Foamed article

Abstract

The present invention relates to a foamed article comprising a polyolefin composition having a density, determined according to ISO 1183-1 (2019), of > = 0.940 and < = 0.970 g / cm3 wherein the olefin composition comprises:-a polyolefin composition having a density, determined according to ISO 1183-1 (2019), gt, determined according to ISO 1183-1 (2019); and-a high density polyethylene composition having a density of > = 0.917 and lt; as determined according to ISO 1183-1 (2019), and < = 0.940 and < = 0.970 g / cm3; the density of the low-density polyethylene composition is 0.940 g / cm < 3 >; wherein the high density polyethylene composition comprises polypropylene and the amount of polypropylene is > = 0.01 and < = 15.0 wt%, for example > = 0.1 and < = 15.0 wt%, preferably > = 0.1 and < = 10.0 wt%, more preferably > = 0.1 and < = 7.5 wt%, more preferably > = 0.1 and < = 5.0 wt%, more preferably > = 0.1 and < = 3.0 wt%, relative to the total weight of the polyolefin composition.

Description

[0001] The present invention relates to foamed articles comprising a polyolefin composition and to a process for preparing such foamed articles.

[0002] Polymer foams are used in a wide range of applications, such as building and construction, automotive applications, household applications (e.g. food packaging and protective packaging) and consumer applications. Foams are popular due to their good mechanical rigidity, their good insulation properties and their cushioning of mechanical impacts. In addition, the use of foams provides a significant contribution to reducing the use of raw materials. In addition, the use of foams allows lightweight solutions, which is not only advantageous from a cost perspective, but also from a transportation perspective, since less energy is required to transport lighter materials.

[0003] Due to increasing awareness of sustainable development, there is a growing demand to reduce the use of virgin plastics and use recycled materials to manufacture foamed articles. However, recycled materials contain impurities that can affect the stability of the foaming process and the achievable density. Impurities can further affect the visual appearance and mechanical properties of the obtained foamed article.

[0004] EP3088452A1 discloses a molded foam which is molded by clamping a divided mold block, a foamed resin obtained by melting and kneading a polyethylene-based resin, wherein the molded foam has an MFR (190°C, g / 10min) of less than 0.8. EP3088452A1 does not mention the use of recycled polyethylene as the polyethylene-based resin for preparing the molded foam.

[0005] EP1449634A1 discloses a method for producing a foam molded article by molding a parison between molds, the parison having a foam layer formed by extruding an expandable molten resin composition containing polyethylene. EP1449634A1 does not mention the use of recycled polyethylene as the polyethylene for preparing the molded foam.

[0006] EP2246175A1 discloses a polyethylene resin foam blow molded product obtained by extruding a foamable resin melt containing a physical foaming agent through a die to form a foamed parison, then inserting the foamed parison into a mold and blow molding the foamed parison. EP2246175A1 does not mention a foamable resin melt containing polypropylene.

[0007] WO2021025578A1 discloses an article produced by foaming a polyethylene composition comprising 20 to 84 wt% LDPE, 10 to 70 wt% HDPE, 5 to 25 wt% LLDPE, 0.5 to 10 wt% polypropylene and 0 to 2 wt% other additives. WO2021025578A1 does not mention the use of recycled polyethylene as the polyethylene for preparing molded foam.

[0008] It is an object of the present invention to provide a foamed article in which the above-mentioned and / or other problems are solved.

[0009] Therefore, the present invention provides a foamed article, the foamed article comprising a foam having a value of ≥0.940 and ≤0.970 g / cm2 measured according to ISO 1183-1 (2019). 3 A polyolefin composition having a density of

[0010] - Having >0.940 and ≤0.970 g / cm2 as measured according to ISO 1183-1(2019) 3 A high-density polyethylene composition having a density of

[0011] -Having a density of ≥ 0.917 and < 0.940 g / cm2 as determined according to ISO 1183-1(2019) 3 A low-density polyethylene composition having a density of

[0012] The high density polyethylene composition comprises polypropylene and the amount of polypropylene is ≥0.01 and ≤15.0 wt%, for example ≥0.1 and ≤15.0 wt%, preferably ≥0.1 and ≤10.0 wt%, more preferably ≥0.1 and ≤7.5 wt%, more preferably ≥0.1 and ≤5.0 wt%, more preferably ≥0.1 and ≤3.0 wt%, based on the total weight of the polyolefin composition.

[0013] The present invention provides a foamed article, the foamed article comprising a foam having a thickness of ≥0.940 and ≤0.970 g / cm2 measured according to ISO 1183-1 (2019) 3 A polyolefin composition having a density of

[0014] - Having >0.940 and ≤0.970 g / cm2 as measured according to ISO 1183-1(2019) 3 A high-density polyethylene composition having a density of

[0015] -Having a density of ≥ 0.917 and < 0.940 g / cm2 as determined according to ISO 1183-1(2019) 3 A low-density polyethylene composition having a density of

[0016] wherein the high density polyethylene composition comprises polypropylene and the amount of polypropylene is ≥0.01 and ≤15.0 wt%, for example ≥0.1 and ≤15.0 wt%, preferably ≥0.1 and ≤10.0 wt%, more preferably ≥0.1 and ≤7.5 wt%, more preferably ≥0.1 and ≤5.0 wt%, more preferably ≥0.1 and ≤3.0 wt%, relative to the total weight of the polyolefin composition,

[0017] in

[0018] The high-density polyethylene composition comprises high-density propylene in an amount of ≥ 95.0 wt. % relative to the high-density polyethylene composition, wherein the high-density propylene has a molecular weight of > 0.940 and ≤ 0.970 g / cm2 as measured according to ISO 1183-1 (2019). 3 The density of

[0019] The amount of low density polyethylene is at least 95% by weight relative to the total weight of the low density polyethylene composition.

