A method for the manufacture of a degradable polymer composition, and a kit of parts for said manufacture

Abstract

There is provided a method for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and: (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium; (ii) a second component which is one or more saturated, or mono- or poly-unsaturated C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof; (iii) a third component which is a rubber, preferably a synthetic rubber; (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the method comprising: a) providing a heat- extruded pelletised first composition (A); b) providing a non-heat-treated, compacted pelletised second composition (B); c) providing a co-polymer or homopolymer of polyethylene and / or polypropylene third composition (C), d) optionally, providing a liquid fourth composition (D), e) coextruding the first composition (A), the second composition (B), the third composition (C) in a weight ratio of: 0.5<A<1.5 to 0.5<B<1.5 to C>4, and, when present, the fourth composition (D) in the ratio 0.05<D<0.8; wherein the first composition (A) comprises, based on the weight of the first composition (A): the third component (iii) in an amount of from 5 to 40wt%, less than 25wt% total of the second component (ii) and fourth component (iv), and a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B): the first component (i) in an amount of at least 20wt%, and at least 20wt% total of the second component (ii) and fourth component (iv); and wherein the liquid fourth composition (D) comprises or consists of the second component (ii).

Description

[0001] A method for the manufacture of a degradable polymer composition, and a kit of parts for said manufacture

[0002] The present invention relates to a method for the manufacture of a degradable polymer composition and, in particular, to a method that uses a heat-extruded pelletised first composition (A), a non-heat-treated, compacted pelletised second composition (B), a copolymer or homopolymer of polyethylene and / or polypropylene third composition (C), and, optionally, a liquid fourth component (D). The invention also relates to a kit of parts suitable for use in said method. The degradable polymer composition formed by the method can be a final polymer composition or a masterbatch (i.e. a concentrated form for inclusion during the manufacturer of further polymer).

[0003] Polymer materials have many benefits and can provide strong, chemically and biologically inert materials at relatively low cost. However, the use of polymer materials has led to a build-up of waste in the natural environment which has negative impacts on the ecosystem. There is growing demand to reduce the amount of non-degradable waste, such as packaging, being disposed of in landfill sites. Exemplary degradable polymer compositions suitable for adaption for use in this invention are described in WO 2018 / 095905 A1 . Other degradable polymer compositions are described in US 3935141 A, US 5416133, and US 2003 / 0236325.

[0004] As the demand for degradable polymer-based products increases, improved methods of manufacturing these products are required. In particular, there is a need for improved methods for large scale manufacture of degradable polymer compositions that consider the nature of the components (including their stability and sensitivity to moisture), the quality of the resulting end product, and the complexity of the production process.

[0005] Accordingly, it is desirable to provide a method that simplifies local production of a degradable polymer composition (or any intermediate masterbatch), that does not negatively impact or deactivate any of the active components, and which allows preparation, storage, and transportation of the key ingredients for preparing a degradable polymer composition without affecting the quality and functionality of the end polymer composition.

[0006] According to a first aspect there is provided a method for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and: (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium

[0007] (ii) a second component which is one or more saturated, or mono- or polyunsaturated, (preferably linear) C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof;

[0008] (iii) a third component which is a rubber, preferably a synthetic rubber;

[0009] (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the method comprising: a) providing a heat-extruded pelletised first composition (A), b) providing a non-heat-treated, compacted pelletised second composition (B), c) providing a co-polymer or homopolymer of polyethylene and / or polypropylene third composition (C), and d) optionally, providing a liquid fourth composition (D), e) coextruding the first composition (A), the second composition (B), and the third composition (C) in a weight ratio of: 0.5<A<1 .5 to 0.5<B<1.5 to C>4, and, when present, the fourth composition (D) in the ratio 0.05<D<0.8; wherein the first composition (A) comprises, based on the weight of the first composition (A):

[0010] • the third component (iii) in an amount of from 5 to 40wt%,

[0011] • less than 25wt% total of the second component (ii) and fourth component (iv), and

[0012] • a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B):

[0013] • the first component (i) in an amount of at least 20wt%, and

[0014] • at least 20wt% total of the second component (ii) and fourth component (iv); and wherein, when present, the liquid fourth composition (D) comprises or consists of the second component (ii).

[0015] According to a preferred embodiment, the method may not include the optional liquid fourth composition (D). There is also provided a method for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and: (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium,

[0016] (ii) a second component which is one or more saturated, mono- or poly-unsaturated, (preferably linear) C14-C24 (preferably C16-C20) carboxylic acid, or an ester, anhydride or amide thereof;

[0017] (iii) a third component which is a rubber, preferably a synthetic rubber;

[0018] (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the method comprising: a) providing a heat-extruded pelletised first composition (A), b) providing a non-heat-treated, compacted pelletised second composition (B), c) providing a copolymer or homopolymer of polyethylene and / or polypropylene third composition (C), d) coextruding the first composition (A), the second composition (B) and the third composition (C) in a weight ratio of: 0.5<A<1.5 to 0.5<B<1.5 to C>4; wherein the first composition (A) comprises, based on the weight of the first composition (A):

[0019] ■ the third component in an amount of from 5 to 40wt%,

[0020] ■ less than 25 wt% total of the second and fourth components, and

[0021] ■ a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B),

[0022] • the first component in an amount of at least 38wt% and

[0023] • at least 20wt% total of the second and fourth components.

[0024] The present invention will now be further described. In the following passages different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0025] The inventors have been providing a masterbatch to their clients for several years based on the teaching of EP 3545032. Within the scope of the composition disclosed therein, specific amounts of the components are optimised in each instance depending on the precise requirements of their customers, such that, for example, the balance will be different and optimised for an agricultural fleece compared to a yoke for holding together cans. Until now, the inventors have been undertaking manufacture of the masterbatch at a central manufacturing location, forming the masterbatch from the constituent ingredients themselves. However, as the demand for the masterbatch and degradable products has significantly increased, it has become necessary to increase the number of production sites and to encourage degradable polymer compositions to be manufactured worldwide. The complex requirements for handling and mixing the raw materials is a considerable hurdle to this scaling up of the production process.

[0026] The inventors have therefore sought to provide an approach that facilitates this scale up in the number of production sites, without compromising on the product consistency or quality, and without requiring considerable local knowledge on the mixing processes and safe raw material handling requirements. That is, the inventors were seeking a suitable approach for allowing fast scale up involving third parties having limited knowledge of the handling requirements of the raw materials.

[0027] The inventors tried a number of different approaches to achieve this, including providing the ingredients as separate dry components. However, this does not reduce the amount of local knowledge required in material safety procedures. They tried providing a more concentrated masterbatch and having third parties dilute this. However, they found that some of the components could not be added in higher concentrations and remain processable.

[0028] The inventors tried coextruding the active ingredients with minimal carrier, but found that this did not form a stable pellet with sufficient structural integrity. This made the product very difficult to work with. There was also the possibility of undesirable reactions occurring at the higher concentrations. They tried dividing the active ingredients into two distinct masterbatch components, but the thermal extrusion process still caused degradation problems.

