Process for producing blended low density polyethylene composition comprising recycled polymer composition

Abstract

A process for producing a blended low density polyethylene composition, the process comprising the step of blending a first component comprising one or more recycled polymer compositions with a second component comprising one or more low density polyethylenes.

Description

Technical Field

[0001] The present disclosure relates to a method for producing a blended low-density polyethylene (LDPE) composition, wherein the blended low-density polyethylene composition comprises a first component, and the first component comprises one or more recycled polymer compositions. The product thus obtained is particularly suitable for foam products, cast films, and / or blown films. Background Art

[0002] Low-density polyethylene is a well-known thermoplastic with a variety of uses. For example, LDPE (especially LDPE obtained by free-radical polymerization of ethylene) is commonly used in various applications such as packaging films, agricultural films, shopping bags, heavy-duty transport bags, foam products, bottle caps and seals, pipes, tubes, automotive parts, household items, medical applications, liners, and toys.

[0003] Depending on the specific application, the polymer needs to have different properties.

[0004] In particular, for foam products, such as foam products for soft packaging and blown films, a fine balance needs to be achieved between the molecular weight (and thus the melt flow index) and the melt strength.

[0005] Given the current market development seeking to reduce the environmental footprint in the value chain of materials (including polymeric materials), the need to reuse materials and reduce the amount of "new" materials used in the production of various products persists.

[0006] In the field of polymeric material applications, this translates into a need to recycle materials and reduce the amount of so-called "virgin" polymeric materials (i.e., polymeric materials provided as new polymers obtained from polymerization methods such as polymerization of monomer materials based on fossil materials and / or bio-derived monomers).

[0007] Therefore, a favorable source of LDPE materials is currently represented by LDPE recyclates, which mainly come from the recycling of post-consumer and / or industrial plastic waste.

[0008] EP 3 838 984 A1 discloses a polymer composition comprising: (A) a first polyolefin component, wherein the first polyolefin component comprises a multimodal polyolefin polymer, preferably consisting of the multimodal polyolefin polymer; (B) a second polyolefin component; and (C) an optional filler. Based on the total weight of the polymer composition, the content of the first polyolefin component (A) is 65% to 99% by weight, and based on the total weight of the polymer composition, the content of the second polyolefin component (B) is 35% to 1% by weight.

[0009] WO 2021 / 122299 A1 relates to a mixed plastic polyethylene composition comprising: - a total of 90.00% to 99.00% by weight of ethylene units (C2 units), and – a total of 0.01% to 5.00% by weight of consecutive units containing 3 carbon atoms corresponding to polypropylene (consecutive C3 units), wherein the total of C2 units and consecutive C3 units is based on the total weight of monomer units in the composition.

[0010] Such LDPE recycled materials are typically obtained by separation from waste streams and usually contain a large amount of other polyethylene components (especially linear low density polyethylene (LLDPE)), whose properties are quite variable and usually require processing such as treatment with free radical initiators to make them suitable for the desired uses.

[0011] Therefore, especially considering the efficiency of recycled materials and environmental issues, efficient processing methods are needed to allow the utilization of a large amount of recycled materials. Summary of the Invention

[0012] The present disclosure provides a method for generating a blended low density polyethylene composition, wherein the method comprises the step of blending a first component and a second component, the first component comprising one or more recycled polymer compositions, the second component comprising one or more low density polyethylenes, wherein the blended low density polyethylene composition has

[0013] a) a density of 0.910 g / cm 3 to 0.940 g / cm 3 , preferably 0.915 g / cm 3 to 0.935 g / cm 3 , measured at 23 °C according to ISO 1183-1:2012;

[0014] b) an MIP / MIE ratio of 1.8 to 6, preferably 2 to 5, where MIP is the melt flow index at 190 °C and a load of 5 kg, and MIE is the melt flow index at 190 °C and a load of 2.16 kg, both measured according to ISO 1133-2:2011;

[0015] c) an MIP value of 3 g / 10 min to 20 g / 10 min, preferably 4 g / 10 min to 15 g / 10 min;

[0016] d) an ER value of 1 to 4, preferably 1.2 to 4, more preferably 1.2 to 3.5;

[0017] e) an MIE / ER ratio of 0.2 to 2.8, preferably 0.3 to 2.5.

[0018] wherein ER is calculated according to the following formula

[0019] ER = (1.781 * 10 -3 ) * G'

[0020] The value of G” = 0.5 kPa (5000 dyn / cm 2 );

[0021] wherein:

[0022] G' = storage modulus

[0023] G” = loss modulus;

[0024] Both G' and G” are measured by dynamic oscillatory shear in a plate - plate rotational rheometer at a temperature of 190 °C,

[0025] and wherein the blended low - density polyethylene composition comprises 30 wt% to 90 wt%, particularly 35 wt% to 80 wt% or 40 wt% to 70 wt% of the first component, based on the total weight of the low - density polyethylene composition.

[0026] The low - density polyethylene product thus obtained not only has a relatively high melt flow index value but also has a high melt strength, as demonstrated by the high F(max) force value required for melt filament breakage in the Rheotens test. It is particularly suitable for foam products and / or blown films.