[0020] The total amount of the high density polyethylene composition, the low density polyethylene composition, the optional nucleating agent and the optional additives is 100 wt % relative to the total weight of the polyolefin composition.

[0021] Preferably, the polyolefin composition comprises less than 5.0 wt% linear low density polyethylene (LLDPE), more preferably less than 4.0 wt%, less than 3.0 wt%, less than 2.0 wt%, less than 1.0 wt%, less than 0.5 wt%, less than 0.1 wt% or 0.0 wt% LLDPE.

[0022] Preferably, it has a value of >0.940 and ≤0.970 g / cm2 as determined according to ISO 1183-1 (2019). 3 The total amount of high density polyethylene, low density polyethylene and polypropylene having a density of greater than 95 wt%, at least 96 wt%, at least 97 wt%, at least 98 wt%, or at least 99 wt% relative to the total weight of the polyolefin composition.

[0023] Preferably, it has a value of >0.940 and ≤0.970 g / cm2 as determined according to ISO 1183-1 (2019). 3 The total amount of high density polyethylene and low density polyethylene having a density of greater than 95 wt%, at least 96 wt%, at least 97 wt%, at least 98 wt%, or at least 99 wt% relative to the total weight of the polyolefin composition.

[0024] The polyolefin composition for preparing the foamed article according to the present invention comprises a high-density polyethylene composition and a low-density polyethylene composition. It has been found that although the high-density polyethylene composition comprises polypropylene, the presence of the low-density polyethylene composition in the polyolefin composition allows the low foam density of the foamed article to be achieved and allows a stable foaming process in a relatively wide range of processing temperatures.

[0025] HDPE Composition

[0026] Because the presence of polypropylene is allowed in the high-density polyethylene composition used in the present invention, the high-density polyethylene composition can advantageously be a composition recycled after consumer or a composition comprising recycled after consumer. The term "composition recycled after consumer" is understood to mean that the composition is obtained from a stream derived from mechanical recycling of consumer waste plastics.

[0027] High density polyethylene compositions that are or comprise post-consumer recycled compositions are commercially available and can be obtained, for example, from SABIC or Morssinckhof.

[0028] The amount of polypropylene is ≥0.01 and ≤15.0 wt.-%, for example ≥0.1 and ≤15.0 wt.-%, preferably ≥0.1 and ≤10.0 wt.-%, more preferably ≥0.1 and ≤7.5 wt.-%, more preferably ≥0.1 and ≤5.0 wt.-%, more preferably ≥0.1 and ≤3.0 wt.-%, based on the total weight of the polyolefin composition.

[0029] Preferably, the amount of polypropylene is ≥0.01 and ≤20.0 wt%, for example ≥0.1 and ≤20.0 wt%, ≥0.1 and ≤15.0 wt%, preferably ≥0.1 and ≤10.0 wt%, more preferably ≥0.1 and ≤7.5 wt%, more preferably ≥0.1 and ≤5.0 wt%, more preferably ≥0.1 and ≤3.0 wt%, relative to the total weight of the high-density polyethylene composition.

[0030] Impurities other than polypropylene may be present in the high-density polyethylene composition. In some embodiments, the high-density polyethylene composition comprises polyethylene terephthalate, such as an amount of ≥0.01 wt % and ≤1.0 wt % relative to the high-density polyethylene composition. Alternatively or additionally, the high-density polyethylene composition may comprise a C4 moiety of ≥0.01 wt % and ≤1.0 wt %, a C6 moiety of ≥0.01 wt % and ≤1.0 wt % and / or a C8 moiety of ≥0.01 wt % and ≤1.0 wt % relative to the high-density polyethylene composition. The presence and amount of polypropylene, polyethylene terephthalate, C4 moiety, C6 moiety and C8 moiety in the high-density polyethylene composition can be measured by 13C NMR, such as by the specific method described in the experimental section of the present disclosure.

[0031] Preferably, the majority of the high-density polyethylene composition is high-density polyethylene. Preferably, the high-density polyethylene composition comprises high-density propylene in an amount of ≥75.0 wt. %, such as ≥80.0 wt. %, ≥90.0 wt. %, ≥93.0 wt. % or ≥95.0 wt. %, relative to the high-density polyethylene composition, wherein the high-density propylene has a molecular weight of >0.940 and ≤0.970 g / cm 2 as determined according to ISO 1183-1 (2019).3 density.

[0032] The high density polyethylene composition may further comprise additives such as flame retardants, pigments, lubricants, slip agents, flow promoters, antistatic agents, processing stabilizers, long term stabilizers and / or UV stabilizers.

