Foamed article

Abstract

The invention relates to a foamed article comprising a foamed article comprising a polymer composition comprising a high density polyethylene composition, wherein the high density polyethylene composition has a melt flow rate MFR2.16 determined according to ASTM D1238 (2013) at 190 ⁰C and 2.16 kg, a melt flow rate MFR21.6 determined according to ASTM D1238 (2013) at 190 ⁰C and 2.16 kg and Mz determined according to ISO16014-1(4):2003, wherein MFR2.16 is at most 0.60 dg / min, MFR21.6 / MFR2.16 is at least 70 and Mz is at least 900 kDa.

Description

[0001] 21POLYOD20-WO-ORD 1

[0002] FOAMED ARTICLE

[0003] The invention relates to a foamed article comprising a polymer composition comprising a high density polyethylene composition. The invention further relates to a process for the preparation of a foamed article using a polymer composition. The invention further relates to use of a polymer composition to prepare a foamed article.

[0004] Polymer foams are used in a wide range of applications, such as building and construction, automotive applications, household applications, such as food packaging and protective packaging; and consumer applications. Foams are popular because of their good mechanical rigidity, their good insulative properties and their cushioning against mechanical shock. In addition, the use of foams provides a significant contribution to the reduction in the use of raw materials. Moreover, the use of foams allows for a lightweight solution, which is not only of advantage from a cost perspective, but also from a transportation point of view as less energy is required to transport a lighter material.

[0005] It is known to make a foamed article from high density polyethylene (HDPE).

[0006] WO2016173967 discloses foam extrusion of high density polyethylene having a quotient of melt strength and apparent viscosity > 2 cN / k.Pa.s. In the examples, HDPE grade CC2056 (melt index of 19.6 g / 10min at 190 °C / 2.16 kg) and CC3054 (melt index of 30 g / 10min at 190 °C / 2.16 kg) were treated by electron beam irradiation and injection moulding foaming was performed.

[0007] It is important for a foamed article to have a low density. Another important property of a foamed article is the type of pores in the foamed article. Open cells are interconnected pores within the foam that enable air and other gases to pass through, while closed cells are isolated pockets of gas that are completely enclosed by the solid foam material. It is important for a foamed article to have a low open cell content.

[0008] It is an objective of the present invention to provide a foamed article by which the above-mentioned and / or other needs are met. 21POLYOD20-WO-ORD 2

[0009] Accordingly, the invention provides a foamed article comprising a polymer composition comprising a high density polyethylene composition, wherein the high density polyethylene composition has a melt flow rate MFR2.16 determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg, a melt flow rate MFR21.6 determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg and

[0010] Mz determined according to IS016014-1(4):2003, wherein

[0011] MFR2.16 is at most 0.60 dg / min, MFR21 .6 / MFR2.16 is at least 70 and Mz is at least 900 kDa.

[0012] According to the invention, it was surprisingly found that a foamed article with low density and low open cell content is obtained by the use of high density polyethylene composition with specific melt flow rate and molecular weight properties.

[0013] It was further surprisingly found that such high density polyethylene composition can be used for making a foamed article without irradiation. Accordingly, preferably, the high density polyethylene composition is a non-irradiated high density polyethylene composition. This is advantageous in that the foamed article can be obtained by a simpler process.

[0014] Typically, high density polyethylene is irradiated before it is subjected to foaming. US5508319 describes typical irradiation conditions. US5508319 describes that the most practical kinds of irradiation are electrons and gamma rays and that preferred are electrons beamed from an electron generator having an accelerating potential of 500- 4,000 kilovolts. US5508319 further describes that preferred are ionizing radiation of about 0.2 to 2.0 megarads, preferably 0.3 to less than 2.0 megarads and most preferably 0.5 to 1.5 megarads, delivered generally at a dose rate of about 1-10,000 megarads per minute, and preferably about 18-2,000 megarads per minute.

