POLYETHYLENE COMPOSITION FOR USE WITH RECYCLED POLYETHYLENE

Abstract

The present invention relates to a polyethylene composition comprising a polyethylene, preferably ≥95.0 wt % of polyethylene, and further (a) ≥100 and ≤500 ppm of a phenolic antioxidant; (b) ≥500 and ≤2500 ppm of an organic phosphite stabiliser; and (c) ≥500 and ≤2500 ppm of a metal stearate with regard to the total weight of the polyethylene composition. Such polyethylene composition, when used in a moulding process with PCR polyethylene, results in a reduction of the quantity of degradation products formed, which may be observed as a reduction of die deposits.

Description

BACKGROUND

In view of current market developments that seek for reduction of environmental footprint in the value chain of materials, including polymer materials, there is an ongoing drive to re-use materials, and to reduce the quantity of ‘new’ materials that are used in the production of a variety of articles.

In the field of applications of polymer materials, this translates to a desire to recycle materials and to reduce the quantity of so-called ‘virgin’ polymer material, i.e. polymer material that is provided as new polymers obtained from polymerisation processes, such as from polymerisation processes of fossil materials-based monomeric materials.

For example, it is desired to increase the quantity of recycle materials in polymer compositions wherein such recycle materials originate from a previous end-consumer use of an application of the polymer. Such recycle materials are commonly referred to as ‘post-consumer recyclate or regrind’ or PCR materials.

However, given that such PCR materials have been previously subjected to steps including both the processing of the material into the desired application, the use in the application itself, and a processing after collection from the consumer into a form that renders it suitable for recycling, which may include for example shredding, cleaning and extrusion steps, the material characteristics of the PCR materials tend to deteriorate to a certain degree.

Such deterioration may result in the forming of degradation products during the use of such PCR materials in a shaping process for forming a new article from the PCR materials. Such shaping process typically involves a melt processing step, wherein the polymer material is molten, and shaped into a new object form prior to consolidation. A particular suitable process that is employed therein is extrusion blow moulding, by means of which objects such as bottles may be formed. Degradation products that emerge during such process may form deposits on the outlet of the melt processing equipment, typically referred to as die deposit.

When such die deposit excessively occurs, the blow moulding process needs to be halted, and the equipment cleaned. This has a detrimental effect on the process efficiency. Would the die deposits not be removed, it would result in defects in the polymer bottles that are produced, which may be both in the form of discolorations or as physical defects, resulting in rejected objects.

SUMMARY

Accordingly, it is required that the formation of such degradation products during injection blow moulding is minimised. Still, there is also the objective of being able to utilise a certain high quantity of PCR materials in the process, in view of a.o. circular materials efficiency and environmental concerns.

A solution for that has now been provided according to the present invention by a polyethylene composition comprising a polyethylene, preferably ≥95.0 wt % of polyethylene, and further

• • (a) ≥100 and ≤500 ppm of a phenolic antioxidant;
  • (b) ≥500 and ≤2500 ppm of an organic phosphite stabiliser; and
  • (c) ≥500 and ≤2500 ppm of a metal stearate with regard to the total weight of the polyethylene composition.

Such polyethylene composition, when used in a moulding process with PCR polyethylene, results in a reduction of the quantity of degradation products formed, which may be observed as a reduction of die deposits.

DETAILED DESCRIPTION

The polyethylene composition may for example comprise ≥100 and ≤500 ppm of the phenolic antioxidant (a), preferably ≥100 and ≤300 ppm, more preferably ≥150 and ≤250 ppm. The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the organic phosphite stabiliser (b), preferably ≥500 and ≤2000 ppm, more preferably ≥750 and ≤1500 ppm. The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the metal stearate, preferably ≥500 and ≤2000, more preferably ≥750 and ≤1500 ppm.

