Flame retardant articles comprising polylactic acid

Abstract

The invention concerns an article comprising a flame retardant polylactic acid polymer composition which comprises, (i) a polylactic acid polymer substrate; (ii) an effective flame retarding amount of at least one sterically hindered amine; and (iii) an effective flame retarding amount of a phosphorus compound selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite, wherein the at least one sterically hindered amine is a sterically hindered amine ether or sterically hindered amine ester, and wherein the article is - a film having a thickness of up to 5 mm or - a fibre having a diameter of up to 200 µm or a tape having a thickness of up to 5 mm. In addition, the invention also includes a method of producing the article comprising a flame- retardant lactic acid and the use of the sterically hindered amine ether or sterically hindered amine ester in conjunction with the phosphorus compound for increasing the flame retardancy of the said article.

Description

[0001] Flame retardant articles comprising polylactic acid Field of the InventionThe present invention is in the field of flame-retardant articles that comprise polylactic acid.The composition comprises a polylactic acid substrate and an effective flame retarding amount of at least one sterically hindered amine. Specifically, the at least one sterically hindered aminewould be a sterically hindered amine ether or sterically hindered amine ester. Further, thearticle is a film or a fibre or a tape. The invention also encompasses the use of at least one of the said sterically hindered amines for improving the flame retardancy of an article, being a film or a fibre or a tape, comprising a polylactic acid composition. Background of the Invention In recent years, due to the increasing depletion of petroleum resources and the increasedconcerns of petroleum-based polymers causing pollution in the environment, moreenvironmentally friendly biodegradable materials have been developed. Among such environmentally friendly materials, polylactic acid (PLA) has received more attention due to itsexcellent mechanical properties. As a result, polylactic acid (PLA) products are becomingmore widely used in several different and durable applications for instance injection moulding parts, films, fibres and the like as replacements for some general-purpose plastics. However, polylactic acid (PLA) is an extremely flammable substance that will drip during the combustion process, thus limiting its applications in several industries. Furthermore, this problem is exacerbated for products produced as thin layers or filaments, typically films, fibres, and tapes. It is known to add flame retardant compounds during the manufacturing of plastic materials with the aim of reducing the flammability of the plastic products. Various compounds have been described in the literature and employed commercially.US Patent Application Publication No US 2011 / 0257310 A1 describes a flame-retardantcomposition that comprises a synergistic flame-retardant mixture which comprises aphosphonic acid derivative. The reference also concerns the use of the flame-retardantcomposition for flame retardant finishing of polymers or polymer blends. Suggested polymer substrates are said to be any of a wide variety of polymer types, including polyolefins,polyesters, polyamides, or ABS polymers. US Patent Application Publication No US 2005 / 014871A1 refers to polylactic acid being made flame retardant by the incorporation of a synergistic mixture of (i) at least one sterically hindered amine stabiliser and (ii) at least one conventional flame retardant selected from the group consisting of the organo-hydrogen, phosphorus -containing, isocyanurate andmelamine-based flame retardants.Japanese Patent Application Publication No JP 2011-105889 A describes providing a polylactic acid racing composition having flame retardancy, mouldability, high rigidity, high toughness, resistance to wet heat, and impact resistance. It is revealed that the polylactic acid resin composition includes a polylactic acid resin, glass fibre, reinforced fibres other than the glass fibre, and a flame retardant. International Application Publication No WO 2013 / 136285 A1 describes employing NOR- HALS (hindered amine light stabiliser) compound for inducing flame retardancy in polymers. The compositions are said to have excellent thermal stability and are therefore especially suited for the application in engineering thermoplastics and epoxy laminates used for the manufacture of electrical and electronic parts and devices.International Application Publication No 2017 / 013028 A1 describes flame-retardant polyolefinarticles. The flame-retardant article is said to comprise a polyolefin substrate having additivesincorporated therein in which the additives comprise a specific phosphinate ester, a synergistic comprising an N-alkoxy hindered amine, and a melamine cyanurate. US2011 / 003917A1 describes a polylactic acid (PLA) resin composition that aims to improve the weatherability while inhibiting crystallization. The invention involves blending a hindered amine compound with a specific structure into the PLA resin.WO2018 / 137883A3, US2015 / 284535A1, and WO2010 / 026230A1 disclose a flame-retardantcomposition that includes a synergistic mixture of flame-retardant components comprising atleast one sterically hindered amine, and various types of polymers that incorporate this flame-retardant composition. Improving the flame retardancy of polylactic acid compositions as filaments or thin layers tends to be problematic in view of the inherent flammability of polylactic acid and as a filament orthin layer there is a large surface area to mass ratio and there is a tendency for flames to travelvery quickly along the filaments or thin layers thus resulting in large lengths or areas of thepolylactic acid product being consumed very quickly, which is also further exacerbated by themelting and dripping effect of the polylactic acid. Thus, there is a need to find a flame retardancy additive which will satisfactorily improve the flame retardancy of films, fibres or tapes comprising compositions comprising polylactic acid. Further, it would be desirable for such flame retardancy to be improved compared to state-of-the-art flame-retardant additives employed for films, fibres or tapes comprising polylactic acidand / or provide improvements in relation to doses or concentrations of the flame-retardantadditives employed. Furthermore, it would be desirable to provide such flame retardancy infilms, fibres or tapes which provide sustainable benefits. Polylactic acid is a thermoplasticpolyester derived from biomass and thus biodegradable, renewable and more environmentallyfriendly. In addition, polylactic acid is biocompatible. Nevertheless, it would be more desirablefor such flame-retardant additives to be also halogen free.It is an objective of the present invention to develop flame retardant additives systems for filament or thin layer polylactic acid (PLA) articles, typically films, fibres and tapes. Summary of the Invention In a first aspect, the present invention relates to an article comprising a flame retardant polylactic acid polymer composition which comprises, (i) a polylactic acid polymer substrate; (ii) an effective flame retarding amount of at least one sterically hindered amine; and (iii) an effective flame retarding amount of a phosphorus compound selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite,wherein the at least one sterically hindered amine is a sterically hindered amine ether orsterically hindered amine ester, and wherein the article is- a film having a thickness of up to 5 mm or- a fibre having a diameter of up to 200 µm or- a tape having a thickness of up to 5 mm.A second aspect of the present invention concerns a method for preparing an article comprising a flame retardant polylactic acid polymer composition comprising introducing an effective flame retarding amount of at least one sterically hindered amine (ii) and an effective flame retarding amount of a phosphorus compound (iii) into a polylactic acid polymer substrate (i), wherein the at least one sterically hindered amine is a sterically hindered amine ether or sterically hindered amine ester,wherein the phosphorus compound is selected from at least one of phosphinate, phosphonate,and alkali metal hypophosphite, andwherein the article is- a film having a thickness of up to 5 mm or- a fibre having a diameter of up to 200 µm or- a tape having a thickness of up to 5 mm.In a third aspect, the present invention concerns the use of at least one sterically hinderedamine, and a phosphorus compound in combination for improving the flame retardancy of anarticle comprising a polylactic acid polymer composition, wherein the sterically hindered amineis a sterically hindered amine ether or a sterically hindered amine ester, wherein the phosphorus compound is selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite, and wherein the article is- a film having a thickness of up to 5 mm or- a fibre having a diameter of up to 200 µm or- a tape having a thickness of up to 5 mm.According to the invention, the term “at least one sterically hindered amine, and a phosphoruscompound” means both a sterically hindered amine or more than one sterically hindered amine and a phosphorous compound. Optionally, also more than one phosphorous compound. Detailed Description of the InventionThe invention is based on the unexpected improvement in the flame retardancy of films, fibresor tapes comprising polylactic acid compositions by including an effective flame retardingamount of at least one sterically hindered amine which is a sterically hindered amine ether orsterically hindered amine ester, and a phosphorous compound selected from at least one ofphosphinate, phosphonate, and alkali metal hypophosphite. In one preferred aspect of the present invention the at least one sterically hindered aminedoes not contain a halogen. More preferably, the polylactic acid composition according to thepresent invention is free of halogen-containing flame retardants. More preferably still, thearticle according to the present invention is halogen free. Suitably the sterically hindered amine ether or the sterically hindered amine ester may be anN-alkoxy- or N-acyloxy- compound. Preferably the sterically hindered amine ether or stericallyhindered amine ester is an N-alkoxy piperidine or an N-acyloxy piperidine. Preferably the sterically hindered amine ether or sterically hindered amine ester comprise at least one group having the structure below. wherein B1 and B3 are independently linear or branched C1-C4 alkyl, preferably methyl, B2 and B4 are independently linear or branched C1-C4 alkyl, preferably methyl or ethyl, R' is independently selected from unsubstituted or substituted, linear or branched C1-C40 alkylor C1-C40 acyl and unsubstituted or substituted C3-C10 cycloalkyl, and* denotes the point of attachment to the remainder of the sterically hindered amine ether or ester molecule. More preferably, in accordance with the flame retardant polylactic acid polymer compositionaccording to the first aspect of the invention and the method according to the second aspectof the invention and the use according to the third aspect of the invention, the at least onesterically hindered amine is selected from the compounds of formula (I), compounds of formula (II), compounds of formula (III), compounds of formula (IV), compounds of formula (V),compounds of formula (VI), compounds of formula (VII) and compounds of formula (VIII), formula (I), wherein R1and R2are independently selected from formula (Ia); R3and R4are independently selected from H and formula (Ia); formula (Ia), R5and R6are independently selected from unsubstituted or substituted, linear or branched C1-12alkyl, preferably C4alkyl; R7and R8are independently selected from unsubstituted or substituted, linear or branched C1-12alkyl and unsubstituted or substituted C3-10cycloalkyl, preferably cyclohexyl; formula (II), wherein m is 1 to 10, R9and R10are independently selected from unsubstituted or substituted, linear or branched C1-12alkyl; R11and R12are independently selected from unsubstituted or substituted, linear or branched C1-12alkoxy and unsubstituted or substituted C3-10cycloalkoxy, formula (III), wherein n is a number from 2 to 14; formula (IV);

