Process for treating an initial polyethylene-containing material to produce a polyethylene composition for injection molding

Abstract

A process for treating an initial polyethylene-containing material to produce a polyethylene composition, the process comprising providing a twin-screw extruder having a thermal regulation device; providing an initial polyethylene-containing material comprising at least 50% by weight of polyethylene based on the total weight of the initial polyethylene-containing material; extruding the initial polyethylene-containing material to obtain a polyethylene composition; wherein the extrusion is carried out with a residence time of less than 20 minutes; and collecting the polyethylene composition; wherein the extrusion comprises heat-treating the initial polyethylene-containing material by self-heating at a temperature of at least 300 °C in one or more hot zones of the extruder to have a maximum barrel temperature in the range of 300 to 460 °C in at least one hot zone of the extruder.

Description

Technical Field

[0001] The present disclosure relates to a process for producing a polyethylene composition suitable for use in injection molding, preferably said polyethylene composition preferably comprising recycled polyethylene. Background Art

[0002] As needed, it is sometimes useful to have the possibility of treating existing polyolefins or existing polyolefin compositions to change some properties. Nowadays, to facilitate the subsequent recycling of polyolefins or polyolefin compositions, treatments and processes are needed that allow such changes to be achieved without blending in other polyolefins and / or additives. Properties that may need to be changed are, for example, melt flow index, viscosity, odor, impurity level, etc.

[0003] PCR (post-consumer recycled) polyethylene containing may have a low melt index value. For PCR polyethylene derived from small containers (shampoo bottles...), the MI2 is typically close to 0.2 g / 10 min, and for PCR polyethylene derived from films, the MI2 is close to 1.0 g / 10 min, which makes them quite unsuitable for injection molding and thus limits the application of recycled polyethylene-containing materials. Therefore, there is a need for a method for treating these recycled polyethylene-containing materials to convert them into polyethylene compositions suitable for injection molding applications.

[0004] A method that can increase and control the melt flow index and / or viscosity of polyethylene or polyethylene-containing materials such as recycled polyethylene-containing materials would create significant added value for recycled polyethylene compositions because it expands their field of application. Such a method can also contribute to the plastic waste problem because more plastics can be converted into useful polyethylene compositions after recycling.

[0005] The increase in the melt index of PCR polyethylene is not obvious at all because during the standard extrusion process, the melt index generally decreases. The situation with polypropylene is slightly different because there are methods for increasing the melt flow index of polypropylene. However, these methods involve reactive extrusion with the addition of peroxides. However, such methods result in polypropylene with peroxide decomposition products, while the demand for "clean" polyolefins is increasing. If a high peroxide content must be avoided, for example, to avoid excessive peroxide residues, the increase in the melt index of polypropylene is limited in the standard extrusion process. In addition, the use of organic peroxides leads to polyethylene branching and crosslinking.

[0006] Even when polypropylene is present in the polyethylene composition, which can be very frequent in PCR polyethylene, a high content of polyethylene of at least 50% by weight will contribute to a decrease in the melt index during standard granulation. Therefore, there is a need for a cleaning method for treating the initial polyethylene-containing material and / or a method for treating the initial polyethylene-containing material, which provides an increase in the melt flow index and improved properties for injection molding applications. Preferably, the method for treating the initial polyethylene-containing material should have a low safety risk, especially in terms of fire risk.

[0007] There is also a need for polyethylene compositions suitable for injection molding applications, and which are preferably derived from recycled polyolefins.

[0008] There is a need to produce polyethylene compositions suitable for injection molding applications with reduced viscosity.

[0009] WO2021 / 064113 discloses a method in which a polyolefin composition is produced using the following method: wherein ultrasound is applied to a material which can be a recycled polyolefin. Although the disclosed method provides very good results, there is still room for further improvement in such fields, especially for implementing methods or processes at an industrial level. There is also a need for simple and cost-effective processes. Summary of the Invention

[0010] It has now been found that by single extrusion of existing polyethylene-containing materials such as recycled polyethylene-containing materials, one or more of the above needs can be met, thereby producing a new polyethylene composition suitable for injection molding.

[0011] According to a first aspect, the present disclosure relates to a process for treating an initial polyethylene-containing material to produce a polyethylene composition, characterized in that it comprises the following steps:

[0012] a) Providing a twin-screw extruder with a heat regulating device;

[0013] b) Providing an initial polyethylene-containing material comprising at least 50% by weight of polyethylene based on the total weight of the initial polyethylene-containing material;

[0014] c) Extruding the initial polyethylene-containing material to obtain a polyethylene composition; wherein the extrusion is carried out with a residence time of less than 20 minutes; and

[0015] d) Collecting the polyethylene composition;

[0016] The extrusion step (c) includes heat-treating the initial polyethylene-containing material by self-heating of the material at a temperature of at least 300 °C in one or more hot zones of the extruder, wherein the one or more hot zones have a total length equal to or greater than 6D, where D is the screw diameter, wherein the extrusion is carried out at a mechanical specific energy of greater than or equal to 0.4 kWh / kg, wherein the screw profile includes at least one hot zone having successive kneading block elements over a length of at least 4D, followed by a left-handed element, where D is the screw diameter, wherein the thermal regulating device is set to an initially applied barrel temperature in the range between 240 and 320 °C and is shut off when the barrel temperature in the zone spontaneously exceeds the applied barrel temperature by at least 1 °C; preferably at least 3 °C without the need for external heat application.

[0017] Surprisingly, it has been found that the initial polyethylene-containing material can be upgraded to a higher melt index and lower viscosity by heat treatment, thus reaching values suitable for injection molding applications; without the need for additives or other specific treatments such as ultrasound. In particular, an increase in the melt index is obtained without using flow modifiers. The remarkable feature of this process lies in its simplicity as it can be carried out in a twin-screw extruder. As shown by the examples, the increase in the melt index can be up to 80-fold.

[0018] This process is also remarkable because there is no chemical way to break the polyethylene chains. At normal processing temperatures and standard extrusion conditions, there is branching of the polyethylene chains (decrease in MI2). The use of organic peroxides leads to polyethylene branching and crosslinking. The substantial increase of at least 10 (e.g., at least 20 or at least 40)-fold in the melt index obtained by specific extrusion conditions, together with the general decrease in the complex viscosity (e.g., flattening of the complex viscosity curve at low frequencies), allows to respond to the long-term needs in the recycling field by expanding the possible applications of recycled raw materials.

[0019] Indeed, as shown by the examples, the remarkable feature of this process is that at both 0.1 rad / s and 100 rad / s, the viscosity of the polyethylene composition is reduced compared to the viscosity of the initial polyethylene-containing material, which makes the treated polyethylene suitable for injection molding applications.

[0020] In one embodiment, the screw profile includes two or more hot zones, wherein the first hot zone includes successive kneading block elements over a length of at least 4D, followed by a left-handed element, where D is the screw diameter, and one or more additional hot zones located downstream of the first hot zone are filled mixing zones, each including kneading block elements over a length of at least 4D, followed by kneading left-handed elements or left-handed elements, where D is the screw diameter.

[0021] In one embodiment, the successive kneading block elements of at least one heat zone of the extruder include disks having a disk offset of 90 degrees and a disk width of at least 0.3D, where D is the screw diameter.

[0022] In one embodiment, one heat zone of the extruder is or includes the melting zone of the extruder.

[0023] In a preferred embodiment, the ratio of the melt index (MI2 T) of the polyethylene composition to the melt index (MI2 R) of the initial polyethylene-containing material is at least 10. This can be achieved by appropriately selecting the temperature and residence time of the heat treatment.

[0024] In a preferred embodiment, the mechanical specific energy used during extrusion is selected such that the ratio of the melt index (MI2 T) of the polyethylene composition to the melt index (MI2 R) of the initial polyethylene-containing material is at least 10.

[0025] For example, the ratio of the melt index (MI2 T) of the polyethylene composition to the melt index (MI2 R) of the initial polyethylene-containing material is at least 10; preferably at least 15; preferably at least 20; preferably at least 30; preferably at least 40.

[0026] In one embodiment, the initial polyethylene-containing material is selected to have:

[0027] - a high load melt index (HLMI R) of at least 1.0 g / 10 min when measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011; and / or

[0028] - a melt index (MI2 R) of at most 3.0 g / 10 min when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011; and / or

[0029] - a density of at least 0.910 g / cm 3 when measured at 23 °C according to ISO 1183-1:2012.

