WO2014167518A1

WO2014167518A1 - Degradable and biodegradable plastic material and a method for making it

Info

Publication number: WO2014167518A1
Application number: PCT/IB2014/060594
Authority: WO
Inventors: Michel Lefebvre
Original assignee: Steripak Pty Ltd
Priority date: 2013-04-12
Filing date: 2014-04-10
Publication date: 2014-10-16
Also published as: AU2013204225A1

Abstract

There is disclosed herein a degradable or biodegradable plastic material containing a first polymer and at least one fractal polymer. There is also disclosed herein a method of making a degradable or biodegradable plastic material comprising mixing a first polymer with a fractal polymer to form a mixture thereof. There is also disclosed herein a degradable plastic material containing a first polymer and a pro-degradation additive with fractal local concentration repartition. There is also disclosed herein a biodegradable plastic material containing a first polymer and a biodegradable additive with fractal local concentration repartition. There is also disclosed herein a method of making a degradable or biodegradable plastic material comprising the step of creating inside the plastic material a fractal repartition of a pro-degradation additive and/or a biodegradation additive.

Description

DEGRADABLE AND BIODEGRADABLE PLASTIC MATERIAL AND A METHOD FOR MAKING IT

Technical Field

[001] The present invention relates to a degradable or biodegradable plastic material and a method of making it.

Background of the Invention

[002] The information provided herein and references cited are provided solely to assist the understanding of the reader, and do not constitute an admission that any of the references or information is prior art to the present invention.

[003] The use of plastics in society has the downside that they are difficult to decompose. The addition of additives to plastic materials to achieve various types of degradation such as photo-degradation, oxo-degradation or biodegradation has been well documented. Reference is made to "An Overview of degradable and biodegradable polyolefins", A. Amala et al., Progress in Polymer Science, 36, 2011 p 1015-1049. However the poor performance of many additives, particularly for biodegradation under various conditions, has also been noted. Reference is made to "Fundamental principles and concepts of biodegradability - sorting through the facts, hypes, and claims of biodegradable plastics in the marketplace" R. Narayan, Bioplastics Magazine 01/09 vol 4.

[004] Degradation of plastics by living microorganisms is achieved when the polymer is used as a nutrient source for the production of by-products such as biogas and the multiplication and organisation of the microorganism in colonies.

[005] The effects of most pro-degradation additives (including biodegradation additives) are concentration dependant but their use is limited not only by cost considerations but by the imperative to maintain physical performance in first use and recycled products.

[006] It would be desirable to provide a plastic material which is degradable or biodegradable, but still maintains its physical performance. It would also be desirable to provide a plastics material which contains an additive which is concentrated locally in a manner such as to lower its overall use but still maintain the degradation or biodegradation performance.

Summary of the Invention

[007] According to a first aspect of the present invention, there is provided a degradable or biodegradable plastic material containing a first polymer and at least one fractal polymer.

[008] According to a second aspect of the present invention, there is provided a method of making a degradable or biodegradable plastic material comprising mixing a first polymer with at least one fractal polymer to form a mixture thereof.

[009] According to a third aspect of the present invention, there is provided a degradable plastic material containing a first polymer and a pro-degradation additive with fractal local concentration repartition.

[0010] According to a fourth aspect of the present invention, there is provided a biodegradable plastic material containing a first polymer and a biodegradable additive with fractal local concentration repartition.

[0011] According to a fifth aspect of the present invention, there is provided a method of making a degradable or biodegradable plastic material comprising the step of creating inside the plastic material a fractal repartition of a pro-degradation additive and/or a biodegradation additive.

Definitions

[0012] The following are some definitions that may be helpful in understanding the description of the present invention. These are intended as general definitions and should in no way limit the scope of the present invention to those terms alone, but are put forth for a better understanding of the following description.

