Composition for increased stability of recycled polyethylene

Abstract

The invention relates to a composition comprising at least one ethylene-based polymer; vitamin E, a secondary antioxidant; and optionally a slip-agent. The composition is particularly suitable to reduce the gel content of polymer compositions comprising recycled polyethylene.

Description

Composition for increased stability of recycled polyethylene

[0001] The present invention relates to a composition comprising an ethylene-based polymer having increased stability, and in particular to a polymer composition comprising a recycled polyethylene formulation having increased stability.

[0002] Polymer materials are ubiquitously used in a wide variety of applications, including in durable and single-use goods, and in rigid and flexible applications. It is well-known that polymer materials may suffer from oxidative and thermal degradation. A particular phenomenon that may occur as a result of degradation is the generation of long chain branches. In particular, such generation of long chain branches is believed to occur due to chain scissions or hydrogen abstraction in the polymer chains, resulting in the formation of certain radicals, which may join to form a polymer chain with increased long chain branches. This phenomenon is particularly known to occur in polyethylene materials. It may be induced thermally and / or mechanically and may be initiated during processing of polymers into a product, as well as during the use of the product.

[0003] Such long chain branch formation can typically be observed as gel formation, wherein the term “gel” refers to a small defect that distorts the appearance and strength of a polymer product. In order to provide a material with adequate appearance and strength, the formation of gels is preferably avoided as much as possible. Therefore, typically stabilizers are added to polymer materials. Such stabilizers prevent gel formation upon processing of polymers and also prevent degradation during the life span of the polymer material.

[0004] Presently, there is an increased emphasis on extending the service life of polymer materials by recycling, thereby reducing their environmental impact. A recycling process may for example involve compiling a suitable polymer composition comprising the polymer material and further additives, and subjecting the polymer composition to a re-shaping process to create a new product that again may find its way to e.g. consumers.

[0005] However, a post-consumer recycle stream is likely to have been exposed to outdoor conditions (oxygen, moisture, elevated temperatures, etc.) and as such may have suffered from thermo-oxidative degradation. In addition, additives present in post-consumer recycle streams may have been depleted partially or in full, further decreasing its resistance against thermo-oxidative degradation. When polymer materials are recycled after use, they typically are subjected to melt-shaping processes in order to convert the polymer materials from the form in which they were obtained as waste into a form that is suitable for renewed use. Suchexposure to high temperatures, such as in extrusion or injection molding processes, is particularly believed to contribute to long chain branch formation.

[0006] It is an objective of the present invention to provide a composition comprising ethylene-based polymer material, that is sufficiently stable to prevent gel formation. It is a further objective of the present invention to provide a composition comprising ethylene-based polymer material, that is sufficiently stable to use also in recycling applications. It is a particular objective of the present invention to provide a composition that can stabilize postconsumer recycled polyethylene, in order to enable recycling of the polyethylene into new products.

[0007] Thereto, the present invention provides a composition comprising: a) at least one ethylene-based polymer; b) vitamin E, the vitamin E being at least one tocopherol or tocotrienol; c) a secondary antioxidant; and d) optionally a slip-agent.

[0008] Such a composition is appropriately stable and sufficiently stable to use also in recycling applications. In particular, the composition can stabilize post-consumer recycled polyethylene.

[0009] Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Tocopherols and tocotrienols both occur in a (alpha), p (beta), y (gamma) and 5 (delta) forms, as determined by the number and position of methyl groups on the chromanol ring. All eight of these vitamers feature a chromane double ring, with a hydroxyl group that can donate a hydrogen atom to reduce free radicals.

[0010] The general structure of the tocopherols is as follows

[0011] For alpha (a)-tocopherol each of the three "R" sites has a methyl group (CH3) attached.For beta (p)-tocopherol: R1 = methyl group, R2 = H, R3 = methyl group. For gamma (y)- tocopherol: R1 = H, R2 = methyl group, R3 = methyl group. For delta (b)-tocopherol: R1 = H, R2 =H, R3 = methyl group. The same configurations exist for the tocotrienols, except that the hydrophobic side chain has three carbon-carbon double bonds whereas the tocopherols have a saturated side chain.