The polyethylene may for example be

• • (i) a high-density polyethylene having a density of ≥945 and ≤970 kg/m³, preferably ≥950 and ≤960;
  • (ii) a low density polyethylene produced by free-radical polymerisation having a density of ≥900 and ≤925 kg/m³, preferably ≥910 and ≤920;
  • (iii) a linear low-density polyethylene having a density of ≥870 and ≤925 kg/m³, preferably ≥905 and ≤922;
  • (iv) a medium-density polyethylene having a density of ≥926 and ≤944 kg/m³, preferably ≥930 and ≤940;
  • or a combination thereof; wherein the density is determined in accordance with ASTM D792 (2008).

It is preferred that the phenolic antioxidant comprises 1-4 phenolic moieties, such as 2, 3 or 4 phenolic moieties, preferably ≥2. It is preferred that the phenolic moieties are 3,5-bis(t-butyl)-4-hydroxybenzene moieties. For example, the phenolic antioxidant may comprise 1-4 phenolic moieties where in the phenolic moieties are 3,5-bis(t-butyl)-4-hydroxybenzene moieties.

For example, the phenolic antioxidant may be selected from octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, isooctyl 3 (3,5 di t butyl 4 hydroxyphenyl)propionate, tri ethylene glycol bis 3 (t butyl 4 hydroxy 5 methyl phenyl) propionate, 1,6 hexane diol bis 3 (3,5 di t butyl 4 hydroxyphenyl) propionate, 2,2′-methylenebis (6-t-butyl-4-methylphenol), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 2,2′-isobutylidenebis (4,6-dimethylphenol), pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate), tris(3,5 di t butyl 4 hydroxybenzyl)isocyanurate, 1,3,5 trimethyl 2,4,6 tris(3,5 di t butyl 4 hydroxybenzyl)benzene, pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate, 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, 1,3,5 tris(3′,5′ di t butyl 4′ hydroxybenzyl) s triazine-2,4,6 (1H,3H,5H)trione, and 1,3,5 tris(4 t butyl 2,6 dimethyl 3 hydroxy benzyl) iso cyanurate, and 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide, preferably ≥1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide.

For example, the polyethylene composition may comprise ≥100 and ≤500 ppm, preferably ≥100 and ≤300 ppm, more preferably ≥150 and ≤250 ppm, of a phenolic antioxidant, wherein the phenolic antioxidant comprises 1-4 phenolic moieties, such as 2, 3 or 4 phenolic moieties, preferably ≥2. For example, the polyethylene composition may comprise ≥100 and ≤500 ppm, preferably ≥100 and ≤300 ppm, more preferably ≥150 and ≤250 ppm, of a phenolic antioxidant, wherein the phenolic antioxidant comprises 1-4 phenolic moieties where in the phenolic moieties are 3,5-bis(t-butyl)-4-hydroxybenzene moieties.

For example, the polyethylene composition may comprise ≥100 and ≤500 ppm, preferably ≥100 and ≤300 ppm, wherein the phenolic antioxidant may be selected from octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, isooctyl 3 (3,5 di t butyl 4 hydroxyphenyl)propionate, tri ethylene glycol bis 3 (t butyl 4 hydroxy 5 methyl phenyl) propionate, 1,6 hexane diol bis 3 (3,5 di t butyl 4 hydroxyphenyl) propionate, 2,2′-methylenebis (6-t-butyl-4-methylphenol), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 2,2′-isobutylidenebis (4,6-dimethylphenol), pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate), tris(3,5 di t butyl 4 hydroxybenzyl)isocyanurate, 1,3,5 trimethyl 2,4,6 tris(3,5 di t butyl 4 hydroxybenzyl)benzene, pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate, 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, 1,3,5 tris(3′,5′ di t butyl 4′ hydroxybenzyl) s triazine-2,4,6 (1H,3H,5H)trione, and 1,3,5 tris(4 t butyl 2,6 dimethyl 3 hydroxy benzyl) iso cyanurate, and 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide.

For example, the polyethylene composition may comprise ≥100 and ≤500 ppm, preferably ≥100 and ≤300 ppm, wherein the phenolic antioxidant is 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide.

