Method for modifying polymer recyclate and compositions therefrom

Abstract

Provided is a method for degrading a polyolefin recyclate. The method comprises introducing into a reaction zone a polyolefin recyclate having a first weight average molecular weight (Mw1). The polyolefin recyclate is exposed to ionizing radiation in an oxygen-deprived atmosphere to form a first reaction product comprising free-radical polyolefin recyclate chain segments. The first reaction product is subjected to second reaction conditions sufficient to deactivate the free radicals. The resulting degraded polyolefin recyclate has a second weight average molecular weight (Mw2), wherein Mw2 is less than Mw1.

Description

METHOD FOR MODIFYING POLYMER RECYCLATE AND COMPOSITIONS THEREFROM FIELD OF THE INVENTION

[0001] The present disclosure relates to radiation visbroken polymer recyclates, methods for making, and articles made therefrom. BACKGROUND OF THE INVENTION

[0002] There has been much research and development to improve the processability of post- consumer recycled (PCR) resins, either alone or as a blend component with virgin polymers. Likewise, there has also been much effort by industry to develop end-use applications that incorporate PCR resins and have quality and / or performance similar or equal to corresponding end-use applications fabricated from virgin polymers. Existing and new environmental regulations provide continued motivation to develop suitable commercial uses of PCR resins while reducing the amount of waste plastics to landfill. Successful development of these commercial pathways will create demand for products incorporating PCR resins.

[0003] Plastic waste is typically segregated by polymer type. Recyclates of polypropylene (PP) and high density polyethylene (HDPE) typically have a low melt flow rate or a low melt index, respectively. Such high melt viscosities make these polyolefin recyclates difficult to process and limit the end-use applications in which they can be used directly. Another limitation for the use of recycled polyolefins is poor organoleptic properties, such as, but not limited to, the presence of unpleasant odors, taste, and / or unintended color coming from volatile organic compounds which may have been absorbed in these polymers during their usage.

[0004] It would be desirable if such PCR resins could be treated to reduce their molecular weights to improve their processability and / or compatibility with virgin polymers. It would further be desirable if such treatment methods could improve organoleptic properties of PCR resins. Ideally, such treatment could be implemented with commonly used equipment and familiar techniques to provide treated PCR resins having utility in a broad range of end-use applications. SUMMARY OF THE INVENTION

[0005] The present disclosure relates to a method for degrading a polymer recyclate, wherein the polymer recyclate comprises a polyolefin. The method comprises introducing into a reaction zone a polyolefin recyclate having a first weight average molecular weight (Mw1). The polyolefin recyclate is subjected to first reaction conditions comprising exposure to a dose of ionizing radiation in an atmosphere, having an active oxygen content of less than or equal to 15%, to form a first reaction product comprising free-radical polyolefin recyclate chain segments. The dose of ionizing radiation is sufficient for free-radical chain scission of an amorphous content of thepolyolefin recyclate to occur but insufficient for gelation to occur. The first reaction product is subjected to second reaction conditions sufficient to deactivate the free radicals. A degraded polyolefin recyclate having a second weight average molecular weight (Mw2) is recovered, wherein Mw2is less than Mw1.

[0006] The foregoing has outlined rather broadly the features and technical advantages of the 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 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 processes 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. DETAILED DESCRIPTION OF THE INVENTION

[0007] 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.

[0008] 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.

[0009] 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

[0010] As used herein, “HDPE” 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.

[0011] As used herein, “LDPE” means ethylene homopolymers and / or 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.

[0012] As used herein, “LLDPE” 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.

[0013] As used herein, “MDPE” 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.

[0014] As used herein, “olefin” and alternatively referred to as “alkene,” is a linear, branched, or cyclic compound of carbon and hydrogen having at least one double bond.

[0015] As used herein, “oligomer” means a polymer consisting of only a few monomer units such as a dimer, trimer, tetramer, etc., or their mixtures, wherein the upper limit of repeating units in an oligomer is less than one hundred, more typically less than 40. In some embodiments, a polypropylene oligomer has a molecular weight of less than or equal to 4,300 Daltons. In some embodiments, a polyethylene oligomer has a molecular weight of less than or equal to 2,000 Daltons.

