AU2021201846B2 - A degradation agent and method of preparation thereof - Google Patents

Abstract

A DEGRADATION AGENT AND METHOD OF PREPARATION THEREOF Abstract There is provided an ionomer degradation agent comprising a transition metal complexed with an ionized cyclic ester. There is also provided a degradation agent comprising a clay intercalated with a transition metal ion dispersed within the clay.

Description

A Degradation Agent and Method of Preparation Thereof

Technical Field The present invention generally relates to a degradation agent for plastics. The present invention also relates to a method of forming the degradation agent.

Incorporation This application is a divisional of Australian patent application No. 2019210653, a itself a divisional of Australian patent application No. 2018200195, which is a divisional of Australian patent application No. 2016213724, which is in turn a divisional of Australian patent application No. 2012310300, a national phase entry of International Patent Application No. PCT/MY2012/000251, the entire contents of all of which are incorporated herein by cross-reference.

Background Thermoplastic polymers are widely used for packaging purposes. However, degradation of these thermoplastic polymers in general is a very slow process. When the thermoplastic polymer is casually disposed of, it is liable to remain substantially unaltered for months or even years. The disposal problem of thermoplastic polymers thus reduces its applicability and commercial value. In this respect, thermoplastic polymers have less satisfactory properties than the conventional packaging materials such as those based on cellulose which degrade rapidly when exposed to the environment. One method to increase the degradability of thermoplastic materials is to add additives to the thermoplastics- polymers. These additives, commonly known as pro degradants, increase the rate of degradation of the polymers by increasing the rate of photo degradation, biological, degradation, and/or chemical degradation. One known method of preparation of degradable polyolefin films utilizes certain organic derivatives of transition metals or transition metal salts, to enhance its degradability in the absence of sunlight. The transition metal is selected from the group comprising cobalt, manganese, copper, cerium, vanadium and iron. However, the exemplified film degrades to an embrittled condition within a short period of time. Furthermore, the utility of such a film is limited as it would likely degrade before use and the high concentrations of toxic transition metals, such as cobalt, used would create an extremely costly and toxic material. Another known method of producing degradable thermoplastic compositions comprises melting the polymer, adding the degradants to the melted polymer, and mixing the degradants and polymer to disperse the degradants within the polymer. However, poor compatibility with and dispersability in thermoplastics may lead to poor bonding between the degradant and polymer, which in turn results in composites with poor mechanical properties. Moreover, such a method is usually detrimental to the quality of the final polymer blend, since each event of heating and melting a polymer tends to result in some degradation of the polymer. In another known method of producing degradable plastic compositions, the polymer is first blended with high concentrations of the pro-degradant. The polymer blend is then combined with the original polymer in a ratio so as to provide the desired final concentration of pro-degradants. An extruder is typically used to mix the two polymer compositions and to disperse the pro degradants throughout the original polymer. However, due to the . high concentrations of degradants, the thermoplastics are susceptible to decomposition and therefore can only be stored for a limited length of time. Hence, the degradable thermoplastic of such composition has to be made just prior to use. Furthermore, the high concentrations of degradants present typically leads to deterioration of the polymer in the final composition and, thus, results in a final polymer that is of inferior quality. This is especially true when the polymer is subjected to the high temperatures necessary in manufacturing operations such as extrusion or film blowing to produce the final article. Accordingly, there is a need to provide a degradation agent for plastics that overcomes, or at least ameliorates, the disadvantages mentioned above.

Summary

According to a first aspect, there is provided an ionomer degradation agent comprising a transition metal complexed with an ionized cyclic ester. Advantageously, the degradation agent may act as a photocatalyst to enhance degradation of a plastic. Advantageously, the transition metal, such as iron, may be non-toxic to the environment and may not have a detrimental effect on the environment. More advantageously, the functional groups on the degradation agent may aid dispersion and adhesion of the degradation agent in the plastic. According to a second aspect, there is provided a method of producing an ionomer degradation agent comprising the steps of (i) providing a polymer having a cyclic ester; (ii) ionizing the cyclic ester and (iii) adding a transition metal ion to said polymer to form a complex with said polymer and thereby form said ionomer degradation agent. According to a third aspect, there is provided a degradation agent comprising a clay intercalated with a transition metal ion dispersed within the clay.

According to a fourth aspect, there is provided a

method of producing a degradation agent comprising a clay intercalated with a transition metal ion dispersed within the clay comprising the steps of (i) providing a metal ion intercalated clay; (ii) adding a surfactant to said metal ion intercalated clay to form a mixture; and (iii) applying a pressure to the mixture from step (ii) to obtain said degradation agent. According to a fifth aspect, there is provided use of the degradation agent as defined above in a polyolefin plastic.

Definitions

The following words and terms used herein shall have the-meaning indicated: The term 'dispersed' is.to be interpreted broadly to refer to the distribution of the degradation agent particles in the plastic. The term 'intercalate', and grammatical variants thereof, is to be interpreted broadly to refer to the interaction between the surfactant modified transition metal ion and the nanoclay. When the nanoclay is intercalated with the surfactant modified transition metal ion, the interlayer spacing between adjacent platelet surfaces is increased as compared to pristine nanoclay. The term "clay" refers to both naturally occurring clay materials and to synthetic clay materials. Clay refers to phyllosilicate minerals and to minerals which impart plasticity and which harden upon drying or firing. See generally, Guggenheim, S. & Martin, R. T., "Definition of Clay and Clay Mineral: Joint Report of the AIPEA Nomenclature and CMS Nomenclature Committees,"

Clays and Clay Minerals 43: 255-256 (1995). Materials composed of clay are characterized by having a mineral structure formed by the arrangement of octahedral units and tetrahedral units or by stacked layers formed by an octahedral sheet and one or more tetrahedral sheets of the atoms that constitute the clay structure.

Illustrative are the two groups of naturally occurring clay minerals. First is the hormite group, defined here as including palygorskite and sepiolite, which have channels .formed by octahedral units and tetrahedral units of the clay mineral structure. Second is the smectite group including montmorillonites and saponite, which are constituted by stacked layers formed by an octahedral sheet and more than one tetrahedral sheet, and mixtures of the foregoing. Smectite is a generic term that refers to a variety of related minerals also found in some clay deposits. Smectite is composed of units made of two silica tetrahedral sheets with a central alumina octahedral sheet. Each of the tetrahedra has a tip that points to the center of the smectite unit. The tetrahedral and octahedral sheets are combined so that the tips of the tetrahedra of each silica sheet and one of the hydroxyl layers of the octahedral sheet form a common layer. In particular, the smectite family of clay minerals includes the various mineral species montmorillonite, beidellite, nontronite, hectorite and saponite, all of which can be present in the clay mineral in varying amounts. The term "synthetic clay" is to be interpreted broadly to include materials related in structure to layered clays and porous fibrous clays such as synthetic hectorite (lithium magnesium sodium silicate). The term "synthetic clay" may include materials that have the same chemical formula and structure as natural clays. The term 'nanoclays' is to be interpreted broadly to include clays and clay minerals whose particles have at least one dimension in the nanoscale range (1-100 nm). The term 'ionomer' is to be interpreted broadly to refer to a polymer which is made up of electrically neutral repeating monomers and a fraction of which are ionized units. The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention. Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements. As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/ 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value. Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Detailed Disclosure of Embodiments

Exemplary, non-limiting embodiments of an ionomer degradation agent comprising a transition metal complexed with an ionized cyclic ester will now be disclosed. The cyclic ester may be a furanone group such as a 2-furanone group or a furan-2,5-dione (also commonly known as maleic anhydride) group. The cyclic ester group may be grafted onto the backbone of a polymer. The polymer may contain about 0.5 wt% to about 6.0 wt% of the cyclic ester by weight. It is to be noted that the higher level of cyclic ester present in the polymer may result in an ionomer with higher iron content.