[0029] Surprisingly, the present inventors have found that they can provide a consistent masterbatch (or go straight to the final polymer composition) using three (or four) components / compositions. The first composition includes the more thermally stable active components. The second composition includes the more thermally sensitive components. The third component is additional carrier because the first and second compositions can be stably formed with higher-than-normal levels of the active component. Through the use of these three (or four) separate components and specific pelletising steps for the first and second compositions, the inventors can allow third parties to reconstitute a masterbatch (or the final product) safely, with minimal local knowledge of the material handling requirements. The inventors have, in particular, found that a non-thermal compaction method should be used to preserve the processibility of the thermally sensitive components, which allows the second composition to be stored, transported, and then further processed to form a masterbatch, or the final product, without losing any of the activity of these thermally sensitive components. The inventors also found that their solution provides enhanced stability compared to other contemplated approaches with reduced need for thermal processing and avoiding the risk of undesirable reaction mechanisms.

[0030] This general approach ensures safe handling of the composition since the components are provided in a readily handleable format. In particular, the separate compositions / components can be supplied and shipped separately, and then added together in a desired ratio. In adopting this approach the inventors found that there were key decisions to be taken regarding which components should be included in which composition, and also the relative amounts that could be included for stable storage and consistent formation of the final product.

[0031] The method of the present invention is for the manufacture of a degradable polymer composition. The term degradable polymer (composition) refers to synthetic polymer compositions which break down into CO2, H2O, biomass and inorganic salts under aerobic terrestrial conditions.

[0032] The degradable polymer composition comprises a copolymer or homopolymer of polyethylene and / or polypropylene. The degradable polymer composition can comprise more than one copolymer and / or homopolymer of polyethylene and / or polypropylene. The degradable polymer composition may, in addition, include other types of polymer that are not ethylene-based or propylene-based. The copolymer or homopolymer of polyethylene and / or polypropylene forms the majority of the composition, such as preferably at least 50wt%, more preferably at least 60 wt.%, and even more preferably at least 70 wt.%. When the degradable polymer composition is a masterbatch, preferably the copolymer or homopolymer of polyethylene and / or polypropylene forms less than 90 wt.%, preferably less than 80 wt.% of the composition.

[0033] The term “Polymer” means a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term “polymer” embraces the terms “homopolymer,” “copolymer,” “terpolymer” as well as “interpolymer”. The polymers employed in the invention comprise repeat units of the general formula -[CH2CRR’]-, preferably wherein R and R’ are individual selected from the list comprising hydrogen, methyl, ethyl, acetate, methyl methacrylate, vinyl alcohol and acrylic acid.

[0034] A “homopolymer” means that the polymer is prepared by the polymerization of only one type of monomer. “Interpolymer” means a polymer prepared by the polymerization of at least two different types of monomers. The generic term “interpolymer” includes the term “copolymer”. A “copolymer” refers to a polymer prepared from two different monomers.

[0035] Non-limiting examples of homopolymers and copolymers of polyethylene include ultralow, low, linear low, medium, high and ultrahigh density polyethylene (i.e. ULDPE, LDPE, LLDPE, MDPE, HDPE, UHDPE). Equivalent homopolymers and copolymers of polypropylene, such as ULDPP, LDPP etc. are available.

[0036] The copolymers of polyethylene comprise a majority amount of ethylene monomers, and the copolymers of polypropylene comprise a majority amount of propylene monomers. By majority amount, it is meant at least 50 wt.%, preferably at least 60 wt%, more preferably at least 70, or 80 wt.%, and most preferably at least 90 wt.%. Homopolymers are the most preferred polymers.

[0037] Preferably, the copolymer or homopolymer of polyethylene and / or polypropylene forms the balance of the degradable polymer composition along with the listed components. That is, preferably the degradable polymer composition consists of the copolymer or homopolymer of polyethylene and / or polypropylene and the listed components. However, the degradable polymer composition may further include up to 5 wt.% of other organic ingredients, more preferably less than 1 wt.%, most preferably the degradable polymer composition is essentially free of further organic ingredients or impurities. The degradable polymer composition may further include up to 50wt% inorganic material such as inert filler materials, preferably less than 10 wt.%, more preferably less than 1wt%, and most preferably the degradable polymer composition is essentially free of further inorganic ingredients or impurities. The presence of fillers is particularly likely when considering the final polymer product and not a masterbatch. In particular, the degradable polymer composition preferably consists of the homopolymer or copolymer of polyethylene and / or polypropylene, and components (i) to (iv).

[0038] As will be appreciated, the copolymer or homopolymer of polyethylene and / or polypropylene are present in the degradable polymer composition as the first carrier material and as the third composition (C). In each case the copolymer or homopolymer of polyethylene and / or polypropylene may be the same or different from each other. Although we have referred to the third composition (c) as a “composition”, it preferably substantially consists of the copolymer or homopolymer of polyethylene and / or polypropylene.

[0039] The degradable polymer composition comprises a first component, (i), which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium, preferably wherein the compound is a transition metal stearate.

[0040] The following description uses the term transition metal to refer to any of the metallic elements of groups IVB-VIII, IB, and IIB, or 4-12 in the periodic table. Preferred transition metals are iron, manganese, copper, cobalt and cerium. These compounds catalyse the degradation of the polymer composition.

[0041] The one or more transition metal compounds are included in such an amount as to provide the desired degradation properties. However, including large amounts of transition metal increases the cost of the degradable composition.

[0042] Preferably, only one transition metal compound is present. When two or more transition metal compounds are present, they are selected from iron, manganese, copper, cobalt and cerium compounds and the transition metals in the two or more transition metal compounds are preferably different.

[0043] By ‘transition metal compounds’ it is meant the transition metal compound when formed as a salt (i.e. with one or more ligands). For example, iron could be provided as iron stearate (i.e. the salt of Iron and stearic acid). Further references to the amount of the transition metal compound (in wt.%) refer to the amount when in a salt.

[0044] Preferably, the ligands of the metal compounds are inorganic ligands and / or saturated organic ligands. Preferably the organic ligands are C6-C20 and are mono- or di-functional. Examples include carboxylic acids, acetylacetone, triazacyclononane and the like. Preferably the transition metal compounds comprise moieties selected from stearate, carboxylate, acetylacetonate, triazacyclononane or combinations of two or more thereof.

[0045] Certain non-ionic ligands that play an active role in the degradation may also be included. Where present, the non-ionic ligands are preferably selected from amines, imines, amides, phosphites, phosphines, and carbenes. Such non-ionic ligands can have an advantageous effect on the degradation rate of the composition whilst maintaining the essential material properties. When present, non-ionic ligands preferably constitute at least 5% of the ligands and preferably up to 50% of the ligands, preferably 10 to 40% of the ligands.

[0046] Preferably, the transition metal ligands are chosen in order to make the transition metal physically and chemically compatible with the polymer. Ligand selection may affect the transition metal’s catalytic activity. The ligands may be chosen to make the metal compatible with the particular polymer used and to control the degradation rate of the polymer composition.