[0027] The MIP / MIE ratio of the low - density polyethylene can be particularly 1.80 to 6.00, preferably 2.00 to 5.00. The MIP value can be 3.00 g / 10 min to 20.00 g / 10 min, preferably 4.00 g / 10 min to 15.00 g / 10 min. The ER value range can be 1.00 to 4.00, preferably 1.20 to 4.00, more preferably 1.20 to 3.50. The MIE / ER ratio can be 0.20 to 2.80, preferably 0.30 to 2.50.

[0028] In some embodiments, at least one of the following additional features applies:

[0029] - The ratio of the MIP / MIE of the first component to the MIP / MIE of the blended low - density polyethylene composition (MIP / MIE first component : MIP / MIE blended LDPE composition ) is 0.50 to 1.80, preferably 0.60 to 1.30, more preferably 0.85 to 1.10;

[0030] - The MIP ratio (MIP blended LDPE composition :MIP first component ) of this blended low-density polyethylene composition to the first component is 1.5 to 15, particularly 1.50 to 15.00, preferably 1.8 to 10, and particularly preferably 1.80 to 10.00;

[0031] - The ER ratio (ER first component :ER blended LDPE composition ) of the first component to this blended low-density polyethylene composition is 0.8 to 3 or 0.80 to 3.00, preferably 1.0 to 2.5 or 1.00 to 2.50, more preferably 1.0 to 1.7, and particularly 1.00 to 1.70.

[0032] In some embodiments, at least one of the following additional features applies:

[0033] - The ratio of MIP / MIE of the first component to MIP / MIE of the second component (MIP / MIE first component :MIP / MIE second component ) is 0.50 to 2.00, preferably 0.60 to 1.80, and more preferably 0.70 to 1.4;

[0034] - The MIP ratio (MIP second component :MIP first component ) of the second component to the first component is 2 to 100, particularly 2.00 to 100.00, preferably 4 to 80, and particularly 4.00 to 80.00;

[0035] - The ER ratio (ER first component :ER second component ) of the first component to the second component is 1.5 to 10, particularly 1.50 to 10.00, preferably 1.9 to 9 or 1.90 to 9.00.

[0036] In some embodiments, the recycled part in this blended low-density polyethylene composition accounts for 20 wt% to 95 wt% or 30 wt% to 90 wt% of the total weight of this blended low-density polyethylene composition, preferably 35 wt% to 80 wt%, and more preferably 40 wt% to 70 wt%.

[0037] In some embodiments, the first component and the second component are melt-blended in an extruder device at a temperature of 180 °C to 250 °C.

[0038] In some embodiments, the first component comprises or consists of a recyclate having a density of 0.910 g / cm 3 to 0.940 g / cm 3 and the recyclate.

[0039] In some embodiments, the method includes a step of homogenizing the first component and the second component. This step can be carried out before or during the melt-blending of the respective components.

[0040] In some embodiments, if this step is carried out before the melt-blending, a mixing device (such as a drum mixer) can be provided for mixing the first component and the second component to form a uniform prepolymer, and then the prepolymer is introduced into the extruder device.

[0041] In some embodiments, the first component and the second component are mixed and blended together without using a visbreaking method. In particular, neither the first component nor the second component is prepared by visbreaking.

[0042] In some embodiments, the extruder device includes at least two screws arranged parallel to each other and operating in a co-rotating manner.

[0043] In some embodiments, the second composition comprises or consists of virgin LDPE.

[0044] In some embodiments, the first component comprises one or more additional polyethylene components selected from HDPE, MDPE, LLDPE, and mixtures thereof.

[0045] In some embodiments, the blended low-density polyethylene composition comprises 1 wt% to 40 wt%, preferably 5 wt% to 35 wt%, more preferably 8 wt% to 30 wt% or 10 wt% to 25 wt% of LLDPE relative to the total weight of the low-density polyethylene composition.

[0046] In some embodiments, the blended low-density polyethylene composition has at least one of the following additional features:

[0047] - MIE is 1 g / 10 min or higher, particularly 1 g / 10 min to 10 g / 10 min or 1 g / 10 min to 8 g / 10 min;

[0048] - Mw is 60,000 g / mol to 180,000 g / mol;

[0049] - The Mw / Mn ratio is from 3 to 18 or from 4 to 13;

[0050] - The F(max) value is 0.04 N or higher, particularly from 0.04 N to 2 N, more preferably from 0.05 N to 0.2 N, measured by a Rheotens apparatus at 190 °C and 2.4 mm / s 2 acceleration.

[0051] The present disclosure also provides a blend low-density polyethylene composition obtainable, in particular, by the method of the present disclosure.

[0052] The present disclosure also provides a manufactured article comprising the blend low-density polyethylene composition of the present disclosure.

[0053] In some embodiments, the manufactured article is in the form of a foam article or a blown film. Detailed Description

[0054] As an alternative, the term "low-density polyethylene" as used herein encompasses both a single ethylene polymer and a polyethylene composition (i.e., a composition comprising two or more ethylene polymers).