[0016] As used herein, “organoleptic properties” refers to one or more sensory properties related to a polymer product, including one or more of appearance, flavor, aroma, texture, and sound. In particular, appearance can relate to any unintended coloration of the polymer product. Flavor can relate to any unintended alteration of the taste of a food or liquid exposed to a polymer product. Aroma can relate to any unintended alteration of the smell of a food or liquid exposed to a polymer product and / or any unintended odor of the polymer product itself.

[0017] As used herein, “polymer recyclate” means post-consumer recycled (“PCR”) polymer and / or post-industrial recycled (“PIR”) polymer. Polymer 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.

[0018] As used herein, “polyolefin” in some embodiments is a type of polymer with the general formula (CH2CHR)nwhere R is an alkyl group, including, but not limited to LDPE, LLDPE, MDPE, HDPE, and PP. PP consists of, but is not limited to, propylene homopolymers, random copolymer, impact (heterophasic or block) copolymers and compounds thereof.

[0019] As used herein, “primary antioxidants” means compounds which function essentially as free radical terminators or scavengers. Primary antioxidants react rapidly with peroxy and alkoxy radicals. The majority of primary antioxidants for polymers are sterically hindered phenols. “Secondary antioxidants” means compounds which function essentially as peroxide decomposers which react to deactivate peroxides and their derivates and are typically phosphites or derivatives thereof.

[0020] As used herein, “processability” refers to how well a polymer composition can be formed into a film (cast, blown, water quenched or mono or biaxially oriented) of commercial quality or molded by injection, compression or rotational molding or extruded into a fiber, sheet, coating, corrugated board, profile or thermoformed or other form into an article of commercial quality at commercially acceptable rates using the equipment and conditions.

[0021] As used herein, “virgin” with respect to HDPE and / or other polymers, means pre- consumer polymers. Pre-consumer polymers are obtained directly or indirectly from petrochemical, bio-based renewable and advanced chemical recycled polymer recyclate 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, devolatization, oligomer removal, steam treatment, compounding and / or other processing completed before the product reaches the end-use consumer. In some embodiments, virgin HDPE may have a single heat history. In some embodiments, a virgin HDPE has more than one heat history. In some embodiments, a virgin HDPE comprises no additives. In some embodiments, a virgin HDPE comprises additives.

[0022] As used herein, “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 micrograms per cubic meter (µg / m3).

[0023] In the present description, the terms “monomer” and “comonomer” are used interchangeably. The terms mean any compound with a polymerizable moiety that is added to a reactor in order to produce a polymer. In those instances in which a polymer is described as comprising one or more monomers, e.g., a polymer comprising propylene and ethylene, the polymer, of course, comprises units derived from the monomers, e.g., —CH2—CH2—, and not themonomer itself, e.g., CH2═CH2. For example, when a copolymer is described as having an “ethylene” content of 35 wt.% to 55 wt.%, it is understood that the mer unit in the copolymer is derived from ethylene in the polymerization reaction and the derived units are present at 35 wt.% to 55 wt.%, based upon the weight of the copolymer.

[0024] The following abbreviations are used herein: ABBREVIATION TERM EAA Copolymer of ethylene with acrylic acid EAO Copolymers of ethylene with at least one alpha-olefin EMAA Copolymer of ethylene with methacrylic acid EVA Copolymer of ethylene with vinyl acetate HDPE High density polyethylene LDPE Low density polyehtylene LLDPE Linear low density polyethylene MDPE Medium density polyethylene PA Polyamides, such as nylon PC Polycarbonate PE Polyethylene (an ethylene homopolymer or copolymer of a major portion of ethylene with one or more alpha-olefins and / or one or more polar comonomers) PP Polypropylene homopolymer or copolymer PS Polystyrene wt% weight percent PB or PB1 Polybutylene

[0025] It is noted that in this disclosure and particularly in the claims and / or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the disclosure. Polymer Recyclate

[0026] The method disclosed herein reduces the molecular weight and the molecular weight distribution of polymer recyclates by radiation visbreaking. The polymer recyclate comprises a polyolefin having a mixture of high molecular weight straight (linear) and branched molecules which are visbroken into smaller polymer chain segments. In some embodiments, the polyolefin recyclate has a crystallinity content of at least 5%, at least 10%, or at least 15%.

