Process for improving melt flow rate of a polyolefin recyclate composition

Abstract

The present application provides a process for improving an initial melt flow rate of a polyolefin recyclate composition. The polyolefin recyclate is a polyolefin mixture containing recycled polypropylene (PP) and recycled polyethylene (PE) and said process comprises of forming a mixture of a polyolefin recyclate and subjecting the mixture to compounding conditions. Particularly, the compounded polyolefin composition is subjected to a thermal treatment at a temperature greater than or equal to 300°C. The article thus produced comprising the polyolefin recyclate composition finds its application in lightweight applications, heat and sound insulation, electromagnetic shielding, tissue engineering, oil spill cleanup, shape memory and flexible materials.

Description

PROCESS FOR IMPROVING MELT FLOW RATE OF A POLYOLEFINRECYCLATE COMPOSITIONFIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to a process for improving melt flow rate of a polyolefin recyclate composition. Specifically, the disclosure relates to a process for increasing the initial melt flow rate of polyolefin mixture including recycled polypropylene (PP), recycled polyethylene (PE) and optionally a compatibilizer, through a compounding process that involves a specific thermal treatment.BACKGROUND OF THE DISCLOSURE

[0002] It is widely known in the art that the processability of propylene homopolymers and copolymers in the molten state is largely influenced by their molecular weight, commonly expressed through melt flow rates (MFR), and their molecular weight distribution (MWD). Polyolefins, such as polypropylene (PP) and polyethylene (PE), are among the most widely used plastics in various industries, including packaging, automotive, and consumer goods. Due to their extensive use, large quantities of polyolefin waste are generated, necessitating efficient recycling processes to reduce environmental impact and conserve resources. Recycling polyolefins not only addresses environmental concerns but also provides economic benefits by reducing the need for virgin materials. One of the primary challenges in recycling polyolefins is maintaining or improving the mechanical and processing properties of the recycled materials.

[0003] Among these properties, the melt flow rate (MFR) is a critical parameter that affects the processability of the recycled material. An improved MFR can facilitate smoother processing and enhance the quality of the final products made from recycled polyolefins. The melt flow rate is a measure of the ease of flow of the melted polymer and is an essential parameter for determining the processing characteristics of thermoplastics. A higher MFR indicates lower viscosity and better flowability, which are desirable characteristics for processes such as injection molding and extrusion. For recycled polyolefins, maintaining or enhancing the MFR is crucial to ensuring that the recycled material can be effectively processed and utilized in manufacturing high-quality products. In general, increasing the melt flow rate allows the resin to be processed at lower temperatures and the resin to be filled into complex part shapes.Compatibilizers can be used to improve the properties of polymer blends by enhancing the interfacial adhesion between different polymer phases.

[0004] Various methods of increasing melt flow rate are disclosed in the art that include melt blending a resin with a compound capable of generating free radicals in an extruder. When this is done, the weight average molecular weight of the polymer decreases and the MFR increases. However, increasing the melt flow rate by reducing the molecular weight of the polyolefin polymer has often been found to adversely affect the strength of the modified polymer.

[0005] It has also been explored in the state of art, to improve the properties of recycled polyolefins involving various other approaches, including blending with virgin polymers, incorporating additives, and optimizing processing conditions. However, these methods often fall short of achieving the desired balance between performance improvement and costeffectiveness. Additionally, high-temperature treatments have been explored to further enhance the properties of recycled polyolefins, but controlling these processes to avoid excessive degradation remains a challenge.

[0006] Bertin et al.-US Pat. No. 6,620,892 functionalizes a resin, a stable free radical selected from nitroxyl radicals containing at least one =N — O. group, and a peroxide compound (trigger). This document discloses a method of modifying a polypropylene homopolymer or copolymer resin by melt blending in the absence of a polymerizable monomer to increase melt flow while maintaining the strength of the polymer resin. However, this process leads to functionalization, even if undesired, and the increase of melt flow only comes as a result of the peroxide presence with the limitations as further described below.

[0007] Horst et al. -U.S. Patent No. 8,618,224 B2 discloses a viscosity breaking process for polypropylene, propylene copolymers and polypropylene blends. Visbreaking of the polymer is carried out, for example, in an extruder in the presence of an initiator (eg peroxide) and a chain transfer agent. Suitable chain transfer agents are thiols, disulfides, phosphites, phosphines, organic iodides, organic chlorides, propionates, aldehydes and tertiary amines. Peroxides can induce chain scission, breaking the polymer chains into shorter segments, thereby increasing the MFR. However, the use of peroxides comes with significant limitations. In the case of polyethylene (PE), peroxides can also lead to cross-linking, which counteracts the desired effect of increasing melt fluidity. Cross-linked PE exhibits decreased MFR and increased viscosity,making it more difficult to process. Additionally, the formation of cross-linked structures can result in inhomogeneous material properties, further complicating the recycling process.

[0008] Consequently, there is a need to addresses these challenges by providing a novel process for improving the melt flow rate of polyolefin recyclate compositions. In view of the foregoing, the inventors of the present disclosure have significantly advanced the state of the art in the field of polypropylene compositions, by offering enhanced melt flow rate performance of the polypropylene composition.

[0009] To this end, an object of the present disclosure is to provide a process for improving an initial melt flow rate of a polyolefin recyclate composition, by subjecting the polyolefin recyclate mixture to compounding conditions, and applying a thermal treatment at temperatures greater than or equal to 300°C. This innovative approach not only improves the melt flow rate but also enhances the mechanical properties of the recycled polyolefin composition, making it suitable for various high-performance applications. The process described in this disclosure provides a practical and effective solution to the limitations of existing recycling methods. By the use of thermal treatment, the process significantly enhances the quality and usability of recycled polyolefins, thereby contributing to more sustainable and efficient recycling practices.SUMMARY OF THE DISCLOSURE

[0010] The present disclosure addresses the limitations of existing polymer technology by providing a process for improving an initial melt flow rate of a polyolefin recyclate composition.