[0012] The general structure of the tocotrienols is as follows

[0013] Any one of these 8 identified compounds as well as any combination thereof is understood to be vitamin E in the present invention.

[0014] Surprisingly, the combination of a secondary antioxidant with vitamin E is particularly effective in reducing the gel count of a composition with ethylene-based polymer as compared to combinations with other primary antioxidants, notably in combination with PCR materials. This is particularly attractive as vitamin E is non-toxic, which poses additional advantages in case of migration of the antioxidant to the surface and subsequent human contact.

[0015] PCR materials are often deficient in secondary anti-oxidant concentration originally introduced during production. The role of secondary anti-oxidants is to reduce peroxides - formed through the interaction of the polymer with oxygen during use - into non-radical forming species (alcohols). Though efficient, these secondary anti-oxidants convert into inactive species themselves upon exhibiting their function. As a result, the concentration of intact secondary anti-oxidant reduces over time, while the concentration of peroxides attached to the polymer backbone increases. If these peroxides are not reduced prior to melting, they rapidly decompose into radical based species, effectively inducing unwanted chemical reactions in the polyolefin (related to gel formation).

[0016] Vitamin E is a highly reactive primary antioxidant which rapidly scavenges any radical formed during processing (i.e. formed by the high temperatures, shear or decomposition of peroxides). The higher the reactivity of the phenolic anti-oxidant, the lower the life-time of a radical and hence the lower number of chemical reactions it can undergo.

[0017] The combination of a secondary antioxidant with vitamin E is capable of rapidly suppressing radical formation during processing and reducing peroxides formed in the plastic upon contact with oxygen during its use.

[0018] The secondary antioxidant may for example be a phosphite. For example, the secondary antioxidant may be a monophosphite, a diphosphite or a polyphosphite.

[0019] Suitable monophosphites that may be used as secondary antioxidant can be selected from trisnonylphenyl phosphite, trilauryl phosphite, tris (2,4-di-t-butyl phenyl) phosphite, diisooctyl phosphite, triisodecyl phosphite, diisodecylphenyl phosphite, diphenyl isodecyl phosphite, triphenyl phosphite, tris(tridecyl) phosphite, diphenyl isooctyl phosphite, 2,2- methylene-bis(4,6-di-t-butyl-phenyl)-octyl-phosphite, 2,2’-ethylenebis(4,6-di-t-butyl- phenyl)fluorophosphonite, disodium hydrogen phosphite, bis(2,4-di-t-butyl-6- methylphenyl)ethyl phosphite, 2,4,6-tri-t-butylphenyl-2-butyl-2-ethyl- 1 ,3-propanediol phosphite, triisooctyl phosphite, tris(dipropyleneglycol) phosphite, diisooctyl octylphenyl phosphite, tris(2,4-di-t-butyl-5-methylphenyl) phosphite, diphenyl phosphite, phenyl neopentyleneglycol phosphite, tristearyl phosphite, dinonylphenyl bis(nonylphenyl) phosphite, isooctyl phenyl phosphite, 2-ethylhexyl diphenyl phosphite, and diphenyl tridecyl phosphite.

[0020] Suitable diphosphites that may be used as secondary antioxidant can be selected from distearyl pentaerythritol diphosphite, tetrakis-(2,4-di-t-butyl-phenyl)-4,4’-bi-phenylene-di- phosphonite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, bis-(2,6-di-t-butyl-4-methyl- phenyl)-pentaerythritol-di-phosphite, bis(2,4,6-tri-t-butylphenyl) pentaerythritol diphosphite, tetrakis isodecyl 4,4’-isopropylidene diphosphite, bis-(2,4-dicumylphenyl)-pentaerythritol diphosphite, tetraphenyl dipropyleneglycol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, diisodecyl pentaerythritol diphosphite, tetra(tridecyl)-4,4’-butylidene-bis(6-t-butyl- 2-methyldiphenyl) diphosphite, and tetrakis(2,4-di-t-butyl-5-methylphenyl)-4,4’-bi-phenylene diphosphonite.