[0013] Unless the context requires otherwise or specifically stated to the contrary, integers, steps or elements of the invention recited herein as singular integers, steps or elements clearly encompass both singular and plural forms of the recited integers, steps or elements. [0014] Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated step or element or integer or group of steps or elements or integers, but not the exclusion of any other step or element or integer or group of elements or integers. Thus, in the context of this specification, the term "comprising" means "including principally, but not necessarily solely".

[0015] By "degradable" is meant that the plastic material is capable of being weakened by outside agents such as atmospheric oxygen or UV light.

[0016] By "biodegradable" is meant that the plastic material is capable of being at least partially consumed by microorganisms. This may occur under composting conditions, under soil conditions, under aerobic condition, under anaerobic conditions or under marine conditions.

[0017] By "fractal polymer" is a polymer having a fractal configuration of structure which is substantially self-similar or is scale invariant at different scales. The polymer has a constructed or in-built reticulated structure.

[0018] By "fractal local concentration repartition" is meant that localised concentration zones of an additive in a polymer are shaped in a fractal form.

Brief Description of the Drawings

[0019] FIG. 1 is a scanning electron microscope image of pure fractal poly ε caprolactam embedded in a polymer matrix showing the fractal structure at micrometre scale;

[0020] FIG. 2 is a scanning electron microscope image of fractal poly ε caprolactam composite within a polymer matrix after staining with phospho-tungstenic acid and shows the fractal repartition of amine radical concentration used as a pro-degradation additive.

Detailed Description of Preferred Embodiments of the Invention

[0021] There is disclosed herein a degradable or biodegradable plastic material containing a first polymer and at least one fractal polymer. [0022] There is also disclosed herein a method of making a degradable or biodegradable plastic material comprising mixing a first polymer with at least one fractal polymer.

[0023] In some embodiments the first polymer may be in the form of a melt or may be melted with the at least one fractal polymer which is retained as a solid in the mixture.

[0024] There is also disclosed herein a degradable plastic material containing a first polymer and a pro-degradation additive with fractal local concentration repartition.

[0025] There is also disclosed herein a biodegradable plastic material containing a first polymer and a biodegradable additive with fractal local concentration repartition.

[0026] Suitably the fractal polymer is present in a concentration of about 2% w/w or lower. For example the fractal polymer may be present in a range of about 0.01% to about 1% w/w or about 0.01 to about 0.1% w/w, or about 0.1 to about 1% w/w or about 1 to about 2% w/w or about 0.05 to about 0.5% w/w. Suitable amounts include 0.01% w/w, 0.02% w/w, 0.03% w/w, 0.04% w/w, 0.05% w/w, 0.06% w/w, 0.07% w/w, 0.08% w/w, 0.09% w/w, 0.1% w/w, 0.2% w/w, 0.3% w/w, 0.4% w/w, 0.5% w/w, 0.6% w/w, 0.7% w/w, 0.8% w/w, 0.9% w/w, 1% w/w, 1.1% w/w, 1.2% w/w, 1.3% w/w, 1.4% w/w, 1.5% w/w, 1.6% w/w, 1.7% w/w, 1.8% w/w, 1.9% w/w or 2% w/w.

[0027] The first polymer may be a polyolefin such as polyethylene or polypropylene, a polystyrene such as high impact polystyrene (HIPS) or oriented polystyrene (OPS), a polyester such as PET, a polyamide and/or an imide such as nylon or MXD6. A mixture of polymers may be used.

[0028] The plastic material may additionally include one or more of a pro- degradation additive and a biodegradable additive. In some embodiments, the additive is localised in the plastics material with fractal local concentration repartition.

[0029] In some embodiments, the pro-degradation additive may be a carbon containing copolymer such as carbon monoxide copolymer. One suitable carbon containing copolymer is poly(ethylene-co-carbon monoxide copolymer). In some embodiments, the pro-degradation additive may be a vinyl ketone copolymer. A vinyl ketone copolymer may be used when photodegradation is desired. One suitable pro- degradation additive is polyamide-12.