[0011] In one aspect the present disclosure, a process for improving an initial melt flow rate of a polyolefin recyclate composition is provided. The polyolefin recyclate is a polyolefin mixture containing recycled polypropylene (rPP) and recycled polyethylene (rPE) in a weight ratio (rPP):(rPE) from 40:60 to 90:10. The process herein comprises a) forming a mixture of a polyolefin recyclate and, optionally, a compatibilizer; and b) subjecting the mixture to compounding conditions to form a molten recycled polyolefin composition; said process being characterized in that the compounded polyolefin composition is subjected to a thermal treatment at a temperature greater than or equal to 300°C such that the final melt flow rate determined according to ISO1133, 230°C / 2.16 Kg, ranges from 5 to 100 g / 10 min, preferably 10 to 80 g / lOmin, and most preferably from 15 to 70 g / lOmin.

[0012] In another aspect of the present disclosure, an article comprising a thermally degraded polyolefin composition; and specifically a molded article and a method thereof is disclcosed.DETAILED DESCRIPTION OF THE DISCLOSURE

[0013] Illustrative embodiments of the subject matter claimed below will now be disclosed.

[0014] The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than the broadest meaning understood by skilled artisans, such a special or clarifying definition will be expressly set forth in the specification in a definitional manner that provides the special or clarifying definition for the term or phrase. It must also be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless otherwise specified.

[0015] For example, the following discussion contains a non-exhaustive list of definitions of several specific terms used in this disclosure (other terms may be defined or clarified in a definitional manner elsewhere herein). These definitions are intended to clarify the meanings of the terms used herein. It is believed that the terms are used in a manner consistent with their ordinary meaning, but the definitions are nonetheless specified here for clarity.

[0016] As used in this specification and the claims, the terms “comprising,” “containing,” or “including” mean that at least the named compound, element, material, particle, or method step is present in the composition, the article, or the method, but does not exclude the presence of other compounds, elements, materials, particles, or method steps even if the other such compounds, elements, materials, particles, or method steps have the same function as that which is named, unless expressly excluded in the claims. It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps before or after the combined recited steps or intervening method steps between those steps expressly identified.

[0017] Moreover, it is also to be understood that the lettering of process steps or ingredients is for identifying discrete activities or ingredients and the recited lettering can be arranged in any sequence, unless expressly indicated.

[0018] For the purpose of the present description and of the claims which follow, except where otherwise indicated, numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified by the term “about”. Also, ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0019] As used herein the term term “copolymer” has to be intended as a polymer containing two or more kind of monomers such as propylene and ethylene or propylene and 1 -butene, or propylene and 1 -hexene or propylene, ethylene and hexene- 1.

[0020] As used herein the phrase “comonomer” or “monomer” can be used interchangeably, refers to molecule that undergoes polymerization along with another type of monomer to form a copolymer.

[0021] As used herein the phrase “alpha-olefins”, referes to a a class of alkenes where the double bond is located at the first carbon atom from the terminal end of the carbon chain. Specifically, any compound with a polymerizable moiety that is added to a reactor in order to produce a polymer. In those instances in which a polymer is described as comprising one or more monomers, e.g., a polymer comprising propylene and ethylene, the polymer, of course, comprises units derived from the monomers, e.g., — CH2 — CH2 — , and not the monomer itself, e g., CH2=CH2.

[0022] As used herein the phrase “Recycled Polyolefin” (r-PO) , recycled PP (r-PP), recycled PE (r-PE) or “Post-Consumer Recycled” can be used interchangeably, refers to materials sourced from products that have been previously used. These materials originate from industrial waste, with materials specifically derived from end-user waste that has undergone collection sorting, cleaning and recycling. Since the sorting and cleaning are not 100% efficient, “Recycled Polyolefin” (r-PO) , recycled PP (r-PP), recycled PE (r-PE) or “Post-Consumer Recycled” are distinguished from their virgin counterparts by the presence of non-polyolefin polymeric contaminants.

[0023] As used herein, the term “post-consumer” refers to a source of material that originates after the end consumer has used the material in a consumer good or product.

[0024] As used herein the phrase “melt flow index” or “melt flow rate (MFR)” can be used interchangeably, refers to the ability of a polymer during polymer processing, to flow or deform under an applied force when it is in a molten or semi-molten state.

[0025] As used herein the phrase “initial melt flow rate” refers to the melt flow rate of the polymer material before it undergoes any treatment for increasing the melt flow rate. This is typically the MFR of the polymer waste as it is received.

[0026] As used herein the phrase “final melt flow rate” refers to the melt flow rate of the polymer material after it has been processed through the recycling process. This includes all steps such as cleaning, melting, reprocessing, and any chemical treatments that may be applied.

[0027] As used herein the phrase “melt-compounding,” or “compounding conditions” can be used interchangeably, refers to temperature, pressure, and shear force conditions implemented in an extruder to provide intimate mixing of polymers and additives to produce a substantially homogeneous polymer product. The compounding conditions will be such that the specific energy from the compounder from shear and / or added heat are sufficient to melt the polymer components and homogenize them.

[0028] As used herein the phrase “thermal treatment” or “thermal visbreaking” can be used interchangeably, refers to reducing the molecular weight of polymers through thermal degradation. Particularly thermal visbreaking is involved in the treatment of polymers such as polypropylene and polyethylene to improve their flow properties and processability, by subjecting the polymer to elevated temperatures typically in the absence of oxygen, causing the long polymer chains to break down into shorter chains.