[0030] For example, the initial polyethylene-containing material is selected to have a melt index ranging from a high load melt index (HLMI R) of at least 1.0 g / 10 min when measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011 to a melt index of at most 3.0 g / 10 min when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011.

[0031] For example, the initial polyethylene-containing material is selected to have:

[0032] - A high load melt index (HLMI R) of at least 1.0 g / 10 min when measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011, a melt index (MI2 R) of at most 0.45 g / 10 min when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, and a density of at least 0.940 g / cm 3 when measured at 23 °C according to ISO 1183-1:2012; or

[0033] - A melt index (MI2 R) in the range of 0.8 to 1.5 g / 10 min when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, and a density in the range of 0.910 g / cm 3 to less than 0.940 g / cm 3 ; preferably 0.910 g / cm 3 to 0.935 g / cm 3 and more preferably 0.910 g / cm 3 to 0.930 g / cm 3 when measured at 23 °C according to ISO 1183-1:2012.

[0034] In one embodiment, the initial polyethylene-containing material further has:

[0035] - An Mz / Mw of at least 4.0 when measured by size exclusion chromatography (SEC); and / or

[0036] - A complex viscosity in the range of 20,000 to 80,000 Pa·s at 190 °C at 1 radian / second; and / or

[0037] - An Mw / Mn in the range of 5.0 to 30.0 when measured by size exclusion chromatography; and / or

[0038] - A complex viscosity ratio of more than 10, where the complex viscosity ratio is the ratio of the complex viscosity at a frequency of 0.1 radian / second to the complex viscosity at a frequency of 100 radian / second when measured at 190 °C.

[0039] In one embodiment, the initial polyethylene-containing material further has a tanδ (G” / G’ measured at 190 °C at 0.1 radian / second) of at most 3.0, preferably at most 2.6.

[0040] In one embodiment, the initial polyethylene-containing material further has a tanδ (G” / G’ measured at 190 °C at 0.1 radian per second) of at least 0.5, preferably at least 0.8.

[0041] In one embodiment, the initial polyethylene-containing material further has a tanδ (G” / G’ measured at 190 °C at 0.1 radian per second) in the range of 0.5 to 3.0; preferably, 0.8 to 2.6.

[0042] For example, the initial polyethylene-containing material comprises at least 80% by weight of polyethylene based on the total mass of the initial polyethylene-containing material; and / or is a recycled polyethylene-containing material.

[0043] For example, the initial polyethylene-containing material contains at least one polymer different from polyethylene in an amount ranging from 0 to 50% by weight based on the total weight of the initial polyethylene-containing material, where the at least one polymer different from polyethylene is selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof.

[0044] For example, the process is carried out without peroxide and / or without ultrasound.

[0045] In a preferred embodiment, step (c) of extruding the initial polyethylene-containing material includes heat treatment by self-heating of the material, where the extrusion is carried out at a mechanical specific energy of greater than or equal to 0.45 kWh / kg, preferably greater than or equal to 0.5 kWh / kg; more preferably greater than or equal to 0.6 kWh / kg.

[0046] For example, step (c) of extruding the initial polyethylene-containing material includes heat treatment by self-heating of the material or by heating the material, where the extrusion is carried out in at least one hot zone at a maximum barrel temperature in the range of 300 to 460 °C; preferably at a maximum barrel temperature in the range of 310 to 450 °C; more preferably at a maximum barrel temperature in the range of 320 to 430 °C; even more preferably at a maximum barrel temperature in the range of 330 to 410 °C, and most preferably at a maximum barrel temperature in the range of 340 to 390 °C.

[0047] For example, the step (c) of extruding the initial polyethylene-containing material includes heat treatment in at least one hot zone at a temperature in the range of 300 to 460 °C; preferably at a temperature in the range of 310 to 450 °C; more preferably at a temperature in the range of 320 to 430 °C; even more preferably at a temperature in the range of 330 to 410 °C; and most preferably at a temperature in the range of 340 to 390 °C, or at a temperature in the range of 320 to 460 °C.

[0048] For example, the step (c) of extruding the initial polyethylene-containing material includes heat treatment at a temperature of at least 300 °C or at least 305 °C; preferably at a temperature of at least 315 or at least 320 °C; more preferably at a temperature of at least 330 °C; even more preferably at a temperature of at least 340 °C; and most preferably at a temperature of at least 350 °C, or at a temperature of at least 355 °C, or at a temperature of at least 360 °C.

[0049] For example, the step (c) of extruding the initial polyethylene-containing material includes heat treatment at a temperature of at most 460 °C; preferably, at most 450 °C; more preferably, at most 440 °C; even more preferably, at most 430 °C; most preferably, at most 420 °C or at most 410 °C or at most 405 °C or at most 400 °C or at most 395 °C or at most 390 °C.

[0050] For example, the step (c) of extruding the initial polyethylene-containing material includes performing the extrusion at a screw speed in the range of 100 to 1200 rpm.

[0051] For example, the step (c) of extruding the initial polyethylene-containing material includes performing the extrusion with a residence time in the range of 10 seconds to 10 minutes; preferably with a residence time in the range of 20 seconds to 5 minutes; more preferably with a residence time in the range of 10 to 180 seconds; even more preferably, 10 to 120 seconds; most preferably, 20 to 100 seconds; and even most preferably, 30 to 80 seconds.

[0052] In one embodiment, the polyethylene composition collected in step (d) has one or more of the following:

[0053] - a density of at least 0.910 g / cm 3 when measured at 23 °C according to ISO 1183-1:2012; and / or

[0054] - a melt index MI2 in the range of 3.0 to 60.0 g / 10 minutes when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011; and / or

[0055] - An unsaturation index higher than 2,000, where the unsaturation index is the product of vinyl unsaturation units per 1,000 carbon atoms and the Mn in daltons as determined by ASTM D6248 - 98:2004; and / or

[0056] - A complex viscosity at 190 °C at 0.1 radian per second of at most 20,000 Pa·s.

[0057] In a preferred embodiment, the polyethylene composition taken in step (d) has:

[0058] - A density of at least 0.910 g / cm 3 when determined at 23 °C according to ISO 1183 - 1:2012;

[0059] - A melt index MI2 in the range of 3.0 to 60.0 g / 10 min when determined at 190 °C under a load of 2.16 kg according to ISO 1133 - 2011;

[0060] - An unsaturation index higher than 2,000, where the unsaturation index is the product of vinyl unsaturation units per 1,000 carbon atoms and the Mn in daltons as determined by ASTM D6248 - 98:2004; and

[0061] - A complex viscosity at 190 °C at 0.1 radian per second of at most 20,000 Pa·s.

[0062] For example, when determined at 23 °C according to ISO 1183 - 1:2012, the polyethylene composition taken in step (d) has a density of at least 0.910 g / cm 3 ; preferably at least 0.912 g / cm 3 .

[0063] For example, when determined at 190 °C under a load of 2.16 kg according to ISO 1133 - 2011, the polyethylene composition taken in step (d) has a melt index MI2 in the range of 3.0 to 60.0 g / 10 min; preferably in the range of 4.0 to 20.0 g / 10 min.

[0064] For example, the polyethylene composition taken in step (d) has an unsaturation index higher than 2,000, preferably higher than 5000, even more preferably higher than 7000, where the unsaturation index is the product of vinyl unsaturation units per 1,000 carbon atoms and the Mn in daltons as determined by ASTM D6248 - 98:2004; where the unsaturation index is the product of vinyl unsaturation units per 1,000 carbon atoms and the Mn in daltons.

[0065] For example, the polyethylene composition obtained in step (d) has a complex viscosity of at most 20,000 Pa·s at 190 °C at 0.1 radian per second; preferably at most 18,000 Pa·s.

[0066] For example, the polyethylene composition obtained in step (d) has a complex viscosity ratio of at most 8.0, where the complex viscosity ratio is the ratio of the complex viscosity at a frequency of 0.01 radian per second to the complex viscosity at a frequency of 100 radian per second when measured at 190 °C.

[0067] Preferably, when determined by size exclusion chromatography, the polyethylene composition obtained in step (d) further has an Mz / Mw of at most 7.0; preferably at most 6.0; preferably at most 5.0.

[0068] For example, when determined by size exclusion chromatography, the polyethylene composition obtained in step (d) further has an Mw / Mn in the range of 2.5 to 10.0.