[0015] The term “non-irradiated high density polyethylene composition” may herein be understood to mean a high density polyethylene composition which has not been subjected to an ionizing radiation of 0.2 megarads or more. Preferably, the nonirradiated high density polyethylene composition is a high density polyethylene composition which has not been subjected an ionizing radiation of 1.0 megarads or more, more preferably of 0.5 megarads or more, more preferably 0.1 megarads or 21POLYOD20-WO-ORD 3 more. The non-irradiated high density polyethylene composition may be a high density polyethylene composition which has been obtained by polymerization in a reactor to obtain a high density polyethylene and optional pelletization of the high density polyethylene from the reactor and optional additives, without an ionizing radiation step after the high density polyethylene is obtained.

[0016] Preferably, the high density polyethylene composition has a branching index g’ of at least 0.50, at least 0.60, at least 0.70, at least 0.80, at least 0.90, at least 0.95, at least 0.98 or at least 0.99.

[0017] The branching index quantifies the degree of long chain branching. The branching index g' is defined as g'=[I ]br / [IV]iinin which g' is the branching index, [IVbr] is the intrinsic viscosity of the tested polyethylene and [I Jiinis the intrinsic viscosity of the linear polypropylene having the same weight average molecular weight (within a range of ±10 %) as the tested polyethylene.

[0018] Preferably, the high density polyethylene composition has a melt strength / apparent viscosity of less than 2 cN / k.Pa.s, wherein the melt strength is determined as described in ISO 16790:2005 and the apparent viscosity is determined as described in ISO11443:2014.

[0019] HDPE composition

[0020] The high density polyethylene composition comprises a high density polyethylene (HDPE) and optionally additives. Preferably, the high density polyethylene composition consists of a high density polyethylene (HDPE) and optionally additives. Preferably, the amount of high density polyethylene in the high density polyethylene composition is at least 95.0 wt%, at least 96.0 wt%, at least 97.0 wt%, at least 98.0 wt%, at least 99.0 wt%, at least 99.5 wt% or at least 99.9 wt%. Preferably, the amount of high density polyethylene composition in the polymer composition is at least 95.0 wt%, at least 96.0 wt%, at least 97.0 wt%, at least 98.0 wt%, at least 99.0 wt%, at least 99.5 wt% or at least 99.9 wt%

[0021] The additives in the HDPE composition may e.g. be flame retardants, pigments, lubricants, slip agents flow promoters, antistatic agents, processing stabilizers, long term stabilisers and / or UV stabilizers. The additives in the HDPE composition may be present in any desired amount to be determined by the man skilled in the art, but are preferably present > 0.001 wt% and < 5.0 wt%, more preferably > 0.01 wt% and < 4.0 21POLYOD20-WO-ORD 4 wt%, even more preferably > 0.01 wt% and < 3.0 wt%, even more preferably > 0.01 wt% and < 2.0 wt% based on the high density polyethylene composition.

[0022] Preferably, the high density polyethylene composition has a density of 0.940 to 0.970 g / cm3, more preferably 0.950 to 0.967 g / cm3, more preferably 0.952 to 0.964 g / cm3, determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0023] The high density polyethylene composition has a melt flow rate MFR2.16 determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg. MFR2.16 of the high density polyethylene composition is at most 0.60 dg / min, preferably 0.10 to 0.60 dg / min. This allows obtaining a foamed article having low density and low open cell content.

[0024] The high density polyethylene composition has a melt flow rate MFR21.6 determined according to ASTM D1238 (2013) at 190 °C and 21.6 kg. Preferably, MFR21.6 of the high density polyethylene composition is 15 to 50 dg / min. This allows obtaining a foamed article having low density and low open cell content.

[0025] MFR21.6 / MFR2.16, i.e. the ratio of MFR21.6 of the high density polyethylene composition to MFR2.16 of the high density polyethylene composition, is at least 70, preferably 70 to 160. This allows obtaining a foamed article having low density and low open cell content.