[0002] formula (V); formula (VI); formula (VII); formula (VIII) wherein R is –OC(O)–C11-C20saturated / C17unsaturated. In the context of this patent application, "an effective flame retarding amount" refers to the quantity of a sterically hindered amine or a phosphorus compound that is sufficient to achieve the desired level of flame retardancy in the polylactic acid polymer composition. This amountis determined based on the specific formulation of the polymer composition. The preciseeffective amount can be established through experimentation and testing to meet the requiredperformance standards. Therefore, it is clear to a skilled person what is meant by "an effectiveflame retarding amount". Preferably, the term “an effective flame retarding amount of aphosphorus compound” refers to an amount of at least 0.1% by weight, based on the weightof the polylactic acid polymer substrate. Preferably, the term “an effective flame retarding amount of at least one sterically hindered amine” refers to an amount of at least 0.05% by weight, based on the weight of the polylactic acid polymer substrate. Preferably the article according to the present invention may contain the at least one sterically hindered amine, as defined herein above, in an amount from 0.05% to 10% by weight based on the weight of the polylactic acid substrate. More preferably the at least one sterically hindered amine should be present in an amount from 0.1% to 5%, more preferably from 0.25%to 2.5%, more preferably from 0.5 % to 2.0%, more preferably still from 1.0% to 1.5% byweight, based on the weight of the polylactic acid polymer substrate.According to all aspects of the invention and the aforementioned more specific definitions ofthe sterically hindered amine, the flame retardancy is further enhanced by the addition of atleast one phosphorus compound, being one or more of phosphinate, phosphonate and alkalimetal hypophosphite. The polymer composition comprises, (iii) an effective flame retarding amount of a phosphorus compound selected from at least one of phosphinate, phosphonate,and alkali metal hypophosphite. The addition of both a sterically hindered amine and aphosphorous compound as defined according to the invention brings about an unexpectedlystrong improvement to the flame retardancy of the polylactic acid polymer composition. Preferably the phosphorus compound is a phosphonate.The phosphonate may be alkyl- or aryl- phosphonic acids, where the alkyl may be a straightor branched chain alkyl group having 1 to 4 carbon atoms, and the aryl group may be a substituted or unsubstituted benzyl, substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, or a salt or ester of the aforementioned phosphonic acid. Preferably the at least one phosphorus compound includes a phosphonate of the formula (IX) formula (IX) wherein A1 and A2 are independently selected from a group consisting of alkyl, optionally substituted alkyl, benzyl, optionally substituted benzyl, phenyl, optionally substituted phenyl, naphthyl, optionally substituted naphthyl, preferably methyl or benzyl and more preferably where A1 and A2 are both methyl or both benzyl.In another suitable Embodiment of the invention the phosphonate may be at least onephosphonate compound of the formula (X) where A3 and A4 independently denote C1-C4 alkyl, preferably methyl or ethyl and A5 denotes a straight or branched chain alkyl having 1 to 4 carbon atoms or a phenyl or benzyl group having up to 3 methyl groups respectively. The at least one phosphorus compound may be a mixture of phosphonate compounds, inparticular a mixture of at least one phosphonate compound according to formula (IX) and atleast one phosphonate compound according to formula (X). Such a mixture may also additionally include other phosphonate compounds, for instance any of the compoundsreferred to as alkyl- or aryl-phosphonates as described above.Suitably the phosphorus compound may be present in the article in an amount of at least 0.1% by weight based on the weight of the polylactic acid substrate. Typically, the phosphorus compound would be present in the article in an amount from 0.1% to 20%, preferably from0.5% to 10%, more preferably from 1.0% to 5.0%, more preferably still from 2.0% to 4.0% byweight, based on the weight of the polylactic acid polymer substrate. In one preferred embodiment, the article comprises the sterically hindered amine (ii) which is a compound of Formula (I) with Formula (Ia), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl. In another preferred embodiment, the article comprises the sterically hindered amine (ii) which is a compound of Formula (IV), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX).In a further preferred embodiment, the article comprises the sterically hindered amine (ii) whichis a compound of Formula (V), and comprises the phosphorus compound (iii) which is aphosphonate of Formula (IX).In yet another preferred embodiment, the article comprises the sterically hindered amine (ii)which is a compound of Formula (VII), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl. In one particularly preferred embodiment, the article comprises the sterically hindered amine (ii) which is a compound of Formula (III), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl. In another particularly preferred embodiment, the article comprises the sterically hindered amine (ii) which is a compound of Formula (VI), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl. Polylactic Acid Polylactic acids of polymers and copolymers as disclosed in US Patent Nos 5,447,962, 5,484,881, 6,114,495 and 6,214,967.Polylactic acid or a copolymer of polylactic acid and hydroxycarboxylic acid can be preparedby using lactic acid or lactide, namely a cyclic dimer of lactic acid, and hydroxycarboxylic acid as raw materials.Exemplary hydroxycarboxylic acids include glycolic acid, hydroxybutyric acid, hydroxyvalericacid, hydroxypentanoic acid, hydroxycaproic acid and hydroxyheptanoic acid. Specifically, glycolic acid, 3-hydroxylactic acid, 4-hydroxylactic acid, 3-hydroxyvaleric acid or 6- hydroxycaproic acid is used preferably. In certain cases, other monomers can be suitably used as a mixture. The lactic acid polymer may be prepared directly from lactic acid by dehydrating polycondensation or may be prepared by ring opening polymerisation of lactide. When a low molecular weight polymer is permitted, the polymer is obtained by dehydrating condensation of lactic acid. When a high molecular weight polymer is required, the polymer is preferably obtained by ring opening polymerisation of lactide. Lactides which can be used for ring opening polymerisation are L-lactide, D-lactide, meso-lactide and a mixture of these lactides. A mixture of D- or L-lactide with a lactide havingopposite optical activity is preferred. Mixing ratios, D- or L-lactide / optical antipode between forexample 95 / 5 to about 50 / 50. By polymerising the pure optical isomers or different blends, polymers may be obtained which have different stereochemical structures, affecting their resilience and crystallinity and also their mechanical and thermal properties. The polymerisation degree of lactic acid base polymer is for example in the range of from about 150 to about 20,000. Polymerisation can be carried out in the presence or absence of a solvent. In view of solvent recovery problem, without solvent is preferred in industry. A process for preparing lactic acid-based polymer by ring opening polymerisation of lactide and glycolide may be desirable. The ring opening polymerisation is carried out in the presence of a catalyst. Catalyst which can be used are generally chloride or carboxylate of zinc or tin and include, for example, stannous octoate, tin tetrachloride, zinc chloride, titanium tetrachloride, iron chloride, boron trifluoride ether complex, aluminium chloride, antimony trifluoride, lead oxide and other polyvalent metal -containing compounds. No particular restriction is imposed upon thepolyvalent metals. Tin compounds and zinc compounds are preferably used.The amount of the catalyst used is for example in the range of from 0.001 to 0.1% by weight or lactide or for the total weight of lactide and glycolide. None chain extenders can be used for polymerisation. Preferred chain extenders or higher alcohols such as lauryl alcohol and hydroxy acids such as lactic acid and glycolic acid. The polymerisation rate increases in the presence of a chain extender and the polymer can be obtained within a short time. The molecular weight of the polymer can also be controlled by varying the amount of the chain extender. However, too much of the chain extender tends to decrease the molecular weight of polymer formed. Hence, the amount of chain extender is preferably 0.1% by weight or less for lactide or for the total weight of lactide and glycolide. Polymerisation or copolymerisation can be carried out in the presence or absence of a solvent. Bulk polymerisation in a molten state of lactide or glycolide is preferably carried out in order to obtain high molecular weight polymer. In the case of molten polymerisation, the polymerisation temperature may be generally above the melting point (around 90°C) of the monomer, lactide or lactide and glycolide. In the case of solution polymerisation which uses solvents such as chloroform, polymerisation can be carried out at temperatures below the melting point of lactide or lactide and glycolide. In any case, polymerisation temperatures above 250°C are unfavourable because decomposition of the formed polymer may develop. Films, Fibres and Tapes The article according to the present invention may be a film, fibre or a tape. When the article is a film, including a single layer film or a multilayer film, the film may be obtained by subjecting the polylactic acid polymer composition to film extrusion or coextrusion process, casting process, blowing process or a biaxially orientation process, usually in thecourse of an extrusion process. The biaxially orientation process, usually during an extrusionprocess may be desirable, yielding so-called biaxially orientated films.In another embodiment, the film of the polylactic acid composition may be subjected tostretching or biaxial orientation, which can be performed by any methods known to those skilled in the art. In another embodiment, the film of the polylactic acid composition is stretched by guiding it over at least one roll, preferably a roll system, or by extending it widthwise. If the film isobtained in the form of a tube, it is likewise possible that the film is stretched by blowing airinto the tube of the film and hand stretching the polymer film. It will be appreciated that combinations of the methods are also possible. In another embodiment, the film of the polylactic acid composition is guided over at least one roll, preferably through a roll system, the film is stretched in extrusion direction i.e. lengthwise.If the said film, by contrast, is extended widthwise, it is stretched at right angles to extrusiondirection. In an embodiment, the said film of the polylactic acid composition, for stretching, is guided over at least one roll, preferably through a roll system, the polymer chains of the polylactic acid composition comprising the sterically hindered amine ether or sterically hindered amine ester and the phosphorus compound as described above are aligned parallel to the direction in which stretching is performed. The stretched polylactic acid film obtained is then uniaxially oriented. The stretched polylactic acid film obtained is likewise uniaxially oriented when said film, for stretching, is extended widthwise. In that case too, the polymer chains of the polylacticacid composition as described above are aligned parallel to the direction in which thestretching is performed. In an embodiment, "uniaxially oriented" means that the polylactic acid chains are aligned essentially in one direction. In an embodiment, the said polylactic acid film, for stretching, is guided over a roll system and additionally extended widthwise, the polymer chains of the polylactic acid composition as described above are aligned parallel to both directions in which stretching is performed. The stretched polylactic acid film obtained is then biaxially oriented. In an embodiment, "biaxially oriented" means that the polymer chains are aligned essentially in two different directions preferably at right angles to one another.In an embodiment, if the above-described processes for stretching the said polymer film arecombined, the polylactic acid film is thus obtained, for example, in tubular form and the film is stretched by blowing air into the tube of the polymer film and simultaneously guided over rolls and likewise stretched; thus, the stretched polylactic acid film (SP) obtained is biaxially oriented.In an embodiment, the said polylactic acid film is typically stretched at a temperature abovethe glass transition temperature (Tg) of the at least one polylactic acid and below the melting temperature (Tm) of the at least one polylactic acid. If the said film is a multilayer film, it is also preferable that the film is stretched at a temperature below the melting temperature (Tm) of the at least one further polymer, especially preferably at a temperature below the melting temperature of the at least one further polymer having the lowest melting temperature.If the article according to the present invention is a film, it has a thickness of up to 5 mm. Inone preferred embodiment, the film has a thickness from 0.1 mm to 5 mm. In someapplications the film may have a thickness, for instance from 0.1 mm to 1 mm, for instance from 0.2 mm to 0.8 mm or from 0.3 mm to 0.7 mm, such as from 0.4 mm to 0.6 mm. In other applications the film may have a thickness in the range from 0.25 mm to 5 mm, such as from 0.3 mm to 4 mm, suitably from 0.4 mm to 3 mm, more preferably from 0.5 mm to 2.5 mm.In another embodiment, the article according to the present invention is a tape having athickness of up to 5 mm. In one aspect the tape may be produced by extruding a melt of the polylactic acid composition through a die in a similar fashion a film as described above. Generally, the extruded polylactic acid would be cut to the required dimensions in order to provide the tape. Alternatively solid or partly melted polylactic acid may be compressed by asuitable pressing device in order to provide the tape. In this case, the compression wouldgenerally achieve a multi-orientated layer can be cut to the relevant dimensions required for the tape. Typically, once the layer has been formed it will often be desirable to stretch the tape layer, for instance by calendaring or other suitable rollers in order to avoid the formed tape stretching during use. The so formed tape may have a thickness analogous to the aforementioned films. Suitably the tape may have a thickness from 0.1 mm to 5 mm. In some applications the tape may have athickness, for instance from 0.1 mm to 1 mm, for instance from 0.2 mm to 0.8 mm or from 0.3mm to 0.7 mm, such as from 0.4 mm to 0.6 mm. In other applications the tape may have a thickness in the range from 0.25 mm to 5 mm, such as from 0.3 mm to 4 mm, suitably from 0.4 mm to 3 mm, more preferably from 0.5 mm to 2.5 mm. The article according to the present invention may be a fibre. Typically, the polylactic acid composition would be extruded to form fibres. Normally this would be achieved by extruding the polylactic acid composition through an extrusion device typically known as a spinneret which is employed to extrude a polymer solution or polymer melt to form fibres. In the case of the present invention, the polylactic acid would more desirably be extruded as a polymer melt.The polylactic acid melt would be ejected from the spinneret as a viscous polymer into air orliquid leading to a phase inversion which allows the polylactic acid to solidify. Suitably individual polylactic acid chains tend to align in the fibre in view of the viscous flow. It may bedesirable to spin the polylactic acid fibres as solid fibres or hollow fibres, preferably the fibresare solid. In such embodiment where the article according to the present invention is a fibre, the fibrehas a diameter of up to 200 µm. Suitable fibres may have a diameter of from 0.1 µm to 200µm, preferably from 0.5 µm to 200 µm, for instance from 0.6 µm to 150 µm, more preferably from 0.75 µm to 100 µm, for instance from 0.7 µm to 75 µm, more preferably still from 0.75 µm to 50 µm. The second aspect of the present invention concerns a method for preparing an article comprising a flame retardant polylactic acid polymer composition comprising introducing aneffective flame retarding amount of at least one sterically hindered amine (ii) and an effectiveflame retarding amount of a phosphorus compound (iii) into a polylactic acid polymer substrate(i), wherein the at least one sterically hindered amine is a sterically hindered amine ether or sterically hindered amine ester, wherein the phosphorus compound is selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite, and wherein the article is- a film having a thickness of up to 5 mm or- a fibre having a diameter of up to 200 µm or- a tape having a thickness of up to 5 mm.Suitably in this second aspect the composition comprising the polylactic acid polymersubstrate (i), the at least one sterically hindered amine (ii) and an effective flame retardingamount of a phosphorus compound (iii) is formed into the article being a film or a fibre or atape. In a preferred embodiment of this inventive method, the sterically hindered amine is introduced prior to or during melt processing of the polylactic acid polymer substrate. More preferably, the sterically hindered amine, including any of the aforementioned sterically hindered amines, can be introduced in the form of a masterbatch. In another preferred embodiment of the inventive method, the phosphorus compound, including any of the aforementioned phosphorus compounds, is introduced prior to or during melt processing of the polylactic acid polymer substrate. More preferably, the phosphorus compound is introduced in the form of a masterbatch.In a more preferred embodiment of the inventive method, both the sterically hindered amine,including any of the aforementioned sterically hindered amines, and phosphorus compound, including any of the aforementioned phosphorus compounds, are introduced in the form of a masterbatch. The third aspect of the present invention concerns the use of at least one sterically hinderedamine, and a phosphorus compound for improving the flame retardancy of an articlecomprising a polylactic acid polymer composition, the article being a film or a fibre or a tape, wherein the sterically hindered amine is a sterically hindered amine ether or a stericallyhindered amine ester. The at least one sterically hindered amine is used in conjunction withthe phosphorus compound, for example as a blend. More preferably still according to this inventive use the at least one sterically hindered amine and / or phosphorus compound are introduced in the form of a masterbatch. Further additives It may be desirable to include further additives into the polylactic acid composition, typically by incorporating one or more of these additives into the polylactic acid in the form of a melt. Such further additives may be at least one selected from the group consisting of UV absorbers and light stabilisers; antioxidants; metal deactivators; phosphites and phosphonites; nitrones; thiosynergists; peroxide scavengers; basic