US20220410458A1

US20220410458A1 - Polymer recyclate processes and products

Info

Publication number: US20220410458A1
Application number: US17/845,727
Authority: US
Inventors: Harilaos Mavridis; Mick C. Hundley; Sameer D. Mehta; Marco Consalvi; Gerhardus Meier; Lindsay E. Corcoran
Original assignee: Equistar Chemicals LP
Current assignee: Equistar Chemicals LP
Priority date: 2021-06-22
Filing date: 2022-06-21
Publication date: 2022-12-29
Also published as: WO2022271720A2; JP2024526562A; KR20240046866A; US20220402188A1; MX2024000061A; EP4359470A2; JP2024526561A; US20230050126A1; EP4359466A1; CA3222511A1; CA3222504A1; WO2022271705A3; KR20240046867A; WO2022271720A3; CA3222509A1; EP4359469A2; KR20240024852A; WO2022271705A2; KR20240046865A; MX2024000055A

Abstract

Methods for processing HDPE recyclates including, but not limited to, polyethylene and polypropylene and compositions therefrom are provided. HDPE recyclate can be visbroken to improve processing characteristics and/or devolatilized to remove waste byproducts to produce processed HDPE recyclates. Processed HDPE recyclates are compounded with pre-consumer polyolefins to produce blend compositions having acceptable or even improved processing characteristics. Such pre-consumer polyolefins can also be visbroken to further tailor processing characteristics of such polymer blends. A combination of extruders and/or extruder zones can be used at the same or different locations for visbreaking and/or compounding of both HDPE recyclate and/or pre-consumer polyolefins.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed under the Patent Cooperation Treaty, which claims the priority of U.S. Provisional Patent Application Ser. No. 63/213,429, entitled “POLYMER RECYCLATE PROCESSES AND PRODUCTS,” filed on Jun. 22, 2021, and U.S. Provisional Patent Application Ser. No. 63/238,655, entitled “POLYMER RECYCLATE PROCESSES AND PRODUCTS,” filed on Aug. 30, 2021, the contents of which are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present disclosure relates to the use of extrusion processes to improve the processing characteristics of polyolefin recyclates, either alone or in combination with other polyolefins. The invention further relates to compositions produced by such processes.

BACKGROUND OF THE INVENTION

Polyolefins, including polyethylene and polypropylene, may be used in many applications, including packaging for food and other goods, electronics, automotive components, and a variety of manufactured articles. Waste plastic materials may be obtained from a variety of sources, including differential recovery of municipal plastic wastes that are constituted of flexible packaging (cast film, blown film and BOPP film), rigid packaging, blow molded bottles and injection molded containers. Often, through a step of separation from other polymers, such as PVC, PET or PS, two main polyolefinic fractions may be obtained, namely polyethylenes (including, HDPE, LDPE, LLDPE) and polypropylenes (including homopolymers, random copolymers, heterophasic copolymers).
The multicomponent nature of the recycled polyolefins or the polyolefinic fractions may result in low mechanical and optical performances of prepared articles or of polyolefin formulations in which part of a virgin HDPE is replaced by recycled polymer. Unpredictable mechanical and/or optical properties can result from variability of one or more characteristics of the recycled polyolefin including, but not limited to, melt index, high load melt index, melt elasticity, complex viscosity, or combinations thereof. In addition, the recycled polyolefins or the polyolefinic fractions may contain impurities or contamination by other components. Moreover, the molecular weight, the molecular weight distribution and/or the comonomer content of the recycled polyolefins or of the polyolefinic fractions can limit the range of virgin HDPEs into which recycled polyolefins can be incorporated. Another limitation for the use of recycled polyolefins may be the presence of unpleasant odors coming from volatile organic compounds which may have been absorbed in these polymers during their usage.
In the case of polyethylenes, it may be desirable to separate polyethylene waste into portions which are predominately HDPE, predominately MDPE, predominately LDPE, predominately LLDPE. This disclosure provides—in the case of the HDPE portion—processes to produce polyolefin compositions comprising recycled HDPE, such polyolefin compositions having a useful combination of properties. Such disclosed processes may be highly flexible and could be implemented with commonly used equipment and familiar techniques to produce a wide variety of products.

SUMMARY OF THE INVENTION

In general, the present disclosure relates to methods for processing polyolefin recyclates, in particular high density polyethylene (“HDPE”) recyclates. Such processing includes implementing in an extruder visbreaking conditions to convert a HDPE recyclate into a visbroken HDPE recyclate having a reduced weight average molecular weight. In some embodiments, the HDPE recyclate is also subjected to devolatilization conditions to convert the HDPE recyclate into a visbroken HDPE recyclate having a reduced weight average molecular weight and a reduced volatile organic compounds (“VOC”) content.
Visbreaking conditions include thermal visbreaking and/or peroxidation visbreaking. Thermal visbreaking includes temperature, pressure, and mechanical shear sufficient to cause polymer chain scission to predominate over polymer chain branching or crosslinking. Peroxidation visbreaking may occur when a peroxide as added to the polymer melt in an extruder followed by thermal decomposition of the peroxide to form free radicals, which react with the polymer chain to result in chain scission. In some embodiments, visbreaking conditions consist of thermal visbreaking at a temperature at least 180° C. above the melting point of the HDPE in the absence of or substantially in the absence of oxygen.
Devolatilization conditions can include reduction of VOC in a polyolefin by a portion of an extruder having an intensive mixing arrangement and devolatilization sections to enable removal of VOC at high temperatures. Devolatilization conditions can be further enhanced by injection of a gas into the extruder, distribution of the gas in the polymer melt to scavenge VOC components, and extraction of the gas and scavenged VOC components by venting and/or vacuum.
In some embodiments, the processed HDPE recyclate can be pelletized as a product at the extruder discharge. In other embodiments, the processed HDPE recyclate can be fed to a second extruder to be compounded or blended with a virgin HDPE. In yet other embodiments, the virgin HDPE can be the polyolefin powder product from a polymerization apparatus, a pelletized polyolefin, or the polyolefin melt, which is the product of a third extruder. In any of the embodiments in this paragraph, the virgin HDPE can have been subjected to a visbreaking process prior to addition to the second reactor.
In some embodiments, virgin HDPE is fed to a third extruder and the polymer melt form the third extruder is co-fed to the second extruder along with processed HDPE recyclate melt.
In some embodiments, a composition is provided where the composition is or comprises a polymer blend of from 5 wt. % to 90 wt. % of a HDPE recyclate and from 10 wt. % to 95 wt. % of a virgin HDPE, wherein all weight percentages are based on the combined weight of the polymer blend and one or both of the HDPE recyclate feedstock and the virgin HDPE are visbroken. Visbreaking can be thermal visbreaking and/or peroxidation visbreaking.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject matter of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other film structures and/or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its structure and method of manufacture, together with further objects and advantages will be better understood from the following description.

BRIEF DESCRIPTION OF THE FIGURES

The claimed subject matter may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 is a simplified flow diagram of the process to obtain a processed HDPE recyclate according to embodiments of the invention;

FIG. 2 is simplified flow diagram of the process to obtain a blend of a processed HDPE recyclate and a virgin HDPE using two extruders according to embodiments of the invention;

FIG. 3 is simplified flow diagram of the process to obtain a blend of a processed HDPE recyclate and a virgin HDPE using three extruders according to embodiments of the invention;

FIG. 4 is an overlaid graph showing the effects of visbreaking an HDPE on complex viscosity according to embodiments of the invention; and

FIG. 5 is an overlaid graph showing the effects of visbreaking an HDPE on molecular weight according to embodiments of the invention.

While the disclosed process and composition are susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments herein described in detail by way of example. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the subject matter claimed below will now be disclosed. In the interest of clarity, some features of some actual implementations may not be described in this specification. It will be appreciated that in the development of any such actual embodiments, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
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.
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.