[0026] The high density polyethylene composition has Z-average molecular weight Mz determined according to IS016014-1 (4):2003 of at least 900 kDa, preferably 900 to 2500 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0027] The high density polyethylene composition has weight average molecular weight Mw determined according to IS016014-1 (4):2003 of preferably at least 130 kDa, preferably 132 to 220 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0028] The high density polyethylene composition has number average molecular weight Mn determined according to IS016014-1 (4):2003 of preferably 9 to 15 kDa. This allows obtaining a foamed article having low density and low open cell content. 21POLYOD20-WO-ORD 5

[0029] Preferably, Mz / Mw, i.e. the ratio of Mz of the high density polyethylene composition to Mw of the high density polyethylene of the composition, is 6.5 to 12. This allows obtaining a foamed article having low density and low open cell content.

[0030] Preferably, Mw / Mn, i.e. the ratio of Mw of the high density polyethylene composition to Mn of the high density polyethylene of the composition, is 10 to 30. This allows obtaining a foamed article having low density and low open cell content.

[0031] Preferably, the high density polyethylene composition has [Mz (kDa) + Mw (kDa)], i.e. sum of Mz (kDa) of the high density polyethylene composition and Mw (kDa) of the high density polyethylene composition, of 1030 kDa, for example 1030 to 2500 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0032] Preferably, the high density polyethylene composition has a ratio of Mz (kDa) to density (g / cm3), i.e. ratio of Mz (kDa) of the high density polyethylene composition to the density (g / cm3) of the high density polyethylene composition, of at least 0.92, preferably 0.92 to 2.5, wherein Mz is determined according to IS016014-1(4):2003 and the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0033] Preferably, the high density polyethylene composition has a ratio of Mw (kDa) to density (g / cm3), i.e. ratio of Mz (kDa) of the high density polyethylene composition to the density (g / cm3) of the high density polyethylene composition, of at least 0.140, preferably 0.140 to 0.250, wherein Mw is determined according to IS016014-1 (4):2003 and the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0034] Preferably, the high density polyethylene has a ratio of [Mz (kDa) + Mw (kDa)] to density (g / cm3), i.e. ratio of sum of Mz (kDa) of the high density polyethylene composition and Mw (kDa) of the high density polyethylene composition to the density (g / cm3) of the high density polyethylene composition, of at least 1.06, for example 1.06 to 3.00, wherein Mz and Mw are determined according to IS016014-1(4):2003 and the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0035] HDPE 21POLYOD20-WO-ORD 6

[0036] The production processes of polyethylene including HDPE are summarised in Handbook of Polyethylene by Andrew Peacock (2000; Dekker; ISBN 0824795466) at pages 43- 66. The catalysts can be divided in three different subclasses including Ziegler Natta catalysts, Phillips catalysts and single site catalysts. The latter class is a family of different classes of compounds, metallocene catalysts being one of them. As elucidated at pages 53-54 of said Handbook a Ziegler-Natta catalysed polymer is obtained via the interaction of an organometallic compound or hydride of a Group l-lll metal with a derivative of a Group IV-VIII transition metal. An example of a (modified) Ziegler-Natta catalyst is a catalyst based on titanium tetra chloride and the organometallic compound triethylaluminium. A difference between metallocene catalysts and Ziegler Natta catalysts is the distribution of active sites. Ziegler Natta catalysts are heterogeneous and have many active sites. Consequently polymers produced with these different catalysts will be different regarding for example the molecular weight distribution and the comonomer distribution.

[0037] The high density polyethylene may be an ethylene homopolymer or may comprise a comonomer. Preferably, the HDPE is an ethylene- 1 -butene copolymer or an ethylene- 1 -hexene copolymer.

[0038] Preferably, the high density polyethylene in the high density polyethylene composition has properties which are the same or similar to the high density polyethylene composition, in particular regarding the density, melt flow rate and molecular weight.

[0039] Preferably, the high density polyethylene has a density of 0.940 to 0.970 g / cm3, more preferably 0.950 to 0.967 g / cm3, more preferably 0.952 to 0.964 g / cm3, determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0040] Preferably, the high density polyethylene has a melt flow rate determined according to ASTM D1238 (2013) at 190 °C and 21.6 kg of at most 0.60 dg / min, preferably 0.1 O to 0.60 dg / min. This allows obtaining a foamed article having low density and low open cell content.