co-stabilisers; nucleating agents; fillers and reinforcing agents; other additives; and benzofuranones and indolinones. Other examples of further additives include slip additives which are used to help film surfaces slide over each other, acid scavengers, for instance as described in Chapter 4 of the Plastic Additives Handbook; lubricants, for instance as described in Chapter 5 of the Plastic Additives Handbook polymer processing aids, for instance as described in Chapter 6 of the Plastic Additives Handbook; anti blocking additives, for instance as given in Chapter 7 of the Plastic Additives Handbook; and antifogging additives, for instance as given in Chapter 9 of the Plastic Additives Handbook. Each refers to Plastic Additives Handbook, 5thEdition, Edited by Hans Zweifel, Hanser Munich, ISBN 3-446-21654-5. Specific examples of these further additives are shown below.1. Antioxidants1.1. Alkylated monophenols, for example 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-di methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol,2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, 2-(a-methylcyclohexyl)-4,6-dimethyl phenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di-tert-butyl-4-meth oxymethylphenol, nonylphenols which arelinear or branched in the side chains, for example, 2,6-di-nonyl-4-methylphenol, 2,4-dimethyl-6-(1'-methylundec-1'-yl)phenol, 2,4-dimethyl-6-(1' methylheptadec-1'-yl)phenol,2,4-dimethyl-6-(1'-methyltridec-1'-yl)phenol and mixtures thereof.1.2. Alkylthiomethylphenols, for example 2,4-dioctylthiomethyl-6-tert-butylphenol,2,4-dioctyl thiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-di-dodecylthiomethyl-4- nonylphenol.1.3. Hydroquinones and alkylated hydroquinones, for example 2,6-di-tert-butyl-4-methoxy phenol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4-octadecyloxyphenol, 2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenylstearate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate.1.4. Tocopherols, for example a-tocopherol, -tocopherol, y-tocopherol, o-tocopherol and mixtures thereof (vitamin E).1.5. Hydroxylated thiodiphenyl ethers, for example 2'-thiobis(6-tert-butyl-4-methylphenol), 2,2'-thiobis(4-octylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-2- methylphenol), 4,4'-thiobis(3,6-di-sec-amylphenol), 4,4'-bis(2,6-dimethyl-4-hydroxyphenyl)disulfide.1.6. Alkylidenebisphenols, for example 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(a-methylcyclohexyl) phenol], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(6-nonyl-4-methylphenol), 2,2'-methylenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butyl phenol), 2,2'-ethylidenebis(6-tert-butyl-4-isobutylphenol),2,2'-methylenebis[6-(a-methylbenzyl)-4-nonylphenol], 2,2'-methylenebis[6-(a,a- dimethylbenzyl)-4-nonylphenol], 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-methylenebis(6-tert-butyl-2-methylphenol), 1,1-bis(5-tert butyl-4-hydroxy-2-methylphenyl)butane, 2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1-bis(5-tert-butyl-4- hydroxy-2-methyl-phenyl)-3-n-dodecylmercaptobutane, ethylene glycol bis[3,3-bis(3'-tert butyl-4'-hydroxyphenyl)butyrate], bis(3-tert-butyl-4-hydroxy-5-methyl-phenyl)dicyclopentadiene,bis[2-(3'-tert-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephtha late,1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butane, 2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 2,2-bis(5-tert-butyl-4-hydroxy2-methylphenyl)-4-n-dodecylmercaptobutane, 1,1,5,5-tetra-(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane.1.7. 0-, N- and S-benzyl compounds, for example 3,5,3',5'-tetra-tert-butyl-4,4'-dihydroxydi benzyl ether, octadecyl-4-hydroxy-3,5-dimethylbenzylmercaptoacetate,tridecyl-4-hydroxy-3,5-di-tert-butylbenzylmercaptoacetate, tris(3,5-di-tert-butyl-4-hydroxybenzyl)amine, bis(4- tert-butyl-3-hydroxy-2,6-dimethylbenzyl)dithioterephthalate, bis(3,5-di-tert-butyl-4-hydroxy- benzyl)sulfide,isooctyl-3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate.1.8. Hydroxybenzylated malonates, for example dioctadecyl-2,2-bis(3,5-di-tert-butyl-(2-hydroxybenzyl)malonate, di-octadecyl-2-(3-tert-butyl-4-hydroxy-5-methylbenzyl)malonate, di dodecylmercaptoethyl-2,2-bis (3,5-di-tert-butyl-4- hydroxybenzyl)malonate, bis[4-(1,1,3,3-tetramethylbutyl)phenyl]-2,2-bis(3,5-di-tert-butyl- 4-hydroxybenzyl)malonate.1.9. Aromatic hydroxybenzyl compounds, for example 1,3,5-tris(3,5-di-tert-butyl-4-hydroxy benzyl)-2,4,6-trimethylbenzene, 1,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol. 1.10. Triazine compounds, for example 2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4-hydroxy anilino)-1,3,5-triazine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-tri azine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,3,5-triazine, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxyphenoxy)-1,2,3-triazine, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, 2,4,6-tris-15 (3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxy-phenylpropionyl) -hexahydro-1,3,5-triazine, 1,3,5-tris(3,5-dicyclohexyl-4-hydroxybenzyl)isocyanurate.1.11. Benzylphosphonates, for example dimethyl-2,5-di-tert-butyl-4-hydroxybenzylphosphonate, diethyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate,dioctadecyl3,5-di-tert-butyl-4-hy- droxybenzylphosphonate, dioctadecyl-5-tert-butyl-4-hydroxy-3-methylbenzylphosphonate, the calcium salt of the monoethyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid.1.12. Acylaminophenols, for example 4-hydroxylauranilide, 4-hydroxystearanilide, octyl N-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate.1.13. Esters of 13-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with mono- orpolyhydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol,thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylol propane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.1.14. Esters of 13-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acid withmono- or poly hydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentylglycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N'-bis-(hydroxyethyl)oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane; 3,9-bis[2-{3-(3-tert butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5] undecane.1.15. Esters of 13-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with mono- orpolyhydric alcohols, e.g. with methanol, ethanol, octanol, octadecanol, 1,6-hexanediol,1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol,diethylene glycol, tri ethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)ox amide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.1.16. Esters of 3,5-di-tert-butyl-4-hydroxyphenyl acetic acid with mono- orpolyhydric alcohols, e.g. with methanol, ethanol, octanol, octadecanol, 1,6-hexanediol,1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethyleneglycol, diethylene glycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)ox amide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha- 2,6,7-trioxabicyclo[2.2.2]octane.1.17. Amides of 13-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid e.g. N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexamethylenediamide, N,N'-bis(3,5-di-tert-butyl-4-hydroxy phenylpropionyl)trimethylenediamide, N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazide, N,N'-bis[2-(3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyloxy)ethyl]oxamide (Nau gard®XL-1, supplied by Uniroyal).1.18. Ascorbic acid (vitamin C)1.19. Aminic antioxidants, for example N,N'-di-isopropyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3- methylpentyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-bis(2-naphthyl)-p phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine, N-cyclohexyl-N' phenyl-p-phenylenediamine, 4-(p-toluenesulfamoyl)diphenylamine, N,N'-dimethyl-N,N'-di-5 sec-butyl-p-phenylenediamine, diphenylamine, N-allyldiphenylamine, 4-isopropoxydiphenyl amine, N-phenyl-1-naphthylamine, N-(4-tert-octylphenyl)-1-naphthylamine, N-phenyl-2-naphthylamine, octylated diphenylamine, for example p,p'-di-tert-octyldiphenylamine, 4-n-butyl aminophenol, 4-butyrylaminophenol, 4-nonanoylaminophenol, 4-dodecanoylaminophenol, 4- octadecanoylaminophenol, bis(4-methoxyphenyl)amine, 2,6-di-tert-butyl-4-dimethylaminomethylphenol, 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, N,N,N',N'-tetra methyl-4,4'-diaminodiphenylmethane, 1,2-bis[(2-methylphenyl)amino]ethane, 1,2-bis(phenyl amino)propane, (o-tolyl)biguanide, bis[4-(1',3'-dimethylbutyl)phenyl]amine, tert-octylatedN phenyl-1-naphthylamine, a mixture of mono- and dialkylated tert-butyl / tert-octyldiphenylamines, a mixture of mono- and dialkylated nonyldiphenylamines, a mixture of mono-and dialkylated dodecyldiphenylamines, a mixture of mono- and dialkylatedisopropyl / isohexyl diphenylamines, a mixture of mono- and dialkylated tert-butyldiphenylamines, 2,3-dihydro- 3,3-dimethyl-4H-1,4-benzothiazine, phenothiazine, amixture of mono- and dialkylated tert-butyl / tert-octylphenothiazines, a mixture of mono-and dialkylated tert-octyl-phenothiazines, N-allylphenothiazine, N,N,N',N'-tetraphenyl-1,4-diaminobut-2-ene.2. UV absorbers and light stabilizers2.1. 2-(2'-Hydroxyphenyl)benzotriazoles, for example 2-(2'-hydroxy-5'-methylphenyl)-benzo triazole, 2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-(1,1,3,3-tetramethylbutyl)phenyl)benzotriazole, 2-(3',5'-di tert-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chloro-benzotriazole,2-(3'-sec-butyl-5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(2' hydroxy-4'-octyloxyphenyl)benzotriazole, 2-(3',5'-di-tert-amyl-2'-hydroxyphenyl)benzotriazole, 2-(3',5'-bis-(a,a-dimethylbenzyl)-2'-hydroxyphenyl)benzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)-5-chloro-benzotriazole, 2-(3'-tert-butyl-5'-[2-(2-ethylhexyl oxy)-carbonylethyl]-2'-hydroxyphenyl)-5-chloro-benzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)-5-chlorobenzotriazole, 2-(3'-tert- butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)benzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-(2-octyloxycarbonyl ethyl)phenyl)benzotriazole, 2-(3'-tert-butyl-5'-[2-(2-ethylhexyloxy)carbonylethyl]-2'-hydroxyphenyl)benzotriazole, 2-(3'-dodecyl-2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-isooctyloxycarbonylethyl)phenylbenzotriazole, 2,2'-methylene-bis[4-(1,1,3,3- tetramethylbutyl)-6-benzotriazole-2-ylphenol]; the transesterification product of 2-[3'-tert-butyl-5'-(2-methoxycarbonylethyl)-2'-hydroxyphenyl]-2H-benzotriazole with polyethyleneglycol 300; – [– R-CH2CH2COO-CH2CH2 –]2 – , where R = 3'-tert-butyl-4'-hydroxy-5'-2H-benzotriazol-2-ylphenyl, 2-[2'-hydroxy-3'-(a,a-dimethylbenzyl)-5'-(1,1,3,3-tetramethylbutyl)-phenyl] benzotriazole; 2-[2'-hydroxy-3'-(1,1,3,3-tetramethylbutyl)-5'-(α,α-dimethylbenzyl)-phenyl]ben zotriazole.2.2. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decyl oxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 2'-hydroxy-4,4'-dimethoxyderivatives.2.3. Esters of substituted and unsubstituted benzoic acids, for example 4-tert-butyl-phenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol,bis(4-tert-butylbenzoyl)resorcinol, benzoyl resorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5- di-tert-butyl-4-hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl-4- hydroxybenzoate.2.4. Acrylates / Cinnamates, for example ethyl α-cyano-β,β-diphenylacrylate,isooctyl α-cyano-β,β-diphenylacrylate, methyl a-carbomethoxycinnamate, methyl a-cyano-b-methyl-p-methoxycinnamate, butyl α-cyano-β,β-methyl-p-methoxycinnamate,methyl α-carbomethoxy-p-methoxycinnamate, N-(β-carbomethoxy- b -cyanovinyl)-2-methylindoline, neopentyl tetra(α-cyano-β,β-diphenylacrylate. Other cyanoacrylates mayalso be used and such compounds are given in EP 3587425. 2.5. Nickel compounds, for example nickel complexes of 2,2'-thio-bis[4-(1,1,3,3-tetramethyl butyl)phenol], such as the 1:1 or 1:2 complex, with or without additionalligands such as n butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickeldibutyldithiocarbamate, nickel salts of the monoalkyl esters, e.g. the methyl or ethyl ester,of 4-hydroxy-3,5-di-tert butylbenzylphosphonic acid, nickel complexes of ketoximes, e.g.of 2-hydroxy-4-methylphenylundecylketoxime, nickel complexes of 1-phenyl-4-lauroyl-5-hydroxypyrazole, with or with out additional ligands.2.6. Sterically hindered amines, for example bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)succinate, bis(1,2,2,6,6- pentamethyl-4-piperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4- piperidyl) n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonate, the condensate of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl- 4-hydroxypiperidine and succinic acid, linear or cyclic condensates of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 4-tert octylamino-2,6-dichloro-1,3,5-triazine, tris(2,2,6,6-tetramethyl-4-piperidyl)nitrilotriacetate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, 1,1'-(1,2-ethanediyl) bis(3,3,5,5-tetramethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis(1,2,2,6,6-pentamethylpiperidyl)-2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)malonate, 3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4- dione, bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate, bis(1-octyloxy-2,2,6,6- tetramethylpiperidyl)succinate, linear or cyclic condensates of N,N'-bis(2,2,6,6-tetramethyl-4- piperidyl)hexamethylenediamine and 4-morpholino-2,6-dichloro-1,3,5-triazine, the condensate of 2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, thecondensate of 2-chloro-4,6-di-(4-n-butylamino- 1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, 8- acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, 3-dodecyl-1- (2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, 3-dodecyl-1-( 1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione, a mixture of 4-hexadecyloxy- and 4-stearyloxy-2,2,6,6-tetramethylpiperidine, a condensate of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 4-cyclohexylamino-2,6-dichloro-1,3,5-triazine, a condensate of 1,2-bis(3-aminopropylamino)ethane and 2,4,6-trichloro-1,3,5-triazine aswell as 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No. [136504-96-6]); acondensate of 1,6-hexanediamine and 2,4,6-trichloro-1,3,5-triazine as well as N,N-dibutylamine and 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No. [192268-64-7]); N-(2,2,6,6- tetramethyl-4-piperidyl)-n-dodecylsuccinimide, N-(1,2,2,6,6-pentamethyl-4-piperidyl)-n- dodecylsuccinimide, 2-undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4,5]decane, a reaction product of 7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa-3,8-diaza-4-oxospiro-[4,5]decane and epichlorohydrin, 1,1-bis(1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyl)-2-(4- methoxyphenyl)ethene, N,N'-bis-formyl-N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexa methylenediamine, a diester of 4-methoxymethylenemalonicacid with 1,2,2,6,6-pentamethyl- 4-hydroxypiperidine, poly[methylpropyl-3-oxy-4-(2,2,6,6-tetramethyl-4-piperidyl)]siloxane, a reaction product of maleic acid anhydride-a-olefin copolymer with 2,2,6,6-tetramethyl-4-aminopiperidine or 1,2,2,6,6-pentamethyl-4- aminopiperidine, 2,4-bis[N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine-4-yl)-N- butylamino]-6-(2-hydroxyethyl)amino-1,3,5-triazine, 1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine, 5-(2-ethylhexanoyl) oxymethyl-3,3,5-trimethyl-2-morpholinone, Sanduvor 3058 (Clariant; CAS Reg. No. 106917-31-1 ] 1-(1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl)-3-dodecylpyrrolidine-2,5-dione, , the reactionproduct of 2,4-bis [(1-cyclohexyloxy-2,2,6,6-piperidine-4-yl)butylamino]-6-chloro-s-triazine with N,N'-bis(3-ami nopropyl)ethylenediamine), 1,3,5-tris(N-cyclohexyl-N-(2,2,6,6-tetramethylpiperazine-3-one-4- yl)amino)-s-triazine, 1,3,5-tris(N-cyclohexyl-N-(1,2,2,6,6-pentamethylpiperazine-3-one-4-yl) amino)-s-triazine.2.7. Oxamides, for example 4,4'-dioctyloxyoxanilide, 2,2'-diethoxyoxanilide, 2,2'-dioctyloxy- 5,5'-di-tert-butoxanilide, 2,2'-didodecyloxy-5,5'-di-tert-butoxanilide, 2-ethoxy-2'-ethyloxanilide, N,N'-bis(3-dimethylaminopropyl)oxamide, 2-ethoxy-5-tert-butyl-2'-ethoxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butoxanilide, mixtures ofo- and p-methoxy-disubstituted oxanilides and mixtures of o- and p-ethoxy-disubstitutedoxanilides.2.8. 2-(2-Hydroxyphenyl)-1,3,5-triazines, for example 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)- 1,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2- (2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4- methylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)- 1,3,5-triazine, 2-(2-hydroxy-4-tridecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2- [2-hydroxy-4-(2-hydroxy-3-butyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-octyloxypropyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine, 2-[4-(dodecyloxy / tridecyloxy-2-hydroxypropoxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)- 1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-dodecyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl phenyl)-1,3,5-triazine, 2-(2-hydroxy-4-hexyloxy)phenyl-4,6-diphenyl-1,3,5-triazine, 2-(2-hydr oxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4,6-tris[2-hydroxy-4-(3-butoxy-2- hydroxypropoxy)phenyl]-1,3,5-triazine, 2-(2-hydroxyphenyl)-4-(4-methoxyphenyl)-6-phenyl-1,3,5-triazine, 2-{2-hydroxy-4-[3-(2-ethylhexyl-1-oxy)-2-hydroxypropyloxy ]phenyl}-4 ,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2,4-bis(4-[2-ethylhexyloxy]-2-hydroxyphenyl)-6-(4- methoxyphenyl)-1,3,5-triazine.3. Metal deactivators, for example N,N'-diphenyloxamide, N-salicylal-N'-salicyloylhydrazine, N,N'-bis(salicyloyl)hydrazine, N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine, 3-salicyloylamino-1,2,4-triazole,bis(benzylidene)oxalyl dihydrazide, oxanilide, isophthaloyl dihydrazide, sebacoylbisphenylhydrazide, N,N'-diacetyladipoyl dihydrazide, N,N'-bis(salicyloyl)oxalyldihydrazide, N,N'-bis(salicyloyl)thiopropionyl dihydrazide.4. Phosphites and phosphonites, for example triphenyl phosphite, diphenylalkylphosphites, phenyldialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite,trioctadecyl phosphite, distearylpentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecylpentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,4-di cumylphenyl)pentaerythritoldiphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, diisodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tris(tert-butylphenyl)pentaerythritol diphosphite,tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylenediphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin, bis(2,4-di-tert- butyl-6-methylphenyl)methyl phosphite, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin, 2,2',2"-nitrilo [triethyltris(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite], 2-ethylhexyl(3,3',5,5'-te tra-tert-butyl-1,1'-biphenyl-2 ,2'-diyl)phosphite, 5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane,poly(4,4'{-isopropylidenediphenol}-octylphosphite), poly(4,4'- {isopropylidenebis[2,6-dibromophenol]}-octylphosphite), poly(4,4'- {2,2'-dimethyl-5,5'-di-t-butylphenylsulfide}-pentaerythrityl diphosphite), phosphorous acid, mixed 2,4-bis(1,1-dimethylpropyl)phenyl and 4-(1,1-dimethylpropyl)phenyl triesters (CAS No. 939402-02-5), phosphorous acid, triphenyl ester, polymer with alpha-hydro-omega-hydroxypoly[oxy(methyl-1,2-ethanediyl)], C10-16alkyl esters (CAS No.1227937-46-3).The following phosphites are especially preferred:Tris(2,4-di-tert-butylphenyl) phosphite (lrgafos®168, BASF SE), tris(nonylphenyl)phosphite,