[0021] Suitable polyphosphites that may be used as secondary antioxidant can be selected from poly(dipropyleneglyocol)phenyl phosphite, 2,2’,2”-nitrilo triethyl-tris(3,3’,5,5’-tetra-t-butyl- 1 ,1 ’-biphenyl-2,2’-diyl) phosphite, dipropyleneglycol phosphite, and 1 ,1 ,3-tris(2-methyl-4- (ditridecyl phosphite)-5-t-butylphenyl)butane.

[0022] Preferably, the secondary antioxidant is a monophosphite. A particularly preferable monophosphate is tris (2,4-di-t-butyl phenyl) phosphite. Also preferred is a compound of formula I:wherein each R is individually selected from 1 ,1 -dimethylpropyl or hydrogen. The latter compound is an FDA approved additive, and as such would render the composition non-toxic if used as the sole secondary antioxidant.

[0023] The composition may optionally comprise a further primary antioxidant. The further primary antioxidant may for example be selected from methylhydroquinone; 2-t-butyl-hydro- quinonone; diamylhydroquinone; 2-t-butyl-4-methylphenol; styrenated phenol; 3-t-butyl-4- hydroxyanisole; 2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethyl-phenol; 2,6-di-t-butyl-a- (di-methyl-amino)-p-cresol; 2,6-di-t-butyl-4-sec-butyl-phenol; 2,6-di-t-butyl-4-nonyl-phenol; 2,4-di-methyl-6-(1-methyl-cyclohexyl) phenol; 2,4-dimethyl-6-(1-methyl-pentadecyl)-phenol; 3- (3,5-di-tert.-butyl-4-hydroxyphenyl)propionic acid-methyl-ester; octadecyl 3-(3,5-di-t-butyl-4- hydroxyphenyl) propionate; 2,6-di-phenyl-4-octadecyl-cyclo-oxy-phenol; a-tocopherol; n- propyl 3,4,5-trihydroxybenzoate; phenol, 4-methyl-2,6-bis(2-phenylethenyl)-2,6-distyryryl-p- cresol;, 2(2-phenylethenyl)-4-methyl-6-(1 ,1-dimethylethyl)-phenol; isooctyl 3-(3,5-di-tert-butyl- 4-hydroxyphenyl)propionate; 6-t-butyl-2,4-dimethyl-phenol; dicyclopentyl-p-cresol; 2,6-di-t- butyl-4-n-butylphenol; 4-hydroxymethyl-2,6-di-t-butyl-phenol; 2,6-di-t-butyl-phenol; 3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionic acid hydrazide; 3-(3,5-di-tert.-butyl-4- hydroxyphenyl)propionic acid; 2,4,6 tris t-butyl phenol; 2,5-di-t-butyl-hydroquinone; p- benzoquinone; hydroquinone; hydroquinone-mono-methyl-ether; 2,2'-bis(6-t-butyl-p- cresyl)methane; 2,2'-methylenebis (6-tert-butyl-4-ethylphenol); 2,2'-methylenebis 6-(1- methylcyclohexyl)-p-cresol; 4,4’-butylidene-bis-(6-t-butyl-m-cresol); 2,2'-ethylidenebis (4,6-di- t-butylphenol); phenol, 4,4'-methylenebis[2,6-bis(1 ,1-dimethylethyl)-4,4'-methylenebis (2,6-di- t-butylphenol); 2,2'-ilsobutylidenebis (4,6-dimethylphenol); bisphenol A; 3,9-bis(2-(3-(3-(tert- butyl-4-hydroxy-5-methyl-phenyl)-propionyl-oxy)-1 ,1-dimethylethyl]-2,4,8,10- tetraoxospiro(5,5)undecane; tri-ethylene-glycol-bis-3-(t-butyl-4-hydroxy-5-methyl-phenyl)- propionate; hexamethylenebis (3,5-di-t-butyl-4-hydroxycinnamate); benzenepropanamide, N,N'-1 ,3-propanediylbis[3,5-bis(1 ,1-dimethylethyl)-4-hydroxy-]N,N'-1 ,3-Propanediylbis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide); 2,2'-methylenebis(6-nonyl-p-cresol); 1 ,1 ,3-tris(2-methyl- 4-hydroxy-5-t-butyl phenyl)butane; 1 ,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene; butyric acid, 3,3-bis(3-t-butyl-4-hydroxyphenyl) ethylene ester; tris(3,5-di-t-butyl-4- hydroxy benzyl) isocyanurate; 1 ,3,5-tris (4-t-butyl-2,6-dimethyl-3-hydroxy-benzyl)-iso- cyanurate; 3-(3,5-di-t-butyl-4-hydroxy-phenyl) propion acid ester with 1 ,3,5-tris (2- hydroxyethyl)-iso-cyanurate; pentaerythritol tetrakis(3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate; 2,6-bis(2’-bis-hydroxy-3’-t-butyl-5’-methyl-phenyl-4-methyl-phenol) or benzenepropanoic acid, 3 , 5- bis ( 1 , 1 -dimethylethyl)-4-hydroxy-, 1 , 1 [2 ,2- bis [[3- [3 , 5- b is( 1 , 1 - dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]-1 ,3-propanediyl] ester. Preferably, the further primary antioxidant is benzenepropanoic acid, 3,5-bis(1 ,1-dimethylethyl)-4-hydroxy-, 1 , 1 [2 ,2-bi s[[3- [3 , 5- bis ( 1 , 1 -dimethylethyl)-4-hydroxyphenyl]-1 -oxopropoxy]methyl]- 1 ,3- propanediyl] ester.