[0055] As used herein, the term "virgin" polymer means a polymer that has not been subjected to any finished product forming method (such as a fiber or sheet forming method for thermoforming). The virgin polymer can be obtained from a polymerization method (such as a polymerization method based on fossil material monomer materials and / or bio-derived monomer materials). Bio-based polyethylene and monomers are derived from natural products and are distinguishable from polymers and monomers obtained from fossil fuel sources. Since bio-based materials are from sources that can actively reduce CO2 in the atmosphere or emit less CO2 during production, such materials are generally regarded as "green" or renewable materials.

[0056] Thus, except for possible pelletizing (which is still considered part of the polymer production method), the virgin polymer has not been post-processed.

[0057] The second component may comprise or consist of virgin LDPE, preferably virgin LDPE obtained from fossil material monomer materials.

[0058] As used herein, the term "reclaimed material" means post-consumer recycled ("PCR") polymers and / or post-industrial recycled ("PIR") polymers. PCR polymers are reclaimed materials (e.g., polyethylene water bottles) derived from end products that have completed their life cycle as consumer goods and would otherwise be disposed of as waste. PIR polymer reclaimed materials are derived from plastic scrap generated as waste in industrial processes. PCR polyolefins include polyolefins that have been collected in commercial and residential recycling programs, including flexible packaging (cast film, blown film, and BOPP film), rigid packaging, blow molded bottles, and injection molded containers.

[0059] The term "about" means the stated value plus or minus the magnitude of the measurement error, or plus or minus 10% if no measurement method is specified.

[0060] As used herein, the term "comprising" has its broad standard meaning of "including", "covering", or "containing". It includes the specifically recited elements and also permits the presence of other elements not recited. As used herein, in addition to this broad encompassing meaning, the term "consisting of" or "comprising" can have a restrictive meaning. This means that any aspect or embodiment of the present application is defined as "consisting of" certain features, also including the meaning of consisting only of the recited features, whether or not this is explicitly stated. Additionally, the term "consisting of" can also have the meaning of "consisting essentially of". The expression "consisting essentially of" permits the presence of elements not explicitly recited, but excludes elements that are present in the prior art or that affect the basic or novel characteristics of the present disclosure.

[0061] The terms "comprising", "having", "including", and "containing" (and their variants) are open-ended conjunctive verbs and permit the addition of other elements when used in a claim.

[0062] The phrase "consisting of" is closed and excludes all additional elements.

[0063] The phrase "consisting essentially of" does not include additional material elements, but permits the inclusion of non-material elements that do not substantially change the nature of the present disclosure.

[0064] Thus, generally speaking, the reclaimed material is a material derived from the article manufacturing process. As used herein, "reclaimed material" also includes "recycled" materials.

[0065] Typically, two main polyolefin fractions are obtained by a step of separating from other polymers such as PVC, PET or PS, namely polyethylene recyclates (including HDPE, MDPE, LDPE, LLDPE) and polypropylene recyclates (including homopolymers, random copolymers, multiphase copolymers). The polyethylene recyclates can be further separated to recover a fraction containing a large amount of LDPE (especially 35 wt% or more relative to the total weight).

[0066] The first component may comprise or consist of recycled material, especially recycled material with LDPE as the main fraction, i.e., recycled LDPE. The content of the LDPE fraction in the recycled material may be more than 25 wt%, preferably more than 30 wt%, more preferably more than 45 wt% relative to the total weight of the first component.

[0067] The density of the first component may especially be 0.910 g / cm 3 to 0.940 g / cm 3 . Preferably, the MIP / MIE ratio of the first component is 2 to 5, and / or the ER ratio is 2 to 6.

[0068] Preferably, at least one of the following additional features applies:

[0069] - The MIP / MIE ratio of the first component to the second component is 0.50 to 2.00, preferably 0.60 to 1.80, more preferably 0.70 to 1.4;

[0070] - The MIP ratio of the second component to the first component is 2 to 100, preferably 4 to 80;

[0071] - The ER ratio of the first component to the second component is 1.5 to 10, preferably 1.9 to 9.

[0072] As used herein, "LDPE" means ethylene homopolymers and ethylene copolymers produced by free radical polymerization.

[0073] The polymerization is typically carried out at high pressure, as will be described in detail later.

[0074] Examples of LDPE copolymers include ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-acrylate copolymers, ethylene-methacrylate copolymers, ethylene-α-olefin copolymers and mixtures thereof.

[0075] Examples of α-olefin comonomers in the LDPE copolymers include C3-C 10 α-olefins such as propylene, 1-butene, 1-hexene, 1-octene and mixtures thereof.

[0076] When a comonomer is present, the content of the comonomer can reach 15 wt%, 10 wt% or 5 wt% relative to the total weight of the copolymer. In some embodiments, based on the total weight of the copolymer, the content of the comonomer ranges from 0.001 wt% to 15 wt%.

[0077] Generally, the term "copolymer" is intended to also include polymers containing more than one comonomer, such as terpolymers.

[0078] There are two basic high-pressure polymerization methods for producing LDPE: the autoclave process and the tubular process.