[0033] Preferably, the amount of the high density polyethylene composition is 60 to 99 wt%, more preferably 61 to 95 wt%, more preferably 62 to 90 wt%, more preferably 63 to 85 wt%, more preferably 64 to 80 wt%, more preferably 65 to 75 wt%, relative to the total weight of the polyolefin composition.

[0034] LDPE composition

[0035] Low Density Polyethylene The composition comprises low density polyethylene.

[0036] Preferably, the amount of low density polyethylene is at least 95 wt%, at least 97 wt%, at least 98 wt%, at least 99 wt% or 100 wt% relative to the total weight of the low density polyethylene composition.

[0037] The low density polyethylene composition may further comprise additives, such as flame retardants, pigments, lubricants, slip agents, flow promoters, antistatic agents, processing stabilizers, long-term stabilizers and / or UV stabilizers. Preferably, the total amount of low density polyethylene and additives is 100 wt % relative to the low density polyethylene composition.

[0038] Low density polyethylene can be produced using autoclave technology or by tubular reactor technology.

[0039] The low density polyethylene may be an ethylene homopolymer or may contain comonomers such as 1-butene or 1-hexene.

[0040] Preferably, the low density polyethylene has a density of <0.940 g / cm2 as determined according to ISO 1183-1 (2019). 3 , preferably ≥0.917 and <0.940 g / cm 3 , preferably ≥0.920 and <0.930 g / cm 3 density.

[0041] Preferably, the low density polyethylene composition has a hardness of ≥0.917 and <0.940 g / cm2 as measured according to ISO 1183-1 (2019). 3 , preferably ≥0.920 and <0.930 g / cm 3 density.

[0042] Preferably, the low density polyethylene composition has a melt mass flow rate of ≥0.10 and ≤5.0 g / 10 min, preferably ≥0.10 and ≤3.0 g / 10 min, preferably ≥0.15 and ≤2.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190°C and 2.16 kg load.

[0043] Preferably, the amount of the low density polyethylene composition is 1 to 40 wt%, more preferably 5 to 39 wt%, more preferably 10 to 38 wt%, more preferably 15 to 37 wt%, more preferably 20 to 36 wt%, more preferably 25 to 35 wt%, relative to the total weight of the polyolefin composition.

[0044] Preferably, the total amount of the high density polyethylene composition and the low density polyethylene composition is at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 97 wt%, at least 98 wt%, at least 99 wt% or 100 wt% relative to the total weight of the polyolefin composition.

[0045] The production methods of HDPE and LDPE are summarized on pages 43-66 in Handbook of Polyethylene by Andrew Peacock (2000; Dekker; ISBN 0824795466).

[0046] Nucleating Agent

[0047] The polyolefin composition may further include a nucleating agent. The nucleating agent may be desirable to increase the pore density and change the dynamics of bubble formation and growth. (Gendron, Thermoplastic foam Processing, 2005, page 209). The amount of the nucleating agent may be, for example, ≥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 %, most preferably ≥0.50 wt % and ≤1.2 wt % based on the polyolefin composition.

[0048] Suitable nucleating agents include, but are not limited to, talc, silicon dioxide, and a mixture of sodium bicarbonate and citric acid. Other suitable nucleating agents include amides, such as azodicarbonamide, amines, and / or saturated or unsaturated aliphatic (C 10 -C 34Examples of suitable amides include fatty acid (bis)amides such as stearamide, caproamide, caprylamide, undecylamide, laurylamide, myristicamide, palmitamide, behenylamide and eicosylamide, hydroxystearamide and alkylenediyl-bis-alkanoamide, preferably (C 2 -C 32 )Alkylene-bis-(C 2 -C 32 )alkaneamides, such as ethylenebisstearamide (EBS), butylenebisstearamide, hexamethylenebisstearamide, ethylenebisbehenamide and mixtures thereof. Suitable amines include or are exemplified by (C 2 -C 18 ) alkylenediamines such as ethylenebishexylamine and hexamethylenebishexylamine. Preferred saturated or unsaturated aliphatic (C 10 -C 34 ) carboxylic acid esters are aliphatic (C 16 -C 24 Preferably, the nucleating agent is selected from the group consisting of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof, more preferably, the nucleating agent is talc.

[0049] In order to prepare foamed articles, it is desirable to use a cell stabilizer. A cell stabilizer is a permeability modifier that slows down the diffusion of, for example, hydrocarbons (e.g., isobutane) to produce dimensionally stable foam. (Gendron, Thermoplastic foam Processing, 2005, pp. 31 and 149) Preferred cell stabilizers include, but are not limited to, glyceryl monostearate (GMS), glyceryl monopalmitate (GMP), palmitamide (palmitide) and / or amides. Suitable amides are, for example, stearyl stearamide, palmitamide and / or stearamide. Suitable mixtures include, for example, mixtures comprising GMS and GMP or mixtures comprising stearamide and palmitamide. Preferably, if a cell stabilizer is used, the cell stabilizer is glyceryl monostearate or stearamide.

[0050] The amount of cell stabilizer to be added depends on the desired cell size and the polyolefin composition used to prepare the foamed article. In general, the cell stabilizer may be added in an amount of ≥ 0.10 and ≤ 3.0 wt. % relative to the polyolefin composition.