[0047] The temperature of the polymer composition as well as its exposure to light may also affect its degradation rate. The choice of transition metal can be used to further tune these effects to suit the end purpose. For example, iron is a more efficient photo catalyst whilst manganese is a more efficient thermal catalyst of the degradation process. The transition metal component may, therefore, be selected to tune the degradation rate depending on the expected exposure to heat and light of a particular product.

[0048] Specific transition metals may have effects on the properties of the polymer composition. For example, iron compounds may colour the polymer composition.

[0049] Additionally, other metals such as copper advantageously increase the degradation rate but may make the polymer composition unsuitable for certain applications such as use as a food wrap, due to its toxicity. Accordingly, in colour sensitive compositions iron may be avoided, whereas if the product is for use in the food industry copper may be avoided. The selection of one or more appropriate transition metal compounds depends on the final product that is to be made.

[0050] The degradable polymer composition comprises (ii) a second component which is one or more saturated, mono- or poly-unsaturated, (preferably linear) C14-C24 (preferably C16 - C20) carboxylic acid, or an ester, anhydride or amide thereof. Preferably the second component contains at least a saturated (preferably linear) C14-C24 (preferably C16 -C20) carboxylic acid, or an ester, anhydride or amide thereof. Preferably the saturated species forms at least 20wt%, preferably at least 40wt%, more preferably at least 60 wt% and most preferably 80wt% or even all of the second component (by weight of the second component). Therefore, the second component may comprise one or more saturated species, or one or more unsaturated species, or a mixture of both. The following description uses the term carboxylic acid to refer to the range of molecules containing a carboxylic acid -(COOH) moiety. The carboxylic acid(s) of the present invention can be saturated (i.e. have only single carbon-carbon bonds), or be mono- or polyunsaturated (i.e. have one or more double carbon-carbon bonds along its carbon backbone) or a mixture thereof. It has a carbon backbone containing between 14 and 24 (preferably 16 and 20) carbon atoms. It can have at least one double bond in the carbon backbone. The carbon backbone of the carboxylic acid may be linear, branched or aromatic, but is preferably linear. Preferably the saturated, mono- or poly-unsaturated carboxylic acid is a C16-C20 carboxylic acid. Preferred carboxylic acids are palmitic, stearic, behenic, oleic, linoleic and cinnamic.

[0051] Alternatively, the degradable polymer composition comprises an ester, anhydride or amide of a saturated, or mono- or poly-unsaturated C14-C24 (preferably C16-C20) carboxylic acid.

[0052] The carboxylic acid or an ester, anhydride or amide components are preferably “free” or “non-coordinated”, in the sense that they do not form a part of a transition metal compound.

[0053] Where the degradable polymer composition comprises an ester of a saturated, or mono- or poly-unsaturated C14-C24 (preferably C16-C20) carboxylic acid the alcohol component preferably comprises a C1-C30 alcohol, more preferably a saturated straight chain C1-C30 alcohol.

[0054] Where the degradable polymer composition comprises an anhydride of a saturated, or mono- or poly-unsaturated C14-C24 (preferably C16-C20) carboxylic acid, the anhydride may or may not be symmetrical. The second carboxylic acid component preferably comprises a C1- C30 carboxylic acid, more preferably a saturated straight chain C1-C30 carboxylic acid.

[0055] Where the degradable polymer composition comprises an amide of a saturated, or mono- or poly-unsaturated C14-C24 (preferably C16-C20) carboxylic acid the amide may be a primary, secondary or tertiary amide. Where a secondary or tertiary amide is present, each of the carbon chains preferably comprises from 1 to 30 carbon atoms, more preferably each carbon chain is a C1-C30 alkyl group.

[0056] Unless otherwise specified, where features of the carboxylic acid are discussed in this description it is intended to also encompass the ester, anhydride or amide thereof. The degradable polymer composition comprises (iii) a third component which is a rubber, preferably a synthetic rubber. The following description uses the term rubber to refer to viscous, elastic polymers. Rubbers are amorphous polymers which exist at temperatures above their glass transition temperature. Preferably, the rubber of the present invention is an unsaturated rubber. Preferably, the unsaturated rubber is one or more copolymers of isobutene and isoprene, and / or a polybutadiene and / or styrene-butadiene-styrene, and / or a natural rubber.

[0057] Natural rubber is generally supplied as a latex emulsion that requires evaporation of the liquid to remove the solvent. Natural rubber can be sticky and difficult to extrude, so can be blended with other synthetic rubbers or appropriate supplements to overcome this difficulty. The natural rubber can be cis or trans natural rubber, and preferably the natural rubber comprises, or consists of trans natural rubber.

[0058] Natural rubber is often called ‘Indian rubber’, ‘latex’, or ‘Amazonian rubber’, and consists of polymers of the isoprene, with minor impurities of other organic compounds. It can be harvested from various natural sources, such as the Gutta-percha tree or the Para rubber tree, or other appropriate sources. In contrast, synthetic rubber is ‘human-made’.

[0059] Preferably, the rubber of the present invention is a synthetic rubber that comprises polyisoprene, styrene-isoprene (SI), styrene-isoprene-styrene (SIS), or a blend of two or more thereof.

[0060] The rubber content may improve the mechanical properties of the polymer composition. Additionally, rubbers are generally less chemically stable than the bulk polyolefin. Accordingly, the rubber content may improve the degradation rate without adversely affecting the physical properties of the polymer. In this way it seems to act as a co-catalyst.

[0061] Advantageously, the presence of the rubber in the polymer composition improves the elasticity. This may help to counteract the embrittlement of the polymer composition caused by the other added components.

[0062] The degradable polymer composition comprises (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers.

[0063] Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. Antioxidants act as radical scavengers and remove peroxy radicals, as well as alkoxy radicals, hydroxyl radicals and alkyl radicals. They can also act to remove organic hydroperoxides formed during the degradation process. The inclusion of one or more antioxidants may delay the onset of degradation increasing the shelf-life of a product.

[0064] The degradable polymer composition preferably comprises at least one antioxidant and at least one acid scavenger. More preferably the degradable polymer composition comprises at least a primary and a secondary antioxidant. Most preferably, the degradable polymer composition comprises a phenolic antioxidant stabiliser, a phosphite antioxidant stabiliser, and an acid scavenger.

[0065] Phenolic antioxidant stabilisers are well known in the art and include, for example, Irganox 1076 (octadecyl-3, 5-di-tert-butyl-4-hydroxyhydrocinnamate). Phenolic antioxidant stabilisers are generally known to be primary antioxidants and remove free radicals to slow down degradation of the polymer composition.

[0066] Phosphite antioxidant stabilisers are also well known in the art and include, for example, Irgafos 168 (Tris(2,4-di-tert-butylphenyl) phosphite). Phosphite antioxidant stabilisers are generally known as secondary antioxidants and remove the organic hydroperoxides.