Definitions

“Antioxidant agents,” as used herein, means compounds that inhibit oxidation, a chemical reaction that can produce free radicals and chain reactions.
“Compounding conditions,” as used herein, means temperature, pressure, and shear force conditions implemented in an extruder to provide intimate mixing of two or more polymers and optionally additives to produce a substantially homogeneous polymer product.
“Devolatilization conditions,” as used herein, means subjecting a polymer melt in an extruder to injection and withdrawal of a scavenging gas, addition of heat, physical mixing, pressure reduction by venting or applying vacuum, or a combination thereof. Devolatilization conditions implemented in an extruder are sufficient to reduce the VOC of a polymer fed to the extruder by a predetermined percentage and/or to a predetermined VOC target for polymer exiting the extruder. Devolatilization conditions are directed to reduction of VOC in a polyolefin by a portion of an extruder having an intensive mixing arrangement and devolatilization sections to enable removal of VOC at high temperatures. Devolatilization conditions can be further enhanced by injection of a gas into the extruder, distribution of the gas in the polymer melt to scavenge VOC components, and extraction of the gas and scavenged VOC components by venting or vacuum.
“Devolatilized HDPE recyclate,” as used herein, means the product obtained by subjecting an HDPE recyclate feedstock to devolatilization conditions as described herein.
“Extruder,” as used herein within the context of the “first extruder,” second extruder,” and “third extruder,” in some embodiments, means separate extrusion apparatuses, and in other embodiments, means separate sections within a single extrusion apparatus. In some embodiments, the first extruder and the second extruder are separate machines. In some embodiments, the first extruder and the second extruder are separate sections in a single machine. In some embodiments, the second extruder and the third extruder are separate machines. In some embodiments, the second extruder and the third extruder are separate sections in a single machine. In some embodiments, the first extruder, the second extruder, and the third extruder are separate machines. In some embodiments, the first extruder, the second extruder, and the third extruder are separate sections in a single machine. “Extruder,” as used herein includes any device or combinations of devices capable of continuously processing one or more polyolefins under visbreaking conditions, compounding conditions, melting conditions, or devolatilization conditions, including, but not limited to, Farrel continuous mixers (FCM™ mixers, available from Farrel Corporation, Ansonia, Conn.).
“HDPE,” as used herein, means ethylene homopolymers and ethylene copolymers produced in a suspension, solution, slurry, or gas phase polymerization process and having a density in the range of 0.940 g/cm³to 0.970 g/cm³.
“HDPE recyclate feedstock,” as used herein, means HDPE recyclate after collection and sorting but prior to being subjected to the processes disclosed herein.
“HDPE recyclate,” as used herein, means post-consumer recycled (“PCR”) HDPE and/or post-industrial recycled (“PIR”) HDPE. Polyolefin recyclate is derived from an end product that has completed its life cycle as a consumer item and would otherwise be disposed of as waste (e.g., a polyethylene water bottle) or from plastic scrap that is generated as waste from an industrial process. Post-consumer polyolefins include polyolefins that have been collected in commercial and residential recycling programs, including flexible packaging (cast film, blown film and BOPP film), rigid packaging, blow molded bottles, and injection molded containers. Usually, through a step of separation from other polymers, such as PVC, PET or PS, two main polyolefinic fractions are obtained, namely polyethylene recyclate (including HDPE, MDPE, LDPE, and LLDPE) and polypropylene recyclate (including homopolymers, random copolymers, and heterophasic copolymers). Polyethylene recyclate can be further separated to recover a portion having HDPE as the primary constituent. In addition to contamination from dissimilar polymers, HDPE recyclate frequently contains other impurities such as PMMA, PC, wood, paper, textile, cellulose, food, and other organic wastes, many of which cause the HDPE recyclate to have an unpleasant odor before and after typical processing.
“LDPE,” as used herein, means ethylene homopolymers and ethylene copolymers produced in a high pressure free radical polymerization and having a density in the range of 0.910 g/cm³to 0.940 g/cm³.
“LLDPE,” as used herein, means ethylene copolymers produced in a suspension, solution, slurry, or gas phase polymerization process and having a density in the range of 0.910 g/cm³to 0.940 g/cm³.
“MDPE,” as used herein, means ethylene copolymers produced in a suspension, solution, slurry, or gas phase polymerization process and having a density in the range of 0.925 g/cm³to 0.940 g/cm³.
“Melting conditions,” as used herein, means temperature, pressure, and shear force conditions, either alone or in combination with one another, that are required to produce a polymer melt from a feed of polymer pellets or powder.
“Processed HDPE recyclate,” as used herein, means the product obtained by subjecting an HDPE recyclate feedstock to visbreaking conditions or to visbreaking conditions followed by devolatilization conditions, as described herein.
“Virgin HDPEs,” as used herein, are pre-consumer polyolefins. Pre-consumer polyolefins are polyolefin products obtained directly or indirectly from petrochemical feedstocks fed to a polymerization apparatus. Pre-consumer polyolefins can be subjected to post polymerization processes such as, but not limited to, extrusion, pelletization, visbreaking, and/or other processing completed before the product reaches the end-use consumer. In some embodiments, virgin HDPEs have a single heat history. In some embodiments, virgin HDPEs have more than one heat history. In some embodiments, virgin HDPEs comprise no additives. In some embodiments, virgin HDPEs comprise additives.
“Visbreaking conditions,” as used herein, means thermal visbreaking and/or peroxidation visbreaking. Thermal visbreaking includes temperature, pressure, and/or mechanical shear sufficient to cause polymer chain scission to predominate of polymer chain branching or crosslinking. Peroxidation visbreaking occurs when a peroxide as added to the polymer melt in an extruder followed by thermal decomposition of the peroxide to form free radicals, which react with the polymer chain to result in chain scission. As used herein, a polymer that has been visbroken will have lower number average and weight average molecular weight, a narrower molecular weight distribution, higher melt index, and a higher high load melt index. In some embodiments, visbreaking conditions consist of thermal visbreaking at a temperature greater than or equal to 300° C., or in the range of from 320° C. to 400° C., in the absence of or substantially in the absence of oxygen.
“Visbreaking,” as used herein, means treating a polymer thermally and/or chemically to produce a reduction in M_n, M_w, and MWD (M_w/M_n), and an increase in melt index I₂(ASTM D-1238, 2.16 kg @ 190° C.) and high load melt index I₂₁(ASTM D-1238, 21.6 kg @ 190° C.) of the HDPE so treated. Applying high temperatures and/or adding radical source such as peroxides to polyolefinic materials results in degradation of the polymer chains and reduction of the average molecular weight of the polymer. In parallel, the molecular weight distribution gets narrower. When intentionally performing such methods for modifying the properties of polymers, these practices are commonly called “visbreaking”.
“Visbroken HDPE recyclate,” as used herein, means the product obtained by subjecting an HDPE recyclate feedstock to visbreaking conditions as described herein.

Processing HDPE Recyclate Feedstock

In FIG. 1 , flow diagram 100 includes a visbreaking extruder 110 having a visbreaking zone 115 and an optional devolatilization zone 120. HDPE recyclate feedstock 125 is added to visbreaking extruder 110 proximate to the inlet end of the extruder. The HDPE recyclate is drawn through the extruder 110 by one or more rotating screw drives in the barrel of the visbreaking extruder 110. The length of the visbreaking extruder 110 is separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, inlets for injection of gas 130, 135, vents or vacuum connections for withdrawal of gas 140, means for addition or withdrawal of heat, inlets for injection of peroxide 145, and inlets for injection of additives in order to impart preselected process conditions including, but not limited to pressure, temperature, and/or shear force.
FIG. 1 shows an embodiment with both a visbreaking zone 115 and an optional devolatilization zone 120. Other embodiments can have a visbreaking zone 115 alone without a devolatilization zone. Process conditions in the visbreaking extruder 110 can further be controlled by rotation speed of the screw drive. Processed HDPE recyclate 150 is withdrawn proximate to the discharge of the visbreaking extruder 110 for further processing or pelletization.
HDPE Recyclate Feedstock
In some embodiments, HDPE recyclate feedstock is derived from ethylene homopolymers, copolymers of units derived from ethylene and units derived from one or more of C₃-C₁₂α-olefins, copolymers of units derived from ethylene and units derived from one or more of alpha mono-olefins. Such C₃-C₁₂α-olefins include, but are not limited to, substituted or unsubstituted C₃to C₁₂alpha olefins such as propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecane, and isomers thereof. When present, comonomers can be present in amounts up to 20 wt %, 15 wt %, 10 wt %, or 5 wt %. HDPE recyclate feedstock can be derived as a portion of post-consumer recycled polyolefin and/or post-industrial recycled polyolefin that is predominately comprised of HDPE recyclate, wherein “predominately” means greater than or equal to 80 wt %, greater than or equal to 85 wt %, greater than or equal to 90 wt %, or greater than or equal to 95 wt %, based on the total weight of the HDPE recyclate feedstock.
Such ethylene homopolymers and/or copolymers can be produced in a suspension, solution, slurry, or gas phase process, using known equipment and reaction conditions. In some embodiments, polymerization temperatures range from about 0° C. to about 300° C. at atmospheric, subatmospheric, or superatmospheric pressures.
Slurry or solution polymerization systems can utilize subatmospheric or superatmospheric pressures and temperatures in the range of about 40° C. to about 300° C. An exemplary liquid phase polymerization system is described in U.S. Pat. No. 3,324,095, the disclosure of which is fully incorporated by reference herein. Liquid phase polymerization systems generally comprise a reactor to which olefin monomer and catalyst composition are added, and which contains a liquid reaction medium for dissolving or suspending the polyolefin. The liquid reaction medium may consist of the bulk liquid monomer or an inert liquid hydrocarbon that is nonreactive under the polymerization conditions employed. Although such an inert liquid hydrocarbon need not function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as solvent for the monomers employed in the polymerization. Among the inert liquid hydrocarbons suitable for this purpose are isopentane, hexane, cyclohexane, heptane, benzene, toluene, and the like. Reactive contact between the olefin monomer and the catalyst composition should be maintained by constant stirring or agitation. The reaction medium containing the olefin polymer product and unreacted olefin monomer is withdrawn from the reactor continuously. The olefin polymer product is separated, and the unreacted olefin monomer and liquid reaction medium are recycled into the reactor.
Gas phase polymerization systems can utilize superatmospheric pressures in the range of from 1 psig (6.9 kPag) to 1,000 psig (6.9 MPag), 50 psig (344 kPag) to 400 psig (2.8 MPag), or 100 psig (689 kPag) to 300 psig (2.1 MPag), and temperatures in the range of from 30° C. to 130° C. or 65° C. to 110° C. Gas phase polymerization systems can be stirred or fluidized bed systems. In some embodiments, a gas phase, fluidized bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluidized bed reactor under reaction conditions and in the presence of catalyst composition at a velocity sufficient to maintain a bed of solid particles in a suspended condition. A stream containing unreacted monomer is withdrawn from the reactor continuously, compressed, cooled, optionally partially or fully condensed, and recycled into the reactor. Product is withdrawn from the reactor and make-up monomer is added to the recycle stream. As desired for temperature control of the polymerization system, any gas inert to the catalyst composition and reactants may also be present in the gas stream.
In some embodiments, a Ziegler-Natta (ZN) catalyst is used. Such catalysts are based on a Group IVB transition metal compound and an organoaluminum compound (co-catalyst). Such transition metals, include, but not limited to, Ti, Zr, and Hf. Nonlimiting examples of ZN catalyst systems include TiCl₄+Et₃Al and TiCl₃+AlEt₂Cl. Such HDPE homopolymers and/or copolymers have some long-chain branching and a density in the range of from 0.940 g/cm³to 0.970 g/cm³.
HDPE recyclate feedstock, derived from HDPE as described above, can be characterized by having:

- i) a density in the range of from 0.940 g/cm³to 0.970 g/cm³;
- ii) a melt index (2.16 kg, 190° C.) less than or equal to less than or equal to 1.0 g/10 min.;
- iii) a molecular weight distribution (M_w/M_n) greater than or equal to 10, greater than or equal to 15, or greater than or equal to 20;
- iv) a weight average molecular weight (“M_w1”) greater than or equal to 100,000 daltons, greater than or equal to 150,000 daltons, greater than or equal to 200,000 daltons, or greater than or equal to 250,000 daltons, and/or less than or equal to 600,000 daltons, less than or equal to 500,000 daltons, less than or equal to 400,000 daltons, or less than or equal to 300,000 daltons; and
- v) a melt elasticity (“ER”) greater than or equal to 1.0, greater than or equal to 2.0, or greater than or equal to 3.0 and/or less than or equal to 8.0, less than or equal to 7.0, or less than or equal to 6.0.

In some embodiments, in addition to the foregoing properties, the HDPE recyclate feedstock can be further characterized by having one or more of:

- vi) a first VOC content;
- vii) a first high load melt index (I₂₁, 21.6 kg, 190° C.;
- viii) a first melt index ratio (MIR, I₂₁/I₂);
- ix) a first long chain branching parameter (g′) in the range of from 0.70 to 0.99, from 0.80 to 0.98, or from 0.85 to 0.97;
- x) a first overall polydispersity ratio (PDR);
- xi) a first complex viscosity ratio (η*_0.1/η*₁₀₀), greater than 12, and η*_0.1is the complex viscosity at 0.1 rad/sec and η*₁₀₀is the complex viscosity at 100 rad/sec, both at a temperature of 190° C.; and
- xii) a first intrinsic viscosity.