The molecular weight of the polymer may be about 1000 Mw to about 20000 Mw. The backbone of the polymer may comprise a polyolefin. The polyolefin may comprise at least one monomer selected from the group consisting of ethylene, propylene, butene, pentene, hexene, heptene, octene, styrene and isoprene. Hence, the polymer may be a polyethylene such as high density polyethylene, "HDPE" 3 3 (densities from 0.940 gram/cm to 0.965 grams/cm ), low density polyethylene, "LDPE" or linear low density polyethylene, "LLDPE" (densities from 0.870 grams/cm 3 to

0.939 grams/cm 3 ), polypropylene, polybutene, polypentene such as poly (4-methylpentene), polyhexene, polyheptene, polyoctene, polystyrene or polyisoprene. The polymer may be a copolymer of a polyolefin and a poly(maleic anhydride). The polyolefin may further comprise at least one monomer selected from the group consisting of a-olefins having between about 3 to about 10 carbon atoms, acrylic acid, methacrylic acid, ethylacrylate, propylacrylate, butyl acrylate, pentyl acrylate and vinyl acetate. The o olefins having between about 3 to about 10 carbon atoms may be propene, butene, pentene, hexene, heptene, octane, nonene and decene. In one embodiment, the polymer may be polypropylene-co-maleic anhydride. The polymer may comprise a transition metal selected from the group consisting of cobalt, chromium, copper, iron, manganese and nickel. In one embodiment, the transition metal may be cobalt or copper. In another

embodiment, the transition metal may be chromium, iron, manganese or nickel. In such materials, the transition

metal may be present in any readily accessible valence state; for example, cobalt may be present in the

cobaltous (+2) or cobaltic (+3) state, copper in the

cuprous (+1) or cupric (+2) state, and iron in the ferrous (+2) or ferric (+3) state. More than one transition metal may be present in the ionomer and the percentage of each transition metal may be adjustable. The polymer having a transition metal therein is

also termed as an "ionomer". The ionomer may be present

in the form of a powder which facilitates the addition of the ionomer to a plastic blend.

In one embodiment, an iron ionomer is formed in which the transition metal is iron (II) and the polymer is of the ethylene-grafted maleic anhydride type (PE-g MAH), as represented by Scheme 1 below: H

CHHCO^ H

00

H

Scheme 1

As shown in the formula above, the ionomer has a free maleic anhydride group which can act as a compatibiliser for inorganic fillers in the plastic polymer. Hence, it may not be necessary to add an external additive.

The degradation agent may be an additive that may be added to a plastic blend. The degradation agent may be compounded with a plastic using an extruder and then the compounded product may be formed as a film sheet having a

thickness of about 10 tm to about 120 pLm, or about 15 ptm

to about 35 tim. The concentration of ionomer in the blend may be in the range of about 1 wt% to about 6 wt%. As mentioned above, if the iron content in the ionomer is high, then a lower dosage of ionomer prodegradant can be used in the plastic blend. The degradation agent can act as a photocatalyst due to the presence of the transition Fe2+ metal ion such as the ion in the lionomer. Hence, the degradation agent functions by absorbing UV light and accelerating the breakdown of the plastic into smaller fragments that can be then broken down by naturally occurring microorganisms. Due to the presence of the maleic anhydride groups which act as a dispersion agent and compatibilizer between the Fe2+ ion and the plastic as a result of van der Waals attraction forces, the degradation agent can be well dispersed within the plastic efficiently. The ionomer may be made according to a process which comprises the following steps: (.i) providing a polymer having a cyclic ester; (ii) ionizing the cyclic ester; and (iii) adding a transition metal ion to said polymer to form a complex with the polymer and thereby form the ionomer degradation agent. The cyclic ester may ionize, resulting in ring opening due to hydrolysis of the maleic anhydride ring. The polymer having a cyclic ester may be provided with a suitable solvent. The solvent may be an alcohol or an aromatic solvent. The solvent may be a mixture of the alcohol and aromatic solvent. The alcohol may be selected from the group consisting of ethanol, propanol, butanol and pentanol. The alcohol may be present in small proportions to reduce the solution viscosity. The aromatic solvent may be toluene, xylene or other non polar solvents. The ratio of the aromatic solvent to the alcohol may be in the range of about 8:1 (w/w) to about 10:1 (w/w). In one embodiment, the ratio of the aromatic solvent to the alcohol is 9:1 (w/w). The solvent(s) may be heated to a temperature in the range of about 50C to about 100°C. The temperature used is dependent on the type of polymer and the solvent(s) used. In an embodiment where the polymer is PE-g-MAH and the solvents used are n-butanol and toluene, the temperature used is 800C (under reflux). After the polymer is mixed with the solvent(s), the transition metal ion is then added to the mixture. When the transition metal is iron, the transition metal ion may be added in the form of a salt such as iron acetate, iron chloride or iron sulphate. The amount of the transition metal ion to be added to the solution is dependent on the degree of neutralization (DN) as represented by the following equation (I): Sx YeAe x 1000 DN = x 100 MpFPe X C X molyrner (I) where v is the valency of the metal ion, mFeAc is the mass of iron acetate added (g), MFene is the molecular weight of the iron acetate, polymer is the mass of PE-g-MAH and Ca is the acidity content expressed in equivalent acid per weight of polymer (eq/kg). The acidity content (Ca) expressed as equivalent acid per weight of polymer is calculated from equation (II):

DG 1000 C= - 100% a. 100% M 1Afl (II) where DG is the degree of grafting of maleic anhydride and MMAf is the molecular weight of maleic anhydride groups. The amount of transition metal ion to be added is based on the DN and may be in the range of about 1% to about 100% or about 70% to about 100%. In one embodiment, the DN is 100%. In another embodiment, the DN is 1.2. After addition of the transition metal ion, the mixture is then stirred under heating. The mixture may be stirred for about 30 minutes to about 90 minutes. in one embodiment, the mixture is stirred for about 60 minutes. The heating temperature may be in the range of about 60°C to about 100°C. In one embodiment, the heating temperature is about 80 0 C. Following which, a portion of the mixture may be removed by distilling under vacuum and the equivalent amount of fresh solvent(s) may be added to the remaining mixture. The mixture may be again stirred for the same time period and temperature as above and subjected to another round of distillation. This process of stirring and distillation may be then repeated as desired until no more transition metal precipitate remains in the mixture.

During the repeated cycles of stirring and distilling, the transition metal ion of the transition metal salt forms a complex with the polymer to thereby form the ionomer degeadation agent. The ionomer may be removed from the mixture by precipitation with a suitable solvent such as a ketone. The ketone may be selected from the group consisting of propanon (or commonly known as acetone), 2-butanone, 2 pentanone, 3-pentanone, 2-hexanone, 3-hexanone and

cyclohexanone. in order to recover the precipitated ionomer from the solvent, the mixture may be subjected to a series of filtration, washing with deionised water and drying steps to obtain the dry precipitated ionomer in the form of a fine powder. In one embodiment, where the ionomer is iron ionomer with PE-g-MAH, the extracting solvent used is acetone.

In an alternative method, the polymer (such as maleated polyolefin) may be dissolved under reflux in a 2S mixture of aromatic solvent and an alcohol. The maleated polyolefin may be a maleated polyethylene or maleated polypropylene. If the maleated polyolefin is a maleated polyethylene, the solvent used is a 9:1 w/w ratio of toluene-isopropanol at a temperature of 800C. If the maleated polyolefin is a maleated polypropylene, the solvent used is a 9:1 w/w ratio of xylene-isopropanol at a temperature of 90°C.

Once the solution is formed, transition metal ion may be added to the solution to obtain a theoretical degree of neutralisation (DN) of 1.2. In one embodiment, the transition metal ion is iron (II) acetate, iron chloride or iron sulphate. In order to achieve a DN of

1.2, the amount of iron (II) acetate used was 8 g per 100 g of PE-g-MA (MA content 3.8 wt%) . The amount of water

used may be 5 %v/v to the aromatic solvent mentioned above.