[0069] For example, the polyethylene composition obtained in step (d) further has a tan δ (G” / G’) of more than 2.5; preferably at least 3.0; more preferably at least 5.0, and even more preferably at least 10.0 at 190 °C at 0.1 radian.

[0070] According to a second aspect, the present disclosure relates to a polyethylene composition, characterized in that it is a polyethylene composition obtained by the process according to the first aspect.

[0071] According to a third aspect, the present disclosure relates to an article produced from the polyethylene composition according to the second aspect, characterized in that the article is an injection molded article; preferably, the article is selected from bottles or containers.

[0072] According to a fourth aspect, the present disclosure relates to a method for producing an injection molded article, characterized in that it comprises producing a polyethylene composition from an initial polyethylene-containing material by the process according to the first aspect, and producing an injection molded article using the polyethylene composition obtained by said process (or using the polyethylene composition according to the second aspect); preferably, the initial polyethylene-containing material is a recycled polyethylene-containing material.

[0073] According to a fourth aspect, the present disclosure relates to a method for producing an injection molded article, characterized in that it comprises, in a first step, producing a polyethylene composition from an initial polyethylene-containing material according to the process defined in the first aspect, and, in a second step, using the polyethylene composition produced in the first step to produce an injection molded article; preferably, the initial polyethylene-containing material is a recycled polyethylene-containing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] - Figure 1 Shows a possible screw profile used in the context of the present disclosure.

[0075] - Figure 2 A graph of MI2 against screw speed plotted for a fixed flow rate of 1.5 kg / h.

[0076] - Figure 3 A graph of MI2 against screw speed plotted for a fixed flow rate of 2.5 kg / h.

[0077] - Figure 4 A graph of the complex viscosity against the angular frequency for various polyethylene-containing compositions compared to the initial polyethylene-containing material.

[0078] - Figure 5 A graph of the complex viscosity against the angular frequency, and further showing the loss (G”) and storage modulus (G’) of PE1 of a polyethylene composition obtained by extrusion at 800 rpm and 360 °C. DETAILED DESCRIPTION

[0079] It should be understood that the present disclosure is not limited to the specific processes or compositions described, as such processes or compositions may of course vary. It should also be understood that the terminology used herein is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0080] When describing the polymers, uses, and processes of the present disclosure, the terms used are explained by the following definitions, unless the context otherwise dictates. For the present disclosure, the following definitions are given:

[0081] As used herein, the singular forms “a,” “an,” and “the” include both singular and plural referents, unless the context otherwise dictates. By way of example, “a composition” means one composition or more than one composition.

[0082] As used herein, the terms "comprising" and "consisting of" are synonymous with "including" or "containing", and are inclusive or open-ended, and do not exclude additional, unrecited members, elements or method steps. The terms "comprising" and "consisting of" also include the term "consisting of".

[0083] The recitation of a numerical range by endpoints includes all integers, and, where appropriate, fractions included within that range (e.g., 1 to 5 can include 1, 2, 3, 4, 5 when referring to, for example, the number of elements, and can also include 1.5, 2, 2.75 and 3.80 when referring to, for example, measurements). The recitation of endpoints also includes the endpoint values themselves (e.g., 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0084] All references cited in this specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references specifically mentioned herein are incorporated by reference. Where no year of a standard is specified, the reference to a standard method for determining a parameter refers to the standard in effect on the priority date of the application.

[0085] References to "an embodiment" or "embodiments" throughout this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the phrases "in an embodiment" or "in embodiments" that appear throughout this specification do not necessarily all refer to the same embodiment, but may. Additionally, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner, as will be apparent to those skilled in the art from the present disclosure. Further, although some embodiments described herein include some features included in other embodiments, but not other features included in other embodiments, combinations of features of different embodiments are intended to be within the scope of the present disclosure and to form different embodiments, as will be understood by those skilled in the art. For example, in the following claims and description, any embodiment can be used in any combination.

[0086] Unless otherwise defined, all terms used in the disclosure of the present disclosure, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this disclosure pertains. By further guidance, including the definitions of terms used in the specification, the teachings of the present disclosure are better understood.

[0087] The terms "polyethylene" (PE) and "ethylene polymer" may be used synonymously. The term "polyethylene" encompasses ethylene homopolymers as well as ethylene copolymer resins, which may be derived from ethylene and selected from C3-C 20One or more comonomers of α-olefins such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0088] The term "polyethylene resin" or "ethylene homopolymer resin" or "ethylene copolymer resin" refers to extruded and / or melted and / or pelletized polyethylene fluff or powder, and can be produced by compounding and homogenizing the polyethylene resin using, for example, mixing and / or extruder equipment as taught herein. As used herein, the term "polyethylene" can be used as a shorthand for "polyethylene resin". The terms "fluff" or "powder" refer to polyethylene materials having hard catalyst particles at the core of each particle, and are defined as the polymer materials after they leave the polymerization reactor (or, in the case of multiple reactors connected in series, the final polymerization reactor).

[0089] The term "post-consumer resin" (which may be abbreviated as "PCR") is used to denote components of municipal waste, household waste, or end-of-life vehicle waste. In other words, PCR is made from recycled products of waste generated by consumers. The term "post-industrial resin" (which may be abbreviated as "PIR") is used to denote waste components from pre-consumer resin during the packaging process. In other words, PIR is made from recycled products produced by manufacturers from scrap.

[0090] The term "recycled polyethylene composition (component, composition)" or "recycled polyethylene-containing material" is contrasted with the terms "virgin polyethylene composition (component, composition)", "virgin polyethylene-containing material", where the term "virgin" is used to denote polyethylene compositions or materials directly obtained from a polyethylene plant. The term "directly obtained" is meant to include that the polyethylene composition may optionally pass through a pelletizing step or an additive step or both.

[0091] Under normal production conditions in the production equipment, it is expected that the melt index (MI2, HLMI, MI5) of the fluff will be different from that of the polyethylene-containing resin. Under normal production conditions in the production equipment, it is expected that the density of the fluff will be slightly different from that of the polyethylene-containing resin (if PCR resin is considered, it is not a problem of fluff (powder) or pellets, but of flakes or pellets). Unless otherwise specified, the density and melt index of the polyethylene-containing resin refer to the density and melt index measured on the polyethylene-containing resin as defined above.

[0092] The present disclosure provides a process for processing an initial polyethylene-containing material to produce a polyethylene composition. The process, the initial polyethylene-containing material, and the polyethylene composition produced by such a process (i.e., the processed polyethylene composition) will be described jointly.

[0093] According to the disclosure, the process for processing an initial polyethylene-containing material to produce a polyethylene composition is notable in that it comprises the following steps:

[0094] a) Providing a twin-screw extruder with a heat-regulating device;

[0095] b) Providing an initial polyethylene-containing material that comprises at least 50 wt% polyethylene based on the total weight of the initial polyethylene-containing material;

[0096] c) Extruding the initial polyethylene-containing material to obtain a polyethylene composition; wherein the extrusion is carried out with a residence time of less than 20 minutes; and

[0097] d) Collecting the polyethylene composition;

[0098] wherein the extrusion step (c) comprises heat-treating the initial polyethylene-containing material by self-heating of the material at a temperature of at least 300 °C in one or more heat zones of the extruder, wherein the one or more heat zones have a total length equal to or greater than 6D, where D is the screw diameter, wherein the extrusion is carried out with a mechanical specific energy of greater than or equal to 0.4 kWh / kg, wherein the screw profile comprises at least one heat zone having successive kneading block elements over a length of at least 4D, followed by a left-handed element, where D is the screw diameter, and wherein the heat-regulating device is set to an initially applied barrel temperature in the range between 240 and 320 °C and is turned off when the barrel temperature in the zone spontaneously exceeds the applied barrel temperature by at least 1 °C without the need for external heat application.

[0099] The process for processing an initial polyethylene-containing material involves increasing the melt index of the initial polyethylene-containing material to produce a polyethylene composition having a melt index increased by more than 6.0-fold k; preferably at least 7.0-fold k; preferably at least 8.0-fold k; preferably at least 10.0-fold k; preferably at least 15.0-fold k; preferably at least 20.0-fold k; preferably at least 30.0-fold k; preferably at least 35.0-fold k; preferably at least 40.0-fold k.