The organic phosphite stabiliser may for example be a triphosphite, preferably a triphosphite comprising 1, 2 or 3 moieties, preferably comprising one or more a substituted or unsubstituted phenyl moieties, such as bis-t-butyl phenyl moieties.

The organic phosphite stabiliser may for example be selected from tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, distearylpentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite, and bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite, preferably tris(2,4-di-tert-butylphenyl) phosphite.

Preferably, the organic phosphite stabiliser is tris(2,4-di-tert-butylphenyl) phosphite.

The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the organic phosphite stabiliser (b), preferably ≥500 and ≤2000 ppm, more preferably ≥750 and ≤1500 ppm, wherein the organic phosphite stabiliser is a triphosphite, preferably a triphosphite comprising 1, 2 or 3 moieties, preferably comprising one or more a substituted or unsubstituted phenyl moieties, such as bis-t-butyl phenyl moieties.

The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the organic phosphite stabiliser (b), preferably ≥500 and ≤2000 ppm, more preferably ≥750 and ≤1500 ppm, wherein the organic phosphite stabiliser is selected from tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, distearylpentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite, and bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite.

The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the organic phosphite stabiliser (b), preferably ≥500 and ≤2000 ppm, more preferably ≥750 and ≤1500 ppm, wherein the organic phosphite stabiliser is tris(2,4-di-tert-butylphenyl) phosphite.

The metal stearate may for example be selected from calcium stearate, magnesium stearate, aluminium stearate, and lithium stearate. It is preferred that the metal stearate is calcium stearate.

The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the metal stearate, preferably ≥500 and ≤2000, more preferably ≥750 and ≤1500 ppm, wherein the metal stearate may for example be selected from calcium stearate, magnesium stearate, aluminium stearate, and lithium stearate. The polyethylene composition may for example comprise ≥500 and ≤2500 ppm of the metal stearate, preferably ≥500 and ≤2000, more preferably ≥750 and ≤1500 ppm, wherein the metal stearate is calcium stearate.

The polyethylene composition may for example comprise:

• • ≥80.0, preferably ≥95.0 wt %, of the high-density polyethylene (i);
  • ≥80.0, preferably ≥95.0 wt %, wt % of the low-density polyethylene(ii);
  • ≥80.0, preferably ≥95.0 wt %, wt % of the linear low-density polyethylene (iii); or
  • ≥80.0, preferably ≥95.0 wt %, wt % of the medium-density polyethylene (iv) with regard to the total weight of the polyethylene composition.

Preferably, the polyethylene composition comprises the high-density polyethylene (i), the low-density polyethylene (ii), the linear low-density polyethylene (iii), or the medium-density polyethylene (iv) as the sole polyethylene material in the composition.

In a particular embodiment of the invention, the polyethylene composition consists essentially of or consists of:

• • the high-density polyethylene (i), the low-density polyethylene (ii), the linear low-density polyethylene (iii), or the medium-density polyethylene (iv);
  • the phenolic antioxidant;
  • the phosphite stabiliser; and
  • the metal stearate.

In a further particular embodiment of the invention, the polyethylene composition consists of:

• • the high-density polyethylene (i), the low-density polyethylene (ii), the linear low-density polyethylene (iii), or the medium-density polyethylene (iv);
  • the phenolic antioxidant, wherein the phenolic antioxidant is 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide;
  • the phosphite stabiliser, wherein the phosphite stabiliser is tris(2,4-di-tert-butylphenyl) phosphite; and
  • the metal stearate, wherein the metal stearate is calcium stearate.

It is particularly preferred that the polyethylene is the high-density polyethylene (i).

The invention also relates to an embodiment wherein the polyethylene composition consists of:

• • the high-density polyethylene (i);
  • the phenolic antioxidant, wherein the phenolic antioxidant is 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide;
  • the phosphite stabiliser, wherein the phosphite stabiliser is tris(2,4-di-tert-butylphenyl) phosphite; and
  • the metal stearate, wherein the metal stearate is calcium stearate.