[0051] Preferably, the total amount of the high density polyethylene composition, the low density polyethylene composition, and the nucleating agent is at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 97 wt%, at least 98 wt%, at least 99 wt% or 100 wt% relative to the total weight of the polyolefin composition.

[0052] additive

[0053] The polyolefin composition may further comprise additives, such as flame retardants, pigments, lubricants, slip agents, flow promoters, antistatic agents, processing stabilizers, long-term stabilizers and / or UV stabilizers. The additives may be present in any desired amount determined by a person skilled in the art, but are preferably present in an amount of ≥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 polyolefin composition.

[0054] Preferably, the total amount of the high density polyethylene composition, the low density polyethylene composition, the nucleating agent and the additives is 100 wt % relative to the total weight of the polyolefin composition.

[0055] Polyolefin composition

[0056] In some preferred embodiments, the polyolefin composition has a melt mass flow rate (hereinafter sometimes referred to as MFR2) of ≥0.05 and ≤10.0 g / 10 min, preferably ≥0.10 and ≤8.0 g / 10 min, preferably ≥0.10 and ≤4.0 g / 10 min, more preferably ≥0.10 and ≤2.0 g / 10 min, more preferably ≥0.10 and ≤1.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190 ° C and 2.16 kg load. In some preferred embodiments, the polyolefin composition has a melt mass flow rate of ≥0.30 and ≤5.0 g / 10 min, ≥0.50 and ≤4.0 g / 10 min, ≥1.5 and ≤3.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190 ° C and 2.16 kg load.

[0057] In some preferred embodiments, the polyolefin composition has a melt mass flow rate (hereinafter sometimes referred to as MFR5) of ≥0.10 and ≤15.0 g / 10 min, preferably ≥0.15 and ≤8.0 g / 10 min, preferably ≥0.20 and ≤4.0 g / 10 min, more preferably ≥0.25 and ≤3.0 g / 10 min, more preferably ≥0.30 and ≤2.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190 ° C and 5 kg load. In some preferred embodiments, the polyolefin composition has a melt mass flow rate of ≥0.50 and ≤8.0 g / 10 min, ≥1.0 and ≤6.0 g / 10 min, ≥2.0 and ≤4.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190 ° C and 5 kg load.

[0058] In some preferred embodiments, the polyolefin composition has a melt mass flow rate (hereinafter sometimes referred to as MFR21) of ≥5.0 and ≤50 g / 10 min, ≥7.0 and ≤45.0 g / 10 min, preferably ≥10.0 and ≤40.0 g / 10 min, more preferably ≥15.0 and ≤35.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190°C and a load of 21.6 kg. In some preferred embodiments, the polyolefin composition has a melt mass flow rate of ≥10.0 and ≤350.0 g / 10 min, ≥20.0 and ≤250.0 g / 10 min, ≥40.0 and ≤100.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190°C and a load of 21.6 kg.

[0059] Preferably, MFR21 / MFR2 is from 10 to 500, from 20 to 400, from 30 to 350 or from 40 to 300.

[0060] Foam products

[0061] In the context of the present invention, "foamed" or "foam" means a shape having a lower density due to the presence of gas bubbles (eg, air) than the density of the same material without the gas bubbles.

[0062] Preferably, the polyolefin composition is present in the foamed article in an amount of ≥80 to 99.9 wt % based on the foamed article. For example, the polyolefin composition is present in the foamed article in an amount of ≥85 wt %, ≥90 wt %, ≥95 wt %, ≥96 wt %, ≥97 wt %, ≥98 wt %, ≥99 wt %, ≥99.5 wt % based on the foamed article. The foamed article may also consist of the polyolefin composition.

[0063] Preferably, the foamed article has a density of ≥ 0.03 and ≤ 0.90 g / cm2 as determined according to the method of ISO 845 (2006). 3 , preferably ≥0.05 and ≤0.90 g / cm 3 , preferably ≥0.10 and ≤0.90 g / cm 3 , preferably ≥0.20 and ≤0.80 g / cm 3 , preferably 0.22 and ≤ 0.75 g / cm 3 , preferably 0.25 and ≤ 0.60 g / cm 3 , preferably 0.30 and ≤ 0.50 g / cm 3 The foam density.

[0064] 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%, wherein the open cell content is determined according to ASTM D6226-10.

[0065] Preferably, the foamed article is a foamed sheet. As defined herein, the sheet is a shape in which the length is longer than the width and the width is greater than the thickness. The thickness of the sheet is not critical in principle, but may be, for example, ≥50 μm and ≤100 cm, for example ≥0.10 mm and ≤10 cm, ≥0.15 mm and ≤5.0 cm, ≥0.20 mm and ≤3.0 cm, ≥0.1 mm and ≤1.0 cm or ≥0.3 and ≤1.0 mm. The thickness of the sheet may be, for example, ≥50 μm and ≤1.0 mm, >1.0 mm and ≤10 cm or >10 cm and ≤50 cm.

[0066] method

[0067] The present invention further provides a method for preparing a foamed article according to the present invention, comprising the following sequential steps:

[0068] a) providing a polyolefin composition,

[0069] b) adding a blowing agent to the polyolefin composition, for example wherein the blowing agent is added in an amount of ≥ 0.10 wt.-% and ≤ 20 wt.-%, based on the polyolefin composition, and

[0070] c) subjecting the mixture of the polyolefin composition and the blowing agent to a foaming process.

