previous claims, wherein the relative amount of biodegradable agent in the inner Iayer is larger than 2 parts per 100 dry parts nitril rubber, preferably larger than 3 parts per 100 dry parts nitril rubber, more preferably larger than 4 parts per 100 dry parts nitril rubber.

Claim 5: A glove as per any of the previous claims, wherein the relative amount of biodegradable agent in the outer layer is lower than or equal to 2 parts per 100 dry parts nitril rubber, preferably between 1 and 2 parts per 100 dry parts nitril rubber.

Claim 8: A glove as per any of the previous claims, wherein the nitril rubber is a soft cured nitril rubber comprising a suifur based crossiinklng agent, not containing any metailic oxide crosslinking agent such as a zinc oxide.

Claim 7: A glove as per any of the previous claims, wherein the biodegradation agents are adapted and optimized for enhanced giove biodegradation in a heated anaerobic digester, the digester working preferably at or around 80 degrees Celsius. Claim 8: A glove as per any of claims 1 - 7, wherein the inner and outer layer are separated by an additional nitri! rubber layer, the additional layer further comprising a biodegradable agent.

Claim 9: A giove as per any of the previous claims, wherein the proportion of the relative amount of biodegradable agent in weight % in the inner layer to the relative amount of biodegradable agent in weight % in the outer layer is greater than 1 .0 , more preferably greater than 1 .4 , even more preferably greater than 2.0 .

Claim 10: A glove as per any of the previous claims, wherein the selected biodegradable agent or agent mixture is preferably adapted for a thermophilic digestion biodegradation process, more preferably adapted to an anaerobic digestion at elevated temperatures above 60 degrees Celsius during a time span of more than 30 days, even more preferably more than 60 days.

Claim 11 : A method of producing an enhanced biodegradable nitril rubber glove, characterized in forming around a glove former a first inner layer of nitril rubber comprising a relative amount of biodegradable agent larger than 2 parts per 100 dry parts nitril rubber, preferably larger than 3 parts per 100 dry parts nitril rubber, more preferably larger than 4 parts per 100 dry parts nitril rubber, followed by forming of an outer layer of nitril rubber comprising a relative amount of biodegradable agent lower than or equal to 2 parts per 100 dry parts nitril rubber, preferably between 1 and 2 parts per 100 dry parts nitril rubber.

Claim 12: A method as according to claim 11 , wherein after the forming of the first layer, and before the forming of the outer layer, an additional intermediate nitril rubber layer is formed on the glove former, the additional intermediate layer also comprising a biodegradable agent mixed inside the nitril rubber composition. Claim 13: A method of biodegrading a nitril rubber glove as according to any of claims 1 - 10, wherein after use, such as by a surgeon in a hospital, the nitril rubber giove is shredded first into smaller particles, followed by an anaerobic digestion in a digester at elevated temperatures, preferably at around 60 degrees Celsius, during a period of in between 20 to 200 days, preferably between 40 to 80 days, more preferably during 60 days, most preferably further In combination with an addition of further shredded medical or hospitai waste such as bandages, clothes and/or linings.

Claim 14: A method of biodegrading a nitri! rubber glove as according to claim 13, wherein during the anaerobic digestion additional biodegrading enhancing supplements and/or agents are added into the digester, in particular in order to enhance the further acceleration of the nitri! rubber degradation.

Claim 15: Use of a glove according to any of claims 1 - 10, or use of a glove produced by a method as in claims 11 or 12.