It is preferred that the polyethylene has a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and/or
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

For example, the polyethylene may have a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

The polyethylene may for example have a melt-mass flow rate of ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg, preferably ≥0.2 and ≤1.5, more preferably ≥0.2 and ≤1.0. The polyethylene may for example have a melt-mass flow rate of ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg, preferably ≥1.0 and ≤5.0 g/10 min, more preferably ≥2.0 and ≤5.0 g/10 min. The polyethylene may for example have a melt-mass flow rate of ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg, preferably ≥25.0 and ≤75.0 g/10 min, more preferably ≥30.0 and ≤50.0 g/10 min.

It is preferred that the high-density polyethylene has a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and/or
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

For example, the high-density polyethylene may have a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

The high-density polyethylene may for example have a melt-mass flow rate of ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg, preferably ≥0.2 and ≤1.5, more preferably ≥0.2 and ≤1.0. The high-density polyethylene may for example have a melt-mass flow rate of ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg, preferably ≥1.0 and ≤5.0 g/10 min, more preferably ≥2.0 and ≤5.0 g/10 min. The high-density polyethylene may for example have a melt-mass flow rate of ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg, preferably ≥25.0 and ≤75.0 g/10 min, more preferably ≥30.0 and ≤50.0 g/10 min.

It is preferred that the low-density polyethylene has a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and/or
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

For example, the low-density polyethylene may have a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

The low-density polyethylene may for example have a melt-mass flow rate of ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg, preferably ≥0.2 and ≤1.5, more preferably ≥0.2 and ≤1.0. The low-density polyethylene may for example have a melt-mass flow rate of ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg, preferably ≥1.0 and ≤5.0 g/10 min, more preferably ≥2.0 and ≤5.0 g/10 min. The low-density polyethylene may for example have a melt-mass flow rate of ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg, preferably ≥25.0 and ≤75.0 g/10 min, more preferably ≥30.0 and ≤50.0 g/10 min.

It is preferred that the linear low-density polyethylene has a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and/or
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

For example, the linear low-density polyethylene may have a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

The linear low-density polyethylene may for example have a melt-mass flow rate of ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg, preferably ≥0.2 and ≤1.5, more preferably ≥0.2 and ≤1.0. The linear low-density polyethylene may for example have a melt-mass flow rate of ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg, preferably ≥1.0 and ≤5.0 g/10 min, more preferably ≥2.0 and ≤5.0 g/10 min. The linear low-density polyethylene may for example have a melt-mass flow rate of ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg, preferably ≥25.0 and ≤75.0 g/10 min, more preferably ≥30.0 and ≤50.0 g/10 min.

It is preferred that the medium-density polyethylene has a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and/or
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

For example, the medium-density polyethylene may have a melt-mass flow rate of:

• • ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;
  • ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg; and
  • ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg.

The medium-density polyethylene may for example have a melt-mass flow rate of ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg, preferably ≥0.2 and ≤1.5, more preferably ≥0.2 and ≤1.0. The medium-density polyethylene may for example have a melt-mass flow rate of ≥1.0 and ≤10.0 g/10 min under a load of 5.0 kg, preferably ≥1.0 and ≤5.0 g/10 min, more preferably ≥2.0 and ≤5.0 g/10 min. The medium-density polyethylene may for example have a melt-mass flow rate of ≥25.0 and ≤100.0 g/10 min under a load of 21.6 kg, preferably ≥25.0 and ≤75.0 g/10 min, more preferably ≥30.0 and ≤50.0 g/10 min.

In the context of the present invention, the melt mass-flow rate is determined in accordance with ASTM D1238 (2013) at a temperature of 190° C.

The present invention also relates, in a certain embodiment, to a polymer formulation comprising the polyethylene composition and a post-consumer recyclate or regrind (PCR) polyethylene material, wherein the PCR material has a density that differs from the density of the polyethylene in the polyethylene composition by at most 20 kg/m³, preferably at most 10 kg/m³, more preferably at most 5 kg/m³.