[0030] One suitable biodegradable additive is EcoPure^® polystyrene based biodegradation additive. Another suitable biodegradable additive is a polypeptide such as a keratin. In some embodiments if biodegradation is required, the biodegradable additive may be a polyamide starch mix or a polymer derivative, for example, from corn starch such as polylactic acid. One suitable biodegradable additive is amylase.

[0031] The fractal polymer may be single polymer or may be mix of polymers. The fractal polymer or mix of fractal polymers may be obtained by phase inversion or coagulation of a polymer or mix of polymers dissolved in a solvent with a gas producing reagent according to U.S. Patent No. 6,001,889 and Australian Patent 696330 entitled "Polymers with fractal structure", both of which are incorporated herein by reference. As set out in U.S. Patent No. 6,001,889, for general preparation of fractal structure polymers the procedure may be as follows:

(a) Preparations of the original base polymers for reaction.

(1) Polymerization, extrusion and chip manufacture, followed by purification (to remove unreacted monomer) and drying.

(2) Spinning and drawing of the polymer at very high drawing ratio to obtain a highly crystalline structure in the base polymer.

(b) Preparation of the liquid phase and controlled depolymerization (produces cut segments).

(3) Mixing of the base crystalline polymer with a liquid reagent breaking cohesion bonds (e.g., the hydrogen bonds) to unfold the polymer micelle in a slow controlled reaction (i.e., step-by-step unfolding).

(4) Addition to the reagent, if necessary, of a depolymerization agent (to cut the structure). (5) Addition to the reagent, if necessary, of a complementary reagent to permit lateral grafting.

(6) Controlled maturation (controlled parameters being time and temperature), (c) Phase Inversion

(7) Preparation of a mixture of a non-solvent liquid for the polymer and a foaming/expanding reagent, soluble in this mixture, and capable of producing a gas by reaction with the dissolution reagent of the base polymer.

(8) Coagulation reaction of (b) in (c) by mixing, film forming of (b) a nd immersion in (c), or extrusion of (b) and (c).

[0032] In some embodiments, the process includes polymerising a polymer solution with or without the addition of one or more of a pro-degradation additive or biodegradable additive; phase inversion and the expansion of the polymer within a solvent containing an expanding reagent; and washing, drying and optionally mixing with one or more of a pro-degradation additive, or biodegradable additive in powder form, to form the fractal polymer or mix of fractal polymers. In some embodiments, in the phase inversion step, a solvent is used which is suitably non-solvent for the polymer, but is a solvent for the expanding reagent. In some embodiments, the washing stage may include the use of a solvent miscible with the previous solvents used.

[0033] When compatible with the solvent used in the polymerisation step, the pro- degradation additives or biodegradable additives can be added at that stage. If not they may be added during a later washing step or alternatively added to a master-batch for forming the final product. The pro-degradation additives and biodegradable additives may be added in solid powder form or in some other form.

[0034] In some embodiments, the fractal polymer or mix of fractal polymers can be made from one or more of polyamides (e.g., polyamide 6, polyamide 6,6, polyamide 4, polyamide 11, polyamide 12 or others), polyesters, cellulosic materials or other polymers. These may be suitable for the manufacture of synthetic semi-permeable membranes by phase inversion. The solvent used may be chosen from the list of solvents for each polymer as established in techniques used for preparation of samples for analysis, as cited in H. Cantow, "Polymer Fractionation," Academic Press: New York, 1967 or in H. Morawetz, "Macromolecules in Solution," John Wiley & Sons, Interscience: New York, 1966. Suitable solvents include 1,2-propylene carbonate, ethylene carbonate, m-cresol, formic acid, dimethyl sulfoxide. The non-solvent may be selected from the above sources. Suitable non-solvents include hexane, methylene chloride and water. In some embodiments, the non-solvent is water.