[0079] LDPE prepared by the autoclave reactor method ("autoclave LDPE") has a high concentration of long-chain branches, resulting in a high strain hardening value and a relatively wide molecular weight distribution, making it easy to process.

[0080] Autoclave polymerization can be carried out in the presence of a free radical initiator selected from organic peroxides.

[0081] The tubular reactor method does not necessarily require the use of organic peroxides. It can be carried out by using only oxygen as a free radical initiator, and thus LDPE without chemical degradation products containing organic peroxides can be prepared.

[0082] The LDPE can also be prepared by a hybrid method combining both an autoclave reactor and a tubular reactor.

[0083] The process operating conditions can include but are not limited to a pressure in the range of 70 MPa to 700 MPa (preferably 140 MPa to 190 MPa) and a temperature in the range of 150 °C to 500 °C (preferably 150 °C to 320 °C).

[0084] The polymerization gas can optionally contain one or more chain transfer agents known in the art, such as propylene, propane, and propionaldehyde.

[0085] Such chain transfer agents are used to adjust the molecular weight.

[0086] The method and the resulting LDPE product are well known in the art. For example, U.S. Patent No. 3,691,145 and U.S. Patent Application No. 2010 / 0076160 disclose methods for producing LDPE in a tubular reactor process.

[0087] Native LDPE polymers having the above-cited properties for the second component are known in the art. Specific examples are commercially available polymers under the brand names Lupolen (LyondellBasell) and Petrothene (Equistar).

[0088] Recyclate compositions having the above-cited properties for the first component are also known in the art. A specific example is a commercially available polyethylene composition under the brand name Nextfilm (Suez).

[0089] The first component (especially LDPE recyclate) and the resulting blend low-density polyethylene composition may comprise one or more additional polyethylene components, especially selected from HDPE (high-density polyethylene, typically having a density of 0.940 g / cm 3 to 0.965 g / cm 3 ), MDPE (medium-density polyethylene, typically having a density of 0.926 g / cm 3 to 0.940 g / cm 3 ), LLDPE (linear low-density polyethylene, typically having a density of 0.910 g / cm 3 to 0.925 g / cm 3 ), and mixtures thereof.

[0090] The additional component can be obtained by a polymerization method in the presence of a coordination catalyst. The methods and the homopolymers and copolymers obtained therefrom are widely described in the art.

[0091] In some embodiments, the blend low-density polyethylene composition may comprise more than two components. For example, a third component can be added, which is HDPE, MDPE, LLDPE, and mixtures thereof.

[0092] In particular, the polymerization method can be carried out in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

[0093] It is well known that Ziegler-Natta catalysts include the reaction products of organometallic compounds of Group 1, Group 2, or Group 13 of the periodic table with transition metal compounds of Groups 4 to 10 (new numbering system) of the periodic table. In particular, the transition metal compound can be selected from compounds of Ti, V, Zr, Cr, and Hf, and is preferably supported on MgCl2.

[0094] Preferred organometallic compounds are organo-Al compounds.

[0095] The single-site catalyst is well known in the art and is generally selected from metallocene single-site catalysts and non-metallocene single-site catalysts.

[0096] Examples of metallocene single-site catalysts are zirconocenes and hafnocenes, such as cyclopentadienyl or indenyl complexes of zirconium or hafnium, such as bis(cyclopentadienyl)zirconium dichloride, bis(indenyl)zirconium dichloride, or bis(indenyl)hafnium dichloride.

[0097] Examples of non-metallocene single-site catalysts are iron complexes preferably having a tridentate ligand.

[0098] In particular, the blend low density polyethylene composition of the present disclosure can be prepared by processing the respective components in an extruder device. The extruder device can be, for example, an extruder or a continuous mixer. These extruders or mixers can be single-stage or two-stage machines that melt and homogenize the low density polyethylene. Examples of extruders are pin barrel extruders, planetary extruders or co-rotating disk processors. Other possibilities are combinations of mixers with discharge screws and / or gear pumps. A preferred extruder is a screw extruder, and in particular a multi-screw extruder, more preferably a twin-screw extruder. Particularly preferred are twin-screw extruders and continuous mixers with discharge elements, and in particular continuous mixers with counter-rotating twin rotors, or an extruder device comprising at least one co-rotating twin-screw extruder. This further ensures the sufficient homogenization of the respective components during the melt blending in the extruder. Alternatively, the respective components can be homogenized by a mixing device (such as a drum mixer) before being fed into the extruder device. This type of machine is conventional in the plastics industry and is manufactured by, for example, Leistritz Extrusionstechnik GmbH, Nuremberg, Germany; Coperion GmbH, Stuttgart, Germany; KraussMaffei Berstorff GmbH, Hannover, Germany; The Japan Steel Works LTD., Tokyo, Japan; Farrel Corporation, Ansonia, USA; or Kobe Steel, Ltd., Kobe, Japan. The extruder device is usually also equipped with a unit for pelletizing the melt, such as an underwater pelletizer.

[0099] In some embodiments, more than two components can be provided to form the blend low density polyethylene composition, where these components can be added in subsequent extrusion steps, or added together with the first and second components.