The reaction mixture may be left to further reflux

for a period of time for neutralization to occur before

precipitation in an alcohol (such as an isopropanol). In one embodiment, the reflux time may be in the range selected from the group consisting of about 15 hours to about 25 hours, about 15 hours to about 17 hours, about 15 hours to about 19 hours, about 15 hours to about 21 hours, about 15 hours to about 23 hours, about 17 hours to about 25 hours, about 19 hours to about 25 hours, about 21 hours to about 25 hours, about 23 hours to about 25 hours and about 19 hours to about 21 hours. In one embodiment, the reflux time may be about 20 hours. After precipitation, a powder was obtained which was recovered via vacuum filtration. The precipitate was then further washed in the alcohol to remove any by-products that may have been formed during neutralization. The precipitate was then dried (for example, in a vacuum oven overnight at 50°C) to eliminate all residual solvents

before a particle size reduction step in order to obtain a fine powder. In one embodiment, the particle size reduction step comprises the step of grinding the dried precipitate in a grinder at room temperature.

In this alternative method, repeated vacuum distillation was not used and it was found that the presence of water in the solution throughout the entire neutralization time may be beneficial in yielding higher amounts of the transition metal being complexed with the ionized cyclic ester. When compared with the earlier method, the alternative method may yield about 14% to about 15% increase in the iron content present in the resultant ionomer. In another alternative method, the ionomer may be made via a reactive extrusion method. This method comprises the addition of the polymer having a cyclic ester group (such as PE-g-MA) to the extruder and melting the polymer in the melt zone to form a molten polymer. An aqueous solution of transition metal ion is then added to the molten polymer via the injection zone. The transition metal ion then reacts with the molten polymer in a reaction zone and the side products are then removed in the devolatilization zone. In the reactive extrusion method, an additional polymer may be used to allow the reactant polymer to be easily extruded and then pelletized. In one embodiment, this additional polymer may be selected from the group consisting of Licocene PE-g-MA, HDPE (such as ETILINAS

HD5301AA, MFI 0.08g/l0min from Polyethylene Malaysia Sdn Bhd), an extrudable grade of PE-g-MA (such as Fusabond

EMB-100D from DuPont of Wilmington of Delaware of the

United States of America) and LLDPE (such as that from

Qenos, Alkathene XLF 175, MFI 4.0g/l0min, of Victoria of Australia). The transition metal ion may be stabilized by the addition of an organic acid. Hence, oxidation of the

transition metal ion may be substantially prevented such

that the oxidation state of the transition metal ion

remains stable. The organic acid may be ascorbic acid. Exemplary, non-limiting embodiments of a degradation agent comprising a clay intercalated with a transition metal ion dispersed within the clay will now be disclosed.

The degradation agent may comprise a transition metal selected from the group consisting of cobalt, chromium, copper, iron, manganese and nickel. In such materials, the transition metal may be present in any readily accessible valence state; for example, cobalt may be present in the cobaltous (+2) or cobaltic (+3) state, copper in the cuprous (+1) or cupric (+2) state, and iron in the ferrous (+2) or ferric (+3) state. In one embodiment, the iron is iron in the ferric state (iron (III)). In another embodiment, the iron is iron in the ferrous state (iron (II)).

The weight percentage of the transition metal ion in the clay may be in the range of about 2 wt% to about 3 wt%.

The clay may be a nanoclay selected from the group consisting of montmorillonite, hectorite, saponite, hectorite, mica, vermiculite, bentonite, nontronite, beidellite, volkonskoite, magadite, kenyaite and mixtures thereof. In one embodiment, the nanoclay is montmorillonite. Synthetic clays may be synthesized based on the chemical formula and structure of known nanoclay, such as those mentioned above. wherein the transition metal ion is treated with a surfactant

The degradation agent may comprise a surfactant. The surfactant may be bonded with the transition metal ion. The surfactant may be selected from the group consisting of polyethylene-polyethylene oxide, polyethylene polypropylene oxide, polyacrylate-polystyrene, polymethacrylate-polyethylene oxide, polyacrylate polyethylene oxide, polyacrylate-polyethylene, polyvinyl acetate-polyethylene, polyacrylate-polybutadiene, polyacrylate-polyisoprene, polyisoprene-polymethyl methacrylate, polyethylene-polymethyl methacrylate and polystyrene-polybutadiene. In one embodiment, the surfactant is polyethylene-polyethylene oxide. The molecular weight of the surfactant may be in the range of about 500 Mw to about 3000 Mw. Synthesis of the clay degradation agent may involve cation exchange of the transition metal ion into the clay structure, followed by treatment (or bonding) with a non ionic surfactant to enhance dispersion of the clay into a plastic blend. According to Scheme 2 below, clay such as nanoclay (for example, montmorillonite) is first treated with iron (II) to form Fe-MMT. The Fe-MMT is then treated with a surfactant such as polyethylene-polyethylene oxide to form the surfactant modified nano-clay. Due to the above modification of the nanoclay, the interspacing between the clay platelets increased due to the presence of the surfactant modified transition metal ion. The interspacing distance may be increased by about 10A to about 20A.

Na-MMT + Fe 2 *Fe-MMT

+1H 0O OH 6 J, AH 5

Scheme 2

The clay degradation agent may be compounded with a plastic in an extruder and the compounded product may be formed as a film sheet via a gas-film, blow-film or thin wall injection moulding process. The film sheet may have a thickness of about 15 Lm to about 35 pm. The concentration of the clay prodegradant in the blend may be in the range of about 1 wt% to about 6 wt%. The presence of the surfactants in the clay may aid to improve the dispersion of the clay in the compounded plastic. Hence, the resultant composite may exhibit properties such as higher heat distortion temperatures, enhanced flame resistance, increased modulus and improved barrier properties. The clay degradation agent functions by absorbing UV light and accelerates the breakdown of the plastic into smaller fragments that can be then broken down by naturally occurring microorganisms. The clay degradation agent may be made according to a process which comprises the following steps: (i) providing a metal ion intercalated clay; (ii) adding a surfactant to the metal ion intercalated clay to form a mixture; and (iii) applying pressure to the mixture from step (ii) to obtain the clay degradation agent. The process may further comprise the steps of: (iv) intercalating a transition metal ion between the platelet sheets of the clay to form the metal ion intercalated clay. The transition metal ion may be provided as a transition metal salt and mixed with the clay particles in a suitable solvent such as water. As the mixture is stirred, the transition metal ion dissociates from the salt and intercalates between the platelet sheets of the clay via cation exchange with the clay. In one embodiment, the transition metal ion is Fe3 and the transition metal salt is iron (III) chloride. In another 2+ embodiment, the transition metal iron is Fe and the transition metal salt is iron (II) sulphate.

The ion-exchanged clay may be then dried and subjected to ball milling. The ball milling step may be carried out at a speed of about 2500 rpm to about 3500 rpm, or about 3000 rpm for a time period of about 10 second to about 30 seconds, or about 20 seconds. The surfactant may be intercalated in the ion exchanged clay by- mixing dry pellets of the surfactant with the ball-milled clay. The mixture may be subjected to high pressures in order to introduce the surfactant into the space between the platelet sheets. The pressure used may be in the range of about 2.0 MPa (300 psi) to about 5.5 MPa (800 psi), or about 3.4 MPa (500 psi). The clay degradation agent is then obtained as a Fine powder. The clay degradation agent may be subjected to a ball milling step in order to reduce the particle size. The ball milling step may be carried out at a speed of 2500 to 3500 rpm and for 10 seconds to 50 seconds. In one embodiment, the ball milling step was carried out at a speed of 3000 rpm for 30 seconds. The clay degradation agent may have a particle size in the range of selected from the group consisting of about 50 nm to about 80 nm, about 50 nm to about 60 nm, about 50 nm to about 70 nm, about 60 nm to about 80 nm, about 70 nm to about 80 nm, about 60 nm to about 70 nm and about 60 nm to about 65 nm. The particle size may be about 63 nm. The ionomer degradation agent or nanoclay degradation agent, or mixtures thereof, may be used as an additive in a plastic blend. The ionomer degradation agent and/or nanoclay degradation agent may aid in the thermal and photodegradation of the plastic after the plastic has been used in order to reduce the harmful effects of such plastic on the environment. The ionomer degradation agent and/or nanoclay degradation agent may aid to break down the molecular structure of the plastic such that the plastic becomes susceptible to microorganism attack. The plastic may be a polyolefin plastic. The plastic may be selected from the group consisting of polyethylene plastics such as HDPE, or LDPE, polyvinyl chloride, polystyrene, polypropylene, and polyethylene terephthalate. In one embodiment, the plastic is a polyolefin plastic such as HDPE. The ionomer degradation agent or nanoclay degradation agent, or mixtures thereof, may be mixed with a polysaccharide in order to maximize the compostability of the plastic. The polysaccharide may be premixed with the polymer pellets in a mixer and then fed through a hopper. The polysaccharide may be represented by the formula (C 6HioO)n where 40 n 3000. The polysaccharide may be selected from the group consisting of starch, glycogen, arabinoxylan, cellulose, chitin and pectin. The starch may be selected from potato starch, native corn starch, native tapioca starch, rice starch, wheat starch, cross-linked starch, dextrin, polydextrin, maltodextrin, carboxymethyl starch, carboxyethyl starch, carboxypropyl starch, starch acetate, oxidized starch, derivatives thereof and mixtures thereof. In one embodiment, the starch may be native tapioca starch. The amount of starch to be added to the plastic may be in the range selected from the group consisting of about 10% to about 50%, about 10% to about 40%, about 10% to about