[0024] Preferably, the composition comprises > 100 and < 4000 ppm by weight of the further primary antioxidant, with regard to the total weight of the ethylene-based polymer, more preferably > 400 and < 2000 ppm, most preferably > 500 and < 1000 ppm.

[0025] Preferably, the ethylene-based polymer is a low-density polyethylene (LDPE), a linear low-density polyethylene (LLDPE), a high-density polyethylene (HDPE), or a mixture thereof. Most preferably, the ethylene-based polymer is a LLDPE.

[0026] Such LDPE may for example have a density of > 900 and < 935 kg / m3, preferably of > 910 and < 925 kg / m3. An LDPE may for example an ethylene-based homopolymer or copolymer produced via free radical polymerisation, such as high-pressure free-radical polymerisation. For example, such LDPE may be produced via high-pressure tubular reactor processes or via high-pressure autoclave reactor processes.

[0027] An LLDPE may for example be an ethylene-based copolymer having a density of > 850 and < 940 kg / m3, preferably of > 890 and < 925 kg / m3, more preferably of > 905 and < 925 kg / m3. The LLDPE may comprise moieties derived from one of more C3-C10 a-olefins, preferably moieties derived from an a-olefin selected from propylene, 1 -butene, 4-methyl-1- pentene, 1 -hexene, or 1 -octene. For example, the LLDPE may comprise > 5.0 and < 25.0 wt%, preferably > 5.0 and < 20.0 wt%, of moieties derived from an a-olefin selected from propylene, 1 -butene, 4-methyl-1 -pentene, 1 -hexene, or 1 -octene, with regard to the total weight of the LLDPE.

[0028] An HDPE may for example be an ethylene-based copolymer or homopolymer having a density of > 940 and < 975 kg / m3, preferably of > 945 and < 970 kg / m3, more preferably of >945 and < 965 kg / m3. The HDPE may comprise moieties derived from one of more C3-C10 a- olefins, preferably moieties derived from an a-olefin selected from propylene, 1 -butene, 4- methyl-1 -pentene, 1-hexene, or 1-octene. For example, the HDPE may comprise > 0.2 and < 5.0 wt%, preferably > 0.5 and < 3.0 wt%, of moieties derived from an a-olefin selected from propylene, 1 -butene, 4-methyl-1 -pentene, 1-hexene, or 1-octene, with regard to the total weight of the HDPE.

[0029] The density of the polyethylenes may be determined in accordance with ASTM D792 (2008).

[0030] Preferably, the ethylene-based polymer has a density of > 900 and < 940 kg / m3, more preferably of > 910 and < 930 kg / m3, most preferably of > 915 and < 925 kg / m3, as determined in accordance with ASTM D792; and / or a melt mass-flow rate (MFR2) of > 0.1 and < 5.0 g / 10 min, more preferably of > 0.1 and < 3.0 g / 10 min, most preferably of > 0.5 and < 1.5 g / 10 min, as determined in accordance with ASTM D1238, at 190°C at a load of 2.16 kg.