[0100] such that the ratio of the melt index (MI2 T) of the polyethylene composition to the melt index (MI2 R) of the initial polyethylene-containing material is greater than 6.0; preferably at least 7.0, preferably at least 8.0; preferably at least 10.0; preferably at least 15.0; preferably at least 20.0; preferably at least 30.0; preferably at least 35.0; preferably at least 40.0.

[0101] Twin-screw extruder with a thermal regulation device and step c) of extruding the initial polyethylene-containing material to obtain a polyethylene composition Polyethylene composition and step d) of collecting the polyethylene composition

[0102] The initial polyethylene-containing material is processed by extrusion to obtain a polyethylene composition, wherein the extrusion is carried out with a residence time of less than 20 minutes, and wherein the extrusion step (c) comprises heat-treating the initial polyethylene-containing material at a temperature of at least 300 °C in one or more hot zones of the extruder.

[0103] The extruder is a twin-screw extruder. The extruder is provided with a screw profile showing an aggressive design, as Figure 1 shown, to impart high mechanical energy to the initial polyethylene-containing material.

[0104] As is known to those skilled in the art, in addition to the heat energy generated by mixing, a heat conditioning device can be used as a heating device to impart heat energy to the initial polyethylene-containing material in the extruder.

[0105] Extrusion mixing varies with the type of screw and the screw profile and can significantly generate mechanical energy, such as shear energy and / or elongation energy. Thus, energy is introduced into the extrusion process in terms of mechanical energy and heat energy. Heating and / or cooling of the barrel can be achieved, for example, by electricity, by steam, or by circulation of a heat control liquid such as oil or water.

[0106] The extruder screw comprises a screw body which is composed of cylindrical elements and a rotating shaft supporting the elements. The rotating shaft extends straight from its base end to its tip end. In a state where the extruder screw is rotatably inserted into the cylinder of the barrel, the base end of the extruder screw is located on one end side of the barrel, on which a supply port is provided, and the tip end of the extruder screw is located on the other end side of the barrel, on which a discharge port is provided.

[0107] The screw extruder has a modular system which allows different screw elements to be pulled into a central shaft to construct a defined screw profile. The extruder screw may include one or more elements selected from conveying elements, kneading elements, right-handed (forward) screw elements, left-handed (reverse) screw elements, and any combination thereof. These elements are arranged in a defined order from the base end to the tip of the extruder screw, and this order as well as the type and number of elements involved define the screw profile. The extruder and screw elements are commercially available, for example, from Leistritz.

[0108] In one embodiment of the present disclosure, the treatment of an initial polyethylene-containing material is manipulated by mechanical energy.

[0109] When high mechanical energy is required, the provided extruder has a specific screw profile which is constructed to be "aggressive", meaning that high mechanical energy will be imparted to the initial polyethylene-containing material. As is known to those skilled in the art, high mechanical energy will cause the temperature to rise in the extruder, thereby effecting heat treatment by self-heating of the material.

[0110] In such an embodiment, a twin-screw extruder is selected to include one or more hot zones, preferably filled mixing zones, where the total length of the one or more hot zones is equal to or greater than 6D, where D is the screw diameter.

[0111] Understand that in the case where the screw profile is selected to include a single hot zone, then the total length of the hot zone is equal to or greater than 6D, where D is the screw diameter. In such a case, the hot zone is also the melting zone of the twin-screw extruder.

[0112] In the case where the screw profile includes two or more hot zones, then the first hot zone includes successive kneading block elements over a length of at least 4D, followed by a left-handed element, where D is the screw diameter, and one or more additional hot zones placed downstream of the first hot zone are filled mixing zones, each including kneading block elements over a length of at least 4D, followed by kneading left-handed elements or left-handed elements, where D is the screw diameter. For example, the twin-screw extruder includes two filled mixing zones, where each of the filled mixing zones has a length equal to or greater than 4D, where D is the screw diameter. Preferably, the first hot zone is or includes the melting zone of the extruder.

[0113] Various mixing elements may be considered in the one or more hot zones, but the most preferred mixing element does not drive any forward conveyance (dispersive kneading block element with a 90-degree disk offset). Other disk offset angles (e.g., 30 degrees, 45 degrees, and / or 60 degrees) may be considered, but 90 degrees is preferred. The preferred minimum width of the disk is 0.3D.

[0114] Thus, preferably, the successive kneading block elements of at least one hot zone include disks having a disk offset of 90 degrees and a disk width of at least 0.3D, where D is the screw diameter.

[0115] For example, the twin-screw extruder includes more than two filled mixing zones, where the total length of the filled mixing zones is equal to or greater than 8D, where D is the screw diameter.

[0116] For example, the strong melting zone of the twin-screw extruder is made of successive mixing elements over a length of 4D, where D is the screw diameter, followed by left-handed elements; preferably full-flight left-handed elements.

[0117] In a preferred embodiment, the thermal regulation device of the twin-screw extruder allows the cooling cylinder, and the process includes shutting down the thermal regulation device when the cylinder temperature in the zone spontaneously exceeds the applied cylinder temperature by at least 1 °C without external heat application; preferably at least 2 °C, preferably at least 3 °C; more preferably at least 5 °C; even more preferably at least 8 °C; and most preferably at least 10 °C.

[0118] Indeed, when starting the extrusion, the thermal regulation device will be turned on, especially in the melting zone, to allow the material to melt. Then, when the polymer self-heats, the thermal regulation device is shut down to allow the temperature inside the extruder to increase.

[0119] In a preferred embodiment, the step (c) of extruding the initial polyethylene-containing material includes extruding with a mechanical specific energy of greater than or equal to 0.45 kWh / kg, preferably greater than or equal to 0.5 kWh / kg; more preferably greater than or equal to 0.6 kWh / kg.

[0120] A high rotational screw speed is preferred, but the exact value of the high rotational screw speed depends on the "extruder diameter". For example, when considering a twin-screw extruder with a diameter D of 18 mm, a high rotational screw speed is considered to be higher than 500 rpm, preferably higher than 800 rpm. For example, when considering a twin-screw extruder with D = 58 mm, a high rotational screw speed is considered to be higher than 250 rpm, preferably higher than 350 rpm.

[0121] Non-limiting examples of suitable extruder screws with specific screw profiles are shown in Figure 1 as PTE1 and PTE2.

[0122] The heat treatment of the material in step (c) is preferably carried out at a maximum barrel temperature in the range of 300 to 460 °C; preferably in the range of 310 to 450 °C; more preferably in the range of 320 to 430 °C; even more preferably in the range of 330 °C to 410 °C, and most preferably in the range of 340 to 390 °C. The maximum barrel temperature is the highest temperature among the temperatures applied or measured along the extruder.

[0123] For example, step (c) of extruding the initial polyethylene-containing material includes heat treatment at a temperature of at least 305 °C in one or more hot zones of the extruder; preferably at a temperature of at least 315 or at least 320 °C; more preferably at a temperature of at least 330 °C; even more preferably at a temperature of at least 340 °C, and most preferably at a temperature of at least 350 °C, or at a temperature of at least 355 °C, or at a temperature of at least 360 °C.

[0124] For example, step (c) of extruding the initial polyethylene-containing material includes heat treatment at a temperature of at most 460 °C in one or more hot zones of the extruder; preferably at most 450 °C; more preferably at most 440 °C; even more preferably at most 440 °C; most preferably at most 430 °C; even most preferably at most 420 °C, or at most 410 °C, or at most 405 °C, or at most 400 °C, or at most 395 °C, or at most 390 °C.

[0125] For example, step (c) of extruding the initial polyethylene-containing material includes heat treatment at a temperature in the range of 300 to 460 °C in one or more hot zones of the extruder; preferably in the range of 310 to 450 °C; more preferably in the range of 320 to 430 °C; even more preferably in the range of 330 to 410 °C, and most preferably in the range of 340 to 390 °C, or in the range of 320 to 460 °C.

[0126] The temperature of the heat treatment is the maximum barrel temperature.

[0127] A person skilled in the art can adjust the extrusion conditions to impart sufficient energy to obtain a polyethylene composition having a melt index (MI2 T) within the target range.

[0128] The screw speed can be adjusted according to the target maximum barrel temperature and the capacity of the extruder. A higher screw speed allows for a higher increase in the polymer temperature. For example, the screw speed ranges from 100 to 1200 rpm; preferably from 110 rpm to 1200 rpm; more preferably from 150 rpm to 1100 rpm; even more preferably from 200 rpm to 1000 rpm; most preferably from 300 rpm to 900 rpm; and even most preferably from 320 to 800 rpm or from 350 to 1200 rpm.