[0041] Preferably, the high density polyethylene has a melt flow rate determined according to ASTM D1238 (2013) at 190 °C and 21.6 kg of 15 to 50 dg / min. This allows obtaining a foamed article having low density and low open cell content. 21POLYOD20-WO-ORD 7

[0042] Preferably, The ratio of the melt flow rate determined according to ASTM D1238 (2013) at 190 °C and 21.6 kg of the high density polyethylene to the melt flow rate determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg of the high density polyethylene is at least 70, preferably 70 to 160. This allows obtaining a foamed article having low density and low open cell content.

[0043] Preferably, the high density polyethylene has Z-average molecular weight Mz determined according to IS016014-1 (4):2003 of at least 900 kDa, preferably 900 to 2500 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0044] Preferably, the high density polyethylene has weight average molecular weight Mw determined according to IS016014-1 (4):2003 of preferably at least 130 kDa, preferably 132 to 220 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0045] Preferably, the high density polyethylene has number average molecular weight Mn determined according to IS016014-1 (4):2003 of preferably 9 to 15 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0046] Preferably, the ratio of Mz of the high density polyethylene to Mw of the high density polyethylene is 6.5 to 12. This allows obtaining a foamed article having low density and low open cell content.

[0047] Preferably, the ratio of Mw of the high density polyethylene to Mn of the high density polyethylene is 10 to 30. This allows obtaining a foamed article having low density and low open cell content.

[0048] Preferably, the high density polyethylene has sum of Mz (kDa) of the high density polyethylene and Mw (kDa) of the high density polyethylene of 1030 kDa, for example 1030 to 2500 kDa. This allows obtaining a foamed article having low density and low open cell content.

[0049] Preferably, the high density polyethylene has a ratio of Mz (kDa) of the high density polyethylene to the density (g / cm3) of the high density polyethylene of at least 0.92, preferably 0.92 to 2.5, wherein Mz is determined according to IS016014-1(4):2003 and 21POLYOD20-WO-ORD 8 the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0050] Preferably, the high density polyethylene has a ratio of Mw (kDa) of the high density polyethylene to the density (g / cm3) of the high density polyethylene of at least 0.140, preferably 0.140 to 0.250, wherein Mw is determined according to IS016014-1 (4):2003 and the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0051] Preferably, the high density polyethylene has a ratio of sum of Mz (kDa) of the high density polyethylene composition and Mw (kDa) of the high density polyethylene to the density (g / cm3) of the high density polyethylene composition of at least 1.06, for example 1.06 to 3.00, wherein Mz and Mw are determined according to ISO16014- 1 (4):2003 and the density is determined according to ASTM D792 (2008). This allows obtaining a foamed article having low density and low open cell content.

[0052] Further components in polymer composition

[0053] The polymer composition may further comprise additives, such as for example flame retardants, pigments, lubricants, slip agents flow promoters, antistatic agents, processing stabilizers, long term stabilisers and / or UV stabilizers. The additives in the polymer composition present in addition to the high density polyethylene composition may be present in any desired amount to be determined by the man skilled in the art, but are preferably present > 0.001 wt% and < 5.0 wt%, more preferably > 0.01 wt% and < 4.0 wt%, even more preferably > 0.01 wt% and < 3.0 wt%, even more preferably > 0.01 wt% and < 2.0 wt% based on the polymer composition.

[0054] The polymer composition may further comprise a nucleating agent. A nucleating agent may be desired to increase the cell density and to modify the dynamics of bubble formation and growth. (Gendron, Thermoplastic foam Processing, 2005, page 209).

[0055] The amount of nucleating agent may for example be > 0.010 wt% and < 5.0 wt%, for example > 0.030 wt% and < 4.0 wt%, for example > 0.050 wt% and < 3.0 wt%, preferably > 0.10 wt% and < 2.5 wt%, more preferably > 0.30 wt% and < 1.5 wt% based on the polymer composition, most preferably > 0.50 wt% and < 1 ,2wt% based on the polymer composition.