[0003] 5. Hydroxylamines, for example N,N-dibenzylhydroxylamine, N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine, N,N-dilaurylhydroxylamine, N,N-ditetradecylhydroxylamine, N,N dihexadecylhydroxylamine, N,N-dioctadecylhydroxylamine, N-hexadecyl-N-octadecylhydrox ylamine, N-heptadecyl-N-octadecylhydroxylamine, N,N-dialkylhydroxylamine derived from hydrogenated tallow amine or derived from vegetable source.6. Nitrones, for example, N-benzyl-alpha-phenylnitrone, N-ethyl-alpha-methylnitrone, N-octyl-alpha-heptylnitrone, N-lauryl-alpha-undecylnitrone, N-tetradecyl-alpha-tridecylnnitrone, N-hexadecyl-alpha-pentadecylnitrone, N-octadecyl-alpha-heptadecylnitrone, N-hexadecyl-alpha-heptadecylnitrone, N-ocatadecyl-alpha-pentadecylnitrone, N-heptadecyl-alpha-hepta decylnitrone, N-octadecyl-alpha-hexadecylnitrone, nitrone derived from N,N-dialkylhydroxyl amine derived fromhydrogenated tallow amine.7. Thiosynergists, for example dilauryl thiodipropionate, dimistrylthiodipropionate, distearyl thiodipropionate, pentaerythritol tetrakis[3-(dodecylthio)propionate] or distearyl disulfide.8. Peroxide scavengers, for example esters of β-thiodipropionic acid, for examplethe lauryl, stearyl, myristyl or tridecyl esters, mercaptobenzimidazole or the zinc salt of 2-mercapto benzimidazole, zinc dibutyldithiocarbamate, dioctadecyl disulfide,pentaerythritol tetrakis(b -dodecylmercapto)propionate.9. Basic further stabilizers, for example melamine, polyvinylpyrrolidone,dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines,polyamides, polyurethanes, alkali metal salts and alkaline earth metal salts of higher fattyacids, for example calcium stearate, zinc stearate, magnesium behenate, magnesiumstearate, sodium ricinoleate and potassium palmitate, antimony pyrocatecholate or zinc pyrocatecholate.10. Nucleating agents, for example inorganic substances, such as talcum, metaloxides, such as titanium dioxide or magnesium oxide, phosphates, carbonates orsulfates of, preferably, alkaline earth metals; organic compounds, such as mono- orpolycarboxylic acids and the salts thereof, e.g. 4-tert-butylbenzoic acid, adipic acid,diphenylacetic acid, sodium succinate or sodium benzoate; polymeric compounds, suchas ionic copolymers (ionomers).11. Fillers and reinforcing agents, for example calcium carbonate, silicates, glassfibers, glass beads, asbestos, talc, kaolin, mica, barium sulfate, metal oxides andhydroxides, car bon black, graphite, wood flour and flours or fibers of other naturalproducts, synthetic fibers.12. Other additives, for example plasticisers, lubricants, emulsifiers, pigments,rheology additives, catalysts, flow-control agents, optical brighteners, flameproofingagents, antistatic agents and blowing agents. Other additives may also include anti-block additives, as referred to above, which are used in films to reduce the negative adhesion of two polyethylene surfaces to one another which would otherwise result in difficulties separating the films. Antifogging agents, as referred to above, may also be added.13. Benzofuranones and indolinones, for example those disclosed in U.S.4,325,863; U.S. 4,338,244; U.S. 5,175,312; U.S. 5,216,052; U.S. 5,252,643; DE-A-4316611; DE-A-4316622; DE-A-4316876; EP-A-0589839, EP-A-0591102; EP-A-1291384or 3-[4-(2-acetoxyethoxy)phenyl]-5,7-di-tert-butylbenzofuran-2-one, 5,7-di-tert-butyl-3-[4-(2-stearoyloxy ethoxy)phenyl]benzofuran-2-one, 3,3'-bis[5,7-di-tert-butyl-3-(4-[2-hydroxyethoxy ]phenyl)benzofuran-2-one], 5,7-di-tert-butyl-3-(4-ethoxyphenyl)benzofuran-2-one, 3-(4-acetoxy-3,5-di methylphenyl)-5,7-di-tert-butylbenzofuran-2-one, 3-(3,5-dimethyl-4-pivaloyloxyphenyl)-5,7-di tert-butylbenzofuran-2-one, 3-(3,4-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one, 3-(2,3-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one, 3-(2-acetyl-5-isooctylphenyl)-5-isooctyl benzofuran-2-one. Suitable benzofuranones also include compounds identified in WO2015 / 121445 and WO2017 / 025431.The co-additive is for example present in the polylactic acid melt in an amount of 0.001 to10 % by weight, preferably 0.001 to 5 % by weight, relative to the weight of the polylacticacid melt. Conventional fillers or reinforcing agents may be present in the polymer melt inamounts of 0.1 to 10 % by weight, preferably 1 to 5 % by weight, in certain cases inamounts up to 70 % by weight, relative to the weight of the polylactic acid melt.Examples of films tapes and fibres and end use products they are used in are illustrated below. 1) Foils for condensers, refrigerators, heating devices, air conditioners, encapsulating of electronics, semi-conductors, coffee machines, and vacuum cleaners. 2) Woven fabrics continuous and staple, fibers (carpets / hygienic articles / geotextiles / monofilaments, such as artificial turf; filters; wipes / curtains (shades) / medical applications), bulk fibers (applications such as gown / protection clothes), nets, ropes, cables, strings, cords, threads, safety seat-belts, clothes, underwear, gloves; boots; rubber boots, intimate apparel, garments, swimwear, sportswear, umbrellas (parasol, sunshade), parachutes, paraglides, sails, “balloon-silk”, camping articles, tents, airbeds, sun beds, bulk bags, and bags. Non- woven fabrics such as medical fabrics and related apparel, industrial apparel, outdoor fabrics, in-home furnishing and construction fabrics. 3) Films (packaging, dump, laminating, agriculture and horticulture, greenhouse, mulch, tunnel, silage), bale wrap, swimming pools, waste bags, wallpaper, stretch film, raffia, desa- lination film, batteries, and connectors. 4) Examples of Tapes include the following.4.1) Big-bags or FIBC (flexible intermediate bulk container), bags: These are large bags madefrom woven polymer tapes that are used for transporting and storing bulk materials such as sand, gravel, food products, chemicals, and more. 4.2) Safety cords: These are high-strength polymer tapes that are used for securing loads on trucks, trailers, and other vehicles. They are also used in construction to secure scaffolding and other equipment. 4.3) Packaging tape: This is a type of polymer tape that is used for sealing boxes and packages. It is available in various widths and strengths depending on the application. 4.4) Strapping tape: This is a heavy-duty polymer tape that is used for bundling and reinforcing heavy items such as pipes, lumber, and machinery. 4.5) Woven polyester tape: This is a polymer tape that is made from woven polyester fibers. It is used for a wide range of applications, including reinforcing seams on industrial fabrics, reinforcing conveyor belts, and securing cargo in transit. The following examples are intended to illustrate the invention using non-limiting embodiments in accordance with the various aspects of the invention.