[0067] An acid scavenger is a chemical added to remove or deactivate impurities and unwanted reaction products. An acid scavenger neutralizes acid residues which may delay the onset of degradation increasing the shelf-life of a product and the period in which the product may be recycled in existing polyolefin recycling streams. The acid scavenger together with the one or more antioxidant stabilisers forms the stabilising system that acts to delay degradation and enable it to be balanced so that the product has a desired shelf life and can have appropriate durability and functionality before the onset of degradation.

[0068] Examples of suitable acid scavengers include metal oxides such as calcium oxide, magnesium oxide, and zinc oxide, layered hydroxide minerals such as hydrotalcites, or metal salts such as calcium, magnesium and zinc stearate. When calcium oxide is present, it is present in an amount of from 0 to 1wt%, preferably from 0 to 0.4wt%, more preferably from 0.1 to 0.3 wt% (based on the weight of the final polymer). The following description uses the term calcium oxide to refer to the crystalline solid with the chemical formula CaO. Advantageously calcium oxide reacts with and immobilises water in the composition. This stabilises the composition during processing and may reduce the occurrence of blemishes and discoloration of the final product. The degradable polymer composition may consist of components (i) to (iv), one or more copolymers and / or homopolymers of polyethylene and / or polypropylene, and / or starch and / or calcium oxide, and / or an oxygen generating species.

[0069] The method comprises step (a) of providing a heat-extruded pelletised first composition (A). Extrusion is a process where the ingredients are melted and formed into a continuous profile. In a typical extrusion process, the ingredients are fed from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten mixture is then forced into a die, which shapes the mixture into a shape that hardens during cooling.

[0070] The standard equipment for heat extrusion is a screw extruder, and in particular a twin-screw extruder. This step provides a relatively uniform composition, meaning a consistent composition across each pellet. The material is formed into pellets following, or during, the heat extrusion process. The pellets are often known as “nurdles” and are a typical size and shape of polymer pellets, such as about 1 to 5 mm in diameter. The temperature of heat extrusion is generally above 100 °C, and preferably at least 150 °C. The materials in the composition (A) are heat-resistant and can withstand the high temperatures experienced in the heat treatment process.

[0071] The first composition (A) comprises, based on the weight of the first composition (A), the third component in an amount of from 5 to 40wt%, less than 25wt% total of the second and fourth components, and a first carrier material which is a co-polymer or homopolymer of polyethylene and / or polypropylene. Most preferably, composition (A) consists of 5 to 40 wt.% of the third component, from 5 to 20 wt.% of a combination of the second and fourth components, and the first carrier material. The first carrier material most preferably makes up the remaining amount of the first composition (A). The components used to form the first composition (A) are typically provided in a dry (i.e. solvent-free), powder form, although some ingredients may be provided in liquid form (e.g. the second component).

[0072] Preferably both the second and fourth components are present. However, especially when the optional liquid fourth composition (D) is present which comprises or consists of the second component, the first composition (A) may be free from the second component.

[0073] This combination of components is heat resistant and can be subjected to the heat extrusion process without impacting the properties and functionality of the components contained therein. The heat-sensitive transition metal compound (i.e. the first component) is preferably not present (i.e. preferably the first composition (A) is free of the first component (i)). The third component should be included in an amount of from 5 to 40 wt.% in order to have the correct bulk density with the polymer carrier material, and still be processible. If the amount of the third component is too high, then thermal degradation may start to occur during the thermal processing. The presence of the second and fourth components aids in masking the specific recipe of the final composition and provides the pellets of composition (A) with an appropriate structural integrity.

[0074] The method comprises step (b) of providing a non-heat-treated, compacted pelletised second composition (B). The second composition is preferably the same, or a similar, size and shape to the pellets of composition (A) (i.e. nurdles). The second composition is compacted in a manner that does not include heat treatment (i.e. is not heated before or during compaction), and generally occurs at room temperature. This technique is a powder compaction technique, also referred to as “polycompaction” herein and involves dry compaction of suitable powder materials. Powder compaction approaches are well known in technical fields such as preparing pharmaceutical pills and tablets. Equipment for polycompaction processes is available on the market, such as from Polytechs. The compaction preferably takes place in the absence of any polymer, and it has a number of advantages including: improved working conditions and safety (no handling of powder and no dust), high dosing accuracy due to constant ratio of different ingredients, constant and regular feeding, and good final dispersibility. The technique broadly involves subjecting the powder ingredients under sufficient pressure to form a cohesive pellet. Exemplary pressures are 1 kN I cm2to 60 kN I cm2. Compacting can take place under a vacuum. More information on suitable equipment and conditions may be found in US2006226404, which is incorporated herein by reference.

[0075] The second composition (B) is heat sensitive, and so subjecting the components of the second composition (B) to heat treatment would deactivate and negatively impact the first component (i). Once incorporated into the final polymer product, the transition metal would, therefore, be unable / less able to catalyse the degradation of the polymer composition sufficiently. Therefore, it is important that the first component (i) be processed in such a manner that does not affect its function in the end polymer product.

[0076] The second composition (B) comprises, based on the weight of the second composition (B), the first component in an amount of at least 20wt%, preferably at least 35wt%, more preferably at least 40wt%, and at least 20wt% total of the second and fourth components. The fourth component in the second composition (B) can be the same or different to the fourth component in the first composition (A). Preferably, the stabilising system (component (iv)) in the second composition (B) is different to the stabilising system (component (iv)) in the first composition (A).

[0077] Preferably both the second and fourth components are present. However, especially when the optional liquid fourth composition (D) is present which comprises or consists of the second component, the second composition (B) may be free from the second component.

[0078] The active transition metal compound is present in an amount of at least 20 wt.% up to a maximum of 80 wt.%. The first component must be less than or equal to 80 wt.% in order for the components to hold together sufficiently. If greater than 80 wt.% of the first component is present, then the pellet is vulnerable to collapse, and parts may fragment. This negatively impacts the components as well as the storage and transport of the pellets. PE or PP powder as used in composition (A) may be added in the second composition (B) to dilute the levels in the mixture for polycompaction. Levels of PE or PP powder may be up to 40wt% of the second composition (B), preferably less than 30wt%, preferably less than 20wt%. In some embodiments there is at least 1wt% PE or PP powder, preferably at least 5wt% and more preferably at least 10wt%. Suitable PE or PP powder is described below as the third composition (C).

[0079] Furthermore, the pellet should be held together with sufficient integrity and rigidity to ensure that it is protected from moisture. If moisture contacts a significant surface area of the components in the second composition (B), then the properties of the first component are negatively affected, resulting in the degradability of the end product being negatively affected.