[0029] The present disclosure provides a process for improving an initial melt flow rate of a polyolefin recyclate composition. The polyolefin recyclate composition in accordance with the present dislcosure is characterized as a polyolefin mixture containing recycled polypropylene (rPP) and recycled polyethylene (rPE) in a weight relative ratio (rPP):(rPE) from 40:60 to 90: 10. Further, the process for improving the melt flow rate of the polyolefin recyclate composition is characterized by subjecting the composition to compounding conditions followed by a thermal treatment at a temperature greater than or equal to 300°C.

[0030] Beneficially, the polyolefin recyclate composition as per the present disclosure has improved melt flow rate thereby making the recycling process more efficient and the recycled products obtained thereof more versatile and higher in quality, and making it suitable for variousapplications. Further beneficially, the enhanced MFR lowers viscosity, which allows them to flow more easily during molding and extrusion processes and also reduces the energy required for processing, leading to cost savings and a smaller environmental footprint. Furthermore, beneficially as per the present disclosure the improved MFR facilitates the blending of recycled polymers with virgin materials or other polymers, enhancing the mechanical properties and performance of the final product. These benefits collectively make the disclosed process more viable and the products produced thereof, more competitive in the market.

[0031] In accordance with the present disclosure a process for improving an initial melt flow rate of a polyolefin recyclate is disclosed. The polyolefin recyclate in accordance with the present disclosure is a polyolefin mixture. The polyolefin mixture contains recycled polypropylene (rPP) and recycled polyethylene (rPE) in every embodiment of the present disclosure.

[0032] In a preferred embodiment the polyolefin mixture is comprised of recycled polypropylene (rPP) and recycled polyethylene (rPE) having a weight ratio of rPP to rPE ranging from 40:60 to 90: 10, preferably from 50:50 to 90: 10, yet more preferably from 60:40 to 90:10, and most preferably from 80:20 to 90: 10.

[0033] In an embodiment the polyolefin mixture comprises from 40 to 90% by weight of recycled polypropylene and from 10 to 60% by weight of recycled polyethylene. In a preferred embodiment, the polyolefin mixture comprises from 60 to 90 % by weight of recycled polypropylene and from 10 to 40 % by weight of recycled polyethylene; and yet more preferably the polyolefin mixture comprises from 80 to 90 % by weight of recycled polypropylene and from 10 to 20 % by weight of recycled polyethylene.

[0034] The specific weight ratio of recycled polypropylene (rPP) to recycled polyethylene (rPE) in the polyolefin mixture in accordance with the present disclosure is important to the performance characteristics and processability of the final recycled polymer composition. The rPP may offer higher stiffness, tensile strength, and melting point, whereas rPE may provide greater flexibility and impact resistance. The inventors of the present application have optimized the PP to PE weight ratio, such that the resulting polymer can be tailored to achieve a desired balance of mechanical properties suitable for specific applications including consumer goods, bottles & containers, industrial packaging, think film over warps for consumer goods, textiles, food & medical packaging, etc.

[0035] In general PP is known to have a higher melting point than PE. In accordance with the present disclosure, the higher PP content in the composition may improve the thermal stability of the mixture, making it suitable for applications that require higher processing or operating temperatures.

[0036] The polyolefin mixture preparation comprises of collecting post-consumer and postindustrial plastic waste. The plastic waste sources is selected from including but not limited to recycled polypropylene, recycled polyethylene, preferably recycled high density polyethylene(HDPE), recycled low density polyethylene(LDPE), recycled linear low density polyethylene(LLDPE), recycled medium density polyethylene(MDPE), recycled polypropylene homopolymer (H-PP), random propylene copolymer (R-PP) or propylene heterophasic copolymers (PP-HECO) and a mixture thereof. Most preferably the polyolefin mixture is comprised of recycled polypropylene (PP) and recycled polyethylene (PE). The collected waste is sorted by polymer type, color, and contamination level using automated systems such as NearInfrared (NIR) spectroscopy, density separation, or manual sorting. In a preferred embodiment the polymer waste is sorted by Near-Infrared (NIR) spectroscopy.

[0037] The polyolefin mixture comprising the Post-Consumer Recycled (PCR) is cleaned subsequent to sorting by using water, detergents, and sometimes caustic solutions to remove dirt, labels, and residues. Further the cleaned polyolefin mixture is dried to remove moisture using mechanical dryers or hot air dryers or any commonly known method to skilled in the art. The cleaned polymer plastic is shredded post the cleaning and sorting plastics into smaller flakes or pieces by using industrial shredders. Subsequent to which grinding the shredded pieces into finer particles or granules suitable for the extrusion process is followed. The grounded plastic particles is herein referred to as the polyolefin recyclate.

[0038] In a preferred embodiment, the polyolefin recyclate is added with a compatibilizer and further additives. Compatibilizers are substances that enhance the interfacial adhesion between incompatible polymers, improving the blend properties. The polyolefin recyclate with or without a compatibilizer is thoroughly mixed by using a high-intensity mixer or a similar mixing device to ensure uniform distribution, thereby forming a polyolefin recyclate mixture.

[0039] In accordance with the present disclosure, the polyolefin recyclate may be further compounded in an extruder. The extruder is designed to apply heat and shear to melt and mixthe polymers. The extruder herein has multiple zones for controlled heating and mixing, typically including a feeding zone, melting zone, and metering zone.