30%, about 10% to about 20%, about 20% to about 50%, about 30% to about 50%, and about 40% to about 50%, based on the amount of starch. In one embodiment, the amount of starch to be added to the plastic may be about 20%..

Brief Description Of Drawings

The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig. 1 is a flowchart showing the steps for the synthesis of Fe-nanoclay in accordance to one embodiment disclosed herein. Fig. 2 is a flowchart showing the steps for the synthesis of Fe-ionomer in accordance to one embodiment disclosed herein. Fig. 3 is a graph showing the tensile strength of high density polyethylene (HDPE) film with different types of pro-degradant additives. Fig. 4 is a graph showing the elongation at break of HDPE film with different types of pro-degradant additives.

Fig. 5 shows photographs of the disintegration of HDPE film with different types of pro-degradant additives after 144 hours of ultraviolet (UV) exposure.

Fig. 6 is a graph showing the tensile strength of HDPE film with at different dosage of Fe-ionomer pro

degradant additive. Fig. 7 is a graph showing the elongation at break of HDPE film at different dosage of Fe-ionomer pro-degradant additive. Fig. 8 is a graph showing the carbonyl index of HDPE film with different types of pro-degradant additives. Fig. 9 is a graph showing the carbonyl index of HDPE film at different dosage of Fe-_onomer pro-degradant additive.

Fig. 10 is an ATR-FTIP spectra of iron-ionomer blends made using the reactive extrusion method and comparing with a sample made from Example 1. The wavenumber ranges from 1500 cm 1 to 1900 cm1. Fig. 11 is a graph comparing the elongation at break between the Fe-ionomer produced in Examples 1 and 2. Fig. 12 is a graph comparing the carbonyl index between the Fe-ionomer produced in Examples 1 and 2. Fig. 13 is a graph showing the molecular weight distribution of an Fe-ionomer film exposed to UV for 1500 hours. Fig. 14 is a series of images showing degraded films after exposure to UV for 499 hours. Fig. 15(a) is a Scanning Electron Microscopy (SEM) image obtained at 2000 X magnification showing the surface of a neat HDPE film after 200 days in a biodegradation unit. Fig. 15(b) is a Scanning Electron Microscopy (SEM) image obtained at 2000 X magnification showing the surface of a HDPE + Fe-ionomer film after 200 days in a biodegradation unit. Fig. 16 is a graph showing the molecular weights of selected films having a thickness of 100 pm before and after exposure to UV for 500 hours. The solid coloured bar columns refer to the unexposed samples while the patterned coloured bar columns refer to the exposed samples. Fig. 17 is a graph showing the molecular weights of selected films having a thickness of 270 pm before and after exposure to UV for 500 hours. The solid coloured bar columns refer to the unexoosed samples while the patterned coloured bar columns refer to the exposed samples.

Fig. 18 is a graph comparing the carbonyl index between HDPE and 50 ppm Fe-KlO of Example 3.

Examples

Non-limiting examples of the invention will be further described in greater detail by reference to specific embodiments and Figures, which should not be construed as in any way limiting the scope of the

invention.

Analysis Protocols

Accelerated UV exposure

Film samples were placed into QUV-A weatherometers (Q-Panel, 340 nm lamps) using a 20h UV / 4h condensation

exposure cycle in accordance with ASTM D5208. The film samples were previously cut into tensile bar specimens and taped onto metal backing plates for insertion into the QUV sample holders. A short condensation cycle was chosen to simulate conditions of natural outdoor moisture exposure, such as simulated sunlight in the short wavelength region from around 365 nm down to 295 nm.

Carbonyl index

Infrared absorbance spectra were analysed via Perkin Elmer FTIR Spectrum 100 spectrometer. 6 scans were collected from 4000 to 450- cm. The extent of oxidation was determined by measuring the level of ketone carbonyl absorbance peak relative to the C-H stretching of the polyolefin, which remains essentially unchanged during oxidation. Typically, the absorbance peak for the ketone carbonyl formed during UV exposure was observed at 1713

cm~1. The carbonyl index was calculated by taking the ratio of the carbonyl absorbance to the absorbance of the

CH stretching at 1464 cm~1. This provides a means of quantifying the oxidative degradation over time. In general the thickness of the film analyzed was about 25

pm ± 3.

Tensile

Tensile testing was conducted by using Universal

Testing Machine (UTM) according to ASTM D882. Film

samples were cut into rectangular shape with the size of 25.4 mm x 150 mm. Cross head speed was set at 500mm/min and load cell used was 500 N.

Composting (Biodegradation Analysis)

After exposure to UV, oxidized samples were exposed to aerobic composting conditions (AS IS014855, Plastic Materials - Determination of the ultimate aerobic biodegradability and disintegration under controlled compositing conditions - Method by analysis of evolved carbon dioxide) Oxidized test materials were collected and cut into coupons less than 5 mm x 5 mm, to minimize any variability in the speed of biodegradation due to differences in their shapes or sizes. Microcrystalline cellulose powder was used as positive reference material for the biodegradation process. Compost samples were collected from piles of 2 to 3 months mature compost and transported to the lab within an hour of collection. Compost characteristics were tested in accordance with

the requirements of Australian standard AS ISO 14855. Compost was sieved through a sterile brass sieve with an 8-mm aperture size (Endecotts) and any glass or stone pieces were manually removed. Compost pH was determined as 8.7, moisture 51.5%, total organic carbon 18.4%, total nitrogen 1.8% and volatile solids were estimated as 47.9% of dry weight. Approximately 300 g of the compost (source of innoculum) was' filled in 2L glass bottles (bioreactors) and approximately 25 g of each oxidized film sample was added and mixed well (2 replicate samples were used for each test specimen).

The bioreactors containing the test mixture were incubated in a water bath maintained at 56+2 °C and set up to allow continuous supply of C02 -free humidified air to bioreactors and discharge of respired gases to a C02 gas analyzer. The bottles were shaken at regular intervals to keep the system well aerated.

Molecular Weight Analysis (Gel Permeation Chromatography)

Gel permeation chromatography (GPC) was employed to determine the molecular weights of the samples before and after exposure to UV

Solutions of each sample were prepared by adding 15 mL of solvent to 15 mg of sample. For samples containing 20wt% starch, 15 mL of solvent was added to 19 mg of the sample to maintain a similar concentration of soluble polymer. The samples were heated at 190°C for 20 minutes whilst. shaking, then cooled to 160°C. The solutions were filtered through a 1 pm glass fibre mesh at 160°C qand part of the filtered solution transferred to glass sample vials. The vials were placed on an autosampler and injection of part of the contents of each vial was carried out automatically. The chromatographic conditions are as follows: Instrument: Polymer Laboratories GPC220,

Columns: PLgel Olexis guard plus 3x PLgel Olexis, 30 cm, 13 pm, Solvent: 1,2,4-trichlorobenzene with anti-oxidant,

Flow-rate: 1.0 mL/minute (nominal) Temperature: 160°C (nominal), Detector: refractive index (& Viscotek differential pressure). Data capture and subsequent data handling was carried out using Polymer Laboratories "Cirrus" software.