[0080] The method includes the step (c) of providing a copolymer or homopolymer of polyethylene and / or polypropylene third composition (C). The copolymer of homopolymer of polyethylene and / or polypropylene is defined in the same way as above in relation to the copolymer or homopolymer in the degradable polymer composition. The pelletised copolymer or homopolymer of polyethylene and / or polypropylene component makes up the additional polymer component that is to be mixed with the first composition (A) and the second composition (B) to form the final diluted product, or a diluted intermediate product, such as a masterbatch, for further dilution to the final polymer product. The third composition (C) can be the same or different to the first carrier material in the first composition (A) or any PP / PE powder added to the second composition (B). The third composition (C) generally forms the bulk of the degradable polymer composition.

[0081] The third composition (C) can be provided in pelletised form. The pellets can be any appropriate size or shape, like the pellets of the first and second compositions (A) and (B). Again, they can be considered as “nurdles”. They can be cylindrical in shape, with a diameter of, for example, 1 to 5mm, and a length up to 1cm. Any appropriate polymer, or mixture of polymers, falling within the above definition of “copolymer or homopolymer of polyethylene and / or polypropylene” can be used, and is generally commercially available on a large scale. Alternatively, the third composition (C) can be provided as a powder.

[0082] The method may further comprise providing a liquid fourth composition (D) which comprises or consists of the second component (ii). Preferably the liquid fourth composition (D) comprises, based on the weight of the fourth composition (D), the second component (ii) in an amount of 80 to 100 wt%. Alternatively, the second component (ii) may be provided dissolved and / or suspended in a solvent in an amount of 60 to 80 wt%, the balance being the solvent, such as white mineral oil.

[0083] Finally, step (d) requires coextruding the first composition (A), the second composition (B) and the third composition (C) in a weight ratio of: 0.5<A<1.5, 0.5<B<1.5 and C>4. When present, the fourth composition (D) in the ratio 0.05<D<0.8, preferably 0.2<D<0.8. This means, for example, that the compositions (A) and (B) are typically present in similar amounts (-1:1) with the third composition being present in a much larger proportion (>4). When the second component (ii) is added as a separate liquid component (the fourth composition (D)), this is typically present in a smaller amount, relative to A or B.

[0084] The co-extruding step uses an extrusion process as described above for step (a). In particular, extrusion is a process where the ingredients are melted and formed into a continuous profile. In a typical extrusion process, the ingredients are fed from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten mixture is then forced into a die, which shapes the mixture into a shape that hardens during cooling.

[0085] The standard equipment for heat extrusion is a screw extruder, and in particular a twin-screw extruder. This step provides a relatively uniform composition, meaning a consistent composition is formed through the end material. The temperature of the extrusion process in step (d) is typically between 180 and 250°C.

[0086] Composition (A), composition (B) and composition (C) are all combined and coextruded (i.e. extruded together) which results in uniform mixing of each of the components in the final polymer product. They are provided in the weight ratio of 0.5<A<1 .5, 0.5<B<1 .5 and C>4 (and, when present, 0.05<D<0.8). In particular, composition (C) is present in the largest ratio, as this forms the bulk of the end product (or intermediate masterbatch). Compositions (A) and (B) are generally provided in similar ratios, although the specific ratio can be tweaked to provide products with slightly different properties, such as tailored degradation rates.

[0087] In one embodiment, the degradable polymer composition is a masterbatch for adding to bulk polymer to render it degradable, wherein in the ratio, C<10, or preferably C<8. In this ratio, the polymer composition (C) is added in a majority amount, but is limited such that it provides a masterbatch that requires further dilution to form the end product. The Masterbatch contains the active ingredients in an amount that is too high for the desired properties of the end product. Such a masterbatch is useful for bulk production of polymer, and portions of the masterbatch can be mixed with different polymers to produce different end products. Such a masterbatch is preferably subsequently used to form a final polymer wherein the masterbatch forms from 0.5 to 4wt% of the final polymer, preferably 1 to 2.5wt% (with the balance being a diluting polymer).

[0088] In one embodiment, the degradable polymer composition is ready for extrusion as a final polymer product, wherein in the ratio, C>50, preferably C>100, and more preferably C>200. The ratio, C, can even be >300.

[0089] In this ratio, (C) forms the vast majority of the composition, diluting the active ingredients to the desired end amounts. This process enables faster and more direct manufacture of the end product.

[0090] Preferably, the final polymer product comprises:

[0091] (i) The first component in a total amount of from 0.03 to 0.6 wt.%, preferably 0.10 to 0.6 wt.%;

[0092] (ii) The second component in an amount of from 0.01 to 0.3 wt.%, preferably 0.02 to 0.08 wt.%; (iii) The third component in an amount of from 0.02 to 0.2 wt.%, preferably 0.03 to 0.2 wt.%; and

[0093] (iv) The fourth component in an amount of from 0.005 to 0.45 wt.%, preferably 0.005 to 0.35 wt.%.

[0094] The amounts of the components (i) to (iv) are the preferred amounts for the end polymer product to have a long enough shelf life to be useful (typically 1-3 years), but to then begin degradation after the programmed service life. The specific degradation properties can be tuned by tweaking the amounts of components (i) to (iv) in the first and second polymer compositions (A) and (B).

[0095] Including more than 0.6 wt.% of the first component can result in degradation that happens too quickly, shortening the lifespan of the product too much. It can also negatively impact the properties of the end product. An amount of less than 0.03 wt.% results in the degradation being too slow / not effective in degrading the entire product.

[0096] Including more than 0.3 wt% saturated, or mono- or poly-unsaturated C16-C20 carboxylic acid may cause the polymer to be excessively air sensitive. Conversely, including less than 0.01 wt.% saturated, or mono- or poly-unsaturated C16-C20 carboxylic acid may lead to a negligible degradation rate.

[0097] Including less than 0.02 wt.% rubber may lead to the polymer being excessively brittle and unsuitable. Including more than 0.2% rubber may lead to rapid degradation rates and may adversely affect the material properties of the polymer. Additionally, it is believed that the rubber content increases the degradation rate without the need to increase the transition metal or carboxylic acid content.

[0098] Preferably, step d) further comprises grinding at least the second composition (B) before mixing with the first composition (A) and the third composition (C), and coextruding (optionally with liquid addition of fourth composition (D) thereafter). This makes the first composition (A) easier to process and gives a more uniform spread of the active components in the final product. The process may comprise grinding both the first composition (A) and the second composition (B) before mixing with composition (C) and coextruding to form the degradable polymer composition. It may even include grinding all of the compositions (A), (B) and (C) before coextruding these compositions / components.

[0099] Preferably, the fourth component (iv) comprises: (I) a primary antioxidant, most preferably a phenolic antioxidant stabiliser;

[0100] (II) optionally a secondary antioxidant, most preferably a phosphite antioxidant stabiliser; and

[0101] (III) a mineral acid scavenger.

[0102] The fourth component in the first composition (A) preferably comprises, or consists, of a phenolic antioxidant stabiliser and a mineral scavenger. The fourth component in the second composition (B) preferably comprises, or consists of, both a phenolic and a phosphite antioxidant stabiliser, and a mineral scavenger. This provides the ideal system for stabilising each composition for the relevant processes (i.e. extrusion or polycompaction).