[0027] In some embodiments, the polyolefin recyclate is a polypropylene. In some embodiments, the polypropylene comprises units derived from propylene and units derived from one or more of ethylene and C4-C20 alpha-olefins or mixtures thereof. In some embodiments, the polypropylene comprises a polypropylene impact copolymer, a polypropylene random copolymer, or a combination thereof. In some embodiments, the polypropylene recyclate has a melt flow rateless than or equal to 125 dg / min. but more typically less than or equal to 35 dg / min and preferably less than or equal to 2.0 dg / min. (2.16 kg, 230°C).

[0028] Polypropylene recyclate comprises a PCR resin containing recyclates derived from propylene homopolymers and copolymers, including plastomers, having of units derived from propylene and units derived one or more of ethylene and C4-C20 alpha-olefins or mixtures thereof. Preferably, the units derived from one or more of ethylene and C4-C10alpha-olefin comonomers are present in amounts up to 35 wt%, based upon the total weight of the copolymer of propylene. The propylene homopolymers and copolymers can be produced using either Ziegler Natta or single-site catalysts, e.g., metallocene catalysts. The propylene homopolymers and copolymers can be produced using a gas phase process, liquid process (condensed monomer), slurry process, or solution process or combination thereof. In some embodiments, when the propylene polymer is a copolymer, it preferably contains 0.4 to 18% copolymer, more typically 2 to 6 wt. %, based upon the total weight of the copolymer, of ethylene derived units as a comonomer.

[0029] In some embodiments, a polypropylene recyclate to be modified by the process herein comprises a polypropylene homopolymer, a random copolymer polypropylene, an impact copolymer polypropylene, or a combination thereof. In some embodiments, propylene homopolymers have an isotactic index of at least 90. In some embodiments random copolymer polypropylene comprise random copolymers of propylene and ethylene or butylene, or random terpolymers of propylene, ethylene, butylene and hexene, wherein the maximum ethylene content, or ethylene plus alpha-olefin content, is 10% by weight, and the random copolymer polypropylene has an isotactic index of at least 80. In some embodiments, the impact copolymer polypropylene comprises a heterophasic propylene polymer materials consisting essentially of by weight, (i) 99-55% of a polymeric material selected from the group consisting of a propylene homopolymer having an isotactic index greater than 90, and a crystalline copolymer of propylene and an alpha-olefin of the formula CH2═CHR, where R is H or a 2-6 carbon linear or branched alkyl group, having an isotactic index of at least 80, the alpha-olefin being less than 10% of the copolymer, and (ii) 1-45% of an elastomeric olefin polymer of propylene and an olefinic material selected from the group consisting of alpha-olefins of the formula CH2═CHR, where R is H or a 2-6 carbon linear or branched alkyl group, the alpha-olefin being 50-70% of the elastomeric polymer.

[0030] In some embodiments, the polyolefin recyclate is a polyethylene recyclate. In some embodiments, the polyethylene recyclate comprises units derived from ethylene and units derived from one or more of C3-C20 alpha-olefins or mixtures thereof. In some embodiments, the polyethylene recyclate comprises a high density polyethylene, a medium density polyethylene, a low density polyethylene, a linear low density polyethylene, or a combination thereof. In someembodiments, the polyethylene recyclate has a melt index less than or equal to 160 dg / min. but more typically less than or equal to 20 dg / min. and preferably less than or equal to 2.0 dg / min. (2.16 kg, 190°C).