[0004] ExamplesFlame retardancy performance of PLA (polylactic acid) 200 µm cast film containing differentN-alkoxyl and N- acyloxyl hindered amine molecules and combination with Phosphorus baseinorganic molecules has been described. The following examples illustrate the improvement in FR (flame retardant) performance (UL94 VTM and DIN 4102 part 1) when the additives of the invention are employed compared to the neat PLA resin. The materials employed in these examples were as follows: a) Polymer Component Polymer component (PLA):^ Luminyl® L130 biobased polylactic acid from Total Corbion, Melt Flow Index: 24 g / 10 minat 210^C / 2.16Kg, density: 1.24 g / cm3^ Luminyl® L175 biobased polylactic acid from Total Corbion, Melt Flow Index: 8 g / 10 min at210^C / 2.16Kg, density: 1.24 g / cm3b) Flame retardant (FR) additiveFR-1: Sterically hindered amine ether of Formula (I) and (Ia), where R5 and R6 are both C4H9;and R7 and R8 are both cyclohexyl.FR-2: Sterically hindered amine ether of Formula (III).FR-3: Sterically hindered amine ether of Formula (VI).FR-4: Sterically hindered hydroxylamine ester of Formula (V).FR-5: Sterically hindered amine ether of Formula (IV).FR-6: Sterically hindered amine ether of Formula (VII).FR-7: Phosphorus compound of Formula IX, where A1 and A2 are both methyl.c) PLA film manufactureUnless stated otherwise, grinded PLA and the corresponding components from FR-1 to FR-7are dry blended in the amounts as indicated in Table 1 and then melt compounded into pellets on a 25 mm co-rotating twin-screw extruder Berstorff ZE25A x 47D, operating at 160 revolutions per minute (rpm) and at set temperatures of 200 °C. The pelletized fully formulated resin is then casted at a maximum temperature Tmaxof 200 °C into 200 µm films using a cast film equipment Collin CR-136 / 350 coupled with an extruder Collin E 30 M. d) Production of Masterbatches containing flame retardant additives FR-4 and FR-6:Unless stated otherwise, PLA (Luminyl L175) and flame-retardant additives FR-4, FR-6 areblended in the amounts as indicated in Table 1 and then melt compounded into pellets on a25 mm co-rotating twin-screw extruder Berstorff ZE25A x 47D, operating at 160 revolutionsper minute (rpm) and at set temperatures of 200 °C, and extruded into pellets. TABLE 1: Concentrations of processing aid components in Masterbatches Products MB-A MB-BPLA (Luminyl L175) 90% 90%FR-4 10%FR-6 10%e) Performance of formulation as flame retardant The produced films are evaluated according to the standards UL 94-VTM and DIN4102-Part 1 (May 1998).Comparative Compositions (compositions not according to the present invention): Ref. 1 toRef.10. Compositions according to the present invention: Inv.1 to Inv.6. UL 94-VTM Test: A flame is applied twice to the lower end of the test specimen positioned vertically. UL 94-VTM is a well-known test for classifying the flame retardancy of very thin material in 3 classes VTM-0, VTM-1 and VTM-2. The best rating is VTM-0.