[0056] Suitable nucleating agents include but are not limited to talc, silica and a mixture of 21POLYOD20-WO-ORD 9 sodium bicarbonate and citric acid. Other suitable nucleating agents include amides, for example azo dicarbonamide, amines and / or esters of a saturated or unsaturated aliphatic (C10-C34) carboxylic acid. Examples of suitable amides include fatty acid (bis)amides such as for example stearamide, caproamide, caprylamide, undecylamide, lauramide, myristamide, palmitamide, behenamide and arachidamide, hydroxystearamides and alkylenediyl-bis-alkanamides, preferably (C2-C32) alkylenediyl- bis-(C2-C32) alkanamides, such as for example ethylene bistearamide (EBS), butylene bistearamide, hexamethylene bistearamide, ethylene bisbehenamide and mixtures thereof. Suitable amines include or instance (C2-Ci8) alkylene diamines such as for example ethylene biscaproamine and hexamethylene biscaproamine. Preferred esters of a saturated or unsaturated aliphatic (C10-C34) carboxylic acid are the esters of an aliphatic (C16-C24) carboxylic acid. Preferably, the nucleating agent is chosen from the group of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof, more preferably, the nucleating agent is talc.

[0057] For the preparation of the foamed article, it may be desired to use a cell stabilizer. Cell stabilizers are permeability modifiers which retard the diffusion of for example hydrocarbons such as isobutane to create dimensionally stable foams. (Gendron, Thermoplastic foam Processing, 2005, pages 31 and 149) Preferred cell stabilizers include but are not limited to glycerol monostearate (GMS), glycerol monopalmitate (GMP), palmitides and / or amides. Suitable amides are for example stearyl stearamide, palmitide and / or stearamide. Suitable mixtures include for example a mixture comprising GMS and GMP or a mixture comprising stearamide and palmitamide. Preferably, in case a cell stabilizer is used, the cell stabilizer is glycerol monostearate or stearamide.

[0058] The amount of cell stabilizer to be added depends on desired cell size and the polymer composition used for the preparation of the foamed article. Generally, the cell stabiliser may be added in an amount > 0.10 and < 3.0 wt % relative to the polymer composition. Preferably, the polymer composition is present in the foamed article in an amount > 95 wt% based on the foamed article. For example, the polymer composition is present in the foamed article in an amount > 96 wt%, > 97 wt%, > 98 wt%, > 99 wt%, > 99.5 wt% based on the foamed article. The foamed article may also consist of the polymer composition.

[0059] Preferably, the density of the foamed article is < 650 kg / m3and > 20kg / m3, preferably < 500 kg / m3and > 30kg / m3, more preferably < 300 kg / m3and > 30kg / m3, more preferably 21POLYOD20-WO-ORD 10

[0060] < 100 kg / m3and > 30kg / m3, wherein the density is determined according to ISO 845:2006.

[0061] Preferably, the foamed article has an open cell content of < 15.0 % , preferably < 12.0%, more preferably < 10.0%, even more preferably < 7.0%, even more preferably < 5.0%, even more preferably < 4.0%, even more preferably < 3.0%, even more preferably < 2.0%, even more preferably < 1 .0%, wherein the open cell content is determined according to the method described in the experimental section.

[0062] Process

[0063] The foamed article according to the invention is obtained by subjecting the polymer composition to a foaming process preferably selected from foam extrusion, foam blow molding, foam injection molding, bead foam extrusion and autoclave bead foaming.

[0064] Preferably, the foamed article according to the invention is obtained by foam extrusion of the polymer composition.

[0065] The foamed article according to the invention may e.g. be a foamed sheet, a foamed film, a foamed rod or a foamed tube.

[0066] Processes for the preparation of foamed articles such as foamed sheets are within the knowledge of the person skilled in the art. In such a process, a melt of a polymer composition mixed with a gaseous or liquid blowing agent is suddenly expanded through a pressure drop. Continuous foaming processes as well as discontinuous processes may be applied. In a continuous foaming process, the polymer composition is melted and laden with gas in an extruder under pressures typically above 20 bar before being extruded through a die where the pressure drop causes the formation of a foam. Processes for foaming are outlined in S. T. Lee, Foam Extrusion, Technomic Publishing (2000). In a discontinuous foaming process, the polymer composition (micro-)pellets are laden with foaming agent under pressure and heated below melting temperature before the pressure in the autoclave is suddenly relaxed. The dissolved foaming agent forms bubbles and creates a foam structure.