[0100] In an extruder device, the specific energy input (SEI) refers to the energy input mechanically applied to the melt by the rotation of the screw and is related to the power consumption of the motor. It can be expressed in units of kWh / kg.

[0101] Indicatively, the SEI value can range from 0.05 kWh / kg to 0.20 kWh / kg, preferably from 0.08 kWh / kg to 0.15 kWh / kg.

[0102] The temperature for carrying out the blending step should preferably be low enough to avoid thermal viscosity reduction cracking, particularly it should be equal to or lower than 250 °C, and more preferably lower than 240 °C.

[0103] The lower limit of the temperature for carrying out the blending step is generally equal to or higher than the melting point of the polymeric material used in such step. Preferably, the lower limit is 180 °C, and more preferably 190 °C.

[0104] Although not essential, additives can be added to the blended low density polyethylene composition. These additives can be added before, during or after the melt blending.

[0105] Such additives are common in the art. The types of additives for preparing polyethylene compositions are, for example, antioxidants, melt stabilizers, light stabilizers, acid scavengers, lubricants, processing aids, anti-blocking agents, slip agents, antistatic agents, antifogging agents, pigments or dyes, nucleating agents, flame retardants or fillers. Usually several additives are added. The various additives can be different types of additives. However, several additives representing one type can also be added to the low density polyethylene. All these types of additives are generally commercially available and are described, for example, in the Plastics Additives Handbook by Hans Zweifel (5th Edition, Munich, 2001).

[0106] As mentioned above, the present low density polyethylene product is particularly suitable for applications where high melt strength is required or desired, such as particularly for preparing foam products (e.g., foam products for soft packaging) or blown films. In fact, it is preferred that the F(max) value is 0.03 N or higher, particularly 0.04 N to 2 N, preferably 0.05 N to 0.2 N, measured by a Rheotens device at 190 °C, 2.4 mm / s 2 acceleration.

[0107] Independent of or in combination with the said F(max) value, the present low density polyethylene product preferably has at least one of the following additional features:

[0108] - Mw is from 60,000 g / mol to 180,000 g / mol;

[0109] - The Mw / Mn ratio is from 3 to 18 or from 4 to 13.

[0110] The foam product can be produced by a chemical blowing method or a physical blowing method. Physically blown polyolefin foams are typically produced with blowing agents such as isobutane, pentane, and cyclopentane. Generally, physically blown polyolefin foams have the advantage over chemically blown polyolefin foams that they have a higher expansion ratio and thus a lower density. The foam can be non-crosslinked or crosslinked.

[0111] In some embodiments, the foam including the present low-density polyethylene has a density in the range of 12 kg / m 3 to 60 kg / m 3 Such foams can be used in protective packaging for electronic products, furniture, fruits, glass articles, toys, etc., or in any other articles that require cushioning protection against shock and / or vibration. These foams can also be used in protective packaging for articles that require thermal insulation.

[0112] Blown film (also known as tubular film) extrusion technology is well known for the production of plastic films. The method involves extruding a molten thermoplastic resin through an annular die and then expanding the molten web in a "bubble" shape.

[0113] Examples

[0114] The various embodiments, compositions, and methods provided herein are disclosed in the following examples. These examples are merely illustrative and are not intended to limit the scope of the appended claims in any way.

[0115] The following analytical methods are used to characterize the polymer compositions.

[0116] Melt flow index

[0117] Determined according to ISO 1133-1 2012-03 at 190 °C and a specified load.

[0118] Density

[0119] Determined according to ISO 1183-1:2012 at 23 °C.

[0120] Molecular weight distribution measurement

[0121] The average Mw and Mn and the derived Mw / Mn are determined by high temperature gel permeation chromatography using the methods described in ISO 16014-1, -2, -4 published in 2003. The details according to the said ISO standard are as follows: solvent 1,2,4-trichlorobenzene (TCB), temperature of the apparatus and solution 135 °C, and PolymerChar (Valencia, Paterna 46980, Spain) IR-4 infrared detector that can be used together with TCB as the concentration detector. Use a WATERS Alliance 2000 equipped with the following pre-columns SHODEX UT-G and separation columns SHODEX UT 806M(3x) and SHODEX UT 807 (Showa Denko Europe GmbH, Konrad-Zuse-Platz 4, 81829 Munich, Germany) connected in series.

[0122] The solvent is vacuum distilled under nitrogen and stabilized with 0.025 wt% 2,6-di-tert-butyl-4-methylphenol. The flow rate used is 1 ml / min, the injection volume is 500 μl, and the polymer concentration is in the range of 0.01% w / w < concentration < 0.05% w / w. The molecular weight calibration is established by using monodisperse polystyrene (PS) standards from Polymer Laboratories in the range from 580 g / mol to 11600000 g / mol (now Agilent Technologies, Herrenberger Str. 130, 71034 Boeblingen, Germany) and additionally hexadecane.