[0005] TABLE 2a:Flaming test on 200 µm PLA cast films according to UL94-VTM flame retardant performance Ref.1 Ref.2 Ref.3 Ref.4 Inv.1 Ref.5 Ref.6PLA Luminyl L130 100% 99% 99.5% 95.5% 99% 99.5%PLA Luminyl L175 100%FR-1 1.0% 0.5% 1.0%FR-2 1.0% 0.5%FR-7 3.5%UL 94-VTM rating VTM-2 VTM-2 VTM-0 VTM-2 VTM-0 VTM-2 VTM-2Average flaming time 17No a) .5 10.5 2.5 5.5bur4.5 4.0[sec]ninga) Average flaming time per specimen and after maximum 2 ignitionsTABLE 2b:Flaming test on 200 µm PLA cast films according to UL94-VTM flame retardant performance Inv. 2 Ref.7 Inv. 3 Ref.8PLA Luminyl L130 95.5% 99% 95.5%PLA Luminyl L175 90% FR-2 1.0%FR-3 1.0% 1.0%MB-A (10% FR-4 10% masterbatch in PLA) FR-5 MB-B (10% FR-6 masterbatch in PLA FR-7 3.5% 3.5%UL 94-VTM rating VTM-0 VTM-2 VTM-0 VTM-2Average flaming time [sec] a) No burning 9.0 No burning 9.5a) Average flaming time per specimen and after maximum 2 ignitionsContinuation TABLE 2b: Flaming test on 200 µm PLA cast films according to UL94-VTM flame retardant performance (continuation)Inv. 4 Ref.9 Inv. 5 Ref.10 Inv. 6PLA Luminyl L130 PLA Luminyl L175 86% 99.0% 95.0% 90% 86%FR-2 FR-3 MB-A (10% FR-4 10% masterbatch in PLA) FR-5 1.0% 1.0%MB-B (10% FR-610% 10%masterbatch in PLA FR-7 4.0% 4.0% 4.0%UL 94-VTM rating VTM-0 VTM-2 VTM-0 VTM-2 VTM-0Average flaming time [sec] a) No burning 5.5No burning3.0 No burninga) Average flaming time per specimen and after maximum 2 ignitionsEfficacy of FR-1 to FR-6 in conjunction with FR-7 as flame retardant is demonstrated withlower average flaming time, and VTM-2 or even VTM-0 classification.DIN 4102-Part 1 Test:The specimen is positioned vertically, and the ignition flame is applied at the lower edge of the specimen (edge ignition test). Classification is based on the time for flames to spread 150 mm of the specimen. If the flame does not reach the 150 mm reference mark within 20 s, the tested film passes the test and is classified B2. If the flame reaches the 150 mm reference mark within 20 s, the tested film is non classified (n.c.). TABLE 3a: Flaming test on 200 µm PLA cast film according to DIN 4102-Part 1 (edge ignition). Ref.1 Ref.2 Ref.3 Ref.4 Inv.1 Ref.5 Ref.6PLA Luminyl L130 100% 99% 99.5% 95.5% 99% 99.5%PLA Luminyl L175 100%FR-1 1.0% 0.5% 0.5%FR-2 1.0% 0.5%FR-7 3.5%DIN4102-B2 ratingpass pass pass pass pass pass passwith 200 µm filmsa)Burning time [sec] b) 13.0 24 5.5 7.5 3.0 14.0 4.5D c)amaged length [mm]82 109 46 49 35 80 34Drips d) Yes Yes Yes Yes No Yes YesBurning e)drips paperNo No No No No No Noignition