[0031] Preferably, the ethylene-based polymer is an ethylene homopolymer or an ethylene copolymer comprising < 25.0 wt%, preferably < 20.0 wt%, of moieties derived from a comonomer selected from 1-butene, 1-hexene and 1-octene. For example, the ethylenebased polymer is an ethylene copolymer comprising > 5.0 and < 25.0 wt%, preferably > 5.0 and < 20.0 wt%, of moieties derived from a comonomer selected from 1-butene, 1-hexene and 1-octene.

[0032] Preferably, the composition comprises > 600 and < 4000 ppm by weight of the secondary antioxidant, with regard to the total weight of the ethylene-based polymer, more preferably > 700 and < 3000 ppm, most preferably > 800 and < 2500 ppm. For example, the composition may comprise > 800 and < 1200 ppm or > 2000 and < 2500 ppm by weight of the secondary antioxidant.

[0033] Preferably, the composition comprises > 40 and < 400 ppm by weight of vitamin E, with regard to the total weight of the ethylene-based polymer, preferably > 45 and < 300 ppm, most preferably > 50 and < 150 ppm.

[0034] The optional slip-agent reduces the viscosity during processing, thereby decreasing the number of radicals (or their lifetime) formed by shear of the polymer chains. Preferably, the slip-agent is a fatty amide, preferably erucamide or oleamide, most preferably erucamide.

[0035] Preferably, the composition comprises > 0.1 and < 5 wt% of the slip-agent, with regard to the total weight of the ethylene-based polymer, more preferably > 0.2 and < 2.5, most preferably > 0.5 and < 1 .5 wt%.

[0036] The composition may further comprise an acid-scavenger such as calcium stearate or zinc stearate to negate the effect of any residual catalyst. For example the composition may comprise > 100 and < 2500 ppm by weight, preferably > 150 and < 750 ppm by weight, more preferably > 200 and < 600 ppm by weight of calcium stearate or zinc stearate, with regard to the total weight of the ethylene-based polymer, preferably calcium stearate.

[0037] The invention further provides a polymer composition comprising the composition of the invention, and further comprising a recycled polyethylene formulation, preferably a postconsumer recycled polyethylene formulation, more preferably a post-consumer recycled polyethylene formulation having: a density of > 900 and < 970 kg / m3, preferably of > 910 and < 960 kg / m3, more preferably of > 910 and < 930 kg / m3, as determined in accordance with ISO 1183-1 (2019); and / or a melt mass-flow rate (MFR2) of > 0.1 and < 5.0 g / 10 min, preferably of > 0.1 and < 2.0 g / 10 min, more preferably of > 0.1 and < 1.0 g / 10 min, as determined in accordance with ISO 1133-1 (2011), at 190°C at a load of 2.16 kg.

[0038] Preferably, the recycled polyethylene formulation comprises > 90.0 wt% of ethylenebased polymers, more preferably > 95.0 wt%, with regard to the total weight of the recycled polyethylene formulation.

[0039] Preferably, the recycled polyethylene formulation comprises < 10.0 wt% of propylene- based polymers, or > 0.1 and < 10.0 wt%, preferably < 5.0 wt%, for example > 1.0 and < 5.0 wt%, with regard to the total weight of the recycled polyethylene formulation.

[0040] In a certain embodiment, the recycled polyethylene formulation comprises polyethylene-based polymers and polypropylene-based polymers, for example the recycled polyethylene formulation may comprise ethylene-based polymers and > 1.0 and < 10.0 wt% of propylene-based polymers, preferably the recycled polyethylene formulation may comprise > 90.0 wt% of ethylene-based polymers and > 1 .0 and < 10.0 wt% of propylene-based polymers.

[0041] Preferably, the polymer composition comprises 10 - 60 wt% of the composition of the invention and 40 - 90 wt% of the post-consumer recycled polyethylene formulation.

[0042] The invention further provides use of a composition according to the invention to reduce the gel content (also: gel count) of polymer compositions comprising recycled polyethylene.