Visbreaking Extruder
HDPE recyclate feedstock is fed to a first extruder and is subjected to visbreaking conditions and optionally devolatilization conditions.
Visbreaking
Visbreaking conditions are implemented in the visbreaking zone of the first extruder and are tailored for HDPE. In some embodiments, visbreaking conditions means thermal visbreaking and/or peroxidation visbreaking. In some embodiments, visbreaking conditions consist of thermal visbreaking, wherein the temperature in the visbreaking zone is greater than or equal to 300° C., where it is believed that chain scission reactions exceed long-chain branching and/or crosslinking reactions. In some embodiments, temperatures in the visbreaking zone can be in the range of from 320° C. to 500° C., from 340° C. to 480° C., or from 360° C. to 460° C. In some embodiments, instrumentation at the first extruder discharge monitors rheology directly or indirectly (I₂, I₂₁, viscosity, melt elasticity, complex viscosity ratio, or the like) to measure and assist in control of visbreaking. In some embodiments, where antioxidant addition is used in conjunction with visbreaking, the antioxidant addition point is at a location on the first extruder after a substantial portion of the visbreaking reaction has taken place. In some embodiments, visbreaking conditions consist of thermal visbreaking the absence of or substantially in the absence of oxygen, wherein substantial absence of oxygen means less than or equal to 1.0 wt %, less than or equal to 0.10 wt %, or less than or equal to 0.01 wt %, based on the total weight of polymer in the extruder. In some embodiments, the visbreaking extruder comprises one or more melt filters.
Devolatilization
Devolatilization conditions are optionally implemented in the first extruder and are directed to reduction of VOC in the HDPE recyclate feedstock by a portion of an extruder having an intensive mixing arrangement and devolatilization sections to enable removal of VOC at high temperatures. Devolatilization conditions can be further enhanced by: injection of a scavenging gas, such as, but not limited to, nitrogen, carbon-dioxide, water, or combinations thereof, into the extruder; distribution of the gas in the polymer melt to scavenge VOC components; and extraction of the gas and scavenged VOC components by venting and/or vacuum.
Processed HDPE Recyclate
A processed HDPE recyclate is withdrawn from the discharge of the visbreaking extruder, wherein “processed” means that the HDPE recyclate feedstock was subjected to visbreaking conditions or visbreaking conditions followed by devolatilization conditions. Processed HDPE recyclate, as described above, can be characterized by having:

- i) a density, wherein the ratio of the density of the processed HDPE recyclate to the density of the HDPE recyclate feedstock is greater than or equal to 1.0;
- ii) a melt index, wherein the ratio of the melt index of the processed HDPE recyclate to the melt index of the HDPE recyclate feedstock is greater than or equal to 5.0, greater than or equal to 50, or greater than or equal to 100, and/or the melt index of the processed HDPE recyclate is greater than or equal to 5.0 g/10 min. or greater than or equal to 10.0 g/10 min.;
- iii) a molecular weight distribution, wherein the ratio of molecular weight distribution of the processed HDPE recyclate to the molecular weight distribution of the HDPE recyclate feedstock is less than or equal to 0.50, and/or the molecular weight distribution of the processed HDPE recyclate is less than or equal to 40;
- iv) a weight average molecular weight (“M_w2”), wherein the ratio of the weight average molecular weight of the processed HDPE recyclate to the weight average molecular weight of the HDPE recyclate feedstock is in the range of from 0.10 to 0.70, from 0.15 to 0.60, or from 0.20 to 0.50; and
- v) a melt elasticity (“ER”), wherein the ratio of the ER of the processed HDPE recyclate to the ER of the HDPE recyclate feedstock is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30, and/or the second melt elasticity is less than or equal to 2.0, less than or equal to 1.5, or less than or equal to 1.0, and/or greater than or equal to 0.10, greater than or equal to 0.20, or greater than or equal to 0.30.

In some embodiments, in addition to the foregoing properties, the processed HDPE recyclate can be further characterized by having one or more of:

- vi) a VOC content, wherein the ratio of the VOC content of the processed HDPE recyclate to the VOC content of the HDPE recyclate feedstock is less than or equal to 0.9, 0.8, 0.7, 0.6, or 0.5, each alone or in combination with a lower limit of greater than or equal to 0.1;
- vii) a high load melt index (I₂₁; 21.6 kg, 190° C.), wherein the ratio of the high load melt index of the processed HDPE recyclate recyclate to the high load melt index of the HDPE recyclate feedstock is greater than or equal to 5.0, greater than or equal to 20, or greater than or equal to 30;
- viii) a melt index ratio (MIR, I₂₁/I₂), wherein the MIR of the processed HDPE recyclate to the MIR of the HDPE recyclate feedstock is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30;
- ix) a long chain branching parameter (g′), wherein the ratio of the g′ of processed HDPE recyclate to the g′ of the HDPE recyclate feedstock is less than or equal to 1.0;
- x) a first long chain branching index (“LCBI”) greater than or equal to 0.30, and the processed HDPE recyclate has a LCBI less than or equal to 0.20;
- xi) an overall polydispersity ratio (PDR), wherein the ratio of the PDR of the processed HDPE recyclate to the PDR of the HDPE recyclate feedstock is less than or equal to 0.40, less than or equal to 0.30, or less than or equal to 0.20;
- xii) a complex viscosity ratio (η*_0.1/η*₁₀₀), wherein the ratio of the complex viscosity ratio of the processed HDPE recyclate to the complex viscosity ratio of the HDPE recyclate feedstock is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30, and/or the second complex viscosity ratio is less than or equal to 10, less than or equal to 8.0, or less than or equal to 6.0, and η*_0.1is the complex viscosity at 0.1 rad/sec and η*₁₀₀is the complex viscosity at 100 rad/sec, both at a temperature of 190° C.; and
- xiii) an intrinsic viscosity [η], wherein the ratio of the intrinsic viscosity of the processed HDPE recyclate to the intrinsic viscosity of the HDPE recyclate feedstock is less than or equal to 0.90, less than or equal to 0.70, or less than or equal to 0.50.

Blending of Processed HDPE Recyclate and and a Polyolefin Blend Component—Two Extruders

In FIG. 2 , flow diagram 200 includes a visbreaking extruder 210 and a compounding extruder 255. Embodiments of the present invention as shown in FIG. 2 include a visbreaking extruder 210 having a visbreaking zone 215 and a devolatilization zone 220. HDPE recyclate feedstock 225 is added to visbreaking extruder 210 proximate to the inlet end of the extruder. The HDPE recyclate feedstock 225 is drawn through the visbreaking extruder 210 by one or more rotating screw drives in the barrel of the visbreaking extruder 210. The length of the visbreaking extruder 210 is separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, inlets for injection of gas 230, 235, vents or vacuum connections for withdrawal of gas 240, means for addition or withdrawal of heat, inlets for injection of peroxide 245, and inlets for injection of additives in order to impart preselected process conditions including, but not limited to pressure, temperature, and shear force.
FIG. 2 shows an embodiment with both a visbreaking zone 215 and a devolatilization zone 220. Other embodiments can have either a visbreaking zone 215 or a devolatilization zone 220 independently without the other. Process conditions in the visbreaking extruder 210 can further be controlled by rotation speed of the screw drive. Processed HDPE recyclate 250 is withdrawn proximate to the discharge of the visbreaking extruder 210 for further processing.
Embodiments of FIG. 2 include a second extruder 255, having a compounding zone 260. Processed HDPE recyclate 250 is added to compounding extruder 255 as a first blend component proximate to the inlet end of the extruder along with a polyolefin blend component 252 and subjected to compounding conditions. The polyolefin blend component 252 comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof. In some embodiments, the virgin polyolefin comprises a virgin HDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof. In some embodiments, the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof. In some embodiments, the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof. In some embodiments, a polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof. The mixture of HDPE recyclate 250 and polyolefin blend component 252 is drawn through the compounding extruder 255 by one or more rotating screw drives in the barrel of the extruder 255. One or more additional inlets proximate to the inlet end of the extruder provide for the addition of antioxidant agent 265 and/or other components 270. The length of the compounding extruder 255 can be separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, means for addition or withdrawal of heat, inlets for injection of additives. and vents or vacuum connections for withdrawal of gas 275, in order to impart preselected process conditions including, but not limited to pressure, temperature, and shear force. A blend 280 of the processed HDPE recyclate 250 and the polyolefin blend component 252 is withdrawn proximate to the discharge of the compounding extruder 255 for further processing or pelletization.
In some embodiments, the polyolefin blend component can be a polyolefin powder product from a polymerization apparatus, a pelletized polyolefin, or the polyolefin melt, which is the product withdrawn from a third extruder. In some of these embodiments, the polymerization apparatus comprises two, three, or more polymerization reactors and/or two, three, or more polymerization zones within a polymerization reactor. More specific polymerization apparatus embodiments include, but are not limited to, two or three gas phase fluidized-bed reactors in series, two or three slurry phase reactors in series, and a gas phase fluidized-bed reactor in series with a multizone circulation reactor.
In some embodiments, the amount of the polyolefin blend component, which itself can comprise two or more polymers, is determined based on the logarithmic mixing rule, wherein blend components satisfy the following equation:
$\log ({MFR}_{blend}) = \sum_{i = 1}^{n} (w_{i} \times \log ({MFR}_{i}))$
wherein:
MFR is I₂, I₂₁, or other selected melt index;
MFR_blendis the target MFR of the final blend product;
n is the number of components in the blend; and
i is the i-th component of an n-component blend.
Blend Components
A first blend component is a processed HDPE recyclate produced from a visbreaking extruder. A second blend component comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof. In some embodiments, the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin polypropylene, or a combination thereof. In some embodiments, the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof. In some embodiments, the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed polypropylene recyclate, or a combination thereof. In some embodiments, a polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof. When the processed HDPE recyclate is blended with another processed HDPE recyclate, the first HDPE recyclate will have at least one parameter that distinguishes it from the second processed HDPE recyclate.
Virgin HDPE
In some embodiments, virgin HDPE is selected from ethylene homopolymers, copolymers of units derived from ethylene and units derived from one or more of C₃-C₁₂α-olefins, copolymers of units derived from ethylene and units derived from one or more of alpha mono-olefins. Such C₃-C₁₂α-olefins include, but are not limited to, substituted or unsubstituted C₃to C₁₂alpha olefins such as propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecane, and isomers thereof. When present, comonomers can be present in amounts up to 20 wt %, 15 wt %, 10 wt %, or 5 wt %.
Such ethylene homopolymers and/or copolymers can be produced in a suspension, solution, slurry, or gas phase process, using known equipment and reaction conditions. In some embodiments, polymerization temperatures range from about 0° C. to about 300° C. at atmospheric, subatmospheric, or superatmospheric pressures.
Slurry or solution polymerization systems can utilize subatmospheric or superatmospheric pressures and temperatures in the range of about 40° C. to about 300° C. An exemplary liquid phase polymerization system is described in U.S. Pat. No. 3,324,095, the disclosure of which is fully incorporated by reference herein. Liquid phase polymerization systems generally comprise a reactor to which olefin monomer and catalyst composition are added, and which contains a liquid reaction medium for dissolving or suspending the polyolefin. The liquid reaction medium may consist of the bulk liquid monomer or an inert liquid hydrocarbon that is nonreactive under the polymerization conditions employed. Although such an inert liquid hydrocarbon need not function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as solvent for the monomers employed in the polymerization. Among the inert liquid hydrocarbons suitable for this purpose are isopentane, hexane, cyclohexane, heptane, benzene, toluene, and the like. Reactive contact between the olefin monomer and the catalyst composition should be maintained by constant stirring or agitation. The reaction medium containing the olefin polymer product and unreacted olefin monomer is withdrawn from the reactor continuously. The olefin polymer product is separated, and the unreacted olefin monomer and liquid reaction medium are recycled into the reactor.
Gas phase polymerization systems can utilize superatmospheric pressures in the range of from 1 psig (6.9 kPag) to 1,000 psig (6.9 MPag), 50 psig (344 kPag) to 400 psig (2.8 MPag), or 100 psig (689 kPag) to 300 psig (2.1 MPag), and temperatures in the range of from 30° C. to 130° C. or 65° C. to 110° C. Gas phase polymerization systems can be stirred or fluidized bed systems. In some embodiments, a gas phase, fluidized bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluidized bed reactor under reaction conditions and in the presence of catalyst composition at a velocity sufficient to maintain a bed of solid particles in a suspended condition. A stream containing unreacted monomer is withdrawn from the reactor continuously, compressed, cooled, optionally partially or fully condensed, and recycled into the reactor. Product is withdrawn from the reactor and make-up monomer is added to the recycle stream. As desired for temperature control of the polymerization system, any gas inert to the catalyst composition and reactants may also be present in the gas stream.
In some embodiments, a Ziegler-Natta (ZN) catalyst is used. Such catalysts are based on a Group IVB transition metal compound and an organoaluminum compound (co-catalyst). Such transition metals, include, but not limited to, Ti, Zr, and Hf. Nonlimiting examples of ZN catalyst systems include TiCl₄+Et₃Al and TiCl₃+AlEt₂Cl. Such HDPE homopolymers and/or copolymers have some long-chain branching and a density in the range of from 0.940 g/cm³to 0.970 g/cm³.
Virgin HDPE can be characterized by having:

- i) a density in the range of from 0.940 g/cm³to 0.970 g/cm³;
- ii) a melt index (2.16 kg, 190° C.) in the range of from 1.0 g/10 min. to 100 g/10 min., from 2.0 g/10 min. to 80 g/10 min., or from 3.0 g/10 min. to 50 g/10 min.;
- iii) a molecular weight distribution (M_w/M_n) greater than 15; and
- iv) a weight average molecular weight less than or equal to 250,000 daltons, less than or equal to 200,000 daltons, less than or equal to 150,000 daltons, or less than or equal to 100,000 daltons.

HDPE Recyclate Feedstock
In some embodiments, HDPE recyclate feedstock is derived from ethylene homopolymers, copolymers of units derived from ethylene and units derived from one or more of C₃-C₁₂α-olefins, copolymers of units derived from ethylene and units derived from one or more of alpha mono-olefins. Such C₃-C₁₂α-olefins include, but are not limited to, substituted or unsubstituted C₃to C₁₂alpha olefins such as propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecane, and isomers thereof. When present, comonomers can be present in amounts up to 20 wt %, 15 wt %, 10 wt %, or 5 wt %. HDPE recyclate feedstock can be derived as a portion of post-consumer recycled polyolefin and/or post-industrial recycled polyolefin that is predominately comprised of HDPE recyclate, wherein “predominately” means wherein “predominately” means greater than or equal to 80 wt %, greater than or equal to 85 wt %, greater than or equal to 90 wt %, or greater than or equal to 95 wt %, based on the total weight of the HDPE recyclate feedstock.
Such ethylene homopolymers and/or copolymers can be produced in a suspension, solution, slurry, or gas phase process, using known equipment and reaction conditions. In some embodiments, polymerization temperatures range from about 0° C. to about 300° C. at atmospheric, subatmospheric, or superatmospheric pressures.
Slurry or solution polymerization systems can utilize subatmospheric or superatmospheric pressures and temperatures in the range of about 40° C. to about 300° C. An exemplary liquid phase polymerization system is described in U.S. Pat. No. 3,324,095, the disclosure of which is fully incorporated by reference herein. Liquid phase polymerization systems generally comprise a reactor to which olefin monomer and catalyst composition are added, and which contains a liquid reaction medium for dissolving or suspending the polyolefin. The liquid reaction medium may consist of the bulk liquid monomer or an inert liquid hydrocarbon that is nonreactive under the polymerization conditions employed. Although such an inert liquid hydrocarbon need not function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as solvent for the monomers employed in the polymerization. Among the inert liquid hydrocarbons suitable for this purpose are isopentane, hexane, cyclohexane, heptane, benzene, toluene, and the like. Reactive contact between the olefin monomer and the catalyst composition should be maintained by constant stirring or agitation. The reaction medium containing the olefin polymer product and unreacted olefin monomer is withdrawn from the reactor continuously. The olefin polymer product is separated, and the unreacted olefin monomer and liquid reaction medium are recycled into the reactor.
Gas phase polymerization systems can utilize superatmospheric pressures in the range of from 1 psig (6.9 kPag) to 1,000 psig (6.9 MPag), 50 psig (344 kPag) to 400 psig (2.8 MPag), or 100 psig (689 kPag) to 300 psig (2.1 MPag), and temperatures in the range of from 30° C. to 130° C. or 65° C. to 110° C. Gas phase polymerization systems can be stirred or fluidized bed systems. In some embodiments, a gas phase, fluidized bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluidized bed reactor under reaction conditions and in the presence of catalyst composition at a velocity sufficient to maintain a bed of solid particles in a suspended condition. A stream containing unreacted monomer is withdrawn from the reactor continuously, compressed, cooled, optionally partially or fully condensed, and recycled into the reactor. Product is withdrawn from the reactor and make-up monomer is added to the recycle stream. As desired for temperature control of the polymerization system, any gas inert to the catalyst composition and reactants may also be present in the gas stream.
In some embodiments, a Ziegler-Natta (ZN) catalyst is used. Such catalysts are based on a Group IVB transition metal compound and an organoaluminum compound (co-catalyst). Such transition metals, include, but not limited to, Ti, Zr, and Hf. Nonlimiting examples of ZN catalyst systems include TiCl₄+Et₃Al and TiCl₃+AlEt₂Cl. Such HDPE homopolymers and/or copolymers have some long-chain branching and a density in the range of from 0.940 g/cm³to 0.970 g/cm³.
HDPE recyclate feedstock, derived from HDPE as described above, can be characterized by having:

Processed HDPE Recyclate
A processed HDPE recyclate is withdrawn from the discharge of the visbreaking extruder, wherein “processed” means that the HDPE recyclate feedstock was subjected to visbreaking conditions or visbreaking conditions followed by devolatilization conditions. Processed HDPE recyclate, as described above, can be characterized by having:

Compounding Extruder
Processed HDPE recyclate and a polyolefin blend component are fed to a second extruder or mixer wherein the blend is subjected to compounding conditions. Compounding conditions are implemented in the compounding zone of the second extruder or mixer and are tailored for mixtures of specific polyolefins and optionally additives. Temperature, pressure, and shear force conditions are implemented in the second extruder or mixer sufficient to provide intimate mixing of the processed HDPE recyclate and the virgin HDPE and optionally additives to produce a substantially homogeneous polymer blend of the processed HDPE recyclate and the virgin HDPE. In some embodiments, compounding conditions comprise a temperature in the compounding zone of less than or equal to 300° C., less than or equal to 250° C. or less than or equal to 200° C. In some embodiments, temperatures in the compounding zone can be in the range of from 125° C. to 195° C., from 130° C. to 180° C., or from 135° C. to 165° C.
Blends of Processed HDPE Recyclate and a Polyolefin Blend Component
In some embodiments, the blend comprises from 5 wt. % to 90 wt. %, 10 wt. % to 80 wt. %, 15 wt. % to 70 wt. %, 20 wt. % to 60 wt. %, or 25 wt. % to 50 wt. %, of a processed HDPE recyclate and from 10 wt. % to 95 wt. %, 20 wt. % to 90 wt. %, 30 wt. % to 85 wt. %, 40 wt. % to 80 wt. %, or 50 wt. % to 75 wt. %, of a polyolefin blend component, respectively, wherein all weight percentages are based on the combined weight of the polymer blend. In some embodiments, the virgin HDPE is visbroken. Such visbreaking of virgin HDPE can be thermal visbreaking and/or peroxidation visbreaking. In some embodiments, such visbreaking conditions for a virgin HDPE consist of thermal visbreaking at a temperature above the melting point of the HDPE, greater than or equal to 300° C., or in the range of from 320° C. to 400° C., in the absence of or substantially in the absence of oxygen.
In some embodiments, the blends of processed HDPE recyclate and a polyolefin blend component, in combination with or independently of the blend ratios in the preceding paragraph, comprise a bimodal polymer, wherein the processed HDPE recyclate product has a weight average molecular weight (“M_w3”), the polyolefin blend component has a weight average molecular weight (“M_w4”); and M_w3/M_w4is either less than or equal to 0.9,0.8, 0.7, 0.6, or 0.5, or alternatively is greater than or equal to 1.1, 1.25, 1.5, 1.75, or 2.0.