[0006] TABLE 3b: Flaming test on 200 µm PLA cast film according to DIN 4102-Part 1 (edge ignition). Inv.2 Ref.7 Inv.3 Ref.8 Inv.4 Ref.9 Inv.5 Ref.Inv.6 10 PLA95.5% 99% 95.5%Luminyl L130 PLA99.0% 95.0% 99.0% 95.0% 99.0% 95.0%Luminyl L175 FR-2 0.5%1.0% 0.5%FR-3 MB-A1.0% 1.0%(10% FR-4 masterbatc h in PLA) FR-5 1.0% 1.0%MB-B1.0% 1.0%(10% FR-6 masterbatc h in PLA FR-7 3.5% 3.5% 4.0% 4.0% 4.0%DIN4102-pass pass pass pass pass pass pass pass passB2 rating with 200 µm filmsa)Burning time [sec] b) 2.0 7.0 3.0 9.0 3.5 5.0 4.0 3.0 2.5Damaged length [mm]13 51 21 50 28 43 29 27 22c) Drips d) No Yes No Yes No Yes No No NoBurningNo No No No No No No No Nodrips pa ion eper ignit )a) Rated "pass" if flaming does not reach the 150 mm gauge mark within 20 seconds afterflame application according to the DIN 4102-Part 1 test norm.b) Burning time, in second, is the duration of the flaming after flame application up to theextinction of flame.c) Damaged length, in mm, is the vertical part of the film being burned after the extinction offlame.d) Rated "no" if molten and burning drips do not fall on the filter paper placed underneath thetest specimen according to the DIN 4102-Part 1 test norm. "no" is the best rating.e) Rated "no" if molten and burning drips that have fallen on the filter paper does not ignitethe paper placed underneath the test specimen according to the DIN 4102-Part 1 test norm. "no" is the best rating.Inventive samples from Inv. 1 to Inv. 6 show significant flame retardancy (FR) performance.The burning times and the damaged lengths of the respective inventive samples areparticularly good. The inventive examples demonstrate a remarkable enhancement in flame retardancycompared to the Ref.1 to Ref.10. The inventive samples, ranging from Inv.1 to Inv.6, exhibitsignificantly improved burning times, which are notably shorter than those observed in the reference examples. Additionally, the damage lengths are considerably reduced, indicating a superior resistance to fire. Importantly, none of the inventive samples produce any drips during combustion, which is a critical factor in preventing the spread of fire. All inventive samples pass the test according to DIN 4102-Part 1, and no burning drips ignite a paper placed underneath the test specimen. This combination of shorter burning times, reduced damage lengths, and the absence of burning drips highlights the unexpected effectiveness of the synergistic inventive formulations comprising both a sterically hindered amine ether or ester and a phosphorous compound in conjunction for enhancing the safety and performance of the material.