[0067] During the extrusion, parameters such as the die opening size and the pulling speed may be adjusted such that sufficient shear stress is applied to result in anisotropic properties, e.g. higher stiffness in the extrusion direction than the thickness direction, of the foamed article obtained. 21POLYOD20-WO-ORD 11

[0068] Preferably, the foamed article is prepared by a process comprising the sequential steps of:

[0069] A) providing the polymer composition,

[0070] B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition and

[0071] C) subjecting the mixture of the polymer composition and the blowing agent to a foaming process, preferably a foam extrusion process, to form the foamed article.

[0072] Preferably, step A) does not comprise irradiation. Preferably, step A) does not comprise an ionizing radiation of 0.2 megarads or more after the high density polyethylene is obtained by polymerization in a reactor. Step A) may consist of polymerization of the high density polyethylene in a reactor and optional pelletization of the high density polyethylene from the reactor and optional additives.

[0073] The amount of blowing agent for example depends on the desired density and the polymer composition used. For example, the blowing agent may be used in an amount > 0.10 wt% and < 20 wt% based on the polymer composition.

[0074] Examples of suitable physical blowing agents include, but are not limited to isobutane, CO2, pentane, butane, nitrogen and / or a fluorohydrocarbon. Preferably, the physical blowing agent is isobutane and / or CO2, most preferably isobutane.

[0075] Examples of suitable chemical blowing agents include, but are not limited to citric acid or a citric acid-based material (e.g. mixtures of citric acid and sodium bicarbonate) and azo dicarbonamide. Such chemical blowing agents are for example commercially available from Clariant Corporation under for example the name Hydrocerol ™ CF- 40E™ or Hydrocerol™ CF-05E™.

[0076] Preferably, step C) is a foam extrusion process comprising melt mixing the mixture and foaming the melt mixture at temperatures in the range of 120 to 140°C.

[0077] The foamed article thus prepared may be stretched monoaxially or biaxially using a manner known per se. This further enhances the anisotropy of the compression strength of the foamed article. 21POLYOD20-WO-ORD 12

[0078] Therefore, the foamed article may be prepared by a process comprising the sequential steps of:

[0079] A) providing the polymer composition of the invention,

[0080] B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition and

[0081] C) subjecting the mixture of the polymer composition and the blowing agent to a foam extrusion process to form the foamed article and

[0082] D) stretching the foamed article in at least one direction.

[0083] The foamed article may be a foamed sheet which has been stretched in at least one direction, for example wherein the foamed sheet has been monoaxially stretched (for example in the machine direction) or for example the foamed sheet has been biaxially stretched, for example in both the machine direction (MD) and in the transverse direction (TD). As is known to the person skilled in the art, the stretching in MD and TD may be carried out simultaneously, or in consecutive steps.

[0084] The draw ratio in MD may for example be > 1.1 and < 7.0, for example > 1.1 and < 3.0. The draw ratio in transverse direction may for example be > 1.1 and < 7.0, for example > 1.1 and < 3.0.

[0085] The foamed article or the foamed sheet of the invention can suitably be used in applications such as building and construction, automotive applications, household applications, such as food packaging and protective packaging; and consumer applications. For example, the sheets can be used for the preparation of cups, trays, containers, bottles, seals, returnable boxes. Other applications of the sheets of the invention are for example: sandwich panels, pipe insulations, concrete joint fillers, insulation materials for houses, water tanks or floors (floor underlayments).

[0086] The very good cushioning properties of the foamed article or the foamed sheet of the invention offer the user safety and comfort. The foamed article or the foamed sheet is applicable in multiple applications requiring non-slip performance, such as footwear, protective guards, sports floor mats and foam rollers.