[0035] Suitable combinations of polymers and solvents which may be used include vinyl polymers (such as polyacrylonitrile) with a 1,2-propylene carbonate (solvent) and hexane (non-solvent) or ethylene carbonate (solvent) and methylene chloride (non- solvent); polyesters such as crystalline polyethyleneteraphthalate with m-cresol (solvent) and hexane (non-solvent), or poly E caprolactam with ethylene carbonate (solvent) and water(non-solvent) or with formic acid (solvent) and hexane (non-solvent); or polyhexamethylene (such as adipamide) with dimethyl sulfoxide (solvent) and water (non- solvent) or with formic acid (solvent) and hexane (non-solvent).

[0036] The fractal polymer or mix of fractal polymers may be in the form of a powder or film. It may have an active surface area greater than about 20,000m²/kg-

[0037] In some embodiments the present invention relates to a master batch comprising a carrier compatible with the first polymer and the fractal polymer or mix of fractal polymers. In some embodiments, the present invention provides a method for mixing and melting the fractal polymer or mix of fractal polymers with a carrier compatible with the first polymer to prepare a master-batch.

[0038] In some embodiments, the present invention provides a method of making a plastic material including mixing the fractal polymer or mix of fractal polymers or the master-batch with a first polymer followed by extrusion, injection moulding, blow moulding or thermoforming to form a product. Suitable products include plastic cups, lids, plates, films, packaging materials and more generally all products obtained by extrusion, injection moulding, blow moulding or thermoforming. [0039] In some embodiments, the present invention provides a method of making a plastic material, suitably of improved degradation and/or biodegradation capability, by creating inside the plastic material a fractal repartition of a pro-degradation additive and/or the biodegradation additive. In these embodiments, the fractal polymer is thought to act as a carrier to create concentration zones of the pro-degradation or biodegradable additive shaped in a fractal form (such as shown in Figure 2). This may permit a faster a nd more complete degradation using a low average concentration and without changing other properties significantly during first use or recycling. During recycling, this geometric effect of fractal repartition will typically disappear during melting and the low concentration of additive ensures that the mechanical properties are maintained.

[0040] In some embodiments, the present invention provides the use of a polymer or polymers with fractal structure to ensure a fractal repartition of one or more commonly used pro-degradation additives or biodegradation additives to improve degradation performance. In some embodiments, this may be achieved by inserting the pro- degradation additive or biodegradable additive into the fractal polymer structure during manufacturing.

[0041] In some embodiments, the present invention provides a method of dispersion of a pro-degradation or biodegradable additive inside a plastic material to achieve a fractal repartition of the additive concentration within the plastic material by use of a fractal polymer or a mix of fractal polymers.

[0042] In some embodiments, the present invention provides a method of making a mix of fractal polymer and a pro-degradation and/or biodegradable additive and a master- batch containing this mix and addition of the mix to a first polymer to achieve a fractal repartition of the additive concentration within the first polymer and the plastic material produced thereby.

[0043] In some embodiments, the present invention provides a method of making a mix of a fractal polymer, one or more of a pro-degradation additive or a biodegradable additive, and a master-batch containing this mix and addition of this mix or master-batch to a first polymer to achieve a fractal repartition of the mix within the first polymer, and the plastics material produced thereby. This may provide a better degradation or biodegradation performance in anaerobic conditions.

[0044] In some embodiments, the present invention provides a method of making a mix of a fractal polymers, one or more of a pro-degradation additive or a biodegradable additive, and a master-batch containing this mix and addition of this mix or master-batch to a first polymer to achieve a fractal repartition of the mix within the first polymer, and the plastics material produced thereby. This may provide a better degradation or biodegradation performance in aerobic conditions.

[0045] The present inventor has found that by providing a fractal polymer within the first polymer, the growth characteristics and colony formation of microorganism may be replicated and as a result faster degradation may occur as in the diffusion limited aggregated growth process characteristic of polymer degradation, colonies grow in a fractal pattern with a very often measurable fractal dimension. Reference is made to "Colony Formation in Bacteria: Experiments and modelling", M. Matsushita et al, Biofilms (2004), 1, pp 305-317.