[0040] The PCR polymer is subjected to compounding in the extruder under controlled temperature and pressure conditions. Heat is applied to the mixture in the extruder to melt the polyolefin recyclate and, if present, the other components. The rotating screws in the extruder are intended to provide shear forces that ensure thorough mixing of the melted materials. This step achieves a homogeneous recycled polyolefin composition. The inventors of the present dislcosure have specifically controlled the temperature of compounding according to the melting points of the polymers PP and PE. For example, compounding can be carried out at temperatures greater than 250 °C, preferably ranging between 300 °C to 500 °C, and pressure greater than 70 MPa, preferably ranging between 70 MPa to 700 MPa. In some embodiments of the present disclosure, the PCR polymer is preferably also compounded as a mixture including compatibilizers, pigments, dyes, process aides, additives, and / or a mixture thereof in the screw extruder under controller temperature and pressure to facilitate homogeneous mixing and distribution of components.

[0041] Non-limiting examples of pigments include organic pigments, such as copper phthalocyanine, inorganic pigments, such as titanium dioxide, and other pigments that may be apparent to those having ordinary skill in the art. A non-limiting example of an organic dye includes Basic Yellow 51. Non-limiting examples of process aides are antistatic agents, such as glycerol monostearate and slip-promoting agents, such as erucamide.

[0042] Non-limiting examples of additives include antioxidants, stabilizers, or colorants. In a specific embodiment the additive is selected from the group comprising antioxidants, stabilizers, or colorants, including BHT (Butylated Hydroxytoluene), BHA (Butylated Hydroxyanisole), Tris(2,4-di-tert-butylphenyl)phosphite (TNPP), Triphenyl phosphite, Dilauryl thiodipropionate (DLTDP), Dimyristyl thiodipropionate (DMTDP), Calcium stearate, Zinc stearate, Titanium dioxide, Iron oxide pigments, Fatty acid esters and / or Calcium stearate. In a preferred embodiment the additive is selected from the group comprising antioxidants, stabilizers, Calcium stearate, Zinc stearate and talc. Use of talc, alone or in combination with other additives, is especially preferred.

[0043] In a specific preferred embodiment of the present disclosure, the compounded polyolefin composition or mixture is subjected to a thermal treatment at a temperature greaterthan or equal to 300°C. The thermal treatment in accordance with the present disclosure is performed during the compounding phase in the extruder. The thermal treatment is referred herein as a thermal visbreaking which is performed for a period of 5 to 60 minutes, in an inert atmosphere to prevent oxidation. During extrusion, the polymer is melted and subjected to controlled thermal degradation. The polymer chains are broken down through the application of heat, sometimes in the presence of a controlled amount of oxygen or other additives, to achieve the desired reduction in molecular weight.

[0044] In all embodiments the thermal visbreaking may involve higher temperatures as high as 350°C or even higher, preferably ranging between 300°C to 400°C, preferably 310°C to 380°C and most preferably 320°C to 360°C, depending on the desired level of molecular weight reduction. In accordance with the present disclosure the thermal treatment at high temperatures facilitates further polymer chain mobility and realignment without inducing cross-linking. This controlled thermal process as delineated by the inventors while undergoing significant inventive challenges, has enhanced the MFR by promoting uniform chain scission and reducing viscosity, thereby improving the processability and quality of the recycled material. Further, the thermal visbreaking is preferably followed by a cooling step at a rate of 10°C to 50°C per minute to solidify the recycled polyolefin composition. Additionally, the polyolefin composition can be pelletized before undergoing the thermal visbreaking process.

[0045] The thermal treatment makes no longer necessary the use of peroxides to increase the melt flow rate. However, if desired, small amount of peroxides usually less than 2000 ppm, preferably less than 1500 ppm especially from 100 ppm to 1000 ppm can be added during the thermal treatment.

[0046] In a preferred embodiment, a ratio of final melt flow rate to the initial melt flow rate of the polyolefin recyclate composition is ranging 2.2 to 70, preferably from 2.2 to 50, and more preferably from 2.2 to 35, especially from 4 to 20, and yet more preferably from 8 to 16. The initial melt flow rate (ISO1133, 230°C / 2.16 Kg) of the polyolefin recyclate composition in accordance with the present disclosure is ranging from 1.0 to 10.0 g / 10 min, preferably 2 to 8 g / lOmin, and most preferably from 3 to 6 g / lOmin. The final melt flow rate (ISO1133, 230°C / 2.16 Kg) of the polyolefin recyclate composition in accordance with the present disclosure ranges from 5 to 100 g / 10 min, preferably 10 to 80 g / lOmin, and most preferably from 15 to 70 g / lOmin.

[0047] It has also been noted that in some cases, after the thermal treatment, the composition of the present disclosure in addition to an increased melt flow rate also show an improved stiffness / impact strength balance with respect to the original compositions.

[0048] In accordance with the present disclosure, the polyolefin recyclate mixtures preferably comprise a compatibilizer. In a preferred embodiment, the compatibilizer is selected from polypropylene heterophasic compositions comprising (i) from 20 wt% to 80 wt% of a crystalline propylene based polymer having a propylene content higher than 60 wt% and (ii) from 20 wt% to 80 wt% of an ethylene based polymer having an ethylene content higher than 70%wt.

[0049] In a most preferred embodiment, the compatibilizer is selected from a polypropylene composition (A) having a melt flow rate MFR(A) (ISO 1133-1:2011, 230°C / 2.16 kg) ranging from 0.05 to 1.2 g / lOmin. The polypropylene composition (A) comprises from 8 to 30% by weight, preferably from 13 to 27% by weight, more preferably from 15 to 25% by weight of a polymer fraction (a) and from 70 to 92% by weight, preferably from 73 to 88% by weight, more preferably from 75 to 85% by weight, of a polymer fraction (b).

[0050] In an embodiment the polymer fraction (a) comprises a propylene polymer is selected from a propylene homopolymer, a propylene copolymer and combinations thereof, the propylene copolymer containing up to and including 10.0% by weight, based on the weight of the copolymer, of units derived from a comonomer selected from ethylene, a CH2=CHR alphaolefin, where R is a linear or branched C2-C8 alkyl group, and combinations thereof.