Claims

Claims1. An article comprising a flame retardant polylactic acid polymer composition whichcomprises, (i) a polylactic acid polymer substrate; (ii) an effective flame retarding amount of at least one sterically hindered amine; and (iii) an effective flame retarding amount of a phosphorus compound selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite, wherein the at least one sterically hindered amine is a sterically hindered amine ether orsterically hindered amine ester, andwherein the article is- a film having a thickness of up to 5 mm or- a fibre having a diameter of up to 200 µm or- a tape having a thickness of up to 5 mm.

2. The article according to claim 1, wherein the at least one sterically hindered amine isselected from the compounds of formula (I), compounds of formula (II), compounds offormula (III), compounds of formula (IV), compounds of formula (V), compounds of formula (VI), compounds of formula (VII) and compounds of formula (VIII),formula (I), wherein R1 and R2 are independently selected from formula (Ia); R3 and R4 are independently selected from H and formula (Ia);R5and R6are independently selected from unsubstituted or substituted, linear or branched C1-12alkyl, preferably C4alkyl; R7 and R8 are independently selected from unsubstituted or substituted, linear or branched C1-12 alkyl and unsubstituted or substituted C3-10 cycloalkyl, preferably cyclohexyl;formula (II), whereinm is 1 to 10, R9and R10are independently selected from unsubstituted or substituted, linear or branched C1-12alkyl; R11and R12are independently selected from unsubstituted or substituted, linear or branched C1-12 alkoxy and unsubstituted or substituted C3-10 cycloalkoxy,formula (III), wherein n is a number from 2 to 14;formula (IV);formula (VIII) wherein R is –OC(O)–C11-C20saturated / C17unsaturated.

3. The article according to claim 1 or claim 2, wherein the at least one phosphorus compoundincludes a phosphonate of the formula (IX)formula (IX) wherein A1 and A2 are independently selected from a group consisting of alkyl, optionally substituted alkyl, benzyl, optionally substituted benzyl, phenyl, optionally substituted phenyl, naphthyl, optionally substituted naphthyl, preferably methyl or benzyl and morepreferably where A1 and A2 are both methyl or both benzyl.

4. The article according to any of claims 1 to 3, wherein the at least one sterically hinderedamine is present in the article in an amount from 0.05% to 10%, preferably from 0.1% to5%, more preferably from 0.25% to 2.5% by weight, based on the weight of the polylactic acid polymer substrate.

5. The article according to any of claims 1 to 4, wherein the phosphorus compound is presentin the article in an amount from 0.1% to 20%, preferably from 0.5% to 10% by weight, based on the weight of the polylactic acid polymer substrate.

6. The article according to any of claims 1 to 5, wherein the article comprises the stericallyhindered amine (ii) which is a compound of Formula (I), preferably the compound whereR1, R2 and R4 are each represented by Formula (Ia) and R3 is H; R5 and R6 are each C4 alkyl; and R7 and R8 are each cyclohexyl, and comprises the phosphorus compound (iii)which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl orare both benzyl.

7. The article according to any of claims 1 to 5, wherein the article comprises the stericallyhindered amine (ii) which is a compound of Formula (III), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl8. The article according to any of claims 1 to 5, wherein the article comprises the stericallyhindered amine (ii) which is a compound of Formula (VI), and comprises the phosphorus compound (iii) which is a phosphonate of Formula (IX), preferably where A1 and A2 are both methyl or are both benzyl.

9. The article according to any of claims 1 to 8, the article being a film having a thicknessfrom 0.25 mm to 5 mm, preferably from 0.5 mm to 2.5 mm.

10. The article according to any of claims 1 to 8, the article being a fibre having a diameterfrom 0.5 µm to 200 µm, preferably from 0.75 µm to 100 µm, more preferably from 0.75 µm to 50 µm.

11. A method for preparing an article comprising a flame retardant polylactic acid polymercomposition comprising introducing an effective flame retarding amount of at least one sterically hindered amine (ii) and an effective flame retarding amount of a phosphoruscompound (iii) into a polylactic acid polymer substrate (i), wherein the article is definedaccording to any of claims 1 to 10.

12. The method according to claim 11, wherein the sterically hindered amine and thephosphorus compound are introduced prior or during melt processing of the polylactic acidpolymer substrate.

13. The method according to claim 12, wherein the sterically hindered amine and / or thephosphorus compound are introduced in the form of a masterbatch.

14. Use of at least one sterically hindered amine, and a phosphorus compound for improvingthe flame retardancy of an article comprising a polylactic acid polymer composition, the article being a film or a fibre or a tape, wherein the sterically hindered amine is a stericallyhindered amine ether or a sterically hindered amine ester, wherein the phosphoruscompound is selected from at least one of phosphinate, phosphonate, and alkali metal hypophosphite.

15. The use according to claim 14 which includes any of the features according to claims 2 to10.

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