[0046] The invention will now be described by way of example only having regard to the following examples.

EXAMPLE 1 - NON-LIMITING EXAMPLE OF APPLICATION TO THE PRODUCTION OF BIODEGRADABLE HIGH IMPACT POLYSTYRENE.

[0047] A fractal polymer in the form of poly-epsilon caprolactam was prepared in accordance with the technique described in Australian patent 696330 (see Figure 1). The fractal polymer was then mixed with 4 times its weight of polyamide-12 powder (as a pro- degradation additive) calibrated at 20 microns and 4 times its weight of amylase powder (as a biodegradable additive) calibrated at 20 microns. An EcoPure^® polystyrene based biodegradation additive was then added to the mix and the mix added to High Impact polystyrene before extrusion at a rate of 0.175% mix with 0.7% EcoPure^® additive. The mix was extruded to form a film which was used in thermoforming of lids for polystyrene disposable cups. Tests performed under ASTM D5511-11 method on the finished product showed that anaerobic biodegradation occurred at a rate more than four times the rate shown by the same product containing the same 0.7% concentration of EcoPure^® additive but without any fractal polymer, with the biogas producing period more than doubled before a plateau is observed.

EXAMPLE 2 - NON-LIMITING EXAMPLE OF APPLICATION OF THE PRODUCTION OF BIODEGRADABLE POLYETHYLENE

[0048] A fractal polymer in the form of a poly-epsilon caprolactam/keratin composite was prepared in accordance with the technique described in Australian Patent 696330 by slow dissolution and depolymerisation of a highly crystalline polyamide 6 fibre (polycaprolactam) mixed with a polypeptide as a biodegradable additive (for example a keratin natural product such as a fine micron wool (or another polypeptide)) with continued mixing in the solvent for 24 hours. After phase inversion, washing and drying the fractal polymer composite (illustrated in Figure 2) was mixed with four times its weight of fine denier viscose fibres and the product then micronized by cryo-crushing. The powder obtained was used at 1% in polyethylene to obtain a biodegradable resin to be used in extrusion or injection moulding.

EXAMPLE 3 - TESTING THE ANAEROBIC BIODEGRADABILITY OF MODIFIED HIGH IMPACT POLYSTYRENE CONTAINING FRACTAL POLYMER

[0049] A modified high-impact polystyrene (HIPS) beverage container lid containing 0.02% (200ppm) embedded fractal polymer with 0.7% EcoPure^® additive was subjected to anaerobic biodegradation testing in accordance with ASTM D5511-11 "Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-Digestion Conditions".

[0050] A sample of about 30 kg of compost (inoculum) was obtained. The moisture content of the inoculum was about 72% dry solids.

[0051] The lid was cut into pieces of about 1.5cm x 1.5cm to obtain a sample mass of 12g. A blank sample containing only compost was also prepared and tested to obtain a baseline of biogas production from the inoculum. For comparison, a lid containing a commercial EcoPure^® additive (0.7%) without fractal polymer was also tested. [0052] Testing was performed in a laboratory oven using 2L (2 litre) glass flasks as the incubation vessel. The temperature of the incubation was maintained at a constant 52°C with an ambient temperature ranging from 15-22°C. Temperature measurement throughout the testing indicated a constant temperature was maintained in all sections of the oven for the duration of the test. During incubation, the biogas generated by the process was collected in sealed oxygen proof polyethylene bags and the volume of gas produced was measured by water displacement.