[0051] In a specific embodiment, the polymer fraction (a) is a propylene copolymer further characterized by one or more of the following:- contains from 0.5 to 10.0% by weight, preferably from 1.0 to 8.0% by weight, more preferably from 2.5 to 5.0% by weight, based on the weight of the fraction (a), of a comonomer selected from ethylene, a CH2=CHR alpha-olefin, where R is a linear or branched C2-C8 alkyl group, and combinations thereof, wherein the comonomer is preferably selected from ethylene, butene- 1, hexene- 1, octene- 1, 3 -methyl- 1 -pentene and combinations thereof, ethylene being particularly preferred; and / or- has solubility in xylene at 25°C XS(a) ranging from 0.5 to 10.0% by weight, preferably from 2.0 to 8.0% by weight, based on the weight of the polymer fraction (a);- has a melt flow rate MFR(a) determined according to ISO 1133-1:2011, 230°C / 2.16 kg ranging from 1 to 20 g / lOmin, preferably from 2 to 15 g / lOmin and especially from 3 to 12 g / lOmin.

[0052] In accordance with the present disclosure, the polymer fraction (b) preferably comprises a first and a second copolymer of ethylene with a comonomer independently selected from a CH2=CHR alpha-olefin, where R is a linear or branched C1-C8 alkyl group, and combinations thereof, the first and the second copolymer containing an amount of units deriving from ethylene equal to or lower than 40% by weight, based on the weight of the respective copolymer, wherein the difference in the amount of units deriving from ethylene of the first and the second ethylene copolymer is greater than 1.0% by weight and wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, based on the weight of the polymer fraction (b).

[0053] In a specific embodiment, the polymer fraction (b) is further characterized by one or more of the following:- the first and the second copolymer of ethylene are a copolymer of ethylene with a comonomer independently selected from propylene, butene- 1, hexene- 1, 3 -methyl- 1 -pentene, octene- 1 and combinations thereof, propylene being the most preferred; and / or- the first and the second ethylene copolymer are copolymers of ethylene with the same comonomer, propylene being the most preferred; and / or- the first copolymer of ethylene contains an amount of units deriving from ethylene ranging from 15 to 32% by weight, preferably from 20 to 30% by weight, based on the weight of the first copolymer; and / or- the second copolymer of ethylene contains an amount of units derived from ethylene ranging from 32 to 40% by weight, based on the weight of the second copolymer; and / or- the weight ratio of the first copolymer of ethylene to the second copolymer of ethylene ranges from 1:5 to 5:1, preferably from 1: 1 to 3: 1; and / or- has a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, preferably ranging from 60% to 95% by weight, more preferably from 70% to 90% by weight, based on the weight of the polymer fraction (b).

[0054] The first and / or the second copolymer of ethylene optionally contain from 0.1 to 10.0% by weight, based on the weight of the polymer fraction (b), of units deriving from a dienepreferably selected from the group consisting of butadiene, 1,4-hexadiene, 1,5 -hexadiene, ethylidene-l-norbonene and combinations thereof. In a most preferred embodiment the amounts of fractions (a) and (b) are based on the sum of the weights of fraction (a) and fraction (b) together.

[0055] In a further specific embodiment, the polypropylene composition (A) preferably has at least one, more preferably all, of the following characterized features:- a total ethylene content C2(A) ranging from 15.0 to 40.0% by weight, more preferably from 20.0 to 35.0% by weight and especially from 23.0 to 30.0% by weight, based on the sum of the weights of fraction (a) and fraction (b); and / or- a melt flow rate MFR( A) (ISO 1133-1 :2011, 230°C / 2.16 Kg) of not higher than 1.0 g / lOmin, preferably ranging from 0.1 to 1.2 g / lOmin, preferably from 0.3 to 1.0 g / lOmin; and / or- has solubility in xylene at 25°C XS(A) of at most 95% by weight, preferably from 65% to 85% by weight, still preferably from 70% to 80% by weight, based on the weight of the polymer fraction (b); and / or- an intrinsic viscosity of the fraction soluble in xylene at 25 °C XSIV(A) ranging from 4.0 to 6.5 dl / g, preferably from 5.0 to 6.0 dl / g, the intrinsic viscosity being determined in tetrahydronaphthalene at 135°C; and / or- flexural modulus (ISO 178:2010) equal to or lower than 80 MPa, preferably equal to or lower than 60 MPa, more preferably ranging from 30 to 80 MPa, more preferably from 35 to 60 MPa; and / or- strength at break (ISO 178:2010) equal to or lower than 15 MPa, preferably ranging from 7.0 to 15.0, more preferably from 8.5 to 12.0 MPa; and / or- elongation at break (ISO 178:2010) equal to or higher than 400%, preferably ranging from 400% to 650%, more preferably from 450% to 600%; and / or- tensile modulus on film (ISO 527-3) equal to or lower than 80 MPa, preferably equal to or lower than 60 MPa, more preferably ranging from 30 to 60 MPa, in MD and ID; and / or- tensile strength at break on film (ISO 527-1,-2) ranging from 5 to 20 more preferably from 10 to 16 MPa in MD and TD; and / or- elongation at break on film (ISO 527-1,-2) equal to or greater than 600%, preferably ranging from 600% to 850%, more preferably from 700% to 800%, in MD and TD; and / or- Shore A (ISO 868, 15 sec) equal to or lower than 90, preferably equal to or lower than 85, ranging from 60 to 85; and / or- Shore D (ISO 868, 15 sec) equal to or lower than 30, preferably equal to or lower than 25, ranging from 5 to 25, more preferably from 10 to 20; and / or- Charpy impact strength, notched at -40°C (ISO 179-1:2010 eA) ranging from 4.0 to 8.0 KJ / m2.