[0103] Preferably, the first composition (A) comprises the third component, optionally the second and / or fourth components, and wherein the balance is the first carrier material. More preferably, the first composition (A) comprises the third component, at least one of the second and fourth components, with the balance being the first carrier material, and even more preferably the second, third and fourth components, with the balance being the first carrier material. In other words, the first composition preferably consists of the second component, third component, fourth component, and the first carrier material. The absence of any ingredients that negatively affect the properties of the composition is beneficial.

[0104] Preferably, the first composition (A) comprises: the third component in an amount of 5- 35wt%, preferably 10 to 30 wt.%, more preferably 10 to 20 wt.%; and / or the second component in an amount of 1-10wt%, preferably 3-7 wt.% (or as low as 0% when forth composition (D) is included); and / or the fourth component in an amount of 1-15wt%, preferably 4-8 wt.%. Preferably, the balance is the first carrier material, and more preferably the first carrier material makes up from 50 to 88 wt.%, preferably 60 to 85 wt.%, more preferably 70 to 80 wt.%, of the first composition (A). These amounts provide the optimum ratio of components to form a stable composition that can form pellets with the desired bulk density and structural integrity.

[0105] Preferably, the second composition (B) comprises: the first component in an amount of 20- 80wt%, preferably 30-70wt%, more preferably 35-60 wt.%; and / or the second component in an amount of 0-25wt%, preferably 1-15wt.%; and / or the fourth component in an amount of 10-80 wt.%, preferably 20-70 wt.%, more preferably 45-65 wt.%. These amounts are preferred for providing a composition that can withstand the polycompaction technique to produce pellets with sufficient structural integrity and resistance to water (i.e. a low sensitivity to water). Preferably, the heat-extruded pelletised first composition (A) is obtained in the steps of melting and extruding the first composition (A) at a temperature of from 150 to 250 °C, preferably from 200 to 225 °C. This is the ideal temperature for efficiently operating the extrusion process to provide the desired pelletised product. A lower temperature would make the process slower and may not sufficiently melt the composition, and a higher temperature would begin to have deleterious effects on the components in the composition, resulting in compounds beginning to degrade.

[0106] Preferably, the non-heat-treated compacted pelletised second composition (B) is obtained in the steps of: forming a dry mixture of the second composition (B); and compacting the dry mixture to form pellets at a temperature of less than 70°C, preferably less than 30°C.

[0107] Preferably, the pellets of the first composition (A), and / or the second composition (B) and / or the third composition (C), are substantially cylindrical and have a diameter of at least 3 mm and a length of at least 1 cm. More preferably, the diameter is from 3 to 5 mm, and most preferably about 4 mm. This size is ideal for processing and transporting.

[0108] Preferably, the method comprises mixing the masterbatch obtainable as described above, together with further polymer material, preferably further polypropylene or polyethylene, preferably a homopolymer or copolymer of polyethylene and / or polypropylene. Such a step can easily produce the desired end product using a concentrated masterbatch, without affecting the properties of the active ingredients.

[0109] Preferably, step (d) of coextruding the first composition (A), the second composition (B) and the third composition (C) is performed by adding the second composition (B) directly to the main hopper (i.e. not through any side feed inlet) of the extrusion device. This step was found to lead to an improved product with better thermal stability.

[0110] According to a further aspect of the invention there is provided a kit of parts for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and:

[0111] (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium,

[0112] (ii) a second component which is one or more saturated, mono- or poly-unsaturated (preferably linear) C14-C24 (preferably C16 -C20) carboxylic acid, or an ester, anhydride or amide thereof;

[0113] (iii) a third component which is a rubber, preferably a synthetic rubber; (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the kit comprising: a) a heat-extruded pelletised first composition (A); b) a non-heat-treated, compacted pelletised second composition (B); c) a copolymer or homopolymer of polyethylene and / or polypropylene third composition (C), wherein the first composition (A) comprises, based on the weight of the first composition (A):

[0114] • the third component (iii) in an amount of from 5 to 40wt%,

[0115] • less than 25wt% total of the second component (ii) and fourth component (iv), and

[0116] • a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B):

[0117] • the first component (i) in an amount of at least 20wt%, and

[0118] • at least 20wt% total of the second component (ii) and fourth component (iv).

[0119] Preferably the kit further comprises: d) a liquid fourth composition (D) comprising and preferably consisting of the second component in a liquid form or in a solvent. In these embodiments, the amount of the second component present in a heat-extruded pelletised first composition (A) and / or the non-heat-treated, compacted pelletised second composition (B) may be reduced, even to zero.

[0120] The preferred features of the degradable polymer composition are as described above for the first aspect of the invention.

[0121] The kit comprises the three or four components used in the method of the first aspect of the invention (i.e. the first composition (A), the second composition (B), and the copolymer or homopolymer of polyethylene and / or polypropylene composition (C); with an optional composition (D)). The preferred features of these compositions / components are the same as described above for the first aspect of the invention. Such a kit is useful in the preparation of the degradable polymer end product. The individual components can be produced, stored, and shipped separately, and then coextruded in a specific ratio (depending on the desired properties of the end product) to provide a degradable polymer composition product that has the required degradation properties for a specific purpose, while being prepared by a third party without undue difficulty. Furthermore, the compositions are stable, hold their structural integrity, and retain the desired effects of the active ingredients in the end product.

[0122] A preferred embodiment of the invention will now be described further in the following numbered clauses. In this embodiment there is preferably no component (D). All the features disclosed in these clauses can be combined with the teaching and fallback positions described generally in the description.

[0123] 1 . A method for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and:

[0124] (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium

[0125] (ii) a second component which is a saturated, or mono- or poly-unsaturated linear C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof;

[0126] (iii) a third component which is a rubber, preferably a synthetic rubber;

[0127] (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the method comprising: a) providing a heat-extruded pelletised first composition (A); b) providing a non-heat-treated, compacted pelletised second composition (B); c) providing a co-polymer or homopolymer of polyethylene and / or polypropylene third composition (C), d) coextruding the first composition (A), the second composition (B) and the third composition (C) in a ratio of: 0.5<A<1.5, 0.5<B<1.5 and C>4; wherein the first composition (A) comprises, based on the weight of the first composition (A):

[0128] (i) the third component (iii) in an amount of from 5 to 40wt%,

[0129] (ii) less than 25wt% total of the second component (ii) and fourth component (iv), and

[0130] (iii) a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B):

[0131] (i) the first component (i) in an amount of at least 20wt%, and

[0132] (ii) at least 20wt% total of the second component (ii) and fourth component (iv).

[0133] 2. The method according to clause 1, wherein the degradable polymer composition is a masterbatch for adding to bulk polymer to render it degradable, wherein in the ratio, C<10.

[0134] 3. The method according to clause 1 , wherein the degradable polymer composition is ready for extrusion as a final polymer product, wherein in the ratio, C>50.