It is preferred that the polymer formulation comprises 20.0 wt % preferably ≥20.0 and ≤80.0 wt %, of the PCR material, with regard to the total weight of the polymer formulation. For example, the polymer formulation may comprise ≥30.0 and ≤65.0 wt % of the PCR, such as 30.0 and ≤50.0 wt %, or 45.0 and ≤65.0 wt %.

It is preferred that the polymer formulation comprises 20.0 wt %, preferably ≥20.0 and ≤80.0 wt %, of the polyethylene composition, with regard to the total weight of the polymer formulation, more preferably ≥30.0 and ≤65.0 wt %.

The invention also relates to an article comprising the polymer formulation, preferably wherein the article is produced by blow-moulding, more preferably wherein the article is a bottle for holding potable liquids.

The invention further also relates to the use of the polyethylene composition for reduction of degradation products in continuous moulding processes in the manufacturing of moulded articles, preferably bottles, from a polymer formulation comprising a post-consumer recyclate or regrind polyethylene material.

The invention will now be illustrated by the following non-limiting examples.

The following polyethylene compositions were used in the examples of the invention:

		Example
Material		1	2 (c)	3 (c)
Polyethylene	SABIC HDPE	99.8	wt %	99.9	wt %	100.0 wt %
	6246LS
Phenolic	Lowinox	160	ppm	80	ppm	—
antioxidant	MD 24
Organic	Irgafos 168	840	ppm	420	ppm	—
phosphite
stabiliser
Metal	Ca stearate	1000	ppm	500	ppm	—
stearate

The polyethylene compositions were prepared by melt extrusion of the materials as per each of the compositions described above, to obtain polymer pellets according to the above compositions. The wt % of the polyethylene relates to the total weight of the polyethylene composition, the ppm of the additives also relate to the total weight of the polyethylene composition.

Using the polymer compositions as prepared, trials were conducted by blow moulding of bottles. In the blow moulding trials, polymer formulations were used comprising the polyethylene compositions 1-3 as above, and a quantity of post-consumer high-density polyethylene regrind material (PCR). The results of the trials are presented below.

Trial	A	B	C	D
Polyethylene	60 wt % of	40 wt % of	60 wt % of	60 wt % of
composition	example 1	example 1	example 2	example 3
PCR	40 wt %	60 wt %	40 wt %	40 wt %
Die deposit	No	No	2 hrs	2 hrs

From the trials, it was observed that in trials A and B, no die deposit was formed after 5 hours of continuous operation. In trials C and D, after 2 hours die deposits were formed in such quantities that required the operation to be halted and the die surfaces to be cleaned prior to further commencing the moulding operations. Die deposits are an accumulation of degradation products that form during the moulding process from the polymer material. It can be understood that the use of the polyethylene composition of the present invention resulted in a reduction of the die deposits to occur.

Claims

1. A polyethylene composition comprising a polyethylene and further (a) ≥100 and ≤500 ppm of a phenolic antioxidant;(b) ≥500 and ≤2500 ppm of an organic phosphite stabiliser; and(c) ≥500 and 2500 ppm of a metal stearatewith regard to the total weight of the polyethylene composition.

2. The polyethylene composition according to claim 1, wherein the polyethylene is (i) a high-density polyethylene having a density of ≥945 and ≤970 kg/m3;(ii) a low density polyethylene produced by free-radical polymerisation having a density of ≥900 and ≤925 kg/m3;(iii) a linear low-density polyethylene having a density of ≥870 and ≤925 kg/m3;(iv) a medium-density polyethylene having a density of ≥926 and ≤944 kg/m3 or a combination thereof; wherein the density is determined in accordance with ASTM D792 (2008).

3. The polyethylene composition according to claim 1, wherein the phenolic antioxidant comprises 1-4 phenolic moieties

4. The polyethylene composition according to claim 1, wherein the organic phosphite stabiliser is a triphosphite.

5. The polyethylene composition according to claim 1, wherein the metal stearate is selected from calcium stearate, magnesium stearate, aluminium stearate, or lithium stearate.