[0056] In a further embodiment the polypropylene composition (A) may also comprise additives such as stabilizers, antioxidants, nucleating agents, fillers, reinforcements, or pigments to further enhance specific properties or achieve desired characteristics, without deviating from the spirit and scope of the present application.

[0057] The polypropylene composition (A) may be prepared by polymerization in sequential polymerization stages, with each subsequent polymerization being conducted in the presence of the polymeric material formed in the immediately preceding polymerization reaction.

[0058] Preferably, the polymer fraction (a) is prepared in a first polymerization stage and the polymer fraction (b) is prepared in a second polymerization stage, each stage being carried out in the presence of the polymeric material prepared in the immediately preceding polymerization stage. The polymerization stage to prepare the polymer fraction (a) is carried out in at least one polymerization reactor and the polymerization stage to produce the polymer fraction (b) is carried out in at least two polymerization reactors. The amount of polymer fraction (a) and of polymer fraction (b) correspond to the split between the polymerization stages, and the amount of the first and the second ethylene copolymer of polymer fraction (b) correspond to the split between the polymerization reactors.

[0059] The polymerization stages are preferably carried out in the presence of a Ziegler- Natta catalyst. According to a preferred embodiment, all the polymerization stages are carried out in the presence of a catalyst comprising the product of the reaction between: i) a solid catalyst component comprising Ti, Mg, Cl, and at least an internal electron donor compound; ii) an alkylaluminum compound and,iii) an external electron-donor compound selected from aromatic acid esters, such as alkyl benzoates, and silicon compounds containing at least one Si-OR bond, where R is a hydrocarbon radical, wherein silicon compounds are particularly preferred.

[0060] The internal donor is preferably selected from the esters of mono or dicarboxylic organic acids such as benzoates, malonates, phthalates, like phthalic acid esters, such as diisobutyl, dioctyl and diphenyl phthalate and benzyl-butyl phthalate, and certain succinates. Examples of internal donors are described in US4,522,930, EP045977A2 and international patent applications WOOO / 63261 and W001 / 57099.

[0061] Further, particularly suitable internal electron donor compound are 1,3-diethers of formulaR1. CH2-ORniR" CH2-ORIVwherein R1and Rn, the same or different from each other, are Cl -Cl 8 alkyl, C3-C18 cycloalkyl or C7-C18 aryl radicals; R111and RIV, the same or different from each other, are C1-C4 alkyl radicals; or are the 1,3-diethers in which the carbon atom in position 2 belongs to a cyclic or polycyclic structure made up of from 5 to 7 carbon atoms and containing two or three unsaturations. Ethers of this type are described in EP361493 and EP728769.

[0062] Representative examples of said dieters are 2-methyl-2-isopropyl-l,3- dimethoxypropane, 2,2-diisobutyl-l ,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-l ,3- dimethoxypropane, 2-isopropyl-2-isoamyl-l,3-dimethoxypropane, and 9,9- bis(methoxymethyl)fluorene.

[0063] The particles of solid component (i) may have substantially spherical morphology and average diameter ranging between 5 and 150pm, preferably from 20 to 100pm and more preferably from 30 to 90pm. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.

[0064] According to one method, the solid catalyst component (i) can be prepared by reacting a titanium compound of formula Ti(OR)q-yXy, where q is the valence of titanium and y is a number between 1 and q, preferably TiCh, with a magnesium chloride deriving from an adduct of formula MgCh’pROH, where p is a number between 0.1 and 6, preferably from 2 to3.5, and R is a hydrocarbon radical having 1-18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride, operating under stirring conditions at the melting temperature of the adduct (100°-130°C). Then, the adduct is mixed with an inert hydrocarbon immiscible with the adduct thereby creating an emulsion which is quickly quenched causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in USP4,399,054 and US4,469,648. The so obtained adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (80°-130°C) so as to obtain an adduct in which the number of moles of alcohol is of lower than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCh; the mixture is heated up to 80°-130°C and kept at this temperature for 0.5-2 hours. The treatment with TiCh can be carried out one or more times. The electron donor compound can be added in the desired ratios during the treatment with T1CI4.

[0065] The alkyl-Al compound (ii) is preferably chosen among the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt2Cl and AhEtsCh, possibly in mixture with the above cited trialkylaluminums. The Al / Ti ratio is higher than 1 and may preferably range between 50 and 2000.

[0066] Preferably, the external donor (iii) is a silicon compound having the general formula (R7)a(R8)bSi(OR9)c, where a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R7, R8, and R9, are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

[0067] Particularly preferred are the silicon compounds (iii) in which a is 1, b is 1, c is 2, at least one of R7and R8is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms and R9is a Ci-Cio alkyl group, in particular methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), diisopropyldimethoxysilane, (2-ethylpiperidinyl)t- butyldimethoxysilane, (2-ethylpiperidinyl)thexyldimethoxysilane, (3,3,3-trifluoro-n-propyl)(2-ethylpiperidinyl)dimethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane. Moreover, are also preferred the silicon compounds in which a is 0, c is 3, R8is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R9is methyl. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.

[0068] The external electron donor compound (iii) is used in such an amount to give a molar ratio between the organoaluminum compound and said external electron donor compound (iii) of from 0.1 to 200, preferably from 1 to 100 and more preferably from 3 to 50.

[0069] Examples of polymerization processes for the preparation of said compositions can be found in EP472946A, the relevant part of which is incorporated herein by reference.