[0043] Gels are to be understood to be distinct polymeric domains in the polymer material that do not show thermoplastic properties, for example wherein individual polymer molecules are chemically bound to each other as a result of crosslinking, or for example wherein polymer molecules of a high molecular weight form physical bonds which are not reversible by exposing the material to a heat processing step such as is the case in thermoplastic processing, for example by forming entanglements and / or dense crystalline domains.

[0044] The gel content may for example be determined via on-line measurement of a film produced in the cast film system using an FSA-100 optical film surface analyser equipped with software version 6.3.4.2 obtainable from Optical Control Systems GmbH, in which the surface analyser is positioned between the chill roll system and the nip rolls. The film surface analyser may comprise a CCD line scan camera with a resolution of 50 pqq, enabling the identification of gels having a dimension of at least 50 pqq length and 50 pqq width. The film surface analyser may comprise a halogen based illumination system. A continuous image of the film surface may be produced. The determination of gels may be performed using image recognition software provided by Optical Control Systems GmbH integrated with the FSA-100 film surface analyser. A film sample with a total surface size of > 1 .0 m2may be tested, alternatively > 5.0 m2, alternatively > 1 .0 and < 10.0 m2, alternatively > 5.0 and < 8.0 m2. The film thickness may be 40 - 60 pm, such as 50 pm.

[0045] The equivalent diameter of a gel is to be understood to be the average of the length and the width of the surface area of the gel as determined via on-line measurement as described above. For example, the equivalent diameter may be the average of the largest diameter of a gel and the largest diameter of said gel in a direction perpendicular direction to said largest diameter of said gel.

[0046] The invention will now be illustrated by the following non-limiting examples.Table 1. Materials used

[0047] A number of compositions (see Table 2) were subjected to extrusion compounding using a twin screw extruder (Krauss-Maffei Berstorff ZE25 UTXi twin-screw extruder with L / D 48, SEI = 0.31-0.33 kWh / kg). The resulting compounds were processed into cast films, followed by the assessment of the gelcount. The cast film extrusion was performed using an OCS extruder running at a maximum set temperature of 230 °C (melt temperature 226 - 227 °C), followed by cooling of the film on chilled rollers (25 °C) at a take up speed of 3.2 m / min.

[0048] The gel content was determined via on-line measurement of the film in the cast film system using an FSA-100 film surface analyser obtainable from Optical Control Systems GmbH software version 6.3.4.2, wherein surface analyser is the positioned between the chill roll system and the nip rolls. The film surface analyser comprised a CCD line scan camera with a resolution of 50 pqq. The smallest defects that could be identified accordingly had adimension of 50 pqq length and 50 pqq width. The film surface analyser comprised halogen based illumination system. A continuous image of the film surface was thus produced. The determination of defects was performed using image recognition software provided by Optical Control Systems GmbH integrated with the FSA-100 film surface analyser. A film sample with a total surface size of 6.0 m<2>was tested.

[0049] It should be noted that the recipes highlight the additional additives (on top of the 750 ppm Irganox 1010 and 1250 ppm Irgafos 168 already present in the commercial material). Table 2.

[0050] In parallel, the compositions of examples 1 - 7 were compounded together with LLDPE PCR material in 50 / 50 wt / wt ratio (SEI = 0.28 - 0.29 KWh / kg & melt temperature of 250 - 260 °C) resulting in the formulations of Table 3. The resulting PCR containing compounds were again subjected to cast film extrusion and gel-count assessment as described above. No significant changes in MFI were observed.Table 3.

[0051] It can be observed that the gel count of reference example 1 is relatively high, which is thought to be related to the harsh processing conditions the sample was subjected to to enforce degradation. Various additives combinations were evaluated, including the introduction of Irganox MD1024 (primary antioxidant; pAO1), Vitamin E (primary antioxidant; pAO3), Irgafos 168 (secondary antioxidant; sAO1) or Weston 705 (secondary antioxidant; sAO2). A composition with slip-agent erucamide was tested as well. Clearly, the best results are obtained upon the introduction of Vitamine E and a secondary antioxidant (examples 5 and 6). Noteworthy, the addition of 1 wt% erucamide improves the gelcount, but results in a sticky film. This may be less desired.