[0129] In a twin-screw extruder with an 18 mm screw diameter, the preferred screw speed is higher than 500 rpm; in a twin-screw extruder with a 58 mm screw diameter, the preferred screw speed is higher than 250 rpm.

[0130] For example, step (c) of extruding the initial polyethylene-containing material includes a residence time in the range of 10 seconds to 10 minutes; preferably a residence time in the range of 20 seconds to 5 minutes; more preferably an extrusion is carried out with a residence time in the range of 10 to 180 seconds, or 10 to 120 seconds, or 20 to 100 seconds, or 30 to 80 seconds.

[0131] Initial polyethylene-containing material and step b) of providing the initial polyethylene-containing material

[0132] The process according to the present disclosure includes step (b) of providing an initial polyethylene-containing material, the initial polyethylene-containing material comprising at least 50 wt% polyethylene based on the total weight of the initial polyethylene-containing material.

[0133] The initial polyethylene-containing material can be a virgin polyethylene-containing material, a recycled polyethylene-containing material, or a mixture of a virgin polyethylene-containing material and a recycled polyethylene-containing material. In some embodiments, the initial polyethylene-containing material is a recycled polyethylene-containing material. As used herein, the term "recycled polyethylene composition" encompasses both post-consumer resin (PCR) and post-industrial resin (PIR).

[0134] Suitable polyethylenes include, but are not limited to, homopolymers of ethylene, copolymers of ethylene and higher α-olefin comonomers. Thus, preferably, the polyethylene in the initial polyethylene-containing material is one or more polyethylene homopolymers, one or more polyethylene copolymers, and any mixture thereof.

[0135] The term "copolymer" refers to a polymer made by linking two different types of monomers in the same polymer chain. Preferred comonomers are α-olefins having 3 to 20 carbon atoms or 3 to 10 carbon atoms. More preferred comonomers are selected from propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and any mixture thereof. Even more preferred comonomers are selected from 1-butene, 1-hexene, 1-octene, and any mixture thereof. The most preferred comonomer is 1-hexene.

[0136] The term "homopolymer" refers to a polymer made by linking only one monomer in the absence of a comonomer. Thus, a homopolymer of ethylene is substantially free of any comonomer. "Substantially free" means that no comonomer is intentionally added during the production of the polyethylene, but may still be present up to 0.2 wt%, preferably up to 0.1 wt%, and most preferably up to 0.05 wt% relative to the total weight of the polyethylene.

[0137] The initial polyethylene-containing material is selected to comprise at least 50 wt% polyethylene based on the total weight of the initial polyethylene-containing material. Preferably, the initial polyethylene-containing material is selected to comprise at least 55 wt%; preferably, at least 60 wt%; preferably, at least 70 wt%; preferably, at least 80 wt%; preferably, at least 90 wt%; preferably, at least 95 wt% polyethylene.

[0138] In one embodiment, the initial polyethylene-containing material is a virgin material and consists of polyethylene (i.e., contains 100 wt% polyethylene).

[0139] In one embodiment, the initial polyethylene-containing material is a recycled polyethylene-containing material. The recycled polyethylene-containing material may contain one or more polymers different from polyethylene.

[0140] In one embodiment, and particularly where the initial polyethylene-containing material is a recycled polyethylene-containing material; the initial polyethylene-containing material contains at least one polymer different from polyethylene in an amount ranging from 0 to 50 wt% based on the total weight of the initial polyethylene-containing material; wherein at least one polymer different from polyethylene is selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof.

[0141] Preferably, the initial polyethylene-containing material contains at least one polymer different from polyethylene in an amount ranging from 0 to 40% by weight, preferably from 0.1 to 20% by weight, more preferably from 0.2 to 10% by weight, and even more preferably from 0.5 to 5% by weight, based on the total weight of the initial polyethylene-containing material.

[0142] For example, PCR polyethylene typically contains a small fraction of polypropylene (e.g., less than 5% by weight).

[0143] In one embodiment, when measured according to ISO 1133-2011 at 190 °C under a load of 21.6 kg, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a high load melt index (HLMI R) of at least 1.0 g / 10 min; preferably at least 1.2 g / 10 min; more preferably at least 1.5 g / 10 min.

[0144] In one embodiment, when measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a melt index (MI2 R) of at least 0.10 g / 10 min; preferably at least 0.15 g / 10 min; more preferably at least 0.2 g / 10 min; even more preferably at least 0.5 g / 10 min, most preferably at least 0.8 g / 10 min, and even most preferably at least 0.9 g / 10 min, or at least 1.0 g / 10 min.

[0145] For example, the initial polyethylene-containing material is selected to have a melt index ranging from a high load melt index (HLMI R) of at least 1.0 g / 10 min when measured according to ISO 1133-2011 at 190 °C under a load of 21.6 kg to a melt index (MI2 R) of at most 3.0 g / 10 min when measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.

[0146] In one embodiment, when measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a melt index (MI2R) of at most 3.0 g / 10 min; preferably at most 2.8 g / 10 min; more preferably at most 2.5 g / 10 min; even more preferably at most 2.2 g / 10 min, most preferably at most 2.0 g / 10 min, and even most preferably at most 1.8 g / 10 min, or at most 1.6 g / 10 min.

[0147] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density of at least 0.910 g / cm 3 .

[0148] In one embodiment, the initial polyethylene-containing material is selected to have a high load melt index (HLMI R) of at least 1.0 g / 10 min when measured at 190 °C under a load of 21.6 kg in accordance with ISO 1133-2011, a melt index (MI2R) of at most 0.45 g / 10 min when measured at 190 °C under a load of 2.16 kg in accordance with ISO 1133-2011, and a density of at least 0.940 g / cm 3 when measured at 23 °C in accordance with ISO 1183-1:2012.

[0149] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density of at least 0.940 g / cm 3 ; preferably, at least preferably, at least 0.945 g / cm 3 ; more preferably, at least 0.948 g / cm 3 ; even more preferably at least 0.950 g / cm 3 ; and most preferably at least 0.951 g / cm 3 .

[0150] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density of at most 0.965 g / cm 3 ; preferably, at most 0.962 g / cm 3 ; and more preferably, at most 0.960 g / cm 3 .

[0151] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density in the range of 0.940 g / cm 3 to 0.965 g / cm 3 ; preferably, in the range of 0.942 g / cm 3 to 0.964 g / cm 3 ; more preferably, in the range of 0.945 g / cm 3 to 0.962 g / cm 3; and even more preferably, in the range of 0.948 g / cm 3 to 0.960 g / cm 3 of density.

[0152] For example, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a melt index ranging from a high load melt index (HLMI R) of at least 1.0 g / 10 min as measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011 to a melt index (MI2 R) of at most 0.45 g / 10 min as measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011.

[0153] For example, when measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a high load melt index (HLMI R) of at least 1.0 g / 10 min; preferably at least 1.2 g / 10 min; more preferably at least 1.5 g / 10 min.

[0154] For example, when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2005, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a melt index (MI2 R) of at most 0.45 g / 10 min; preferably, at most 0.42 g / 10 min; more preferably at most 0.40 g / 10 min; even more preferably in the range of at most 0.35 g / 10 min.

[0155] In another embodiment, the initial polyethylene-containing material is selected to have a melt index (MI2 R) in the range of 0.8 to 1.5 g / 10 min as measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, and a density in the range of 0.910 g / cm 3 to less than 0.940 g / cm 3 ; preferably in the range of 0.910 g / cm 3 to 0.935 g / cm 3 and more preferably in the range of 0.910 g / cm 3 to 0.930 g / cm 3 of density.

[0156] Preferably, when measured at 23 °C according to ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has at least 0.910 g / cm3 ; Preferably, at least preferably, at least 0.912 g / cm 3 ; More preferably, at least 0.915 g / cm 3 ; And even more preferably at least 0.916 g / cm 3 of density.

[0157] For example, when measured at 23 °C according to ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density of less than 0.940 g / cm 3 ; Preferably, at most 0.935 g / cm 3 ; More preferably, at most 0.930 g / cm 3 ; Even more preferably, at most 0.928 g / cm 3 ; And most preferably, at most 0.925 g / cm 3 of density.