Blending of Processed HDPE Recyclate and a Polyolefin Blend Component—Three Extruders

In FIG. 3 , flow diagram 300 includes a visbreaking extruder 310, a melting extruder 357, and a compounding extruder 355. Embodiments of the present invention as shown in FIG. 3 include a visbreaking extruder 310 having a visbreaking zone 315 and a devolatilization zone 320. HDPE recyclate feedstock 325 is added to visbreaking extruder 310 proximate to the inlet end of the extruder. The HDPE recyclate feedstock 325 is drawn through the visbreaking extruder 310 by one or more rotating screw drives in the barrel of the visbreaking extruder 310. The length of the visbreaking extruder 310 is separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, inlets for injection of gas 330, 335, vents or vacuum connections for withdrawal of gas 340, means for addition or withdrawal of heat, inlets for injection of peroxide 345, and inlets for injection of additives in order to impart preselected process conditions including, but not limited to pressure, temperature, and shear force.
FIG. 3 shows an embodiment with both a visbreaking zone 315 and a devolatilization zone 320. Other embodiments can have either a visbreaking zone 315 or a devolatilization zone 320 independently without the other. Process conditions in the visbreaking extruder 310 can further be controlled by rotation speed of the screw drive. Processed HDPE recyclate 350 is withdrawn proximate to the discharge of the visbreaking extruder 310 for further processing.
Embodiments of FIG. 3 include a second extruder 355 having a compounding zone 360 and a third extruder 357 having a melting zone 362. A third blend component 383 is added to melting extruder 357 proximate to the inlet end of the extruder optionally along with antioxidant agent 365 and other components 370. The polyolefin blend component 352 comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof. In some embodiments, the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof. In some embodiments, the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof. In some embodiments, the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof. In some embodiments, a polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof. The mixture of third blend component 352 and optional antioxidant 365 and/or other components 370 is drawn through the melting extruder 357 by one or more rotating screw drives in the barrel of the melting extruder 357. The length of the melting extruder 357 can be separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, means for addition or withdrawal of heat, inlets for injection of additives, and vents or vacuum connections for withdrawal of gas, in order to impart preselected process conditions including, but not limited to, pressure, temperature, and shear force. A melt of the polyolefin blend component 352 is withdrawn proximate to the discharge of the melting extruder 357 for further processing or pelletization.
Processed HDPE recyclate 350 is added to compounding extruder 355 proximate to the inlet end of the extruder along with the melt of the polyolefin blend component 352. The mixture of processed HDPE recyclate 350 and polyolefin blend component 352 is drawn through the compounding extruder 355 by one or more rotating screw drives in the barrel of the compounding extruder 355 and the mixture is subjected to compounding conditions. The length of the compounding extruder 355 can be separated into one or more zones. Each zone can have one or more of a specified thread pitch on the screw drive, means for addition or withdrawal of heat, inlets for injection of additives, and vents and/or vacuum connections for withdrawal of gas 375, in order to impart preselected process conditions including, but not limited to pressure, temperature, and shear force. A blend 380 of the processed HDPE recyclate 350 and the polyolefin blend component 352 melt is withdrawn proximate to the discharge of the compounding extruder 355 for further processing or pelletization.
In some embodiments, the polyolefin blend component can be a polyolefin powder product from a polymerization apparatus, a pelletized polyolefin, or the polyolefin melt, which is the product withdrawn from a third extruder. In some of these embodiments, the polymerization apparatus comprises two, three, or more polymerization reactors and/or two, three, or more polymerization zones within a polymerization reactor. More specific polymerization apparatus embodiments include, but are not limited to, two or three gas phase fluidized-bed reactors in series, two or three slurry phase reactors in series, and a gas phase fluidized-bed reactor in series with a multizone circulation reactor.
In some embodiments, the amount of the polyolefin blend component, which itself can comprise two or more polymers, is determined based on the logarithmic mixing rule, wherein blend components satisfy the following equation:
$\log ({MFR}_{blend}) = \sum_{i = 1}^{n} (w_{i} \times \log ({MFR}_{i}))$
wherein:
MFR is I₂, I₂₁, or other selected melt index;
MFR_blendis the target MFR of the final blend product;
n is the number of components in the blend; and
i is the i-th component of an n-component blend.
Blend Components
A first blend component is a processed HDPE recyclate produced from at from a visbreaking extruder. A second blend component comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof. In some embodiments, the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof. In some embodiments, the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof. In some embodiments, the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof. In some embodiments, the second blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof. When the processed HDPE recyclate is blended with another processed HDPE recyclate, the first HDPE recyclate will have at least one parameter that distinguishes it from the second processed HDPE recyclate.
Virgin HDPE
In some embodiments, virgin HDPE is selected from ethylene homopolymers, copolymers of units derived from ethylene and units derived from one or more of C₃-C₁₂α-olefins, copolymers of units derived from ethylene and units derived from one or more of alpha mono-olefins. Such C₃-C₁₂α-olefins include, but are not limited to, substituted or unsubstituted C₃to C₁₂alpha olefins such as propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecane, and isomers thereof. When present, comonomers can be present in amounts up to 20 wt %, 15 wt %, 10 wt %, or 5 wt %.
Such ethylene homopolymers and/or copolymers can be produced in a suspension, solution, slurry, or gas phase process, using known equipment and reaction conditions. In some embodiments, polymerization temperatures range from about 0° C. to about 300° C. at atmospheric, subatmospheric, or superatmospheric pressures.
Slurry or solution polymerization systems can utilize subatmospheric or superatmospheric pressures and temperatures in the range of about 40° C. to about 300° C. An exemplary liquid phase polymerization system is described in U.S. Pat. No. 3,324,095, the disclosure of which is fully incorporated by reference herein. Liquid phase polymerization systems generally comprise a reactor to which olefin monomer and catalyst composition are added, and which contains a liquid reaction medium for dissolving or suspending the polyolefin. The liquid reaction medium may consist of the bulk liquid monomer or an inert liquid hydrocarbon that is nonreactive under the polymerization conditions employed. Although such an inert liquid hydrocarbon need not function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as solvent for the monomers employed in the polymerization. Among the inert liquid hydrocarbons suitable for this purpose are isopentane, hexane, cyclohexane, heptane, benzene, toluene, and the like. Reactive contact between the olefin monomer and the catalyst composition should be maintained by constant stirring or agitation. The reaction medium containing the olefin polymer product and unreacted olefin monomer is withdrawn from the reactor continuously. The olefin polymer product is separated, and the unreacted olefin monomer and liquid reaction medium are recycled into the reactor.
Gas phase polymerization systems can utilize superatmospheric pressures in the range of from 1 psig (6.9 kPag) to 1,000 psig (6.9 MPag), 50 psig (344 kPag) to 400 psig (2.8 MPag), or 100 psig (689 kPag) to 300 psig (2.1 MPag), and temperatures in the range of from 30° C. to 130° C. or 65° C. to 110° C. Gas phase polymerization systems can be stirred or fluidized bed systems. In some embodiments, a gas phase, fluidized bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluidized bed reactor under reaction conditions and in the presence of catalyst composition at a velocity sufficient to maintain a bed of solid particles in a suspended condition. A stream containing unreacted monomer is withdrawn from the reactor continuously, compressed, cooled, optionally partially or fully condensed, and recycled into the reactor. Product is withdrawn from the reactor and make-up monomer is added to the recycle stream. As desired for temperature control of the polymerization system, any gas inert to the catalyst composition and reactants may also be present in the gas stream.
In some embodiments, a Ziegler-Natta (ZN) catalyst is used. Such catalysts are based on a Group IVB transition metal compound and an organoaluminum compound (co-catalyst). Such transition metals, include, but not limited to, Ti, Zr, and Hf. Nonlimiting examples of ZN catalyst systems include TiCl₄+Et₃Al and TiCl₃+AlEt₂Cl. Such HDPE homopolymers and/or copolymers have some long-chain branching and a density in the range of from 0.940 g/cm³to 0.970 g/cm³.
Virgin HDPE can be characterized by having:

Melting Extruder
The polyolefin blend component and optional antioxidants and/or other components are fed to a third extruder or mixer wherein the blend is subjected to melting conditions. Melting conditions are implemented in the meting zone of the third extruder or mixer and are tailored for mixtures of specific polyolefins and optionally additives. Temperature, pressure, and shear force conditions are implemented in the second extruder or mixer sufficient to provide intimate mixing of the processed HDPE recyclate and the virgin HDPE and optionally additives to produce a substantially homogeneous polymer blend of the processed HDPE recyclate and the virgin HDPE. In some embodiments, melting conditions comprise a temperature in the melting zone in the range of from 130° C. to 250° C. or from 150° C. to 230° C.
Compounding Extruder
Processed HDPE recyclate and a polyolefin blend component are fed to a second extruder or mixer wherein the blend is subjected to compounding conditions. Compounding conditions are implemented in the compounding zone of the second extruder or mixer and are tailored for mixtures of specific polyolefins and optionally additives. Temperature, pressure, and shear force conditions are implemented in the second extruder or mixer sufficient to provide intimate mixing of the processed HDPE recyclate and the virgin HDPE and optionally additives to produce a substantially homogeneous polymer blend of the processed HDPE recyclate and the virgin HDPE. In some embodiments, compounding conditions comprise a temperature in the compounding zone of less than or equal to 300° C., less than or equal to 250° C. or less than or equal to 200° C. In some embodiments, temperatures in the compounding zone can be in the range of from 125° C. to 195° C., from 130° C. to 180° C., or from 135° C. to 165° C.
Blends of Processed HDPE Recyclate and a Polyolefin Blend Component
In some embodiments, the blend comprises from 5 wt. % to 90 wt. %, 10 wt. % to 80 wt. %, 15 wt. % to 70 wt. %, 20 wt. % to 60 wt. %, or 25 wt. % to 50 wt. %, of a processed HDPE recyclate and from 10 wt. % to 95 wt. %, 20 wt. % to 90 wt. %, 30 wt. % to 85 wt. %, 40 wt. % to 80 wt. %, or 50 wt. % to 75 wt. %, of a polyolefin blend component, respectively, wherein all weight percentages are based on the combined weight of the polymer blend. In some embodiments, the virgin HDPE is visbroken. Such visbreaking of virgin HDPE can be thermal visbreaking and/or peroxidation visbreaking. In some embodiments, such visbreaking conditions for a virgin HDPE consist of thermal visbreaking at a temperature above the melting point of the HDPE, greater than or equal to 300° C., or in the range of from 320° C. to 400° C., in the absence of or substantially in the absence of oxygen.
In some embodiments, the blends of processed HDPE recyclate and a polyolefin blend component, in combination with or independently of the blend ratios in the preceding paragraph, comprise a bimodal polymer, wherein the processed HDPE recyclate product has a weight average molecular weight (“M_w3”), the polyolefin blend component has a weight average molecular weight (“M_w4”); and M_w3/M_w4is either less than or equal to 0.9,0.8, 0.7, 0.6, or 0.5, or alternatively is greater than or equal to 1.1, 1.25, 1.5, 1.75, or 2.0.