[0123] Then the calibration curve is adapted to polyethylene (PE) by the universal calibration method (Benoit H., Rempp P. and Grubisic Z., & in J. Polymer Sci., Phys 5, 753 (1967)). The Mark-Houwing parameters used here are as follows: for PS, k PS = 0.000121 dl / g, α PS = 0.706, and for PE, k PE = 0.000406 dl / g, α PE= 0.725, effective in TCB at 135°C. Data recording, calibration and calculations were performed using NTGPC_Control_V6.02.03 and NTGPC_V6.4.24 (hs GmbH, Hauptstraβe 36, D-55437 Ober-Hilbersheim, Germany) respectively.

[0124] Complex shear viscosity η 0.02 (eta(0.02)) and ER

[0125] Measurements were made as follows at an angular frequency of 0.02 rad / s and 190°C.

[0126] The sample was melt-pressed at 200°C and 200 bar for 4 minutes to form a 1 mm thick plate. Disc specimens with a diameter of 25 mm were punched and inserted into a rheometer preheated to 190°C. Any commercially available rotational rheometer can be used for the measurement. Here, an Anton Paar MCR 300 with a plate-plate geometry was used. At T = 190°C, a so-called frequency sweep was performed at a constant strain amplitude of 5% (after annealing the sample for 4 minutes at the measurement temperature), and the stress response of the material in the range of excitation frequencies ω from 628 rad / s to 0.02 rad / s was measured and analyzed. The standardized basic software was used to calculate the rheological properties, namely the storage modulus G', the loss modulus G", the phase lag δ (= arctan(G" / G')) and the complex viscosity η*, as a function of the applied frequency, i.e., η*(ω) = [G'(ω)2 + G"(ω)2] 1 / 2 / ω. The value of the latter at an applied frequency ω of 0.02 rad / s is η 0.02 .

[0127] ER was determined by the following method: R. Shroff and H. Mavridis, "New Measures of Polydispersity from Rheological Data on Polymer Melts", Journal of Applied Polymer Science, 57 (1995) 1605 (see also column 10, lines 20 to 30 of US Patent No. 5,534,472). Calculated from:

[0128] ER = (1.781 * 10 -3 ) * G'

[0129] The value of G" = 5,000 dyn / cm 2 .

[0130] As will be recognized by those skilled in the art, when the lowest G" value is greater than 5,000 dyn / cm2 When determining the ER, extrapolation is involved. The calculated ER value will then depend on the non-linearity in log G' versus log G". The temperature, plate diameter, and frequency range are chosen such that within the resolution of the rheometer, the lowest G" value is close to or less than 5,000 dyn / cm 2 .

[0131] Comonomer content

[0132] The comonomer content was determined by IR using a Tensor 27 FT-IR spectrometer from Bruker according to ASTM D 6248 98

[0133] Melt strength

[0134] The melt strength of a polymer is a parameter in melt processing operations where one or more stages of the process involve stretching or drawing. It depends on molecular parameters such as molecular weight, molecular weight distribution, and / or polymer branching. The test apparatus measures the tensile properties of a polymer melt by stretching a vertical melt filament under a constant force at a constant draw speed or linearly accelerating speed on a Rheotens spinning line located below a capillary die

[0135] Melt strength analysis was carried out at 190 °C using a Rheotester 1000 (barrel diameter 12 mm, capillary die L / D = 20 / 2) equipped with a RHEOTENS 71.97 device. The RHEOTENS consists of two upper and two lower driven counter-rotating wheels that are connected to a very sensitive balance system. The vertical gap between these wheels is 0.3 mm. After a 10-minute melting time, the polymer was extruded at a shear rate of 50 1 / s. The polymer filament left the capillary die, and the die exit velocity v0 was recorded. When the filament length was 74 mm, the two upper wheels pulled the melt filament downward at an acceleration of 2.4 mm / 2 and the velocity v was recorded (the two lower wheels were only used to additionally stabilize the filament during the drawing process). The draw ratio l = v / v0 at break, the velocity at break, and the breaking force of the melt filament (F(max) = melt strength) were recorded

[0136] Example 1

[0137] Recycled LDPE was used as the first component. The characteristics of this recycle are listed in Table 1, where this recycle is identified as "R1".

[0138] Use the commercial grade Lupolen 1800S sold by LyondellBasell Industries as the second component. Lupolen is a trademark owned and / or used by the LyondellBasell group of companies and is registered with the United States Patent and Trademark Office.

[0139] Lupolen 1800S is a virgin LDPE with the properties listed in Table 1, where this component is identified as "LP1800S".

[0140] The low density polyethylene product of Example 1 is obtained by extruding the first component and the second component in an extruder.

[0141] The machine parameters are as follows:

[0142] Rotational speed: 300 rpm;

[0143] Throughput: 30 kg / h;

[0144] Temperature:

[0145] Zone 1: 200 °C, Zone 2: 220 °C, Zones 3 to 10: 240 °C, Die: 240 °C;

[0146] SEI: 0.092 kWh / kg.