[0031] In some embodiments, a polyethylene recyclate to be modified by the process herein comprises a PCR resin containing recyclates derived from a low density polyethylene (LDPE), a high density polyethylene (HDPE), a copolymer of ethylene with a C3-10alpha-olefin, (generally referred to as linear low density polyethylene (LLDPE)), of commerce are normally solid, somewhat flexible, thermoplastic polymers formed by the polymerization of the particular monomer(s) by various methods well known in the art. For example, such polymers can be prepared by free-radical polymerization at high pressures, or by low pressure processes, such as fluidized-bed, gas phase technology, with molybdenum-based catalysts, with chromium-based catalysts, with vanadium-based catalysts, with Ziegler-Natta catalysts systems, or with metallocene catalyst systems. The high pressure processes produce polymers with long chain branching and the low pressure processes produce essentially linear polymers with controlled levels of short chain branching. In Ziegler-Natta catalyst systems, the catalyst is formed by an inorganic compound of a metal of Groups I-III of the Periodic Table, (for example, an aluminum alkyl), and a compound of a transition metal of Groups IV-VIII of the Periodic Table, (for example, a titanium halide). A typical crystallinity is about 21 to about 75 wt. % by the method of Wunderlick & Guar, J. Phys. Chem. Ref. Data, Vol 10, No.1 (1981). Also, the typical melt index of said ethylene homopolymers or copolymers is from 0.2 and 50 g / 10 minutes (measured according to ASTM 1238, Condition E).

[0032] Suitable polyethylenes for a polyolefin recyclate include ethylene homopolymers and copolymers of units derived from ethylene and units derived from one or more of C3-C20alpha- olefins or mixtures thereof. In some embodiments, the units derived from the one or more C3-C8 alpha-olefin comonomers are present in amounts up to 15 wt. %, based upon the total weight of the copolymer of ethylene. The ethylene homopolymers and copolymers can be produced using either Ziegler Natta catalyst, chromium-based catalyst, vanadium-based catalyst or single-site catalyst, e.g., metallocene catalyst. The ethylene homopolymers and copolymers can be produced using a gas phase process, high pressure process, slurry process, or solution process. Ethylene homopolymers and ethylene-C3-C8alpha-olefin copolymers include very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE) and high density polyethylene (HDPE). VLDPE is defined as having a density of 0.860 to 0.910 g / cm3, as measured by ASTM D-1505 “Column Method.” LDPE and LLDPE are defined as having densities in the range of from 0.910 to 0.930 g / cm3. MDPE is defined as having a density of 0.930 to 0.945 g / cm3. HDPE is defined as having a densityof at least 0.945 g / cm3, preferably from 0.945 to 0.969 g / cm3. The ethylene homopolymers and copolymers preferably have melt indexes (MIs), as measured by ASTM D 1238, condition 190°C / 2.16 kg, from 0.01 to 400 dg / min., preferably, from 0.1 to 200 dg / min., more preferably from 1 to 100 dg / min.

[0033] In some embodiments, LDPE homopolymers can be produced in a high pressure, free- radical polymerization process, such as in one or more tubular reactors, one or more autoclave reactors, or a combination thereof. Operating conditions for the high-pressure process can include, but are not limited to, a pressure in the range of from 70 MPa to 700 MPa and a temperature in the range of from 150°C to 500°C. Such homopolymers have a high degree of long-chain branching and a density in the range of from 0.910 g / cm3to 0.940 g / cm3.

[0034] In some embodiments, LDPE copolymers of ethylene and C3-C12alpha-olefins can be produced in a high pressure, free-radical polymerization process, such as in one or more tubular reactors, one or more autoclave reactors, or a combination thereof. Such C3-C12alpha-olefins include, but are not limited to, substituted or unsubstituted C3 to C12 alpha 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 15 wt%, 10 wt%, or 5 wt%. Operating conditions for the high-pressure process can include, but are not limited to, a pressure in the range of from 70 MPa to 700 MPa and a temperature in the range of from 150°C to 500°C. Such homopolymers have a high degree of long-chain branching and a density in the range of from 0.910 g / cm3to 0.940 g / cm3.

[0035] LDPE as described above, can be characterized by having: i) a density in the range of from 0.910 g / cm3to 0.940 g / cm3or from 0.915 g / cm3to 0.935 g / cm3; ii) a melt index (2.16 kg, 190°C) less than or equal to 70 g / 10 min., less than or equal to 2.0 g / 10 min., less than or equal to 0.5 g / 10 min., less than or equal to 0.2 g / 10 min., or less than or equal to 0.1 g / 10 min.; iii) a molecular weight distribution (Mw / Mn) greater than 4.0, greater than 8.0, or greater than 15, and / or less than 35, less than 30, or less than 25; iv) a weight average molecular weight (Mw) 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 1.4, or greater than or equal to 2.0.