[0158] For example, when measured at 23 °C according to ISO 1183-1:2012, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a density in the range of 0.910 g / cm 3 to less than 0.940 g / cm 3 ; Preferably, in the range of 0.910 g / cm 3 to 0.935 g / cm 3 ; More preferably, in the range of 0.910 g / cm 3 to 0.930 g / cm 3 ; Even more preferably in the range of 0.912 g / cm 3 to 0.928 g / cm 3 ; Most preferably, in the range of 0.915 g / cm 3 to 0.925 g / cm 3 ; And even most preferably, in the range of 0.916 g / cm 3 to 0.925 g / cm 3 of density.

[0159] For example, when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a melt index (MI2R) in the range of 0.8 to 1.5 g / 10 min; preferably, in the range of 0.8 to 1.4 g / 10 min; more preferably in the range of 0.9 to 1.3 g / 10 min; even more preferably in the range of 1.0 to 1.2 g / 10 min.

[0160] In some embodiments, when measured by gel permeation chromatography, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has an Mz / Mw of at least 4.0; preferably in the range of 4.0 to 50.0; preferably 5.0 to 25.0; preferably 7.0 to 15.0.

[0161] In some embodiments, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a complex viscosity in the range of 20,000 to 80,000 Pa·s at 190 °C at 0.1 radian / second; preferably in the range of 22,000 to 70,000 Pa·s; more preferably in the range of 25,000 to 60,000 Pa·s; and even more preferably in the range of 30,000 to 50,000 Pa·s.

[0162] In some embodiments, when measured by gel permeation chromatography, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has an Mw / Mn in the range of 5.0 to 30.0; preferably in the range of 6.0 to 20.0; preferably in the range of 7.0 to 15.0.

[0163] In some embodiments, the initial polyethylene-containing material or the polyethylene in the initial polyethylene-containing material has a complex viscosity ratio of more than 10; preferably at least 11; more preferably at least 12.

[0164] In one embodiment, the initial polyethylene-containing material further has a tan δ (G” / G’ measured at 190 °C at 0.1 radian / second) of at most 3.0; preferably at most 2.6.

[0165] In one embodiment, the initial polyethylene-containing material further has a tan δ (G” / G’ measured at 190 °C at 0.1 radian / second) in the range of 0.5 to 3.0; preferably 0.8 to 2.6.

[0166] Obtained polyethylene composition and step d) of collecting the polyethylene composition

[0167] Step d) includes collecting the polyethylene composition as the treated initial polyethylene-containing material.

[0168] For example, when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, the polyethylene composition has a melt index (MI2 T) in the range of 3.0 to 60.0 g / 10 min. For example, when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, the polyethylene composition has a melt index (MI2 T) in the range of 3.5 to 40.0 g / 10 min; preferably in the range of 4.0 to 20.0 g / 10 min; more preferably in the range of 4.5 to 15.0 g / 10 min; even more preferably in the range of 5.0 to 10.0 g / 10 min.

[0169] The polyethylene composition corresponds to the treated starting material; wherein the melt index increases. However, unexpectedly, the treatment also provides other characteristics to the polyethylene composition, making it particularly suitable for injection molding.

[0170] In particular, it has been found that the ratio of the complex viscosity of the polyethylene composition at a frequency of 0.01 rad / s to the complex viscosity at a frequency of 100 rad / s is at most 10; preferably at most 9.0; more preferably at most 8.5; even more preferably at most 8.0; and most preferably at most 7.0, the ratio being measured at 190 °C.

[0171] In one embodiment, the polyethylene composition has a complex viscosity at 0.1 rad / s at 190 °C of at most 20,000 Pa·s; preferably at most 18,000 Pa·s; more preferably at most 15,000 Pa·s; even more preferably at most 12,000 Pa·s; most preferably at most 10,000 Pa·s; and even most preferably at most 9,000 Pa·s; or at most 8,000 Pa·s, or at most 5,000 Pa·s.

[0172] In one embodiment, the polyethylene composition has a complex viscosity at 0.1 rad / s at 190 °C in the range of 200 to 20,000 Pa·s; preferably 250 to 18,000 Pa·s; more preferably 300 to 15,000 Pa·s; even more preferably 400 to 12,000 Pa·s; most preferably 410 to 10,000 Pa·s; and even most preferably 410 to 9,000 Pa·s; or 400 to 8,000 Pa·s, or 400 to 5,000 Pa·s.

[0173] Preferably, when determined by size exclusion chromatography, the polyethylene composition has an Mz / Mw of at most 7.0; preferably at most 6.0; preferably at most 5.0.

[0174] For example, when measured by size exclusion chromatography, the polyethylene composition further has an Mw / Mn in the range of 2.5 to 10.0; preferably 2.6 to 8.0; more preferably 2.7 to 6.0; even more preferably 2.8 to 5.0 or 2.9 to 4.5.

[0175] For example, the polyethylene composition further has a tan δ (G” / G') at 190 °C at 0.1 radian that is above 2.5; preferably at least 3.0; more preferably at least 5.0, and even more preferably at least 10.0.

[0176] The density of the polyethylene composition is higher than the density of the initial polyethylene-containing material.

[0177] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the polyethylene composition has a density of at least 0.910 g / cm 3 For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the polyethylene composition has a density of at least 0.912 g / cm 3 ; preferably, at least preferably, at least 0.915 g / cm 3 ; more preferably, at least 0.918 g / cm 3 ; even more preferably at least 0.920 g / cm 3 ; and most preferably, at least 0.930 g / cm 3 of density.

[0178] In one embodiment, when measured at 23 °C in accordance with ISO 1183-1:2012, the polyethylene composition has a density of at most 0.965 g / cm 3 ; preferably, at most 0.962 g / cm 3 ; and more preferably, at most 0.960 g / cm 3 ; and even more preferably, at most 0.958 g / cm 3 of density.

[0179] For example, when measured at 23 °C in accordance with ISO 1183-1:2012, the polyethylene composition has a density in the range of 0.920 g / cm 3 to 0.965 g / cm 3 ; preferably, in the range of 0.930 g / cm 3 to 0.960 g / cm 3 of density.

[0180] In one embodiment, when measured at 23 °C in accordance with ISO 1183-1:2012, the polyethylene composition has a density of at least 0.910 g / cm 3; Preferably, at least preferably, at least 0.912 g / cm 3 ; More preferably, at least 0.915 g / cm 3 ; And even more preferably, at least 0.916 g / cm 3 of density. For example, when measured at 23 °C according to ISO 1183-1:2012, the polyethylene composition has at most 0.930 g / cm 3 ; Preferably, at most 0.928 g / cm 3 ; And more preferably, at most 0.925 g / cm 3 of density. For example, when measured at 23 °C according to ISO 1183-1:2012, the polyethylene composition has a density in the range of 0.910 g / cm 3 to less than 0.940 g / cm 3 ; Preferably, in the range of 0.910 g / cm 3 to 0.935 g / cm 3 ; More preferably, in the range of 0.910 g / cm 3 to 0.930 g / cm 3 ; Even more preferably, in the range of 0.912 g / cm 3 to 0.928 g / cm 3 ; Most preferably, in the range of 0.915 g / cm 3 to 0.925 g / cm 3 ; And even most preferably, in the range of 0.916 g / cm 3 to 0.925 g / cm 3 of density.

[0181] In one embodiment, when measured at 23 °C according to ISO 1183-1:2012, the polyethylene composition has at least 0.940 g / cm 3 ; Preferably, at least preferably, at least 0.945 g / cm 3 ; More preferably, at least 0.948 g / cm 3 ; Even more preferably, at least 0.950 g / cm 3 ; And most preferably, at least 0.951 g / cm 3 of density. For example, when measured at 23 °C according to ISO1183-1:2012, the polyethylene composition has at most 0.965 g / cm 3 ; Preferably, at most 0.962 g / cm 3 ; And more preferably, at most 0.960 g / cm 3The density. For example, when measured at 23 °C according to ISO 1183-1:2012, the polyethylene composition has a density in the range of 0.940 g / cm 3 to 0.965 g / cm 3 ; preferably, in the range of 0.942 g / cm 3 to 0.964 g / cm 3 ; more preferably, in the range of 0.945 g / cm 3 to 0.962 g / cm 3 ; and even more preferably, in the range of 0.948 g / cm 3 to 0.960 g / cm 3 of density.