[0135] 4. The method according to clause 3, wherein the final polymer product comprises:

[0136] (i) The first component in a

[0137] 5. The method according to any preceding clause, wherein step d) further comprises grinding at least the second composition (B) before mixing with the first composition (A) and the third composition (C) and coextruding.

[0138] 6. The method according to any preceding clause, wherein the fourth component (iv) comprises:

[0139] (I) a phenolic antioxidant stabiliser;

[0140] (II) a phosphite antioxidant stabiliser; and

[0141] (III) a mineral acid scavenger.

[0142] 7. The method according to any preceding clause, wherein the first composition (A) comprises the third component (iii), optionally the second component (ii) and / or fourth component (iv), and wherein the balance is the first carrier material.

[0143] 8. The method according to any preceding clause, wherein the first composition (A) comprises: the third component (iii) in an amount of 5-35wt%; and / or the second component (ii) in an amount of 1-10wt%; and / or the fourth component (iv) in an amount of 1-15wt%.

[0144] 9. The method according to any preceding clause, wherein the second composition (B) comprises: the first component (i) in an amount of 20-80 wt%; and / or the second component (ii) in an amount of 0-25 wt%; and / or the fourth component (iii) in an amount of 10-80 wt%.

[0145] 10. The method according to any preceding clause, wherein the heat-extruded pelletised first composition (A) is obtained in the steps of melting and extruding the first composition (A) at a temperature of from 150 to 250°C.

[0146] 11. The method according to any preceding clause, wherein the non-heat-treated, compacted pelletised second composition (B) is obtained in the steps of: forming a dry mixture of the second composition (B); and compacting the dry mixture to form pellets at a temperature of less than 70 °C.

[0147] 12. The method according to any preceding clause, wherein the polycompacted pellets of the second composition (B), are substantially cylindrical and have a diameter of at least 3 mm and a length of at least 1 cm.

[0148] 13. The method according to any preceding clause, wherein the third composition (C) is in the form of pellets or a powder .

[0149] 14. The method according to any preceding clause, wherein the method comprises mixing the masterbatch obtainable according to clause 2, together with further polymer material, preferably further polypropylene and / or polyethylene.

[0150] 15. A kit of parts for the manufacture of a degradable polymer composition comprising polyethylene and / or polypropylene, and:

[0151] (i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium,

[0152] (ii) a second component which is a mono- or poly-unsaturated linear C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof;

[0153] (iii) a third component which is a rubber, preferably a synthetic rubber;

[0154] (iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the kit comprising: a) a heat-extruded pelletised first composition (A); b) a non-heat-treated, compacted pelletised second composition (B); c) a polyethylene and / or polypropylene third composition (C), wherein the first composition (A) comprises, based on the weight of the first composition (A):

[0155] ■ the third component (iii) in an amount of from 5 to 40wt%,

[0156] ■ less than 25wt% total of the second component (ii) and fourth component (iv), and

[0157] ■ a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B): the first component (i) in an amount of at least 20wt%, and at least 20wt% total of the second component (ii) and fourth component (iv).

[0158] Examples

[0159] Four Comparative Examples and one Inventive Example were carried out as described below.

[0160] Inventive Example 1a

[0161] An inventive working example within the scope of the invention was carried out according to the method of the invention. In particular, first and second compositions were provided with the following components in the recited amounts.

[0162] The components of composition A were coextruded using a twin-screw extruder at an elevated temperature of 210°C, and pelletised.

[0163] The components of composition B were processed by polycompaction and pelletised.

[0164] After pellets of compositions A and B were separately transported to the final location for preparation of the polymer composition, composition B was ground to a powder, and then the ground powder of composition B was blended with the pellets of the first composition A and with polypropylene pellets C in the following amounts:

[0165] 14.0 wt.% composition A;

[0166] 14.1 wt.% composition B; and

[0167] 71 .9 wt.% polypropylene C.

[0168] This represents an approximate ratio of (A:B:C) 1 : 1 : 5

[0169] The mixture of compositions / components were then extruded at 210°C, and formed into final masterbatch pellets. The masterbatch was used in a 2wt% proportion with additional polypropylene to give the final degradable polymer composition. This final product showed the desired properties of good degradation, stability, and processibility.

[0170] Comparative Example 1

[0171] The method of Inventive Example 1 was repeated. However, the components of Composition B were dry-blended without polycompaction. This led to an issue with transporting the mixed powders and granules, leading to demixing of the blend. It was then difficult to further process composition B with the other compositions / components A and C.

[0172] Comparative Example 2

[0173] The components of Compositions A, B were hot extruded with Composition C with A and B at 3x concentration compared to Inventive Example 1.

[0174] Upon trying to extrude the mixture of compositions into the concentrated pellets, it was found that it would not form a regular pellet and could therefore not be further processed.

[0175] Comparative Example 3

[0176] The method of Comparative Example 2 was repeated, but the hot-extruded composition B was included in a concentrate form that was 2x the concentration of the masterbatch (rather than 3x). When extruding the compositions A and B with the polypropylene C, it was found to be processable, but the high concentration combined with heat treating (when preparing the pellets of composition B) led to degradation of the transition metal compound component (i.e. the manganese stearate).

[0177] This degradation was observed both in the concentrated Masterbatch, and also in the final product which contained 2% of the masterbatch. In particular, the decrease in the stability of the final product was in the range of 25-60 %. This was observed through oxidative induction time measured by DSC analysis. For example, a film containing the masterbatch concentrated 2x had an oxidative induction time (OIT) of 0.89 min. This value was compared to several films made in accordance with the method described in inventive example 1 (each with slightly different recipes within the scope of the invention). These inventive films gave a OIT of between 1.21 and 2.14 min. OIT measured the level of thermal stabilization of the material tested. Thus, the products produced using the inventive method, with components falling with the scope of the invention, show better thermal stability.

[0178] Comparative Example 4

[0179] A further example was carried out, where a composition B was prepared with different amounts of the components. In particular, the transition metal compound made up 96 wt.% of the composition. The remaining amount was made up of the stabiliser system.

[0180] The components were subjected to the polycompaction technique and formed into pellets. However, the compacted powder was vulnerable to disintegration upon handling, including transportation from the compaction line to the extrusion line. Although the final product had equal performance. Therefore, the metal compound in such a high amount was deemed to result in pellets that were not sufficiently structurally sturdy.

[0181] Inventive Example 1b

[0182] An alternative approach to example 1a was performed, wherein composition (D) may be used to incorporate at least some of the second component (here all of it).

[0183] The components of composition A were coextruded using a twin-screw extruder at an elevated temperature of 210°C, and pelletised.

[0184] The components of composition B were processed by polycompaction and pelletised. Composition D was added during the final extrusion of the material using a liquid-dosing side feeder.

[0185] After pellets of compositions A and B were separately transported to the final location for preparation of the polymer composition, composition B was ground to a powder, and then the ground powder of composition B was blended with the pellets of the first composition A and with polypropylene pellets C in the following amounts, with composition D added via a side feeder directly into the barrel during extrusion:

[0186] 13.5 wt.% composition A;

[0187] 13.6 wt.% composition B;

[0188] 70.9 wt.% polypropylene C, and

[0189] 2 wt.% composition D.