6. The polyethylene composition according to claim 2, wherein the composition comprises: ≥80.0 wt % of the high-density polyethylene (i);≥80.0 wt % of the low-density polyethylene(ii);≥80.0 wt % of the linear low-density polyethylene (iii); or≥80.0 wt % of the medium-density polyethylene (iv)with regard to the total weight of the polyethylene composition.

7. The polyethylene composition according to claim 2, wherein the composition comprises the high-density polyethylene (i), the low-density polyethylene (ii), the linear low-density polyethylene (iii), or the medium-density polyethylene (iv) as the sole polyethylene material in the composition.

8. The polyethylene composition according to claim 2, wherein the composition consists essentially of: the high-density polyethylene (i), the low-density polyethylene (ii), the linear low-density polyethylene (iii), or the medium-density polyethylene (iv);the phenolic antioxidant;the phosphite stabiliser; andthe metal stearate.

9. The polyethylene composition according to claim 2 wherein the polyethylene is the high-density polyethylene (i).

10. The polyethylene composition according to claim 2 wherein the high-density polyethylene has a melt-mass flow rate of: ≥0.1 and ≤2.0 g/10 min under a load of 2.16 kg;≥1.0 and 10.0 g/10 min under a load of 5.0 kg; and/or≥25.0 and ≤100.0 g/10 min under a load of 21.6 kgas determined in accordance with ASTM D1238 (2013) at a temperature of 190° C.

11. The polymer formulation comprising the polyethylene composition according to claim 1 and a post-consumer recyclate or regrind (PCR) polyethylene material, wherein the PCR material has a density that differs from the density of the polyethylene in the polyethylene composition by at most 20 kg/m3.

12. The polymer formulation according to claim 11, wherein the formulation comprises ≥20.0 wt % of the PCR material, with regard to the total weight of the polymer formulation.

13. The polymer formulation according to claim 11, wherein the formulation comprise ≥20.0 wt % of the polyethylene composition, with regard to the total weight of the polymer formulation.

14. An article comprising the polymer formulation according to claim 11.

15. (canceled)

16. The polyethylene composition according to claim 1 comprising ≥95.0 wt % of polyethylene.

17. The polyethylene composition according to claim 3, wherein the phenolic moieties are 3,5-bis(t-butyl)-4-hydroxybenzene moieties.

18. The polyethylene composition according to claim 3, wherein the phenolic antioxidant is selected from octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, isooctyl 3 (3,5 di t butyl 4 hydroxyphenyl)propionate, tri ethylene glycol bis 3 (t butyl 4 hydroxy 5 methyl phenyl) propionate, 1,6 hexane diol bis 3 (3,5 di t butyl 4 hydroxyphenyl) propionate, 2,2′-methylenebis (6-t-butyl-4-methylphenol), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 2,2′-isobutylidenebis (4,6-dimethylphenol), pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate), tris(3,5 di t butyl 4 hydroxybenzyl)isocyanurate, 1,3,5 trimethyl 2,4,6 tris(3,5 di t butyl 4 hydroxybenzyl)benzene, pentaerythritol tetrakis(3 (3,5 di t butyl 4 hydroxyphenyl)propionate, 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, 1,3,5 tris(3′,5′ di t butyl 4′ hydroxybenzyl) s triazine-2,4,6 (1H,3H,5H)trione, and 1,3,5 tris(4 t butyl 2,6 dimethyl 3 hydroxy benzyl) iso cyanurate, and 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide, preferably ≥1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide.

19. The polyethylene composition according to claim 4, wherein the organic phosphite stabiliser is a triphosphite comprising one or more a substituted or unsubstituted phenyl moieties.

20. The polyethylene composition according to claim 4, wherein the organic phosphite stabiliser is selected from tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, distearylpentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite, and bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite.

21. The polyethylene composition of claim 5, wherein the metal stearate is calcium stearate.