Certain Embodiments

In some embodiments, a method for processing high density polyethylene (HDPE) recyclate comprises providing a HDPE recyclate feedstock, adding the HDPE recyclate to a first extruder to produce a first HDPE recyclate melt, and subjecting the first HDPE recyclate melt to visbreaking conditions to produce a second HDPE recyclate melt. The HDPE recyclate feedstock has: a first density in the range of from 0.940 g/cm³to 0.970 g/cm³; a first melt index (2.16 kg, 190° C.) less than or equal to 1.0 g/10 min; a first molecular weight distribution (M_w/M_n) greater than or equal to 10, greater than or equal to 15, or greater than or equal to 20; a first weight average molecular weight (“M_w1”) greater than or equal to 100,000 daltons, greater than or equal to 150,000 daltons, greater than or equal to 200,000 daltons, or greater than or equal to 250,000 daltons, and/or less than or equal to 600,000 daltons, less than or equal to 500,000 daltons, less than or equal to 400,000 daltons, or less than or equal to 300,000 daltons; and a first melt elasticity (“ER”) greater than or equal to 1.0, greater than or equal to 2.0, or greater than or equal to 3.0 and/or less than or equal to 8.0, less than or equal to 7.0, or less than or equal to 6.0.
The second HDPE recyclate melt has: a second density, wherein the ratio of the second density to the first density is greater than or equal to 1.0; a second melt index, wherein the ratio of the second melt index to the first melt index is greater than or equal to 5.0, greater than or equal to 50, or greater than or equal to 100, and/or the melt index of the processed HDPE recyclate is greater than or equal to 5.0 g/10 min. or greater than or equal to 10.0 g/10 min.; a second molecular weight distribution, wherein the ratio of second molecular weight distribution to the first molecular weight distribution is less than or equal to 0.50, and/or the molecular weight distribution of the processed HDPE recyclate is less than or equal to 40; a second weight average molecular weight (“M_w2”), wherein M_w2/M_w1is in the range of from 0.10 to 0.70, from 0.15 to 0.60, or from 0.20 to 0.50; and a second melt elasticity, wherein the ratio of the second melt elasticity to the first melt elasticity is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30, and/or the second melt elasticity is less than or equal to 2.0, less than or equal to 1.5, or less than or equal to 1.0, and/or greater than or equal to 0.10, greater than or equal to 0.20, or greater than or equal to 0.30.
In further embodiments, the method is additionally characterized by one or more of the following:

- a) the HDPE recyclate feedstock comprises post-consumer recycled waste, post-industrial recycled waste, or a combination thereof;
- b) the visbreaking conditions consist of thermal visbreaking, which in some instances is performed at a temperature greater than or equal to 300° C., or at a temperature in the range of from 320° C. to 400° C.;
- c) the first HDPE recyclate melt is further subjected to devolatilization conditions to produce the second HDPE recyclate melt, wherein the HDPE recyclate feedstock has a first volatile organic compound content, the first HDPE recyclate melt has a second volatile organic compound content, and the ratio of the second volatile organic compound content to the first volatile organic compound content is less than or equal to 0.9, and in some instances, the devolatilization conditions further comprise:
  - i) injection and withdrawal of a scavenging gas, and in some instances the scavenging gas comprises nitrogen, carbon-dioxide, water, or combinations thereof;
  - ii) vent conditions, vacuum conditions, or a combination thereof;
- d) the second HDPE recyclate melt is passed through a melt filter;
- e) an antioxidant agent is added to the first extruder; and
- f) the HDPE recyclate feedstock has a first high load melt index (21.6 kg, 190° C.), the second HDPE recyclate melt has a second high load melt index, and the ratio of the second high load melt index to the first high load melt index is greater than or equal to 5.0, greater than or equal to 20, or greater than or equal to 30;
- g) the HDPE recyclate feedstock has a first melt index ratio (I₂₁/I₂), the second HDPE recyclate melt has a second melt index ratio, and the ratio of the second melt index ratio to the first melt index ratio is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30;
- h) the HDPE recyclate feedstock has a first long chain branching parameter (g′), the second HDPE recyclate melt has a second g′, and the ratio of the second g′ to the first g′ is in the range from 0.70 to 0.99, from 0.80 to 0.98, or from 0.85 to 0.97, and/or the ratio of the g′ of processed HDPE recyclate to the g′ of the HDPE recyclate feedstock is less than or equal to 1.0;
- i) the HDPE recyclate feedstock has a first long chain branching index (“LCBI”) greater than or equal to 0.30, and the processed HDPE recyclate has a LCBI less than or equal to 0.20;
- j) the HDPE recyclate feedstock has an overall polydispersity measure (“PDR”), the second HDPE recyclate melt has a second PDR, and the ratio of the second PDR to the first PDR is less than or equal to 0.40, less than or equal to 0.30, or less than or equal to 0.20;
- k) the HDPE recyclate feedstock has a first complex viscosity ratio (η*_0.1/η*₁₀₀), the second HDPE recyclate melt has a complex viscosity ratio, and the ratio of the second complex viscosity ratio to the first complex viscosity ratio is less than or equal to 0.50, less than or equal to 0.40, or less than or equal to 0.30, and/or the second complex viscosity ratio is less than or equal to 10, less than or equal to 8.0, or less than or equal to 6.0, and η*_0.1is the complex viscosity at 0.1 rad/sec and η*₁₀₀is the complex viscosity at 100 rad/sec, both at a temperature of 190° C.; and
- l) the HDPE recyclate feedstock has a first intrinsic viscosity [η], the second HDPE recyclate melt has an intrinsic viscosity, and the ratio of the second intrinsic viscosity to the first intrinsic viscosity is less than or equal to 0.90, less than or equal to 0.70, or less than or equal to 0.50.

In some embodiments, the foregoing method further comprises forming a HDPE recyclate product by withdrawal of the second HDPE recyclate melt from the first extruder for further processing or pelletizing of the second HDPE recyclate melt.
In further embodiments of the foregoing method, the HDPE recyclate product and a first polyolefin blend component are added to a second extruder, and compounding conditions are effected in the second extruder to form a polyolefin product comprising the melt-blended mixture of the processed HDPE recyclate product and the first polyolefin blend component. In some embodiments, such compounding condition include a temperature less than or equal to 300° C. In some embodiments, the first polyolefin blend component comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof. In yet further embodiments: the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof; and the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof. In some embodiments, the first polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof.
In further embodiments of the foregoing method, the HDPE recyclate product: is added in an amount in the range of from 5 wt. % to 90 wt. %, or from 20 wt. % to 60 wt. %, based on the combined weight of the HDPE recyclate product and the first polyolefin blend component; and/or the HDPE recyclate product has third weight average molecular weight (“M_w3”), the first polyolefin blend component has a fourth weight average molecular weight (“M_w4”), and the M_w3/M_w3is either less than or equal to 0.8 or greater than or equal to 1.25.
In further embodiments of the foregoing method, the first polyolefin blend component is a first virgin HDPE comprising a polymer product prepared in a first polymerization apparatus, wherein in some instances, the polymer product was subjected to a visbreaking process after polymerization, and in some embodiments, the visbreaking process comprises thermal visbreaking, peroxide visbreaking, or a combination thereof.
In further embodiments of the foregoing method, the first polyolefin blend component comprises a polyolefin powder prepared in a first polymerization apparatus.
In further embodiments of the foregoing method, an antioxidant agent is added to the second extruder.
In further embodiments of the foregoing method, the method further comprises: adding a second polyolefin blend component to a third extruder; effecting melt conditions in the third extruder to produce a second polyolefin blend component melt; and withdrawing the second polyolefin blend component melt as the first polyolefin blend component.
In further embodiments of the foregoing method, the second polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof.
In further embodiments of the foregoing method, the second polyolefin blend component is subjected to a visbreaking process after polymerization, wherein in some instances, the visbreaking process consists of thermal visbreaking.
In further embodiments of the foregoing method, the second polyolefin blend component comprises polyethylene powder prepared in a second polymerization apparatus and/or polyethylene pellets.
In further embodiments of the foregoing method, the first and/or second polymerization apparatus each comprise two more polymerization reactors and/or two or more polymerization zones within a polymerization reactor.
In further embodiments of the foregoing method, the first and/or second polymerization apparatuses each comprise two or more gas phase fluidized-bed reactors in series, two or more slurry phase reactors in series, or a gas phase fluidized-bed reactor in series with a multizone circulation reactor.
In further embodiments of the foregoing method, an antioxidant agent is added to the third extruder.
In some embodiments, a composition comprise a polymer blend of a first polymer and a second polymer. The first polymer is a first processed HDPE recyclate and is present in an amount in the range of from 5 wt. % to 90 wt. %. The second polymer is a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof, and is present in an amount in the range of from 10 wt. % to 95 wt. %. All weight percentages are based on the combined weight of the first and second polymers.
In further embodiments of the foregoing composition: the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof; the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof; and the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof.
In further embodiments of the foregoing composition, processed means subjected to thermal visbreaking or subjected to thermal visbreaking and devolatilization. In some embodiments, a blend comprises a visbroken HDPE, having a first I₂and a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof, having a second I₂, wherein:
$\log ({(I_{2})}_{blend}) = \sum_{i = 1}^{n} (w_{i} \times \log ({(I_{2})}_{i}))$
(I₂)_blendis the target melt index of the final blend product;
n is the number of components in the blend; and
i is the i-th component of an n-component blend.
The following examples illustrate the invention; however, those skilled in the art will recognize numerous variations within the spirit of the invention and scope of the claims. To facilitate a better understanding of the present invention, the following examples of preferred embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES

The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.
The following examples use commercial HDPE compositions having a low melt index as proxies for HDPE recyclate feedstocks. After processing, as described herein, the visbroken low melt index HDPEs, either alone or in blends with other components, are compared to higher melt index virgin HDPEs.