[0147] As is known to those skilled in the art, there are different methods for calculating the specific energy input SEI. SEI can be calculated by dividing the motor power by the material flow rate. The motor power is equal to the torque multiplied by the angular velocity. The equation for SEI is as follows:

[0148]

[0149] where 2*π*n represents the angular velocity ω, M D represents the torque, and represents the material flow rate. When the motor torque cannot be directly measured, SEI can also be approximately calculated using the maximum current and the actual current of the motor according to the following equation.

[0150]

[0151] where "n" represents the screw rotational speed, "I" represents the current, and "η transmission " represents the transmission efficiency.

[0152] The properties of the blended low density polyethylene composition thus obtained are listed in Table 1, where this blended low density polyethylene composition is identified as "Blend1". Relative to the total weight of the blended low density polyethylene composition, the relative content of the first component in the blend is 50 wt%, and the relative content of the second component is 50 wt%.

[0153] For comparison, Table 1 lists the properties of a virgin LDPE composition (i.e., the commercial grade Lupolen 2420H), which is identified as "LP 2420H" in the table and is generally suitable for foaming applications and / or blown films.

[0154] Table 1

[0155] R1 LP 1800S Blend1 LP 2420H MIP [g / 10min] 0.97 66.3 7.06 7.74 MIE [g / 10min] 0.23 19.1 1.74 1.93 <![CDATA[Density [g / cm 3 > 0.928 0.917 0.925 0.922 Mw [g / mol] 195799 74622 134878 109464 Mw / Mn 10.6 7.5 10.5 7.1 MIP / MIE 4.2 3.5 4.1 4.0 ER 4.2 1.1 2.8 1.9 MIE / ER 0.06 17.69 0.615 1.01 F(max) [N] 0.177 n.a. 0.090 0.088

[0156] Examples 2 and 3

[0157] Compared with Example 1, different LDPE recyclates were used in Example 2 and Example 3. The properties of this recyclate are listed in Table 2, where this recyclate is identified as "R2".

[0158] As in Example 1, the commercial grade Lupolen 1800S sold by LyondellBasell Industries was used as the second component.

[0159] The low density polyethylene products of Example 2 and Example 3 were obtained by extruding the first component and the second component in an extruder.

[0160] The machine parameters were:

[0161] Rotation speed: 300 rpm;

[0162] Throughput: 30 kg / h;

[0163] Temperature:

[0164] Zone 1: 200 °C, Zone 2: 220 °C, Zones 3 to 10: 240 °C, Die: 240 °C;

[0165] SEI: 0.092 kWh / kg for Example 2 and 0.093 kWh / kg for Example 3.

[0166] The properties of the obtained blended low density polyethylene compositions are listed in Table 2, where the blended low density polyethylene compositions are identified as "Blend2" and "Blend3" respectively. For "Blend2", relative to the total weight of the blended low density polyethylene composition, the relative content of the first component in the blend is 50 wt%, and the relative content of the second component is 50 wt%; for "Blend3", relative to the total weight of the blended low density polyethylene composition, the relative content of the first component in the blend is 60 wt%, and the relative content of the second component is 40 wt%.

[0167] Table 2

[0168]

[0169]

[0170] Example 4

[0171] For Example 4, the first component is the same as that of Example 2 and Example 3.

[0172] However, for the second component, the commercial grade Lupolen 2420K sold by LyondellBasell Industries was used.

[0173] Lupolen 2420K is a virgin LDPE with the properties listed in Table 3, where the component is identified as "LP2420K".

[0174] The low-density polyethylene product of Example 4 was obtained by extruding the first component and the second component in an extruder.

[0175] The machine parameters were:

[0176] Rotational speed: 300 rpm;

[0177] Throughput: 30 kg / h;

[0178] Temperature:

[0179] Zone 1: 200 °C, Zone 2: 220 °C, Zones 3 to 10: 240 °C, Die: 240 °C;

[0180] SEI: 0.081 kWh / kg.

[0181] The properties of the resulting blended low-density polyethylene composition are listed in Table 1, where the blended low-density polyethylene composition is identified as "Blend4". Relative to the total weight of the blended low-density polyethylene composition, the relative content of the first component in the blend is 30 wt%, and the relative content of the second component is 70 wt%.

[0182] Table 3

[0183] R2 LP 2420K Blend4 MIP [g / 10min] 2.84 14.37 6.53 MIE [g / 10min] 0.79 3.53 1.65 <![CDATA[Density [g / cm 3 > 0.928 0.923 0.925 Mw [g / mol] 163257 97540 110140 Mw / Mn 8.1 7.8 7.8 MIP / MIE 3.6 4.1 4.0 ER 2.9 1.4 2.1 MIE / ER 0.272 2.451 0.771 F(max) [N] 0.122 0.038 0.084

[0184] Tables 1 to 3 show that by blending recycled LDPE materials with virgin LDPE that is not itself used in foaming applications, a low-density polyethylene composition similar in properties to a commercial-grade low-density polyethylene composition suitable for foaming applications can be produced. Thus, a blended low-density polyethylene material with a high recycled material content can be produced. It has also been found that the "blend" contains approximately 25 wt% of LLDPE relative to the total weight of the blended low-density polyethylene composition. LLDPE is generally not used in such foaming applications because the melt strength of LLDPE is typically low, which can lead to high pressure buildup during foaming and thus cause the device to shut down. However, unexpectedly, the blended composition can contain a relatively high content of LLDPE and still be suitable for foaming applications.