[0087] The foamed article or the foamed sheet of the invention can be used as a replacement for applications wherein polystyrene foam is typically used, such as disposable food containers. 21POLYOD20-WO-ORD 13

[0088] The invention further provides use of the polymer composition as described herein to prepare a foamed article.

[0089] It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the compositions according to the invention; all combinations of features relating to the processes according to the invention and all combinations of features relating to the compositions according to the invention and features relating to the processes according to the invention are described herein.

[0090] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

[0091] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0092] Materials

[0093] The grade names and properties of the high density polyethylene compositions used are shown in Table 1 , they are commercially available from SABIC.

[0094] Talc: POLYBATCH® FPE 50 T, which is a 50% masterbatch of talcum in polyethylene and is used as nucleating agent and is commercially available from LyondellBasell.

[0095] GMS: Atmer™ 7300 50%MB, which is a 50% concentrate in polyethylene containing an anti-static agent (glycerol monostearate) and which is commercially available from Croda. 21POLYOD20-WO-ORD 14

[0096] PBA: Physicial blowing agent. In the below foaming experiments, iso-butane was used as physical blowing agent.

[0097] Preparation of the foamed samples by extrusion

[0098] HDPE composition (96 wt%) having properties shown in Table 1 , talc (2 wt%) and GMS (2 wt%) were dosed at the start of a co-rotating twin-screw extruder. The extruder was a 30mm double screw foam extruder from Theysohn having a length over diameter ratio (l / d) of 40. This extruder consists of nine electrical heating zones quipped with water-cooling followed by a cooling section, a static mixer and a die. The PBA was dosed in an amount of 10wt% based on the polymer composition in zone 8. The molten mixture as obtained was then cooled using a melt cooler. After cooling, the melt was extruded through an adjustable slit die at a throughput of 10kg / h. The die pressure was set to 30 bar. Samples were taken after 30 minutes stabilization time. Foam density and open cell content were determined and are shown in Table 1 .

[0099] Measurement methods

[0100] Melt flow rate (MFR)

[0101] The melt flow rate of the HDPE composition was determined in accordance with ASTM D1238 (2013) at a temperature of 190 °C (MFR190) under a load of 2.16 kg or 21.6 kg.

[0102] The density of the HDPE composition was determined in accordance with ASTM D792 (2008).

[0103] Molecular weight distribution

[0104] The number average molecular weight (Mn), the weight average molecular weight (Mw) and the z-average molecular weight (Mz) were determined using ISO16014- 1 (4):2003.

[0105] Foam density

[0106] Density of the foam (kg / m3) is the apparent overall density and was determined according to ISO 845:2006. To this end, first the weight (m) of a foamed sample was determined with a scale in air. Secondly, the foamed sample was placed into a perforated metal cage. The volume (V) of the foamed sample was determined under water by measuring buoyancy force using a scale. The (buoyancy) is directly related 21POLYOD20-WO-ORD 15 with the geometric volume of the sample. The foam density can be calculated using following equation: p =

[0107] 21POLYOD20-WO-ORD 16

[0108] Open cell content

[0109] The open cell content was determined as follows.

[0110] Three specimen of known weight (Wtdry) of the same foam sample having a fixed length of 2, 4 and 8 cm are placed in a desiccator filled with demineralized water and connected to a vacuum pump. After hermetically closing the desiccator, an under pressure equivalent to half of ambient pressure (around 500 mbar) is applied to the closed environment. Following a waiting time of 10 minutes after the set pressure is reached in the desiccator, the under pressure is released and the foam specimen are collected and dried from the adhering water by using an absorbent paper towel. The specimen are subsequently weighted again to determine Wtwet.

[0111] The open cell content is calculated per each sample length by the ratio between the volume of water penetrated inside the foam cells and the total volume occupied by the foam cells and corrected by a factor 2 since it is assumed that only half of the volume of the open cells is filled with the absorbed water (being the applied pressure half of the ambient pressure).