[0052] Taking the same 7 samples after compounding with the 50% PCR phase results in halving the overall concentration of the additives. Though the gelcount is still high (also due to the presence of gels which are not related to polymer degradation), it can be observed that the presence of additional vitamin E and a secondary antioxidant results in a 10 - 20% reduction in gelcount compared to the reference or the samples with only secondary antioxidant. Clearly, as observed for the virgin material, also in mixtures with PCR the presence of additional vitamin E and a secondary anti-oxidant is boosting the resistance of the material against gel formation during extrusion.

Claims

CLAIMS1. Composition comprising: a) at least one ethylene-based polymer; b) vitamin E, the vitamin E being at least one tocopherol or tocotrienol; c) a secondary antioxidant; and d) optionally a slip-agent.

2. Composition according to claim 1 , wherein the secondary antioxidant is a phosphite, preferably a monophosphite, more preferably tris (2,4-di-t-butyl phenyl) phosphite3. Composition according to claim 1 or 2, wherein the ethylene-based polymer is a low- density polyethylene (LDPE), a linear low-density polyethylene (LLDPE), a high-density polyethylene (HDPE), or a mixture thereof, preferably wherein the ethylene-based polymer is a LLDPE.

4. Composition according to any one of the preceding claims, wherein the ethylene-based polymer has:• a density of > 900 and < 940 kg / m3, preferably of > 910 and < 930 kg / m3, more preferably of > 915 and < 925 kg / m3, as determined in accordance with ASTM D792; and / or• a melt mass-flow rate (MFR2) of > 0.1 and < 5.0 g / 10 min, preferably of > 0.1 and < 3.0 g / 10 min, more preferably of > 0.5 and < 1 .5 g / 10 min, as determined in accordance with ASTM D1238, at 190°C at a load of 2.16 kg.

5. Composition according to any one of the preceding claims, wherein the ethylene-based polymer is an ethylene homopolymer or an ethylene copolymer comprising < 25.0 wt%, preferably < 20.0 wt%, of moieties derived from a comonomer selected from 1 -butene,1 -hexene and 1 -octene.

6. Composition according to any one of the preceding claims, wherein the composition comprises > 600 and < 4000 ppm by weight of the secondary antioxidant, with regard to the total weight of the ethylene-based polymer, preferably > 700 and < 3000 ppm, most preferably > 800 and < 2500 ppm.

7. Composition according to any one of the preceding claims, wherein the composition comprises > 40 and < 400 ppm by weight of vitamin E, with regard to the total weight of the ethylene-based polymer, preferably > 45 and < 300 ppm, most preferably > 50 and < 150 ppm.

8. Polymer composition comprising the composition according to any one of the preceding claims, and further comprising a recycled polyethylene formulation, preferably a postconsumer recycled polyethylene formulation, more preferably a post-consumer recycled polyethylene formulation having:• a density of > 900 and < 970 kg / m3, preferably of > 910 and < 960 kg / m3, more preferably of > 910 and < 930 kg / m3, as determined in accordance with ISO 1183-1 (2019); and / or• a melt mass-flow rate (MFR2) of > 0.1 and < 5.0 g / 10 min, preferably of > 0.1 and < 2.0 g / 10 min, more preferably of > 0.1 and < 1.0 g / 10 min, as determined in accordance with ISO 1133-1 (2011), at 190°C at a load of 2.16 kg; preferably wherein the recycled polyethylene formulation comprises > 90.0 wt% of ethylene-based polymers and > 1.0 and < 10.0 wt% of propylene-based polymers..

9. Polymer composition according to claim 8, wherein• the recycled polyethylene formulation comprises > 90.0 wt% of ethylene-based polymers, preferably > 95.0 wt%, with regard to the total weight of the recycled polyethylene formulation; and / or• the recycled polyethylene formulation comprises < 10.0 wt% of propylene-based polymers, preferably < 5.0 wt%, with regard to the total weight of the recycled polyethylene formulation.

10. Polymer composition according to claim 8 or 9, comprising 10 - 60 wt% of the composition according to claim 1 and 40 - 90 wt% of the post-consumer recycled polyethylene formulation.

11. Use of a composition according to any one of claims 1 - 7 to reduce the gel content of polymer compositions comprising recycled polyethylene.

Images