[0185] The foamability was tested on an extruder equipped with a foaming die. It was found that the blended composition could continuously produce foam products at a throughput of 100 kg / h to 200 kg / h. When only LP2420K and LP 1800S were used, there was no foamability, resulting in breakage and holes. If only R1 or R2 was used, it was found that pressure buildup would occur, leading to the shutdown of the extruder.

Claims

1. A method for producing a blended low density polyethylene composition, wherein the method comprises the step of blending a first component with a second component, the first component comprising one or more recycled polymer compositions, and the second component comprising one or more low density polyethylenes, wherein the blended low density polyethylene composition has a) 0.910 g / cm 3 to 0.940 g / cm 3 , preferably 0.915 g / cm 3 to 0.935 g / cm 3 of density, measured at 23 °C according to ISO 1183-1:2012; b) an MIP / MIE ratio of 1.8 to 6, preferably 2 to 5, where MIP is the melt flow index at 190 °C and a load of 5 kg, and MIE is the melt flow index at 190 °C and a load of 2.16 kg, both determined according to ISO 1133-2:2011; c) an MIP value of 3 g / 10 min to 20 g / 10 min, preferably 4 g / 10 min to 15 g / 10 min; d) an ER value of 1 to 4, preferably 1.2 to 4, more preferably 1.2 to 3.5; e) an MIE / ER ratio of 0.2 to 2.8, preferably 0.3 to 2.5; where ER is calculated according to the following formula ER = (1.781 * 10 -3 ) * G' Value of “G” = 0.5 kPa (5000 dyn / cm 2 ); where: G' = storage modulus G'' = loss modulus; both G' and G'' are measured by dynamic oscillatory shear in a plate-plate rotational rheometer at a temperature of 190 °C, and wherein the blended low density polyethylene composition comprises 30 wt% to 90 wt%, particularly 35 wt% to 80 wt% or 40 wt% to 70 wt% of the first component relative to the total weight of the blended low density polyethylene composition.

2. The method according to claim 1, wherein at least one of the following additional features applies: - the MIP / MIE ratio of the first component to the blended low density polyethylene composition is 0.50 to 1.80, preferably 0.60 to 1.30; - the MIP ratio of the blended low density polyethylene composition to the first component is 1.5 to 15, preferably 1.8 to 10; - the ER ratio of the first component to the blended low density polyethylene composition is 0.8 to 3, preferably 1.0 to 2.

5.

3. The method according to claim 1 or 2, wherein at least one of the following additional features applies: - the MIP / MIE ratio of the first component to the second component is 0.50 to 2.00, preferably 0.60 to 1.80; - the MIP ratio of the second component to the first component is 2 to 100, preferably 4 to 80; - the ER ratio of the first component to the second component is 1.5 to 10, preferably 1.9 to 9.

4. The method according to any one of claims 1 to 3, wherein the blended low density polyethylene composition comprises 30 wt% to 90 wt%, particularly 35 wt% to 80 wt% or 40 wt% to 70 wt% of a recycled material portion relative to the total weight of the blended low density polyethylene composition.

5. The method according to any one of claims 1 to 4, wherein the first component and the second component are melt-blended in an extruder device at a temperature of 180 °C to 250 °C, preferably 190 °C to 240 °C.

6. The method according to claim 5, wherein the method further comprises the step of homogenizing the first component and the second component before or during the melt blending.

7. The method according to any one of claims 1 to 6, wherein the second component comprises virgin LDPE or consists of the virgin LDPE.

8. The method according to any one of claims 1 to 7, wherein the first component comprises one or more additional polyethylene components selected from HDPE, MDPE, LLDPE, and mixtures thereof.

9. The method according to any one of claims 1 to 8, wherein the blended low-density polyethylene composition comprises 1 wt% to 40 wt%, preferably 5 wt% to 35 wt%, more preferably 8 wt% to 30 wt% or 10 wt% to 25 wt% of LLDPE based on the total weight of the low-density polyethylene composition.

10. The method according to any one of claims 1 to 9, wherein the blended low-density polyethylene composition has at least one of the following additional characteristics: - MIE is 1 g / 10 min or higher, particularly 1 g / 10 min to 10 g / 10 min or 1 g / 10 min to 8 g / 10 min; - Mw is 60,000 g / mol to 180,000 g / mol; - Mw / Mn ratio is 3 to 18 or 4 to 13; - The value of -F(max) is 0.04 N or higher, particularly 0.04 N to 2 N, preferably 0.05 N to 0.2 N, and is measured by a Rheotens device at 190 °C and an acceleration of 2.4 mm / s 2 under the acceleration.

11. A blended low-density polyethylene composition obtainable by the method according to any one of claims 1 to 10.

12. A manufactured article comprising the blended low-density polyethylene composition according to claim 11.

13. The manufactured article according to claim 12, wherein the manufactured article is in the form of a foam article, a cast film, or a blown film.

Images