Test Methods

Densities are determined in accordance with ASTM D-4703 and ASTM D-1505/ISO-1183.
High load melt index (“I₂₁”) was determined by ASTM D-1238-F (190° C./21.6 kg).
Shear rheological measurements are performed in accord with ASTM 4440-95a, which characterize dynamic viscoelastic properties (storage modulus, G′, loss modulus, G″ and complex viscosity, η*, as a function of oscillation frequency, ω). A rotational rheometer (TA Instruments) is used for the rheological measurements. A 25 mm parallel-plate fixture was utilized. Samples were compression molded in disks (˜29 mm diameter and ˜1.3 mm thickness) using a hot press at 190 ° C. An oscillatory frequency sweep experiment (from 398.1 rad/s to 0.0251 rad/s) was applied at 190° C. The applied strain amplitude is ˜10% and the operating gap is set at 1 mm. Nitrogen flow was applied in the sample chamber to minimize thermal oxidation during the measurement.
Melt elasticity (“ER”) is determined as discussed in R. Shroff and H. Mavridis, “New Measures of Polydispersity from Rheological Data on Polymer Melts,” J. Applied Polymer Science 57 (1995) 1605. See also U.S. Pat. Nos. 7,238,754, 6,171,993 and 5,534,472 (col. 10, lines 20-30), the teachings of which are incorporated herein by reference. Thus, storage modulus (G′) and loss modulus (G″) are measured. The nine lowest frequency points are used (five points per frequency decade) and a linear equation is fitted by least-squares regression to log G′ versus log G″. ER is then calculated from:
ER=(1.781×10⁻³)×G′
at a value of G″=5,000 dyn/cm². The same procedure and equation for the ER calculation was used for both linear and long-chain-branched polyolefins.
PDR, or “Overall Polydispersity Measure” is determined as discussed in R. Shroff and H. Mavridis, “New Measures of Polydispersity from Rheological Data on Polymer Melts,” J. Applied Polymer Science 57 (1995) 1605, equation 27 on page 1619, with G*_ref,1=1.95*10⁴dyn/cm²and log₁₀(G*_ref,1)=2. The same procedure and equation for the PDR calculation was used for both linear and long-chain-branched polyolefins.
The ratio η*_0.1/η*₁₀₀of complex viscosities, η*_0.1, at a frequency of 0.1 rad/sec and η*₁₀₀, at a frequency of 100 rad/sec, is used as an additional measure of shear sensitivity and thus rheological breadth, or polydispersity, of the polymer melt.
Melt index (“I₂”) was determined by ASTM D-1238-E (190° C./2.16 kg).
Molecular weight distribution (“MWD”) as well as the molecular weight averages (number-average molecular weight, M_n, weight-average molecular weight, M_w, and z-average molecular weight, M_z) are determined using a high temperature Polymer Char gel permeation chromatography (“GPC”), also referred to as size exclusion chromatography (“SEC”), equipped with a filter-based infrared detector, IR5, a four-capillary differential bridge viscometer, and a Wyatt 18-angle light scattering detector. M_n, M_w, M_z, MWD, and short chain branching (SCB) profiles are reported using the IR detector, whereas long chain branch parameter, g′, is determined using the combination of viscometer and IR detector at 145° C. Three Agilent PLgel Olexis GPC columns are used at 145° C. for the polymer fractionation based on the hydrodynamic size in 1,2,4-trichlorobenzene (TCB) with 300 ppm antioxidant butylated hydroxytoluene (BHT) as the mobile phase. 16 mg polymer is weighted in a 10 mL vial and sealed for the GPC measurement. The dissolution process is obtained automatically (in 8 ml TCB) at 160° C. for a period of 1 hour with continuous shaking in an Agilent autosampler. 20 μL Heptane was also injected in the vial during the dissolution process as the flow marker. After the dissolution process, 200 μL solution was injected in the GPC column. The GPC columns are calibrated based on twelve monodispersed polystyrene (PS) standards (provided by PSS) ranging from 578 g/mole to 3,510,000 g/mole. The comonomer compositions (or SCB profiles) are reported based on different calibration profiles obtained using a series of relatively narrow polyethylene (polyethylene with 1-hexene and 1-octene comonomer were provided by Polymer Char, and polyethylene with 1-butene were synthesized internally) with known values of CH₃/1000 total carbon, determined by an established solution NMR technique. GPC one software was used to analyze the data. The long chain branch parameter, g′, is determined by the equation:
g′=[η]/[η]_lin
where, [η] is the average intrinsic viscosity of the polymer that is derived by summation of the slices over the GPC profiles as follows:
$[η] = \frac{Σ {c_{i} [η]}_{i}}{Σ c_{i}}$
where c_iis the concentration of a particular slice obtained from IR detector, and [η]_iis the intrinsic viscosity of the slice measured from the viscometer detector. [η]_linis obtained from the IR detector using Mark-Houwink equation ([η]_lin=ΣKM_i ^α) for a linear high density polyethylene, where M_iis the viscosity-average molecular weight for a reference linear polyethylene, K and α are Mark-Houwink constants for a linear polymer, which are K=0.000374, α=0.7265 for a linear polyethylene and K=0.00041, α=0.6570 for a linear polypropylene.
Volatile Organic Compounds (“VOC”) is measured by pyrolysis-gas chromatography/mass spectrometry (“P-GC/MS”) in parts per billion (ppb), parts per million (ppm), or and micrograms per cubic meter (μg/m³).
Zero-shear viscosity, η₀, is determined using the Sabia equation fit of dynamic complex viscosity versus radian frequency, as described in of Shroff & Mavridis, (1999) “A Long Chain Branching Index for Essentially Linear Polyethylenes”, Macromolecules, 32, 8454-8464 (with focus on Appendix B), the disclosure of which is fully incorporated by reference herein in its entirety.
LCBI is determined using equation 13:
$\begin{matrix} L C B I = \frac{η_{0}^{0.179}}{[η]} \frac{1}{4.8} - 1 & (13) \end{matrix}$
Equation 13 and its application are described in of Shroff & Mavridis, (1999) “A Long Chain Branching Index for Essentially Linear Polyethylenes”, Macromolecules, 32, 8454-8464, the disclosure of which is fully incorporated by reference herein in its entirety.
Long Chain Branching frequency, characterized by the ratio of Long Chain Branches per million carbon atoms, or LCB/10⁶C, was determined by the method of Janzen & Colby (J. Janzen and R. H. Colby, “Diagnosing long-chain branching in polyethylenes”, Journal of Molecular Structure, Vol 485-486, 10 Aug. 1999, Pages 569-583), using eqs. (2-3) and the constants of Table 2 in the above reference. Specifically, the zero-shear viscosity at 190° C., η*₀, is determined by extrapolation of the complex viscosity data via the Sabia equation, as described separately. The weight-average-molecular weight, Mw, is determined via GPC. With these two parameters and the methodology of Janzen & Colby, the Long Chain Branching frequency, LCB/10⁶C, can be determined numerically such that all 3 parameters (η₀, M_wand LCB/10⁶C) satisfy eqs. (2-3) in the above reference. The Janzen & Colby methodology predicts that the ratio, η₀/η_0,linearof the zero-shear viscosity of the material, over the zero-shear viscosity of a perfectly linear polymer (LCB/10⁶C=0) of the same average molecular weight, exhibits a maximum at a certain value of LCB/10⁶C and therefore for every value of η₀/η_0,linear, there exist two levels, or values, of LCB/10⁶C that such ratio is possible. For the purposes of the present calculations, the lowermost value of LCB/10⁶C was always selected at the given ratio of η*₀/η*_0,linear.

Raw Materials

Raw materials used herein are shown in Table 1, below.

TABLE 1

		Polymer	MFR	Density
Composition**	Use in Examples	Label	(g/10 min)*	(g/cc)

Alathon ™	Proxy for HDPE	P1	0.06	0.949
L5005 HDPE	recyclate feedstock

*190° C./2.16 kg
**All materials available from LyondellBasell Industries NV

Examples 1-3

Examples 1 and 2 in TABLE 2 show the results of visbreaking a HDPE resin. P1 is believed to fairly represent an HDPE recyclate feedstock. Prior to processing, P1 (HDPE recyclate feedstock proxy) has a nominal density of 0.949 g/cm³and melt index I₂of 0.06 g/10 min. Example 1 results in TABLE 2 show a number of other properties of P1.
Example 2 was prepared by visbreaking a portion of P1. Visbreaking was performed by feeding P1 into a Werner and Pfleiderer ZSK40 twin screw extruder at a feed rate of 50 pounds per hour, a screw speed of 600 rpm and with a target temperature profile of 200/250/325/325/325/325/325/325/325° C. (from feed inlet to die). The extrudate was comminuted to pellets.
Example 2 shows that melt index I₂of P1 is increased by visbreaking by a factor of 252, while density increased only nominally, and high load melt index I₂₁of P1 is increased by visbreaking by a factor of 45, thus producing a reduction of melt index ratio (I₂₁/I₂) from 167 to 30. Melt elasticity (“ER”) and overall polydispersity measure (“PDR”) are reduced by about 79% and 78%, respectively.
As compared to P1, complex viscosities η₀, η*_0.1, and η*₁₀₀, are all reduced by orders of magnitude, and complex viscosity ratio η*_0.1/η*₁₀₀is reduced by nearly 95%, in Example 2. Intrinsic viscosity [η] is reduced by 38% in Example 2.
As compared to P1, number average molecular weight (M_n) is reduced by 11%, weight average molecular weight (M_w) is reduced by 74%, and Z-average molecular weight (M_z) is reduced by 82% in Example 2. Molecular weight distribution (M_w/M_n) is reduced by 70% and molecular weight ratio (M_z/M_w) is decreased by 82% in Example 2.