[0053] Over time it was found that the high impact polystyrene container lid containing the fractal polymer produced biogas. The biogas production was relatively constant for the first 30 days; this was followed by a decreased production rate until after 50 days where the production rate increased again. This cycle was repeated after day 100 and the test was terminated after 216 days. The biogas production profile was consistent with the growth cycles of anaerobic bacterial responsible for biogas production. Using data from the amount of biogas obtained from a blank sample, the volume of biogas produced in the test vessel was 4.3L over the test period for the polystyrene lid containing the fractal polymer. This was significantly more than the 1.9L biogas produced over the test period for the lid containing the commercial EcoPure^® additive.

[0054] The percentage biodegradation was calculated based on the total production of biogas (methane and carbon dioxide) relative to the carbon content of the sample. In HIPS, the total carbon content was approximately 91% based on the components, polystyrene (67%) and butadiene rubber (33%). Since 22.4mL of biogas contains lmmol of carbon, the amount of carbon in the produced biogas can be determined and the subsequent percentage biodegradation can be calculated based on the equation:

%biodegradation = (C_s - C_b)/Q x 100

where C_s and C_b are the carbon contents generated by the samples and the blank respectively, and Q is the total mass of the original test specimens.

[0055] The percent biodegradation of the test samples was found to be 24.2% for the lid containing the embedded fractal polymer and 10.2% for the lid containing the EcoPure^® additive. [0056] A Scanning Electron Microscope (SEM) image determined using a JOEL NeoScope (JCM-5000) of a sample, dried overnight and coated with 2nm of gold using a NeoCoater (MP19020NCTR) prior to imaging showed significant microbial growth on the surface of the lid containing the fractal polymer. The growth of bacterial populations appeared to anchor securely on the HIPS surface. The image clearly showed evidence of cocci archaea linked at the surface by a fractal network. The microbial growth was also not restricted to the surface of the HIPS surface but extended to the interior of the polymer suggesting that although the microbial growth originated on the surface, the bacteria were able to penetrate the material to establish growth inside and could ultimately lead to total biodegradation of the material. The microbial growth appeared to follow a fractal pattern which is consistent with the fractal additive promoting fractal growth.

[0057] The foregoing description of preferred embodiments and best mode of the invention known to the applicant at the time of filing the application have been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in the light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.

Claims

1. A degradable or biodegradable plastic material containing a first polymer and at least one fractal polymer.

2. The plastic material according to claim 1 wherein the at least one fractal polymer is present in a concentration of 2% w/w or lower.

3. The plastic material according to claim 2 wherein the at least one fractal polymer is present in a range of 0.01% to 1% w/w.

4. The plastic material according to any one of claims 1 to 3 wherein the first polymer is a polyolefin, a polystyrene, a polyester, a polyamide, an imide or a mixture of any two or more of these.

5. The plastic material according to any one of claims 1 to 4 further comprising a pro- degradation additive and/or a biodegradable additive.

6. The plastic material according to claim 5 wherein the additive is localised in the plastic material with fractal local concentration repartition.

7. The plastic material according to any one of claims 1 to 6 wherein the at least one fractal polymer is a polyamide, polyester, cellulosic material, polyhexamethylene or a vinyl polymer.

8. The plastic material according to any one of claims 1 to 7 wherein the fractal polymer is poly ε caprolactam.

9. A method of making a degradable or biodegradable plastic material comprising mixing a first polymer with a fractal polymer to form a mixture thereof.

10. The method of claim 9 wherein the fractal polymer includes a pro-degradation additive and/or a biodegradable additive within its structure or a pro-degradation and/or a biodegradable additive is added to the mixture.

11. The method of claim 9 or 10 further comprising extruding, injection moulding, blow moulding or thermoforming the mixture.

12. The method of claim 11 wherein the product is selected from a cup, lid, plate, film or packaging material.

13. A degradable plastic material containing a first polymer and a pro-degradation additive with fractal local concentration repartition.

14. A biodegradable plastic material containing a first polymer and a biodegradable additive with fractal local concentration repartition.

15. A method of making a degradable or biodegradable plastic material comprising the step of creating inside a plastic material, a fractal repartition of a pro-degradation additive and/or a biodegradation additive.