[0071] In some preferred embodiments, the foamed article is a foamed sheet.

[0072] The process of preparing polyolefin foam and foamed sheet is within the knowledge of those skilled in the art. In such a process, the melt of the polyolefin composition mixed with a gaseous or liquid foaming agent is suddenly expanded by pressure reduction. Continuous foaming process and discontinuous process can be applied. In a continuous foaming process, the polyolefin composition is melted and filled with gas before being extruded through a die in an extruder at a pressure typically greater than 20 bar, wherein the pressure reduction causes the formation of foam. For example, HE Naguib, CB Park, N. Reichelt, Fundamental foaming mechanisms governing the volume expansion of extruded polypropylene foams, Journal of Applied Polymer Science, 91, 2661-2668 (2004) explain the mechanism of foaming polypropylene in such foam extrusion process. STLee, Foam Extrusion, Technomic Publishing (2000) summarizes the foaming process. In the discontinuous foaming process, polyolefin composition (micro) pellets are filled with a blowing agent under pressure and heated below the melting temperature before the pressure in the autoclave is suddenly released. The dissolved blowing agent forms bubbles and produces a foam structure.

[0073] Preferably, the foamed sheet of the present invention is prepared by a foam extrusion process.

[0074] The amount of blowing agent depends, for example, on the desired density and the polymer composition used. For example, blowing agent can be used in an amount of ≥ 0.10 wt. % and ≤ 20 wt. %, based on the polyolefin composition.

[0075] Examples of suitable physical blowing agents include, but are not limited to, isobutane, CO2, pentane, butane, nitrogen and / or fluorocarbons. Preferably, the physical blowing agent is isobutane and / or CO2.

[0076] Examples of suitable chemical blowing agents include, but are not limited to, citric acid or citric acid-based materials (e.g., a mixture of citric acid and sodium bicarbonate) and azodicarbonamide. Such chemical blowing agents are available, for example, from Clariant Corporation under the name Hydrocerol TM CF-40E TM or Hydrocerol TM CF-05E TM Commercially available.

[0077] The present invention further provides a method for preparing the foamed sheet according to the present invention, which comprises the following sequential steps:

[0078] a) providing a polyolefin composition,

[0079] b) adding a blowing agent to the polyolefin composition, e.g. wherein the blowing agent is added in an amount of ≥ 0.10 wt.-% and ≤ 20 wt.-%, based on the polyolefin composition,

[0080] c) subjecting the mixture of the polyolefin composition and the blowing agent to a foaming process, preferably a foam extrusion process, to form a foamed sheet, and

[0081] Optionally d) stretching the foamed sheet in at least one direction.

[0082] Preferably, step a) comprises melt mixing the high density polyethylene composition and the low density polyethylene composition and optional components such as nucleating agents and / or additives.

[0083] The present invention also relates to a foamed sheet of the present invention, which is stretched in at least one direction, for example the present invention relates to a foamed sheet of the present invention, wherein the foamed sheet is stretched uniaxially (for example in the longitudinal direction) or for example the present invention relates to a foamed sheet of the present invention, wherein the foamed sheet is stretched biaxially (for example in both the longitudinal direction (MD) and the transverse direction (MD). As known to those skilled in the art, stretching in MD and TD can be performed simultaneously or in consecutive steps.

[0084] The stretch ratio in MD can be, for example, ≥1.1 and ≤7.0, such as ≥1.1 and ≤3.0. The stretch ratio in transverse direction can be, for example, ≥1.1 and ≤7.0, such as ≥1.1 and ≤3.0.

[0085] The articles (particularly sheets) of the present invention can be suitably used in applications such as building and construction, automotive applications, household applications (e.g. food packaging and protective packaging) and consumer applications. For example, the articles (particularly sheets) can be used to make cups, trays, containers, bottles, seals, returnable boxes. Other applications of the articles (particularly sheets) of the present invention are, for example: sandwich panels, pipe insulation, concrete joint fillers, insulating materials for houses, sinks or floors (floor underlays).

[0086] Thus, in another aspect, the present invention relates to an article comprising the foamed sheet of the present invention. In yet another aspect, the present invention relates to the use of the foamed sheet of the present invention in applications such as building and construction, automotive applications, household applications (e.g., food packaging and protective packaging) and consumer applications.

[0087] The invention also relates to the use of the foamed sheet according to the invention for the preparation of an article, for example wherein the article is a cup, a tray, a container, a bottle, a seal, a returnable box, a sandwich panel, pipe insulation, a concrete joint filler, an insulating material for houses, sinks or floors (floor underlays), footwear, protective equipment, a (sports) mat or a foam roller.

[0088] The sheets can be used as a replacement for applications where polystyrene foam is typically used, such as disposable food containers.

[0089] The present invention further provides a multilayer system comprising at least three layers A, B and C in this order, wherein layer B is a foamed sheet according to the invention and preferably

[0090] Layer A comprises a polyethylene composition A, which comprises, for example, LDPE, LLDPE and / or HDPE. Preferably, the polyethylene composition A has a molecular weight of ≥0.940 and ≤0.970 g / cm 3 density, and / or

[0091] Layer C comprises a polyethylene composition C, which comprises, for example, LDPE, LLDPE and / or HDPE. Preferably, the polyethylene composition C has a molecular weight of ≥0.940 and ≤0.970 g / cm 3 The density of

[0092] Density is determined according to ISO 1183-1(2019).