[0112] Wherein:

[0113] Ov = Open cell content [%] nifoam.wet = mass foam sample wet mfoam dry = mass foam sample dry Pwater = density water 10OOkg / m3Pfoam = density foam sample Ppoiymer = density of the polymer

[0114] The average value of the open cell content is obtained by considering the values measured for the 3 different sample lengths. 21POLYOD20-WO-ORD 17

[0115] Table 1

[0116] It can be understood that foamed articles according to the invention have very low open cell content (Ov%) and low density.

Claims

21POLYOD20-WO-ORD 18CLAIMS1 . A foamed article comprising a polymer composition comprising a high density polyethylene composition, wherein the high density polyethylene composition has a melt flow rate MFR2.16 determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg, a melt flow rate MFR21.6 determined according to ASTM D1238 (2013) at 190 °C and 2.16 kg andMz determined according to IS016014-1(4):2003, whereinMFR2.16 is at most 0.60 dg / min, MFR21 .6 / MFR2.16 is at least 70 and Mz is at least 900 kDa, wherein high density polyethylene composition consists of a high density polyethylene (HDPE) and optionally additives, wherein the amount of high density polyethylene composition in the polymer composition is at least 95.0 wt%, wherein the polymer composition is present in the foamed article in an amount > 95 wt% based on the foamed article.

2. The foamed article according to claim 1 , wherein the high density polyethylene composition is a non-irradiated high density polyethylene composition.

3. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition comprises a high density polyethylene which comprises or is an ethylene homopolymer, an ethylene- 1 -butene copolymer and / or an ethylene- 1 -hexene copolymer, preferably the high density polyethylene is an ethylene- 1 -butene copolymer or an ethylene- 1 -hexene copolymer.

4. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has a density of 0.940 to 0.970 g / cm3, more preferably 0.950 to 0.967 g / cm3, more preferably 0.952 to 0.964 g / cm3, determined according to ASTM D792 (2008).

5. The foamed article according to any one of the preceding claims, wherein MFR21.6 is 15 to 50 dg / min.

6. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has weight average molecular weight Mw21POLYOD20-WO-ORD 19 determined according to IS016014-1 (4):2003 of at least 130 kDa, preferably 132 to 220 kDa.

7. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has number average molecular weight Mn determined according to IS016014-1 (4):2003 of preferably 9 to 15 kDa.

8. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has a ratio of Mz (kDa) to density (g / cm3) of at least 0.92, preferably 0.92 to 2.5, wherein the density is determined according to ASTM D792 (2008).

9. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has a ratio of Mw (kDa) to density (g / cm3) of at least 0.140, preferably 0.140 to 0.250, Mw is determined according to ISO16014- 1 (4):2003 and the density is determined according to ASTM D792 (2008).

10. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has [Mz (kDa) + Mw (kDa)] of 1030 kDa, for example 1030 to 2500 kDa, wherein Mw is determined according to ISO16014- 1 (4):2003.

11. The foamed article according to any one of the preceding claims, wherein the high density polyethylene composition has a ratio of [Mz (kDa) + Mw (kDa)] to density (g / cm3) of at least 1.06, for example 1 .06 to 3.00, wherein Mw is determined according to IS016014-1(4):2003 and the density is determined according to ASTM D792 (2008).

12. The foamed article according to any one of the preceding claims, wherein the polymer composition further comprises a nucleating agent, preferably wherein the nucleating agent is present in an amount > 0.01 wt% and < 5.0 wt% based on the composition and / or preferably wherein the nucleating agent is the nucleating agent is chosen from the group of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof.21POLYOD20-WO-ORD 2013. The foamed article according to any one of the preceding claims, wherein the polymer composition is present in the foamed article in an amount > 95 wt% based on the foamed article.

14. The foamed article according to any one of the preceding claims, wherein the foamed article is obtained by subjecting the polymer composition to a foaming process preferably selected from foam extrusion, foam blow molding, foam injection molding, bead foam extrusion and autoclave bead foaming.

15. A process for the preparation of the foamed article of any one of claims 1-14, comprising the sequential steps of:A) providing the polymer composition of any one of claims 1-14 andB) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition andC) subjecting the mixture of the polymer composition and the blowing agent to a foaming process, preferably a foam extrusion process, to form the foamed article.

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