[0070] All the polymerization stages preferably occur in gas phase. The reaction temperature in the polymerization stage for the preparation of the polymer fraction (a) and in the preparation of the copolymer fraction (b) can be the same or different, and is preferably from 40° to 90°C; more preferably, the reaction temperature ranges from 50° to 80°C in the preparation of the fraction (a), and from 40° to 80°C for the preparation of components (b). The pressure of the polymerization stages to prepare the fractions (a) and (b), is from 5 to 30bar in gas phase. The residence times relative to the two stages depend on the desired ratio between the fractions (a) and (b), and can usually range from 15 minutes to 8 hours. Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen or ZnEt2), may be used.

[0071] In a particularly preferred embodiment, in addition to the polypropylene composition A as compatibilizer, also talc is present as an additive. The polypropylene composition A can be is present in amount ranging from 3 to 30% wt, preferably from 5 to 25%wt based on the total weight of the composition subject to thermal treatment. The amount of talc may range from 5 to 40% wt preferably 10 to 30%wt based on the total weight of the composition subject to thermal treatment.

[0072] Different applications demand different properties from the polymer. For example, packaging materials might benefit from a higher PE content for flexibility, while automotive components might require a higher PP content for rigidity and thermal resistance. Accordingly without deviating from the scope and spirit of the application the PP to PE ratio can be optimizedand further subjected to compounding conditions, followed by thermal visbreaking, to meet specific end-use requirements.

[0073] By effectively managing the PP to PE ratio and subjecting the compounded polyolefin recyclate to thermal visbreaking, manufacturers can produce high-quality recycled products, thereby supporting environmental sustainability.

[0074] The present disclosure further provides a method for producing a molded article comprising the polyolefin recyclate composition produced as per the dislcosure. The method in accordance with the present disclosure includes, providing an obtained a recycled polymer feedstock and subjecting it to melt-compounding conditions sufficient to form an article. The compounding conditions are implemented in the compounding zone of a twin screw extruder or mixer and are tailored for mixtures. For example in some embodiments, the obtained recycled polymer is compounded along with specific polyolefins, comptabilizers, chain extenders or peroxides, additional additives and optionally a virgin polymer. The addition of additives under controlled temperature of 170 to 240°C, pressure, and shear force conditions are implemented in the extruder or mixer sufficient to provide homogeneous mixing of the recycled polymer and the additives to produce a substantially homogeneous polymer blend. In another embodiment the obtained recycled polymer is compounded without any addition of additives.

[0075] The method as disclosed, the compounding conditions will be such that the specific energy from the compounder from shear and / or added heat are sufficient to melt the recycled polymer composition and homogenize them. In some embodiments, compounding conditions comprise a thermal treatment in the compounding zone of greater than 300°C, preferably ranging between 300°C to 400°C, preferably 310°C to 380°C and most preferably 320°C to 360°C. Further, the recycled polymer can be pelletized and obtained in the form of recycled polymer pellets.

[0076] In accordance with the method of the present disclosure, the recycled polymer pellets can be further processed to produce a recycled polymer article. In a first step, the recycled polymer pellets can be thoroughly cleaned and processed to remove contaminants and impurities. The cleaned recycled polymer pellets are then melted using heat. This is performed in an extruder, where the pellets are subjected to high temperatures to become a molten, viscous material.

[0077] The molten polymer can then be extruded through a hollow tube of plastic or a parison and placed within a mold cavity. Once the parison is in the mold, pressurized air is injected into it which causes the molten plastic to expand and take the shape of the mold. The mold is further cooled to solidify the plastic in the desired article form. The molded product or molded article is further allowed to cool within the mold. In accordance with the present dislcosure, the cooling time is crucial for ensuring the product retains its shape and structural integrity. After solidification and cooling, the mold is opened, and the formed product or article is ejected. In some embodiments of the present discloure this can be an automated or manual process.

[0078] In one embodiment of the present disclosure the additives is introduced after the addition of the recycled polymer feedstock. In some embodiments, the additive is introduced simultaneously during the addition of the recycled polymer feedstock. In another embodiment, the additve is introduced as a masterbatch with the recycled polymer feedstock.

[0079] In accordance with the present disclosure, the process has imparted superior melt flow rate of the polyolefin recyclate composition, and processing properties to the polypropylene composition. This innovative process significantly enhances the melt flow characteristics of recycled polyolefin mixtures, making them more suitable for various applications that demand high-quality, high-performance recycled polymers. This approach not only optimizes the recyclability of polypropylene and polyethylene but also contributes to more sustainable manufacturing practices by improving the usability of recycled materials by offering several advantages over traditional methods that rely on peroxides. Particularly, the combination of compatibilizer addition to optimised rPP:rPE weight ratio and high-temperature treatment results in a recycled polyolefin composition with enhanced mechanical properties, such as tensile strength and impact resistance, making it suitable for various high-performance applications. Such applications including but not limited to packaging, automotive parts, construction materials, and consumer goods. The specific advantages in most preferred embodiments of the present disclosure include improved melt flow rate, melt strength, fomability in addition to improved stiffness, impact resistance, heat resistance, and processability compared to conventional polypropylene composition with low melt flow rate.

[0080] In order to illustrate the disclosure more clearly, the following examples are given explaining the preferred modes of carrying it into effect and the advantageous results obtainedthereby. The use of examples in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification.EXAMPLESMaterials

[0081] rPE is QCP5603: MFR 0.3g / 10’ a recycled PE available on the market

[0082] rPP is QCP300P: MFR 14g / 10’ a recycled PP available on the market

[0083] mixPOE is a recycled polyolefin mixture coming from municipality in which the rPP / rPE ratio is 60 / 40.