[0093] Preferably, the multilayer system consists of layers A, B and C.

[0094] Examples of multilayer systems include cups, trays, containers, bottles, seals, returnable boxes, sandwich panels, pipe insulation, concrete joint fillers, insulation materials for houses, sinks or floors (floor underlays), footwear, protective gear, (sports) mats or foam rollers.

[0095] The polyethylene composition A may, for example, comprise a homopolymer of ethylene or a copolymer of ethylene and an α-olefin selected from 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene, for example in an amount of ≥80.0 wt.-%, preferably ≥90.0 wt.-%, relative to the total weight of the polyethylene composition A. The amount of moieties derived from 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene may, for example, be ≤5.0 wt.-%, relative to the copolymer.

[0096] The polyethylene composition C may, for example, comprise a homopolymer of ethylene or a copolymer of ethylene and an α-olefin selected from 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene, for example in an amount of ≥ 80.0 wt.-%, preferably ≥ 90.0 wt.-%, relative to the total weight of the polyethylene composition C. The amount of moieties derived from 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene may, for example, be ≤ 5.0 wt.-%, relative to the copolymer.

[0097] It is noted that the present invention relates to the subject matter defined in the independent claims, alone or in combination with any possible combination of features described herein (particularly preferred are those combinations of features present in the claims). It will therefore be understood that all combinations of features associated with the composition according to the invention; all combinations of features associated with the method according to the invention, as well as all combinations of features associated with the composition according to the invention and with features associated with the method according to the invention are described herein.

[0098] It is also noted that the term "comprising / including / containing" does not exclude the presence of other elements. However, it is also understood that a description of a product / composition comprising certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous because it provides a simpler and more economical method for preparing the product / composition. Similarly, it is also understood that a description of a method comprising certain steps also discloses a method consisting of these steps. A method consisting of these steps may be advantageous because it provides a simpler and more economical method.

[0099] The invention will now be illustrated by the following examples without, however, being restricted thereto.

[0100] Material

[0101] Post-consumer mechanically recycled high density polyethylene compositions

[0102] PCR1 PCR2 density <![CDATA[kg / m 3 ]]> 968.6 957.2 MFR2 at 190℃, 2.16kg g / 10min 0.28 0.38 190℃, 5kg, MFR5 g / 10min 1.3 1.86 190℃, 21.6kg, MFR21 g / 10min 38 42 MFR21 / MFR2 136 111 <![CDATA[By 13 composition analysis of 13C NMR]]> PP weight% 1.8 0.6 C4 weight% 0.3 0.2 C6 weight% 0.3 0.3 C8 weight% 0.1 0.1 EVA weight% PET weight% 0.4 0.1

[0103] C4, C6, C8 each indicate the amount of C4, C6 or C8 moieties, respectively, in the high density polyethylene composition.

[0104] PP stands for polypropylene.

[0105] EVA stands for ethylene vinyl acetate.

[0106] PET stands for polyethylene terephthalate.

[0107] LDPE

[0108]

[0109]

[0110] Original HDPE

[0111]

[0112] The MFR in the above table is a value measured according to ISO1133-1:2011.

[0113] Nucleating agent: POLYBATCH FPE 50T NAT (masterbatch of talc in LDPE obtained from Lyondell-Basell)

[0114] 13 C NMR

[0115] In 10mm NMR tube, add about 150mg sample.To this tube, add about 2-3ml tetrachloroethane-d2 (7mg / 20ml) that is stabilized with BHT.Pipe is placed in the Büchi furnace that runs at 130 ℃.Rotate this tube with about 20rpm until sample is completely dissolved.During dissolution, sample is evenly homogenized by the metal rod coated with glass, this metal rod coated with glass is added to solution and moves with the strong magnet on the outside of NMR tube.Before sample is inserted into NMR spectrometer, remove the metal rod coated with glass from sample tube and rinse sample with N2.Measure under suitable conditions on the high field NMR spectrometer equipped with 10mm cryogenic cooling probe (cryo-cooled probehead)13C NMR spectrogram.The number of these branches and polymer impurities is calculated from the integral of each peak corresponding to branch / impurity.

[0116] Preparation of foamed sheets

[0117] The components shown in Table 1 were melt mixed and a foamed sheet was prepared. The foam density was measured according to the method according to ISO 845 (2006) as shown in Table 1.

[0118] The preparation of the foamed sheets was carried out on a 30 mm twin-screw foam extruder from Theysohn with a length to diameter ratio (l / d) of 40. The extruder consisted of nine electrically heated zones equipped with water cooling, a subsequent cooling section, a static mixer and a die. CO was added in an amount of 0.48 wt. %. 2 As a physical foaming agent. A 35 mm slit die with an adjustable die gap was used to produce the foamed sheet. The die pressure was adjusted by adjusting the die gap so that the pressure before the die was 30 bar. The foamed sheet was transferred via a roller and a double belt traction unit. After the traction unit, the foamed samples were collected for analysis.