Scanning Electron Microscopy (SEM)

SEM characterization was performed using a Phillips XL30 FEG-SEM. Imaging of the samples was performed in high vacuum mode using an accelerating voltage of 2kV, spot size 2 and a working distance of 7.5 mm.

Example 1

Materials

HDPE resin and EcoAdd pro-degradant

The high density polyethylene (HDPE) used in this example was ETILINAS HD5301AA High Density Polyethylene with the melt index of 0.08 g/10min supplied by PETRONAS. EcoAdd pro-degradant additives (Cobalt based) with melting point of 95 - 114 0 C used was supplied by Dragon Pack Industries Malaysia.

Cellulose powder

Microcrystalline cellulose powder from Sigma-Aldrich was used as positive reference material for the biodegradation process.

Fe-Nanoclay pro-degradant

The sodium montmorillonite (Na-MMT) was supplied by Southern Clay Products. The montmorillonite K10 (K10 surface area 220-270 m 2 /g) was purchased from Sigma Aldrich, this is a catalytic grade of montmorillonite which has been treated with sulphuric acid. The iron chloride (FeCl3 ) (Mw of 162.21g/mol) was purchased from Sigma Aldrich. The polyethylene- polyethylene oxide (PE PEO) nonionic surfactants (Mw 525, 1400 and 2250 g/mol containing 20wt%, 5Owt% and 80wt% ethylene oxide respectively) were purchased from Sigma Aldrich.

Fe-Ionomer pro-degradant

The ionomer base polymer of polyethylene-graft maleic anhydride (PE-g- MAH) was purchased from Sigma Aldrich. The maleic anhydride content was 2.80%wt with a Mw of -15,000 g/mol. The. peak melting temperature was 105°C as determined by differential scanning calorimetry (DSC). These properties were taken from the manufacturer's specification sheet. Iron acetate of 95%wt purity was also purchased from Sigma-Aldrich.

Pro-degradant synthesis

Synthesis of Fe-nanoclay

Montmorillonite K10 is a commercially available catalytic grade of smectite clay, which has been acid treated with sulfuric acid. Referring to Fig. 1, the processing method to synthesize Fe-nanoclay is as follows: As represented by.Step 1-1, 200g of Montmorillonite K10, 405g of Iron Chloride (FeCl3 ) and 2000ml of distilled water was added into a 4L beaker. The solution was stirred using the top mechanical stirrer for 24 hours. As represented in Step 1-2, the solution was then filtered, and the solid was repeatedly washed using distilled water until it was free of chloride ions. (This was checked using AgNO 3 , where the formation of AgCl precipitate indicated that there were still chloride ions present.)

The ion-exchanged clay (Fe-Ki) was dried in the 0 oven at 105 C for 12 hours subsequently, as represented in Step 1-3. Using the speed mixer, the dried Fe-K1O was ball-milled (100g at a time) at a speed of 3000rpm for 20s, repeated five times for each 100g portion as represented in Step 1-4. For the intercalation of polyethylene-block-poly (ethylene-glycol) into Fe-K10, pellets of polyethylene block-poly (ethylene-glycol) were placed in the grinder cup and immersed in liquid nitrogen to cool the pellets. Once all of the liquid nitrogen has evaporated, the cup

was fitted into the grinder and the pellets were grinded to powder. The powder was dried at 50°C for 24 hours. 75 g of Fe-K10 was then combined with 25g of polyethylene-block-poly (ethylene-glycol) in the powder mixer and mixed for 20s as shown in Step 1-5. The mixed powder was transferred into a steel mould, and pressed in the pressing machine until the pressure reached 500 psi at room temperature. The pressed powder was placed in an oven of 95°C for 12 hours. The pressing and drying steps are represented by Step 1-6 in Fig. 1 to finally obtain Fe-nanoclay pro-degradant 100. The ion-exchange reaction was confirmed via X-ray diffraction (XRD) in which the dOl spacing (corresponding to the intergallery spacing between clay platelets) was shown to increase slightly (from 9.992 to 10.000A), use of an inductively coupled plasma (ICP) also confirmed the increase in Fe content from 2.16 to 3.14%. Further expansion of the intergallery spacing (up to

18.303n) was also observed with the addition of the three different molecular weight PE-PEO non-ionic surfactants.

It is believed that this expansion is the precursor to improving the dispersion of these clay platelets when compounded with HDPE.

Synthesis of Fe-ionomer

Referring now to Fig. 2, there is shown a flowchart providing the steps for the synthesis of Fe-ionomer in accordance to one embodiment disclosed herein. The introduction of iron into PE-g-MAH, commonly

referred to as "neutralization", was carried out in solution. Firstly, 30 g of PE-g-MAH was dissolved under reflux at 80 °C in 300 g of toluene and n-butanol mixed solvent (9:1 w/w), represented by Step 2-1. After complete dissolution, the required amount of aqueous iron acetate solution was introduced to the polymer solution (1.58 g of iron acetate in 30 mL deionised water) as represented by Step 2-2. The amount of iron acetate added was equivalent to a theoretical degree of neutralization (DN) of 100%, as calculated by equations (I) and (II) above. After addition of the aqueous iron acetate solution, the two phase solution was vigorously stirred for 1 hour at 80 °C. Thereafter, about one third of the solution mixture was distilled off under vacuum and the equivalent amount of fresh mixed solvent was added. The reaction

mixture was again refluxed at 80 °C for another hour and about one third of the solvent was distilled off and the equivalent amount of fresh solvent was added. This process was repeated for a total of 8 times until no iron acetate precipitate remained. Recovery of the iron ionomer from solution was done via precipitation in acetone drop wise to obtain a fine powder. The ionomer precipitate was then filtered under vacuum followed by washing with deionised water. The wet precipitate was dried under vacuum at 40 °C overnight. The washing, filtration and drying steps are represented by Step 2-3 in Fig. 2 to finally obtain Fe-ionomer pro-degradant 200.

Compounding

Pro-degradant additives were compounded with HDPE via Theysohn twins screw extruder (Theysohn 030 mm, L/D 40) with screw configuration of two mixing zones. Temperature was set at 170/ 180/ 200 °C from feeding zone to die zone. The compounds were extruded at a screw speed of 85rpm. Compounded samples then were blown into film sheet using YEI HDM series of single screw blown film extruder. The temperature was set from 180 to 195°'C with

the output of 10 kg/hour. The thickness of the film sheet is 25 ± 5 pm.

Result

Tensile after UV

Effect of pro-degradant system on tensile properties of HDPE film is showed in Fig. 3 and 4. In general, it can be observed that most of the films including HDPE

showed decreasing tensile and elongation at break properties as the UV exposure time increased. Exposure of polymer film to UV had generated free' radical on the polymer chain and then initiated chain oxidation. Tensile and elongation properties of Fe-ionomer film significantly dropped after 48 hours QUV exposure. The decrease of the Fe-ionomer film properties is more than

50% from its original properties (prior to UV exposure). As can be observed, Fe-ionomer at 0.2% demonstrated

remarkable film degradation as compared to 0.2% EcoAdd and 0.2% Fe-nanoclay, indicating that the efficiency of Fe-ionomer additives as a photo 'degradation agent. While not being bound by theory, it is believed that incorporation of PE-g MAH ionomer into Fe particles

introduced carbonyl group such as carboxylic acid and anhydride which could induce chain oxidation more rapidly. In addition, the presence of this ionomer could also improve the dispersion of the pro-degradant additives in HDPE film. The reduction of tensile properties for 0.2 Fe-nanoclay systems is slightly lower than Fe-ionomer. It was found that both of Fe-ionomer and Fe-nanoclay films were disintegrated after 144 hours of UV exposure. The photo of films disintegration is shown in Fig 5. A comparison of HDPE film degradation properties at different Fe-ionomer dosage is also shown in Fig. 6 and 7. Referring to these Figs., increasing the Fe-ionomer dosage did not seem to give significant effect on the degradation rate of the film as the trend in the decrease in the tensile properties was almost the same. The trend demonstrated that lower dosage of Fe-ionomer offered better Fe dispersion in HDPE film and generated the same amount of free radical in polymer chain with higher dosage (3% of weight). Presence of free radical rendered significant degradation to the film.