[0182] In one embodiment, the polyethylene composition collected in step (d) has one or more of the following:

[0183] - When measured at 23 °C according to ISO 1183-1:2012, a density of at least 0.910 g / cm 3 ; and / or

[0184] - When measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, a melt index MI2 in the range of 3.0 to 60.0 g / 10 min; and / or

[0185] - An unsaturation index higher than 2,000, where the unsaturation index is the product of vinyl unsaturated units per 1,000 carbon atoms and Mn in daltons when measured by ASTM D6248-98:2004; and / or

[0186] - A complex viscosity at 190 °C at 0.1 rad / s of at most 20,000 Pa·s.

[0187] In a preferred embodiment, the polyethylene composition collected in step (d) has:

[0188] - When measured at 23 °C according to ISO 1183-1:2012, a density of at least 0.910 g / cm 3 ;

[0189] - When measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, a melt index MI2 in the range of 3.0 to 60.0 g / 10 min;

[0190] - An unsaturation index greater than 2,000, where the unsaturation index is the product of vinyl unsaturation units per 1,000 carbon atoms and the Mn in daltons as determined by ASTM D6248-98:2004; and

[0191] - A complex viscosity at 190 °C at 0.1 radian per second of at most 20,000 Pa·s.

[0192] For example, the polyethylene composition further has a VOC content lower than that of the initial polyethylene-containing material.

[0193] VOC is the amount of volatile organic compounds (VOC) in ppm, where the volatile compounds are defined as having 12 carbon atoms or fewer in the chain. This reduction in VOC is beneficial, but a very significant reduction in such content is required to eliminate odors.

[0194] This disclosure encompasses articles produced from the polyethylene composition as defined above, where the articles are injection molded articles; preferably, the articles are selected from bottles or containers.

[0195] For example, the article is produced using 40 wt% to 100 wt% of the initial polyethylene-containing material as recycled and has a lower VOC content than the initial polyethylene-containing material.

[0196] Test methods

[0197] Of polyethylene Melt flow index MI2 Is determined at 190 °C under a load of 2.16 kg according to ISO 1133-2011.

[0198] Of polyethylene HLMI Is determined at 190 °C under a load of 21.6 kg according to ISO 1133-2011.

[0199] Mn, Mw, Mz, Mw / Mn and Mz / Mw : The molecular weight (M n (number average molecular weight), M w(Weight-average molecular weight) and molecular weight distribution D (Mw / Mn). Briefly, using a GPC-IR5 from Polymer Char: 10 mg of the polyethylene sample was dissolved in 10 ml of trichlorobenzene at 160 °C for 1 hour. Injection volume: approximately 400 μl, automatic sample preparation, and injection temperature: 160 °C. Column temperature: 145 °C. Detector temperature: 160 °C. Two Shodex AT-806MS (Showa Denko) and one Styragel HT6E (Waters) columns were used, with a flow rate of 1 ml / min (eluent: trichlorobenzene). Detector: infrared detector (2800 - 3000 cm -1 ). Calibration: Narrow standards of polystyrene (PS) (commercially available). The molecular weight Mi of each fraction i of the eluted polyethylene was calculated based on the Mark-Houwink relationship (log 10 (M PE ) = 0.965909 x log 10 (M PS ) – 0.28264) (low molecular weight end cut-off at M PE = 1000).

[0200] The molecular weight averages used to establish the molecular weight / property relationship are the number-average (M n ), weight-average (M w ), and z-average (M z ) molecular weights. These averages are defined by the following expressions and are determined from the calculated M i :

[0201]

[0202] where N i and W i are the number and weight of molecules with molecular weight Mi, respectively. The third representation (farthest right) in each case defines how to obtain these averages from the SEC chromatogram. h i is the height of the SEC curve at the i-th elution fraction (from the baseline), and M i is the molecular weight of the species eluting in that increment.

[0203] Then the Molecular weight distribution (MWD) was calculated as Mw / Mn.

[0204] 13 C-NMR analysisPerformed using a 400 MHz or 500 MHz Bruker NMR spectrometer under conditions such that the signal intensity in the spectrum is proportional to the total number of carbon atoms contributing in the sample. These conditions are well known to those skilled in the art and include, for example, sufficient relaxation time, etc. In practice, the intensity of the signal is obtained from its integral (i.e., the corresponding area). The data was obtained using proton decoupling, a 10 mm room temperature probe (room temperature through) with 2000 to 4000 scans per spectrum or a 10 mm cryoprobe with 240 scans per spectrum, a pulse repetition delay of 11 seconds, and a spectral width of 25000 Hz (+ / - 3000 Hz). The sample was prepared by dissolving a sufficient amount of the polymer in 1,2,4-trichlorobenzene (TCB, 99%, spectroscopic grade) at 130 °C and stirring occasionally to homogenize the sample, followed by adding hexadeuterobenzene (C6D6, spectroscopic grade) and a small amount of hexamethyldisiloxane (HMDS, 99.5+ %), where HMDS acts as an internal standard. As an example, about 200 mg to 600 mg of the polymer was dissolved in 2.0 mL of TCB, followed by adding 0.5 mL of C6D6 and 2 to 3 drops of HMDS.

[0205] After data acquisition, the signal of the chemical shift reference internal standard HMDS, which is assigned a value of 2.03 ppm.

[0206] The comonomer content in polyethylene was determined by C-NMR analysis of pellets according to the method described by G.J. Ray et al. (Macromolecules, 1977, 10, (4), 773 - 778). 13 C-NMR analysis.

[0207] Crystallization temperature (Tc) and Melting temperature (Tm) Determined on a DSC Q2000 instrument from TA Instruments according to ISO 11357-3:2018. To eliminate the thermal history, the sample was first heated to 220 °C and held at 220 °C for 3 minutes. Then the polymer was cooled to up to 20 °C at -20 °C / minute and held at 20 °C for 3 minutes. The crystallization temperature was determined during this cooling step. The crystallization temperature Tc corresponds to the temperature of the extremum of the plot that presents the heat flux associated with the polymer as a function of the temperature during its cooling. Then the polymer was melted to up to 220 °C at 20 °C / minute and the melting temperature was determined during this heating step. The melting temperature corresponds to the temperature of the extremum of the plot that presents the heat flux associated with the polymer as a function of the temperature during its melting.

[0208] Measured at a temperature of 23 °C according to the method of standard ISO 1183-1:2012 (immersion method). Density .

[0209] Complex shear modulus and viscosity : The complex shear modulus G*(w) = G’(w) + jG”(w) (J 2 = -1, G’(w): storage modulus and G”(w): loss modulus) was measured using a DHR-2 (a stress-controlled rheometer from TA Instruments). From 100 to 0.01 radian·s under a nitrogen flow at 190 °C -1 A frequency sweep was performed in the linear regime (1% strain) to prevent thermal oxidative degradation. The geometry used was 25 mm diameter parallel plates with a 2 mm gap. Samples (25 mm diameter, 2 mm thickness) for these experiments were pre-obtained using an injection press (Babyplast type).

[0210] Complex viscosity η * (ω) was calculated according to the following formula for linear viscoelasticity:

[0211]

[0212] Example

[0213] The following non-limiting examples illustrate the present disclosure

[0214] PE1 = Polyethylene HDPE 5502 commercialized by TotalEnergies. The density according to ISO 1183-1:2012 is 0.954 g / cm 3 ; The MI2 according to ISO 1133-2011 (190 °C, 2.16 kg) is 0.25 g / 10 min; The HLMI according to ISO 1133-2011 (190 °C, 21.6 kg) is 22 g / 10 min. The polyethylene was produced using a chromium-based catalyst.

[0215] The storage modulus (G’) measured at 0.1 radian and 190 °C was 1,855 Pa, and the loss modulus (G”) measured at 0.1 radian and 190 °C was 2,798 Pa; resulting in a tanδ (G” / G’) of 1.5.

[0216] From the perspective of melt index, PE1 was chosen because it represents the melt index of the recycled polyethylene flux, and it makes sense to convert it into an injection (recycled) grade.

[0217] Example 1: Machining

[0218] The extruder used in the experiment was a Leistritz ZSE 18HPe. The screw design was modified from the standard configuration as Figure 1The PTE1 and PTE2 screw designs shown in . Both the PTE1 and PTE2 screw designs include two left-handed screw sections, one in zone Z2 and one in zone Z5. Z2 is the melting zone and Z5 is the mixing zone. Both the PTE1 and PTE2 screws are designed with a section having kneading blocks in Z4 (i.e., placed between the two left-handed screw sections).