[0119] Table 1

[0120]

[0121] Despite the presence of impurities, the foamed sheets of Ex 2-3 had an appearance similar to the foamed sheets of CEx 1, 4, and 5.

[0122] The foamed sheets made from the compositions of Ex 2-3 containing post-consumer HDPE and LDPE show lower foam density than those made from the compositions of CEx 1 and CEx 4-5 containing no LDPE. In addition, the deviation of the foam density of the foamed sheets made from the compositions of Ex 2-3 is relatively small within the processing temperature range.

[0123] From Ex 2 and 3, it can be understood that higher amount of LDPE leads to lower foam density.

[0124] Mechanical properties of the composition

[0125] The compositions of Table 2 were molded into 1 mm plaques via the following procedure:

[0126] ■Fill the mould (10x10 cm) with + / - 12 g of granules.

[0127] ■Place the mold into the press.

[0128] ■Close the press with a force of 10kN.

[0129] ■ Raise the temperature from the compression plate to 180°C.

[0130] ■After reaching the temperature set point, wait 5 minutes.

[0131] ■Increase the pressure to 100kN and continue for 5 minutes.

[0132] ■ Allow the sample to cool before removing from the mold.

[0133] Extensional viscosity and strain hardening

[0134] The extensional viscosity of the samples was measured at a fixed temperature of 175 °C and at three different strain rates: 0.5, 1.0 and 5.0 s -1 .

[0135] The strain hardening as a function of time and Hencky strain rate was calculated from the extensional viscosity measurements, (see equation below) where is the instantaneous extensional viscosity that varies with time and Hencky strain rate and η E0(t) is the transient extensional viscosity in the linear viscoelastic regime, which can be determined in two different but equivalent ways: by tripling the transient shear viscosity growth curve at very low strain rates, or by extrapolating the superposition of extensional curves at different strain rates.

[0136]

[0137] Calculated at 0.5, 1.0 and 5.0 s for all materials analyzed -1 Strain hardening under and at determined times (4.8 s, 2.8 s and 0.5 s, respectively).

[0138] Flexural modulus

[0139] Sample dimensions from injection moulded strips produced on a Babyplast injection moulding machine:

[0140] ■Length (l): 63.5mm

[0141] ■Width (b): 12.7mm

[0142] ■Thickness (h): 3.2mm

[0143] Test strips according to ISO-178 on a universal testing machine:

[0144] Test setup:

[0145] ■Span length (L): 51.2mm

[0146] ■Test speed: 2mm / min

[0147] Table 2

[0148]

[0149] It can be understood from Table 2 that the addition of LDPE decreases the flexural modulus.

[0150] Addition of LDPE to post-consumer mechanically recycled HDPE compositions containing impurities resulted in good foam. Additionally, improvements in extensional viscosity and strain hardening were observed.

Claims

1. A foamed article comprising a foam having a thickness of ≥0.940 and ≤0.970 g / cm2 as measured according to ISO 1183-1 (2019) 3 A polyolefin composition having a density of - Having >0.940 and ≤0.970 g / cm2 as measured according to ISO 1183-1(2019) 3 A high-density polyethylene composition having a density of -Having a density of ≥ 0.917 and < 0.940 g / cm2 as determined according to ISO 1183-1(2019) 3 A low-density polyethylene composition having a density of The high density polyethylene composition comprises polypropylene and the amount of polypropylene is ≥0.01 and ≤15.0 wt%, such as ≥0.1 and ≤15.0 wt%, preferably ≥0.1 and ≤10.0 wt%, more preferably ≥0.1 and ≤7.5 wt%, more preferably ≥0.1 and ≤5.0 wt%, more preferably ≥0.1 and ≤3.0 wt%, relative to the total weight of the polyolefin composition.

2. The foamed article of claim 1, wherein the high density polyethylene composition is or comprises a post-consumer mechanically recycled composition.

3. The foamed article according to any one of the preceding claims, wherein the amount of polypropylene is ≥0.01 and ≤20.0 wt. %, such as ≥0.1 and ≤20.0 wt. %, ≥0.1 and ≤15.0 wt. %, preferably ≥0.1 and ≤10.0 wt. %, more preferably ≥0.1 and ≤7.5 wt. %, more preferably ≥0.1 and ≤5.0 wt. %, more preferably ≥0.1 and ≤3.0 wt. %, relative to the total weight of the high-density polyethylene composition.

4. The foamed article according to any one of the preceding claims, wherein the high-density polyethylene composition comprises ≥0.01 wt% and ≤1.0 wt% polyethylene terephthalate, ≥0.01 wt% and ≤1.0 wt% C4 structural parts, ≥0.01 wt% and ≤1.0 wt% C6 structural parts and / or ≥0.01 wt% and ≤1.0 wt% C8 structural parts, relative to the high-density polyethylene composition.

5. The foamed article according to any one of the preceding claims, wherein the high-density polyethylene composition comprises high-density propylene in an amount of ≥ 95.0 wt. % relative to the high-density polyethylene composition, the high-density propylene having a molecular weight of > 0.940 and ≤ 0.970 g / cm2 as determined according to ISO 1183-1 (2019). 3 The density of The amount of low-density polyethylene is at least 95% by weight relative to the total weight of the low-density polyethylene composition. The total amount of the high density polyethylene composition, the low density polyethylene composition, the optional nucleating agent and the optional additives is 100 wt % relative to the total weight of the polyolefin composition.