Carbonyl index after UV

Fourier transform infrared spectroscopy (FTIR)

analysis was used to provide information regarding accumulation of carbonyl containing product as a function of UV exposure time. In general, the carbonyl index provides a quantitative measure of film degradation. A higher carbonyl index value demonstrates higher degradation on the polymer chain.

Fig. 8 shows the carbonyl index result over UV exposure time. Referring to Fig. 8, it can be observed that there had been an increase in carbonyl index over time for the 0.2% Fe-ionomer film as compared to the benchmark samples of 0.2% EcoAdd and the neat HDPE film without any pro-degradant additives. The increase in the carbonyl index for Fe-ionomer film was obvious after 96 hours of UV exposure. It had been proven in the previous tensile result that incorporation and reaction of ionomer in Fe particles has led to a significant increase in carbonyl index and degradation, which indicated that the activity of this pro-degradant appeared to be greater than other pro-degradant system. Referring to Fig. 9, it can be observed that increasing the Fe-ionomer dosage resulted in an increase in the carbonyl index value, particularly after 48 hours of UV. However, at 144 hours, increasing the Fe-ionomer dosage did not seem to have a significant effect on carbonyl index as the results obtained did not show an appreciable difference. As shown in tensile properties result, carbonyl groups presented at lower dosage of 0.2% Fe-ionomer after 144 hours UV yield about similar results to higher dosage of Fe-ionomer pro-degradant. The result demonstrated that PE-g-MAH ionomer used in this system might improve Fe dispersion in polymer chain and as a result provide higher degradation rate even at lower dosage of additive.

Biodegradation results

Results obtained after 323 days revealed that the cellulose sample reached more than 90% biodegradation within 45 days of compositing. This indicates that there is an active microflora in the compost innoculum in accordance with ISO 14855. The cumulative carbon dioxide results show a steady increase which indicates that the materials are continuing to biodegrade. After 323 days, the test film samples containing Fe prodegradants show levels of evolved carbon dioxide of between 9.1 and 12.4%. Actual values are reported in Table 1 below. A standard error of +5% should be considered when comparing the % biodegradation values. The samples "HDPE + Fe ionomer prodegradant" and "HDPE + Fe-K10 nanoclay prodegradant" contained CPO and were made into films using a Haake extruder.

Sample % Biodegradation + 5% Neat HDPE 8.1 Ecoplus 5.9 HDPE + Fe-ionomer prodegradant 9.1 HDPE + Fe-K10 nanoclay prodegradant 12.4 Table 1

Conclusion

The above example discusses the HDPE film degradation performance at different pro-degradant system under an accelerated UV exposure weatherometer. Decrease in the tensile properties and increase in the carbonyl index were apparently observed for the Fe-ionomer system, which indicated the improved efficiency of this Fe ionomer in decomposing hydrocarbon chain or hydroperoxides, leading to the generation of free radicals. Presence of ionomer (PE-g-MAH) increased the degradation rate by introducing the carbonyl group which accelerated photo degradation of the polymer chain. On the other hand, the presence of ionomer improved the Fe dispersion in HDPE and this led to a similar degradation rate of the film even when lower dosage of pro-degradant was used. In addition, use of clay particles, which is good in barrier properties in Fe-Nanoclay systems, could minimize and control degradation rate of the polymer.

Example 2

Reactive Extrusion of Fe-ionomer

Reactive extrusion was performed on a Theysohn twin screw extruder (screw diameter 30 mm; L/D 40) fitted with a liquid injection port and venting zone. The melt temperature used depended on the blend of polymer used with PE-g-MA. Since LLDPE was used as the additional polymer in the blend, the melt temperature used was 130 to 14 0 °C. Table 2 below shows the formulations and %Fe of the blends used in this method.,

- C) 0.LU

Example 2F'ao

C, C)

Cr) 0) C) Cr C

M~ O N I-

- C)

Example 2E

tx I-

*U, .r Lr) a

4ft 0

Example 2D

I) LO I U0C) C4

>M LU t

Example 2B C) CN N

CL

0*0

- L 6- C: -j

0) Cr C N

.2 Z. 2) C) C) i

0- Q

CL)

CL C)LCr. - - 0) ~U- ) C l W- 'UL C)

The above results showed that a high level of Fe was achieved in this method. The results also showed that the presence of ascorbic acid did not significantly alter the %Fe. The use of this method offers a cost advantage and potential for similar performance as compared to the method in Example 1 above.

Characterisation of Fe-ionomer

ATR-FTIR

ATR-FTIR was used to confirm the degree of neutralization of the samples made in the reactive extrusion method. This was compared with the samples

made in the method according to Example 1. As seen in Fig. 10, the peaks, located between 1500 and 1900 cm-1, are due to carbonyl functionalities. The main peak appearing at 1708 cm' was due to free C=O bonds of the hydrolysed anhydride ring. From the peak intensities, complete neutralization was not achieved, even for the samples made by the solution method. This incomplete neutralization is commonly found in literature.

The peaks or shoulders that appear at 1600 to 1650 cm had been identified as Fe-carboxylate groups. The presence of peaks or shoulders within this region was seen for all samples, confirming that the iron had bonded with the carboxyl groups from the anhydride ring. Comparing the spectra of LLDPE-Fe-ionomer blend made via the two different methods, no appreciable differences were observed, confirming that reactive extrusion was a

suitable synthesis method without the use of solvents. It is also to be noted that the use of ascorbic acid (AA)

did not affect the neutralization reaction, as the spectra of that with and without AA was identical.

Fig. 11 is a graph comparing the elongation at break (based on tensile data) between the Fe-ionomer produced in Examples i and 2 while Fig. 12 is a graph comparing the carbonyl index (based on FTIR data) between the Fe ionomer produced in Examples 1 and 2.

Molecular Weight Analysis (GPC)

A film sample of Fe-ionomer made in this example having a thickness of 100 pm was exposed to UV for up to 500 hours. A second film sample was exposed for 1000~ hours. A third film sample was exposed for 1500 hours. The molecular weight of the unexposed film sample was 216,000. The GPC data is shown .in Table 3 below.

Sample Molecular weight average % below Mw 5000 Fe-ionomer 12, 950 (500 hours Fe-ionomer 8,045 56 (1000 hours) Fe-ionomer 9,410 60 (1500 hours) Table 3 As seen in Table 3 above, it can be observed that the molecular weight of the Fe-ionomer decreased significantly after exposure to 500 hours of UV. A further exposure to an additional 500 hours of UV (total 1000 hours) decreased the molecular weight of the Fe ionomer even further to 8,045. This represented a

reduction in molecular weight of 96% as compared to the original polymer. As the molecular weight appeared to have increased when comparing between the samples exposed for 1000 hours and 1500 hours, the molecular weight distribution for the Fe-ionomer film exposed up to 1500 hours was determined, as can be seen in Fig. 13. For the film sample exposed to 1500 hours, Fig. 13 shows that a significant reduction in molecular weight had occurred. The molecular weight polydispersity had increased slightly and two peaks were apparent after 1000 hours. The GPC data revealed that about 60% of the Fe ionomer containing film had a molecular weight of below 5000. This result is very positive since the guidelines for ASTM D6954 suggest this as the target molecular weight reduction for oxo-biodegradable polymers.