[0084] Talc (T): available from IMIFabi

[0085] Peroxide: EnoxlOlCompatibilizer A

[0086] The polypropylene composition (A) was prepared according to the procedure reported in example 2 of EP1279699A1 in the polymerization conditions reported in table 1 and using a Ziegler-Natta catalyst system comprising:- a titanium solid catalyst component prepared with the procedure described in EP395083, Example 3, using diisobutyl phthalate as internal donor,- triethylaluminum (TEAL) as cocatalyst; and- dicyclopentyldimethoxysilane (DCPMS) as external donor, with a TEAL / DCPMS weight ratio of 5. The characterization and specific polymerization conditions are reported belowTable 1Comparative Examples (CE):

[0087] The comparative examples in Table 2 illustrate that the melt flow rate does not increase enough when the thermal visbreaking (TV) is carried out at 340°C on a rPP / rPE composition not according to the disclosure.Table 2Inventive examples:

[0088] The inventive examples in Table 3 and 4 illustrate the increased melt flow rate where a thermal visbreaking is carried out at 340°C on rPP / rPE compositions in accordance with the disclosure.Table 3Table 4

[0089] The above data clearly show an increased melt flow rate for the compositions of the present disclosure subjected to thermal treatment.

Claims

CLAIMS1. A process for improving an initial melt flow rate of a polyolefin recyclate composition, wherein the polyolefin recyclate is a polyolefin mixture containing recycled polypropylene (PP) and recycled polyethylene (PE) in a weight ratio (PP):(PE) from 40:60 to 90:10, the process comprising: a) forming a mixture of a polyolefin recyclate and, optionally, a compatibilizer; and b) subjecting the mixture to compounding conditions to form a molten recycled polyolefin composition, said process being characterized in that the compounded polyolefin composition is subjected to a thermal treatment at a temperature greater than or equal to 300°C such that the final melt flow rate determined according to ISO1133, 230°C / 2.16 Kg, ranges from 5 to 100 g / 10 min, preferably 10 to 80 g / lOmin, and most preferably from 15 to 70 g / lOmin.

2. The process according to claim 1, wherein the thermal treatment consists of visbreaking at a temperature ranging between 300°C to 400°C, preferably 310°C to 380°C and most preferably 320°C to 360°C.

3. The process according to claim 1 , wherein the weight ratio of recycled polypropylene and recycled polyethylene is ranging from 50:50 to 80:20.

4. The process according to claim 1 , wherein the polyolefin mixture comprises from 40 to 90% by weight of recycled polypropylene and from 10 to 50% by weight of recycled polyethylene.

5. The process according to claim 1, wherein a ratio of final melt flow rate to the initial melt flow rate of the polypropylene recyclate composition is ranging from ranging 2.2 to 70, preferably from 2.2 to 50, and more preferably from 2.2 to 35, especially from 4 to 20, and yet more preferably from 8 to 16.

6. The process according to claim 2, wherein the thermal visbreaking is performed for a period of 5 to 60 minutes, in an inert atmosphere to prevent oxidation.

7. The process according to claim 1, wherein the mixture optionally comprises of peroxides in an amount ranging from 100 ppm to 1000 ppm.

8. The process according to any of the preceding claims, wherein the compatibilizer is selected from a polypropylene composition (A) having a melt flow rate MFR(A) (ISO 1133- 1:2011, 230°C / 2.16 kg) ranging from 0.05 to 1.2 g / lOmin comprising:from 8 to 30% by weight, preferably from 13 to 27% by weight, more preferably from 15 to 25% by weight of a polymer fraction (a) comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, the propylene copolymer containing up to and including 10.0% by weight, based on the weight of the copolymer, of units derived from a comonomer selected from ethylene, a CH2=CHR alpha-olefin, where R is a linear or branched C2-C8 alkyl group, and combinations thereof, the polymer fraction (a) having solubility in xylene at 25°C XS(a) equal to or lower than 10.0% by weight, based on the weight of the polymer fraction (a); and from 70 to 92% by weight, preferably from 73 to 88% by weight, more preferably from 75 to 85% by weight, of a polymer fraction (b) comprising a first and a second copolymer of ethylene with a comonomer independently selected from a CH2=CHR alpha-olefin, where R is a linear or branched C1-C8 alkyl group, and combinations thereof, the first and the second copolymer containing an amount of units deriving from ethylene equal to or lower than 40% by weight, based on the weight of the respective copolymer, wherein the difference in the amount of units deriving from ethylene of the first and the second ethylene copolymer is greater than 1.0% by weight and wherein the polymer fraction (b) comprises a fraction soluble in xylene at 25°C equal to or greater than 60% by weight, based on the weight of the polymer fraction (b), wherein the amounts of fractions (a) and (b) are based on the sum of the weights of fraction (a)+fraction (b).

9. The process according to any of the preceding claims, wherein the polyolefin recyclate composition further comprises talc.

10. The process according to any of the preceding claims, wherein the polypropylene composition A is present in amount ranging from 3 to 30% wt preferably 5 to 25%wt based on the total weight of the composition subject to thermal treatment.

11. The process according to any of the preceding claims, wherein the amount of talc ranges from 5 to 40% wt preferably 10 to 30%wt based on the total weight of the composition subject to thermal treatment.

12. The process according to claim 1, wherein the initial melt flow rate (ISO1133, 230°C / 2.16 Kg) of polyolefin recyclate composition ranging from 1.0 to 10.0 g / 10 min preferably 2 to 8 g / lOmin, and most preferably from 3 to 6 g / lOmin.

13. The process according to claim 1, wherein the final melt flow rate (ISO1133, 230°C / 2.16 Kg) of polypropylene recyclate composition ranging from 10 to 80 g / lOmin, and most preferably from 15 to 70 g / lOmin.

14. A polypropylene recyclate composition olefin composition having melt flow rate (ISO1133, 230°C / 2.16 Kg) ranging from 5 to 100 g / 10 min being obtained by the process according to anyone of claims 1-13.

15. An article comprising the polypropylene recyclate compositions according to claim 14.

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