	TABLE 2

	Example

Parameter

Units

	1	2

Polymer Label	—	P1	P1-vb
I₂	g/10 min	0.056	14.2
I₂-vb/I₂-original	—	—	252
Density	g/cc	0.950	0.954
I₂₁	g/10 min	9.4	421
I₂₁-vb/I₂₁-original	—	—	45
MIR (I₂₁/I₂)	—	167	30
ER	—	3.16	0.66
ER-vb/ER-original	%	—	0.21
PDR	—	26.7	3.3
PDR-vb/PDR-original	%	—	0.12
η₀	poise	5.89 × 10⁷	7.40 × 10⁴
η*_0.1	poise	8.93 × 10⁵	7.06 × 10⁴
η*₁₀₀	poise	2.12 × 10⁴	3.27 × 10³
η_0.1/η₁₀₀	—	42.1	2.2
Vinyl/1000 C (NMR)	—	—	—
M_n	daltons	9,911	8,855
M_w	daltons	267,600	69,600
M_z	daltons	1,395,800	247,700
MWD (M_w/M_n)	—	27	7.9
Mz/M_w	—	5.2	3.6
M_w-vb/M_w-original	—	—	0.26
M_z-vb/M_z-original	—	—	0.18
(M_z/M_w)-vb/(M_z/M_w)-orig.	—	—	0.68
Intrinsic Viscosity [η]	dl/bg	2.53	0.96
g′ (long chain branching	—	0.98	0.91
parameter)
LCBI	—	0.34	0.07
LCB/10⁶C	—	6	21
SPE	hp · hr/lb	—	0.354
SPE	kW · hr/kg	—	0.581

vb = visbroken

Dynamic oscillatory data generated based on analysis of samples of P1 and P1-vb are shown in TABLE 3 below. The data in TABLE 3 show that complex viscosity decreases as frequency increases for both P1 and P1-vb. TABLE 3 further shows that visbreaking P1 results in a lower complex viscosity (η*) for P1-vb for all tested values of frequency. Additionally, the difference in complex viscosity between P1 and P1-vb decreases as frequency increase. Applicant believes this to show, without wishing to be bound by any particular theory, that visbreaking has a bigger impact, that is more chain scission, on higher molecular weight chains in LLDPE and further indicates a narrower MWD (M_w/M_n) for P1-vb as compared to P1. FIG. 4 a comparison of curves generated for Examples 1 and 2 from the data in TABLE 3. The overlaid graphs show the log of complex viscosity (η*) in poise as a function of the log of the oscillatory frequency in radians per second.

TABLE 3

Oscillation	Example 1 (P1)	Example 2 (P2)

Freq.	Log	η*		η*
(rad/sec)	(freq.)	(poise)	Log(η*)	(poise)	Log η*)

0.0251	−1.60	1,430,000	6.16	—	—
0.0398	−1.40	1,230,000	6.09	7,080	3.85
0.0631	−1.20	1,050,000	6.02	7,070	3.85
0.100	−1.00	893,000	5.95	7,060	3.85
0.158	−0.80	752,000	5.88	7,020	3.85
0.251	−0.60	628,000	5.80	6,980	3.84
0.398	−0.40	518,000	5.71	6,910	3.84
0.631	−0.20	423,000	5.63	6,810	3.83
1.00	0.00	342,000	5.53	6,670	3.82
1.58	0.20	271,000	5.43	6,500	3.81
2.51	0.40	214,000	5.33	6,280	3.80
3.98	0.60	167,000	5.22	6,030	3.78
6.31	0.80	128,000	5.11	5,730	3.76
10.0	1.00	97,500	4.99	5,400	3.73
15.8	1.20	73,400	4.87	5,020	3.70
25.1	1.40	54,500	4.74	4,610	3.66
39.8	1.60	40,200	4.60	4,180	3.62
63.1	1.80	29,300	4.47	3,710	3.57
100	2.00	21,200	4.33	3,270	3.51
158	2.20	15,200	4.18	2,850	3.45
251	2.40	10,800	4.03	2,470	3.39
398	2.60	7,590	3.88	2,080	3.32

FIG. 5 a comparison of molecular weight curves generated for Examples 1 and 2. The overlaid graphs demonstrate both the reduction in molecular weight and narrowing of molecular weight distribution accomplished through visbreaking.
For the sake of brevity, only certain ranges are explicitly disclosed herein. However, in addition to recited ranges, any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the processes, machines, film structures, composition of layers, means, methods, and/or steps described in the specification. As one of the ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, film structures, composition of layers, means, methods, and/or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein, may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, film structures, composition of layers, means, methods, and/or steps.

Claims

What is claimed is:

1. A method for processing high density polyethylene (HDPE) recyclate comprising:

a. providing a HDPE recyclate feedstock having:

i) a first density in the range of from 0.940 g/cm³to 0.970 g/cm³;

ii) a first melt index (I₂) less than or equal to 1.0 g/10 min;

iii) a first molecular weight distribution (M_w/M_n) greater than 10;

iv) a first weight average molecular weight (“M_w1”) greater than or equal to 100,000 daltons; and

v) a first melt elasticity (“ER”) greater than or equal to 1.0;

b. adding the HDPE recyclate to a first extruder to produce a first HDPE recyclate melt; and

c. subjecting the first HDPE recyclate melt to visbreaking conditions to produce a second HDPE recyclate melt having:

i) a second density, wherein the ratio of the second density to the first density is greater than or equal to 1.0;

ii) a second melt index, wherein the ratio of the second melt index to the first melt index is greater than or equal to 5.0;

iii) a second molecular weight distribution, wherein the ratio of second molecular weight distribution to the first molecular weight distribution is less than or equal to 0.70;

iv) a second weight average molecular weight (“M_w2”), wherein M_w2/M_w1is in the range of from 0.10 to 0.70; and

v) a second melt elasticity, wherein the ratio of the second melt elasticity to the first melt elasticity is less than or equal to 0.50.

2. The method of claim 1, wherein the HDPE recyclate feedstock comprises post-consumer recycled waste, post-industrial recycled waste, or a combination thereof.

3. The method of claim 1, wherein the visbreaking conditions consist of thermal visbreaking.

4. The method of claim 3, wherein thermal visbreaking is performed at a temperature greater than or equal to 300° C.

5. The method of claim 1, further comprise further subjecting the first HDPE recyclate melt to devolatilization conditions to produce the second HDPE recyclate melt wherein:

the HDPE recyclate feedstock has a first volatile organic compound content;

the first HDPE recyclate melt has a second volatile organic compound content; and

the ratio of the second volatile organic compound content to the first volatile organic compound content is less than or equal to 0.9.

6. The method of claim 5, wherein devolatilization conditions comprise injection and withdrawal of a scavenging gas.

7. The method of claim 1, wherein the method is characterized by one or more of the following:

i) the HDPE recyclate feedstock has a first high load melt index (I₂₁), the second HDPE recyclate melt has a second high load melt index, and the ratio of the second high load melt index to the first high load melt index is greater than or equal to 5.0;

ii) the HDPE recyclate feedstock has a first melt index ratio (I₂₁/I₂), the second HDPE recyclate melt has a second melt index ratio, and the ratio of the second melt index ratio to the first melt index ratio is less than or equal to 0.50;

iii) the HDPE recyclate feedstock has a first long chain branching parameter (g′), the second HDPE recyclate melt has a second g′, and the ratio of the second g′ to the first g′ is less than to 1.0, and/or the first g′ is in the range from 0.70 to 0.99;

iv) the HDPE recyclate feedstock has a first long chain branching index (“LCBI”) greater than or equal to 0.30, and the second HDPE recyclate melt has a second LCBI”) less than or equal to 0.20;

v) the HDPE recyclate feedstock has a first overall polydispersity measure (“PDR”), the second HDPE recyclate melt has a second PDR, and the ratio of the second PDR to the first PDR is less than or equal to 0.40;

vi) the HDPE recyclate feedstock has a first complex viscosity ratio, the second HDPE recyclate melt has a second complex viscosity ratio, and the ratio of the second complex viscosity ratio to the first complex viscosity ratio is less than or equal to 0.20, and/or the second complex viscosity ratio is less than or equal to 10; and

vii) the HDPE recyclate feedstock and/or MDPE recyclate feedstock have a first intrinsic viscosity, the second HDPE recyclate melt and/or MDPE recyclate melt has a second intrinsic viscosity, and the ratio of the second intrinsic viscosity to the first intrinsic viscosity is less than or equal to 0.90.

8. The method of claim 1, wherein a HDPE recyclate product is formed by withdrawal of the second HDPE recyclate melt from the first extruder for further processing or pelletizing of the second HDPE recyclate melt.

9. The method of claim 8, further comprising:

adding the HDPE recyclate product and a first polyolefin blend component to a second extruder; and

effecting compounding conditions in the second extruder to form a polyolefin product comprising the melt-blended mixture of the processed HDPE recyclate product and the first polyolefin blend component.

10. The method of claim 9, wherein the first polyolefin blend component comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof.

11. The composition of claim 10, wherein:

a. the virgin polyolefin comprises a virgin LDPE, a virgin LLDPE, a virgin HDPE, a virgin MDPE, a virgin polypropylene, or a combination thereof;

b. the polyolefin recyclate feedstock comprises a LDPE recyclate feedstock, a LLDPE recyclate feedstock, a HDPE recyclate feedstock, a MDPE recyclate feedstock, a polypropylene recyclate feedstock, or a combination thereof; and

c. the processed polyolefin recyclate comprises a processed LDPE recyclate, a processed LLDPE recyclate, a second processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof.

12. The method of claim 11, wherein the first polyolefin blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof.

13. The method of claim 9, wherein the HDPE recyclate product is added in an amount in the range of from 5 wt. % to 90 wt. % based on the combined weight of the HDPE recyclate product and the first polyolefin blend component.

14. The method of claim 9, wherein the compounding conditions include a temperature less than or equal to 300° C.

15. The method of claim 9, further comprising:

adding a second polyolefin blend component to a third extruder;

effecting melt conditions in the third extruder to produce a second polyolefin blend component melt; and

withdrawing the second polyolefin blend component melt as the first polyolefin blend component.

16. The method of claim 15, wherein the second blend component comprises a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof.

17. A composition comprising a polymer blend of:

a. a first polymer, wherein the first polymer:

i) is a first processed HDPE recyclate; and

ii) is present in an amount in the range of from 5 wt. % to 90 wt. %; and

b. a second polymer, wherein the second polymer:

i) is a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof; and

ii) is present in an amount in the range of from 10 wt. % to 95 wt. %;

wherein all weight percentages are based on the combined weight of the first and second polymers.

18. The composition of claim 17, wherein:

19. The composition of claim 17, wherein processed means subjected to thermal visbreaking and optionally subjected to devolatilization.

20. A blend comprising:

a visbroken HDPE, having a first I₂; and

a virgin HDPE, a HDPE recyclate feedstock, a processed HDPE recyclate, or a combination thereof, having a second I₂;

wherein:

\log ({(I_{2})}_{blend}) = \sum_{i = 1}^{n} (w_{i} \times \log ({(I_{2})}_{i}))

(I₂)_blendis the target melt index of the final blend product;

n is the number of components in the blend; and

i is the i-th component of an n-component blend.