Example 3

Synthesis of Clay Degradation Agent from FeSO 4

200 g of Clay-KiO and 40g of FeSO 4 (30 wt% solution, obtained from Alfa Aesar of Ward Hill of Massachusetts of the United States of America) were added into a 4L beaker with 2L deionized water. The solution was stirred with a top-head mechanical stirrer for 24 hours. The precipitation was filtered and washed repeatedly using deionized water three times. The Fe-clay-K10 was dried in an oven at 70°C for 12 hours. The iron content was

analysed using ICP and the resulting %Fe was 2.6%. The dried Fe-K10 was then mixed with polyethylene block poly(ethylene glycol) Mw=1400 with weight ratio of 0.25 using a blender, and then pressed at room temperature at a pressure of 500 psi. The pressed powder was heated in an oven at a temperature of 90°C for 12 hours. The intercalated Fe-KlO was grounded using a speed mixer/ball milling method at a speed of 3000 rpm for 30 seconds. This process was repeated three times.

Film samples were placed in a. QUV-A weatherometer

(Q-Panel, 340 nm lamps) using a 20 h UV / 4 H condensation exposure cycle in accordance with ASTM D5208. Samples of 100 pm film were removed at intervals of 49.5, 98, 210, 354 and 499 hours. FTIR spectra were collected on a Perkin Elmer FTIR Spectrum 100 spectrometer. 8 scans were collected from 4000 to 450cm-1 .

The carbonyl index plotted aginst QUV exposure time is shown in Fig. 18.

Example 4

Starch-based Samples

CPO treated Tapioca starch was premixed with polymer

pellets then fed into hopper. The samples used are labeled as "20% starch", "50ppm Fe-ioncmer+AA+ 20% starch", "50ppm Fe-ionomer no AA+20% starch" and "50ppm

Fe-K10+20% starch". Tapioca starch was obtained from the Manildra Group. Here, HDPE and EcoAdd were used as the control samples. HDPE and EcoAdd were obtained from the respective suppliers as mentioned in Example 1 above. The HDPE and EcoAdd films were extruded at a thickness of 270 pm. The extruded HDPE film was prepared using a haake Rheocord single screw extruder with sheet die (19 mm simple conveying screw with screw ratio 2:1). The film was extruded using a water cooled 3 roller system with positive tension. The screw rpm was set at 70 rpm for

most samples and the temperature profile from the feeding zone to die was 170, 210, 210 and 1800 C.

UV Trial

Samples of 270 pm thickness were removed from a Q Panel QUV accelerated weatherometer at intervals of 98,

210, 354 and 499 hours. Infrared absorbance spectra were collected on a Perkin Elmer FTIR Spectrum 100 spectrometer using an attenuated total reflectance single bounce diamond/ZnSe accessory. 8 scans were collected from 4000 to 650 cm~1 on an average of 2 to 3 areas of film. Images of the degraded films after 499 hours are shown Fig. 14. From Fig. 14, it can be seen that the samples containing Fe- ionomer as prodegradant (samples 4 and 5) have significant degradation. Similarly, the sample containing Fe-K10 (sample 6) showed obvious signs of degradation. The sample containing starch alone (sample 3) also showed signs of degradation, although visually this did not appear as bad as the samples containg Fe degradation agents. The EcoAdd sample (sample 2) did not appear to be visually degraded.

Example 5

Characterization and Comparison of Above Samples

Biodegradation Analysis

The samples examined for the biodegradation analysis were (1) neat HDPE, (2) EcoAdd, (3) HDPE + Fe-ionomer (from Example 2), (4) HDPE + Fe-K10 nanoclay (from Example 3) , (5) HDPE + 20% starch, (6) HDPE + 20% starch + Fe-ionomer (from Example 4) and (7) HDPE + 20% starch

+ Fe-K1O nanoclay (from Example 4). HDPE were incorporated into the above films using a Haake extruder. The thickness of the film for samples (1) to (4) was 100 pm while the thickness of the film for samples (5) to (7) was 270 pm. The biodegradation results at 150 days are shown in Table 4 below.

Sample % Biodegradation + 5% Neat HDPE 0.0 Ecoplus -1.5 HDPE + Fe-ionomer 4.5 HDPE + Fe-K10 nanoclay 2.9 HDPE + 20% starch 10.5 HDPE + 20% starch + Fe-ionomer 7.5 HDPE + 20% starch + Fe-K10 nanoclay 7.5 Table 4

The results from Table 4 appeared to show that the starch containing samples showed higher levels of

% biodegradation compared to the films without starch. This may be due to the faster degradation of starch. However, it should be noted that these films were significantly thicker at 270 pm compared to the thinner 100 pm films. In addition, there was still 80% polyolefin in these films that surrounded the starch particles, so that an immediate loss of starch will not be apparent.

Film samples (1) and (3) were further subjected to a SEM analysis. These samples were recovered carefully from the post-degradation compost and were carefully rinsed with de-ionised water or ethanol to remove any surface debris that may have adhered to the post degraded samples. Pieces of the degraded samples were carefully mounted onto a sample puck using conductive tape and the samples were coated with iridium. SEM analysis was then carried out according to the protocol described above. Fig. 15(a) and- Fig. 15(b) .showed the SEM images of samples (1) and (3) respectively. It could be seen that the surface of sample (3) was colonized by microorganisms and that there is evidence that these microorganisms had removed mass from the polymer as depicted by the arrow which indicated significant degradation or hole formation. Fig. 15(b) also clearly showed that sample (3) contained filamentous microorganisms that are typical of fungi (as shown by the dotted arrow). In contrast,

the neat HDPE film of Fig. 15(a) did not show any sign of microbial colonization and only showed minor surface defects. These results strongly suggested that given a longer time period, sample (3) can be expected to fully biodegrade in the environment due to the presence of the Fe-ionomer.

The film sample was compared to other products commonly found in the market such as d2W (from Symphony Environmental of Herts of the United Kingdom), Reverte

(from Wells Plastics Ltd of Staffordshire of the United

Kingdom) and Total Degradable Plastics Additives (TDPA", from EPI Environmental Plastics Inc of British Columbia

of Canada). The active components in d2W are metal stearates and stabilizers (mainly Mn). The active components of Reverte are metal ion prodegradant and

micronized cellulose. The active components of TDPA are metal stearates (Fe, Ce, Cc) and citric acid (typically Co).

Table 5 below shows the comparison between sample (3) and the above commonly marketed products.

Product Degradation Claims Biodegradation Claims Embrittlement Molecular cO2 Evidence of weight evolution Microbial Growth d2W Not Not reported reported Reverte Not /60% after reported 700 days TDPA . / 6,720 /13% after (thickness 300 days unknown) (60% after 600 days) Sample /< 5% / 8,045 /13% after I/ SEN shows (3) elongation (100 pm) 300 days proof of to break I microorganisms Table 5

Table 5 shows that the prodegradant made herein exhibited behaviour that is consistent or better than that disclosed by the above marketed products. Many of the marketed products do not report any evidence of specific molecular weight reduction or CO 2 behaviour.

Studies conducted on the marketed products showed that the biodegradation of oxidized polyolefin samples was very slow and it increased only after incubation for at least 100 to 150 days (approximately 3 to 4 months) in compost and/or soil. It should also be noted that this study involved re-innoculation of samples after an incubation period which was not performed in this example.