[0219] In the first experiment, extrusion was carried out at different screw speeds with a fixed flow rate of 1.5 kg / h, and the temperature profile was as shown in Table 1. These temperatures corresponded to the values applied during the start of the test. When progressing to steady-state conditions, the barrel temperature exceeded these targets due to the conversion of mechanical heat in the barrel into polymer heat. When the temperature in a zone exceeded the target by more than 10 °C, the temperature regulation in that zone was turned off, and the temperature of that zone could increase and stabilize at a higher value.

[0220] Table 1

[0221]

[0222] Figure 2 Results for MI2 are provided in (polymer analysis was carried out when steady-state conditions were reached), where it can be seen that the initial MI2 of 0.2 g / 10 min could be increased to up to approximately 10 g / 10 min (a factor of 50). The obtained polyethylene composition showed an unsaturation index of approximately 13,700.

[0223] In the second experiment, extrusion was carried out at different screw speeds with a fixed flow rate of 2.5 kg / h, and the temperature profile was as shown in Table 2. Here, these temperatures also corresponded to the values applied during the start of the test. When progressing to steady-state conditions, the barrel temperature exceeded these targets due to the conversion of mechanical heat in the barrel into polymer heat. When the temperature in a zone exceeded the target by more than 10 °C, the temperature regulation in that zone was turned off, and the temperature of that zone could increase and stabilize at a higher value.

[0224] Table 2

[0225]

[0226] Results for MI2 are provided in Figure 3 (polymer analysis was carried out when steady-state conditions were reached), where it can be seen that the initial MI2 of 0.2 g / 10 min could be increased to up to approximately 16 g / 10 min (a factor of 80). The obtained polyethylene composition showed an unsaturation index of approximately 13,500.

[0227] Example 2: Thermal processing

[0228] A series of experiments were then carried out, in which heat treatment was carried out by heating the material at a temperature rising from 320 °C to 390 °C. The experiments were carried out at screw speeds of 400 and 800 rpm. In Figure 4 The complex viscosity obtained on the treated samples was reported and compared with the initial material HDPE 5502. It was found from the results that a significant reduction in the complex viscosity was obtained. For all samples treated at a temperature of 340 °C or higher, the complex viscosity ratio (about 13) of HDPE 5502 dropped below 8.

[0229] Figure 5 An increase in tanδ (G” / G’) obtained for the treated material is shown.

Claims

1. A process for treating an initial polyethylene-containing material to produce a polyethylene composition, characterized in that, It includes the following steps: a) Providing a twin-screw extruder with a heat regulation device; b) Providing an initial polyethylene-containing material that contains at least 50% by weight of polyethylene based on the total weight of the initial polyethylene-containing material; c) Extruding the initial polyethylene-containing material to obtain a polyethylene composition; wherein the extrusion is carried out with a residence time of less than 20 minutes; and d) Collecting the polyethylene composition; wherein the extrusion step (c) includes heat-treating the initial polyethylene-containing material by self-heating of the initial polyethylene-containing material at a temperature of at least 300 °C in one or more heat zones of the extruder, wherein the one or more heat zones have a total length equal to or greater than 6D, where D is the screw diameter, wherein the extrusion is carried out with a mechanical specific energy of greater than or equal to 0.4 kWh / kg, wherein the screw profile includes at least one heat zone having successive kneading block elements over a length of at least 4D, followed by left-handed elements, where D is the screw diameter, and wherein the heat regulation device is set to an initially applied barrel temperature in the range between 240 °C and 320 °C and shuts off when the barrel temperature in the at least one heat zone spontaneously exceeds the applied barrel temperature by at least 3 °C without external heat application.

2. The process according to claim 1, wherein The heat treatment is carried out by self-heating of the initial polyethylene-containing material and consists in that the screw profile includes two or more heat zones, wherein the first heat zone includes successive kneading block elements over a length of at least 4D, followed by left-handed elements, where D is the screw diameter, and one or more additional heat zones located downstream of the first heat zone are filled mixing zones, each including kneading block elements over a length of at least 4D, followed by kneading left-handed elements or left-handed elements, where D is the screw diameter.

3. The process according to claim 1 or 2, characterized in that, The heat treatment is carried out by self-heating of the initial polyethylene-containing material and consists in that the successive kneading block elements of at least one heat zone of the extruder include disks having a disk offset of 90 degrees and a disk width of at least 0.3D, where D is the screw diameter.

4. The process according to any one of claims 1 to 2, characterized in that, One heat zone of the extruder includes the melting zone of the extruder.

5. The process according to any one of claims 1 to 2, characterized in that The initial polyethylene-containing material is selected to have a high load melt index HLMI R of at least 1.0 g / 10 min when measured according to ISO 1133-2011 at 190 °C under a load of 21.6 kg.

6. The process according to any one of claims 1 to 2, characterized in that The initial polyethylene-containing material is selected to have a melt index MI2 R of at most 3.0 g / 10 min when measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.

7. The process according to any one of claims 1 to 2, characterized in that The initial polyethylene-containing material is selected to have a density of at least 0.910 g / cm when measured at 23 °C in accordance with ISO 1183-1:2012 3 .

8. The process according to any one of claims 1 to 2, characterized in that, The initial polyethylene-containing material is selected to have: a high load melt index HLMI R of at least 1.0 g / 10 min when measured at 190 °C under a load of 21.6 kg according to ISO 1133-2011, a melt index MI2 R of at most 0.45 g / 10 min when measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, and a density of at least 0.940 g / cm when measured at 23 °C according to ISO 1183-1:2012 3 3 9. The process according to any one of claims 1 to 2, characterized in that, The initial polyethylene-containing material is selected to have: a melt index MI2R in the range of 0.8 to 1.5 g / 10 min as measured at 190 °C under a load of 2.16 kg according to ISO 1133-2011, and a density in the range of 0.910 g / cm 3 to 0.930 g / cm 3 as measured at 23 °C according to ISO 1183-1:2012.

10. The process according to any one of claims 1 to 2, characterized in that, The ratio of the melt index MI2 T of the polyethylene composition measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg to the melt index MI2 R of the initial polyethylene-containing material measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg is at least 10.

11. The process according to any one of claims 1 to 2, characterized in that, The polyethylene composition collected in step (d) has a melt index MI2T in the range of 3.0 to 60.0 g / 10 min as measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.

12. The process according to any one of claims 1 to 2, characterized in that, The initial polyethylene-containing material comprises at least 80 wt% polyethylene based on the total weight of the initial polyethylene-containing material.

13. The process according to any one of claims 1 to 2, characterized in that, The initial polyethylene-containing material is a recycled polyethylene-containing material.

14. The process according to any one of claims 1 to 2, characterized in that, The step (c) of extruding the initial polyethylene-containing material comprises extruding with a residence time in the range of 10 to 180 seconds.

15. The process according to any one of claims 1 to 2, characterized in that, The step (c) of extruding the initial polyethylene-containing material comprises a heat treatment at a temperature in the range of 320 to 460 °C.

16. The process according to any one of claims 1 to 2, characterized in that, The polyethylene composition collected in step (d) has: - A density of at least 0.910 g / cm³ when determined at 23 °C in accordance with ISO 1183-1:2012 3 ; - a melt index MI2T in the range of 3.0 to 60.0 g / 10 min as measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; - an unsaturation index higher than 2,000, where the unsaturation index is the product of the vinyl unsaturation units per 1,000 carbon atoms and the number average molecular weight Mn in daltons as determined by ASTM D6248-98:2004; and - a complex viscosity at 190 °C at 0.1 rad / sec of at most 20,000 Pa·s.

17. The process according to any one of claims 1 to 2, characterized in that, One heat zone of the extruder is the melting zone of the extruder.

18. The process according to any one of claims 1 to 2, characterized in that, The polyethylene composition collected in step (d) has a melt index MI2T in the range of 4.0 to 20.0 g / 10 min as measured according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.

19. A method for producing an injection molded article, characterized in that, The method comprises producing a polyethylene composition from an initial polyethylene-containing material according to the process of any one of claims 1 to 18, and using the polyethylene composition obtained by said process to produce injection molded articles.

20. The method according to claim 19, wherein The initial polyethylene-containing material is a recycled polyethylene-containing material.

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