6. The foamed article according to any one of the preceding claims, wherein the low density polyethylene composition has a hardness of ≥0.917 and <0.940 g / cm2 as determined according to ISO 1183-1 (2019). 3 , preferably ≥0.920 and <0.930 g / cm 3 The invention relates to a polymer having a density of ≥0.10 and ≤5.0 g / 10 min, preferably ≥0.10 and ≤3.0 g / 10 min, preferably ≥0.15 and ≤2.0 g / 10 min, measured at 190° C. and 2.16 kg load according to ISO 1133-1 (2011).

7. A foamed article according to any one of the preceding claims, wherein The amount of the high density polyethylene composition is 60 to 99 wt%, preferably 61 to 95 wt%, more preferably 62 to 90 wt%, more preferably 63 to 85 wt%, more preferably 64 to 80 wt%, more preferably 65 to 75 wt%, relative to the total weight of the polyolefin composition, and The amount of the low density polyethylene composition is 1 to 40 wt%, preferably 5 to 39 wt%, more preferably 10 to 38 wt%, more preferably 15 to 37 wt%, more preferably 20 to 36 wt%, more preferably 25 to 35 wt%, relative to the total weight of the polyolefin composition.

8. The foamed article according to any one of the preceding claims, wherein the polyolefin composition further comprises a nucleating agent, preferably wherein the nucleating agent is present in an amount of ≥ 0.01 wt.-% and ≤ 5.0 wt.-% based on the polyolefin composition and / or wherein the nucleating agent is selected from the group consisting of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof.

9. The foamed article according to any one of the preceding claims, wherein the polyolefin composition has A melt mass flow rate MFR2 of ≥0.05 and ≤10.0 g / 10 min, preferably ≥0.10 and ≤8.0 g / 10 min, preferably ≥0.10 and ≤4.0 g / 10 min, more preferably ≥0.10 and ≤2.0 g / 10 min, more preferably ≥0.10 and ≤1.0 g / 10 min, measured according to ISO 1133-1 (2011) at 190°C and 2.16 kg load, and / or A melt mass flow rate MFR5 of ≥0.10 and ≤15.0 g / 10 min, preferably ≥0.15 and ≤8.0 g / 10 min, preferably ≥0.20 and ≤4.0 g / 10 min, more preferably ≥0.25 and ≤3.0 g / 10 min, more preferably ≥0.30 and ≤2.0 g / 10 min, measured at 190 ° C and 5.0 kg load according to ISO 1133-1 (2011), and / or A melt mass flow rate MFR21 of ≥5.0 and ≤50 g / 10 min, ≥7.0 and ≤45.0 g / 10 min, preferably ≥10.0 and ≤40.0 g / 10 min, more preferably ≥15.0 and ≤35.0 g / 10 min, measured at 190°C and 21.6 kg load according to ISO 1133-1 (2011), Preferably wherein MFR21 / MFR2 is from 10 to 500, from 20 to 400, from 30 to 350 or from 40 to 300.

10. The foamed article according to any one of the preceding claims, wherein the foamed article has a density of ≥ 0.20 and ≤ 0.80 g / cm3 as measured according to the method of ISO 845 (2006). 3 , preferably 0.30 and ≤ 0.50 g / cm 3 The foam density.

11. The foamed article according to any one of the preceding claims, wherein the foamed article is a foamed sheet, wherein the foamed sheet has a thickness of, for example, ≥50 μm and ≤100 cm, ≥0.10 mm and ≤10 cm, ≥0.15 mm and ≤5.0 cm, ≥0.20 mm and ≤3.0 cm, ≥0.1 mm and ≤1.0 cm or ≥0.3 mm and ≤1.0 mm.

12. A method for preparing a foamed article according to any one of the preceding claims, comprising the following sequential steps: a) providing the polyolefin composition, b) adding a blowing agent to the polyolefin composition, for example wherein the blowing agent is added in an amount of ≥ 0.10 wt.-% and ≤ 20 wt.-% based on the polyethylene composition, and c) subjecting the mixture of said polyolefin composition and said blowing agent to a foaming process.

13. The method of claim 12, wherein the foamed article is a foamed sheet and step c) is a foam extrusion process to form the foamed sheet, and the method optionally comprises d) stretching the foamed sheet in at least one direction.

14. The method according to claim 12 or 13, wherein step a) comprises melt mixing the high density polyethylene composition and the low density polyethylene composition.

15. A multilayer system comprising at least three layers A, B and C in this order, wherein the layer B is a foamed sheet according to any one of claims 1 to 10, and preferably The layer A comprises a polyethylene composition A, which comprises, for example, LDPE, LLDPE and / or HDPE. Preferably, the polyethylene composition A has a molecular weight of ≥0.940 and ≤0.970 g / cm 3 density, and / or The layer C comprises a polyethylene composition C, which comprises, for example, LDPE, LLDPE and / or HDPE. Preferably, the polyethylene composition C has a molecular weight of ≥0.940 and ≤0.970 g / cm 3 The density of The density is determined according to ISO 1183-1 (2019).

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