Molecular Weight Analaysis

Gel permeation chromatography (GPC) was employed to determine the molecular weights of the samples before and after exposure to UV for 500 hours. The samples determined here are (1) neat HDPE (thickness of 100 pm and 270 pm), (2) EcoAdd (thickness of 100 pm and 270 pm), (3) 50 ppm Fe-ionomer REX (from Example 2) (thickness of 100 pm), (4) 50 ppm Fe-K1O nanoclay (from Example 3) (thickness of 100 pm), (5) 20% starch (thickness of 270 pm), (6) 20% starch + 50 ppm Fe-ionomer REX (from Example

4) (thickness of 270 pm) and (7) 20% starch + 50 ppm Fe K10 nanoclay (from Example 4) (thickness of 270 pm). The results from this analysis are summarized in Fig. 16 and 17. The initial molecular weight for the unexposed samples was typically 200,000. After 500 hours of UV exposure, this value decreased significantly. The data for the 100 pm films (see Fig. 16) showed the Fe-ionomer film being reduced to a molecular weight of 12,950 and that of the Fe-K1O film being reduced to 13,850. For the 270 pm films (see Fig. 17), the exposed neat HDPE-film was found to have a molecular weight of 26,900 while the film containing Fe-ionomer and starch had a molecular weight of 11,500. This represented a loss of about 94% in molecular weight of the polymer. A similar decrease was also observed for the Fe-K10 and starch containing film which had a molecular weight of 14,300. The film containing starch alone showed a reduction to 18,700 while

EcoPlus was 16,650.

Applications The disclosed degradation agent of the present invention

may be applied in numerous industrial applications, not least

in any products which have been made from plastics, for example,

packaging materials, films, shock absorbing materials, or blow

molded bottles, and in the preparation of agricultural films.

The use of clay particles in the degradation agent of the

present invention minimizes and provides better control of the

degradation rate of the polymer. Advantageously, the

degradation agent of the present invention is environmentally

friendly and contains non-toxic or low toxicity components.

More advantageously, the presence of functional groups on

the ionomer degradation agent results in better adhesion between

the degradation agent and the plastic polyolefin, which in turn

results in plastic polyolefin with enhanced degradation

performance. Even more advantageously, the degradation rate of

the polyolefin is maintained even when a low dosage of the pro

degradant is used.

It will be apparent that various other modifications and

adaptations of the invention will be apparent to the person

skilled in the art after reading the foregoing disclosure

without departing from the spirit and scope of the invention and

it is intended that all such modifications and adaptations come

within the scope of the appended claims.

Forms of the Invention

Forms of the present invention include:

1. An ionomer degradation agent comprising a transition

metal complexed with an ionized cyclic ester.

2. The ionomer degradation agent according to form 1, wherein said cyclic ester is at least one of 2-furanone and

furan-2,5-dione.

3. The ionomer degradation agent according to form 1,

wherein said cyclic ester is grafted onto the backbone of a

polymer.

4. The ionomer degradation agent according to form 3,

wherein said polymer is a polyolefin.

5. The ionomer degradation agent according to form 1,

wherein said polymer is a copolymer of a polyolefin and a

poly(maleic anhydride).

6. The ionomer degradation agent according to form 4 or

form 5, wherein said polyolefin comprises at least one monomer

selected from the group consisting of ethylene, propylene,

butylene, pentylene, hexylene, heptylene, octylene, styrene and

isoprene.

7. The ionomer degradation agent according to form 6,

wherein said polyolefin further comprises at least one monomer

selected from the group consisting of acrylic acid, methacrylic

acid, ethylacrylate, propylacrylate, butyl acrylate, pentyl

acrylate and vinyl acetate.

8. The ionomer degradation agent according to form 1,

wherein said transition metal is selected from the group

consisting of cobalt, chromium, copper, iron, manganese and

nickel.

9. The ionomer degradation agent according to form 8,

where said transition metal is iron (II) or iron (III).

10. A method of producing an ionomer degradation agent

comprising the steps of:

(i) providing a polymer having a cyclic ester;

(ii)ionizing the cyclic ester; and

(iii) adding a transition metal ion to said polymer

to form a complex with said polymer and thereby form said

ionomer degradation agent.

11. The method according to form 10, further comprising

the steps of:

(iv) removing said polymer from said mixture;

(v) adding fresh polymer to said transition metal ion;

and

(vi) repeating steps (iv) and (v) until substantially

no transition metal ion remains.

12. The method according to form 11, wherein step (iv)

comprises the step of distilling said polymer from said mixture.

13. The method according to form 10, wherein the amount

of transition metal ion added to said polymer results in a degree

of neutralization in the range of 1% to 100%.

14. The method according to form 10, further comprising

the step of:

(iv') refluxing the transition metal ion and polymer

for a period of time until neutralization occurs.

15. The method according to form 14, wherein the reflux

time is undertaken for a period selected from the range of 15

hours to 25 hours.

16. A method of producing an ionomer degradation agent

comprising the steps of:

(i)adding a first polymer having a cyclic ester group

to the melt zone of an extruder to form a molten polymer;

(ii) adding a transition metal ion to the molten

polymer; and

(iii) reacting the transition metal ion with the

molten polymer in the reaction zone of said extruder to

form a complex with said polymer to thereby form said

ionomer degradation agent.

17. The method according to form 16, comprising the step

of adding a second polymer to enhance the extrudability of said

first polymer.

18. The method according to form 17, wherein said second

polymer is selected from the group consisting of Licocene PE-g-

MA, high density polyethylene, an extrudable grade of PE-g-MA

and linear low density polyethylene.

19. The method according to form 16, wherein the

transition metal ion is added with a stabilizer.

20. The method according to form 19, wherein the

stabilizer is an organic acid selected from ascorbic acid.

21. A degradation agent comprising a clay intercalated

with a transition metal ion dispersed within the clay.

22. The degradation agent according to form 21, wherein

said transition metal is selected from the group consisting of

cobalt, chromium, copper, iron, manganese and nickel.

23. The degradation agent according to form 21, wherein

said nanoclay is selected from the group consisting of

montmorillonite, hectorite, saponite, hectorite, mica,

vermiculite, bentonite, nontronite, beidellite, volkonskoite,

magadite, kenyaite and mixtures thereof.

24. The degradation agent according to form 21, wherein

said clay is a nanoclay.

25. The degradation agent according to form 24, wherein

the transition metal ion is bonded to a surfactant.

26. The degradation agent according to form 25, wherein

said surfactant is one of polyethylene-polyethylene oxide and

polyethylene-polypropylene oxide.

27. A method of producing a degradation agent comprising

a clay intercalated with a transition metal ion dispersed within

the clay comprising the steps of:

(i) providing a metal ion intercalated clay;

(ii) adding a surfactant to said metal ion

intercalated clay to form a mixture; and

(iii) applying pressure to the mixture from step (ii)

to obtain said degradation agent.

28. The method according to form 18, wherein the pressure

in said applying step (iv) is selected from the range of 300 to

800 psi.

29. The method according to form 19, wherein the pressure

is 500 psi. 30. Use of the degradation agent according to form 1 or

form 13 in a polyolefin plastic.

31. Use according to form 21, wherein the concentration

of said degradation agent in the polyolefin plastic is 1 wt% to

6 wt%.

Claims (9)

Claims

1. An ionomer degradation agent comprising a transition metal complexed with an ionized cyclic ester, wherein said transition metal is selected from the group consisting of chromium, copper, manganese, and nickel.

2. The ionomer degradation agent according to claim 1, wherein said cyclic ester is at least one of 2-furanone and furan-2,5-dione.

3. The ionomer degradation agent according to claim 1 or 2, wherein said cyclic ester is grafted onto the backbone of a polymer.

4. The ionomer degradation agent according to claim 3, wherein said polymer is a polyolefin.

5. The ionomer degradation agent according to claim 3, wherein said cyclic ester grafted onto the backbone of a polymer is a copolymer of an olefin and a maleic anhydride.

6. The ionomer degradation agent according to claim 4 or claim 5, wherein said polyolefin or copolymer comprises at least one monomer selected from the group consisting of ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, styrene and isoprene.

7. The ionomer degradation agent according to claim 6, wherein said polyolefin or copolymer further comprises at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, ethylacrylate, propylacrylate, butyl acrylate, pentyl acrylate and vinyl acetate.

8. Use of the ionomer degradation agent according to any one of claims 1 to 7 in a polyolefin plastic.

9. The use according to claim 8, wherein the concentration of said degradation agent in the polyolefin plastic is 1 wt% to 6 wt%.

Petroliam Nasional Berhad (Petronas)

Patent Attorneys for the Applicant/Nominated Person

SPRUSON&FERGUSON