[0190] This represents an approximate weight ratio of (A:B:C:D) 1 : 1 : 5 : 0:15

[0191] As used herein, the singular form of “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. The use of the term “comprising” is intended to be interpreted as including such features but not excluding other features and is also intended to include the option of the features necessarily being limited to those described. In other words, the term also includes the limitations of “consisting essentially of” (intended to mean that specific further components can be present provided they do not materially affect the essential characteristic of the described feature) and “consisting of’ (intended to mean that no other feature may be included such that if the components were expressed as percentages by their proportions, these would add up to 100%, whilst accounting for any unavoidable impurities), unless the context clearly dictates otherwise.

[0192] Unless otherwise indicated, all percentages are by weight.

[0193] It will be understood that, although the terms "first", "second", etc. may be used herein to describe various elements, layers and / or portions, the elements, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, layer or portion from another, or a further, element, layer or portion. It will be understood that the term “on” is intended to mean “directly on” such that there are no intervening layers between one material being said to be “on” another material. Spatially relative terms, such as “under”, "below", "beneath", "lower", “over”, "above", "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s). It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device as described herein is turned over, elements described as "under” or “below" other elements or features would then be oriented “over” or "above" the other elements or features. Thus, the example term "under" can encompass both an orientation of over and under. The device may be otherwise oriented and the spatially relative descriptors used herein interpreted accordingly.

[0194] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.

Claims

Claims:1 . A method for the manufacture of a degradable polymer composition comprising a copolymer or homopolymer of polyethylene and / or polypropylene, and:(i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium(ii) a second component which is one or more saturated, or mono- or polyunsaturated C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof;(iii) a third component which is a rubber, preferably a synthetic rubber;(iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the method comprising: a) providing a heat-extruded pelletised first composition (A); b) providing a non-heat-treated, compacted pelletised second composition (B); c) providing a co-polymer or homopolymer of polyethylene and / or polypropylene third composition (C), d) optionally, providing a liquid fourth composition (D), e) coextruding the first composition (A), the second composition (B), the third composition (C) in a weight ratio of: 0.5<A<1.5 to 0.5<B<1.5 to C>4, and, when present, the fourth composition (D) in the ratio 0.05<D<0.8; wherein the first composition (A) comprises, based on the weight of the first composition (A):• the third component (iii) in an amount of from 5 to 40wt%,• less than 25wt% total of the second component (ii) and fourth component (iv), and• a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B):• the first component (i) in an amount of at least 20wt%, and• at least 20wt% total of the second component (ii) and fourth component (iv); and wherein the liquid fourth composition (D) comprises or consists of the second component (ii).

2. The method according to claim 1 , wherein the degradable polymer composition is a masterbatch for adding to bulk polymer to render it degradable, wherein in the ratio, C<10.

3. The method according to claim 1, wherein the degradable polymer composition is ready for extrusion as a final polymer product, wherein in the ratio, C>50.

4. The method according to claim 3, wherein the final polymer product comprises:(i) The first component in a total amount of from 0.03 to 0.6 wt.%;(ii) The second component in an amount of from 0.01 to 0.3 wt.%;(iii) The third component in an amount of from 0.02 to 0.2 wt.%; and(iv) The fourth component in an amount of from 0.005 to 0.45 wt.%.

5. The method according to any preceding claim, wherein step d) further comprises grinding at least the second composition (B) before mixing with the first composition (A) and the third composition (C) and coextruding.

6. The method according to any preceding claim, wherein the fourth component (iv) comprises:(I) a phenolic antioxidant stabiliser;(II) a phosphite antioxidant stabiliser; and(III) a mineral acid scavenger.

7. The method according to any preceding claim, wherein the first composition (A) comprises the third component (iii), optionally the second component (ii) and / or fourth component (iv), and wherein the balance is the first carrier material.

8. The method according to any preceding claim, wherein the first composition (A) comprises: the third component (iii) in an amount of 5-35wt%; and / or the second component (ii) in an amount of 0-10wt%, preferably 1-10wt%; and / or the fourth component (iv) in an amount of 0-15wt%, preferably 1-15wt%.

9. The method according to any preceding claim, wherein the second composition (B) comprises: the first component (i) in an amount of 20-80 wt%; and / or the second component (ii) in an amount of 0-25 wt%; and / or the fourth component (iii) in an amount of 10-80 wt%.

10. The method according to any preceding claim, wherein the liquid fourth composition (D) comprises, based on the weight of the fourth composition (D), the second component (ii) in an amount of 80 to 100 wt%, or the second component (ii) in a solvent in an amount of 60 to 80 wt%.

11. The method according to any preceding claim, wherein the heat-extruded pelletised first composition (A) is obtained in the steps of melting and extruding the first composition (A) at a temperature of from 150 to 250°C.

12. The method according to any preceding claim, wherein the non-heat-treated, compacted pelletised second composition (B) is obtained in the steps of: forming a dry mixture of the second composition (B); and compacting the dry mixture to form pellets at a temperature of less than 70 °C.

13. The method according to any preceding claim, wherein the pellets of the first composition (A), and / or the second composition (B), are substantially cylindrical and have a diameter of at least 3 mm and a length of at least 1 cm.

14. The method according to any preceding claim, wherein the third composition (C) is pelletised and, preferably, the pellets are substantially cylindrical and have a diameter of at least 3 mm and a length of at least 1 cm.

15. The method according to any preceding claim, wherein the method comprises mixing the masterbatch obtainable according to claim 2, together with further polymer material, preferably further polypropylene and / or polyethylene.

16. A kit of parts for the manufacture of a degradable polymer composition comprising polyethylene and / or polypropylene, and:(i) a first component which is one or more transition metal compounds, wherein the transition metal is selected from iron, manganese, copper, cobalt and cerium,(ii) a second component which is one or more saturated, or mono- or polyunsaturated C14 -C24 carboxylic acid, or an ester, anhydride or amide thereof;(iii) a third component which is a rubber, preferably a synthetic rubber;(iv) a fourth component which is a stabiliser system comprising one or more antioxidants and / or acid scavengers; the kit comprising: a) a heat-extruded pelletised first composition (A);b) a non-heat-treated, compacted pelletised second composition (B); c) a polyethylene and / or polypropylene third composition (C), wherein the first composition (A) comprises, based on the weight of the first composition (A):• the third component (iii) in an amount of from 5 to 40wt%,• less than 25wt% total of the second component (ii) and fourth component (iv), and• a first carrier material which is a copolymer or homopolymer of polyethylene and / or polypropylene; wherein the second composition (B) comprises, based on the weight of the second composition (B):• the first component (i) in an amount of at least 20wt%, and• at least 20wt% total of the second component (ii) and fourth component (iv).

17. The kit according to claim 16, wherein the kit further comprises: d) a liquid fourth composition (D) comprising and preferably consisting of the second component in a liquid form or in a solvent.

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