[0036] It should be noted that the polyolefins described above, both polyethylene and polypropylene, are the virgin polymers that entered the stream of commerce. The polymer recyclates herein are what is recovered after use and disposal by the consumer or post-industrial use. Such consumer waste plastic is collected, sorted, and processed to produce various grades ofpolyolefin recyclates. The original properties are lost by such reprocessing of a mixture of multiple polymers and typically have higher molecular weight than is desirable for reuse in many applications. The polyolefin recyclates also contain contaminants such as volatile organic compounds, which make the polyolefin recyclates unsuitable for reuse in many applications. Irradiation Process

[0037] In the irradiation process, the degraded polyolefin recyclate disclosed herein is made by irradiating a polyolefin recyclate as disclosed herein high-energy ionizing radiation at a dose rate in the range of about from 1 kGy to 1×105kGy per minute for a period of time sufficient for a substantial amount of chain scission of the amorphous content of the material to occur, but insufficient to cause gelation of the material. The irradiation is performed in an environment in which the active oxygen concentration is established and maintained at less than about 15%, preferably less than 5%, and more preferably less than about 1%, by volume of the environment. The most preferred concentration of active oxygen is 0.004% or lower by volume.

[0038] In some embodiments, the pressure in the reaction zone during irradiation is less than or equal to 70 kPa-g, less than or equal to 7 kPa-g, less than or equal to atmospheric pressure to as low as 3 mm mercury absolute, 1 mm mercury absolute, or 0.001 mercury absolute.

[0039] The expression “active oxygen” means oxygen in a form that will react with the irradiated propylene polymer material. It includes molecular oxygen, which is the form of oxygen normally found in air. The active oxygen content requirement of the process of this invention can be achieved by use of a vacuum or by replacing part, almost all, or all of the air in the environment by an inert gas such as, for example, nitrogen. Control of the oxygen level in the fluid bed gas stream is accomplished by the addition of air at the suction side of the blower. Air or oxygen must be constantly added to compensate for the oxygen consumed by the formation of peroxides in the polymer. The fluidizing medium can be, for example, nitrogen or any other gas that is inert with respect to the free radicals present, e.g., argon, krypton, and helium.

[0040] The ionizing radiation used to produce the irradiated polymer that constitutes the starting material for the process of the present invention should have sufficient energy to penetrate to the extent desired the mass of linear, propylene polymer material and / or polyethylene material being irradiated. The energy must be sufficient to ionize the molecular structure and to excite atomic structure, but not sufficient to affect atomic nuclei. The ionizing radiation can be of any kind, but the most practical kinds comprise electrons and gamma rays. Preferred are electrons beamed from an electron generator having an accelerating potential of 500-4,000 kilovolts. In the case of propylene polymer material without a polymerized diene content, satisfactory results are obtained at a dose of ionizing radiation of about 10-120 kiloGrays (kGy), preferably 30-80 kGy, delivered generally at a dose rate of about 10-105kGy per minute, and preferably about 180-20,000kGy per minute. In the case of propylene polymer material having a polymerized diene content, satisfactory results are obtained with a dose of about 02.5 kGy--about 15.0 kGy, preferably about 05.0 kGy –15.0 kGy, delivered at the foregoing dose rates.

[0041] The term “Gray (Gy)” is usually defined as that quantity of ionizing radiation that results in the absorption of 1 Joule of energy per kilogram of irradiated material, regardless of the source of radiation. In the usual practice of the process described in the aforementioned European application publication, energy absorption from ionizing radiation is said to be measured by the well-known conventional dosimeter, a measuring device in which a strip of fabric containing a radiation sensitive dye is the energy absorption sensing means. Hence, as used in this specification the term “Gray” means that quantity of ionizing radiation resulting in the absorption of the equivalent of 1 J of energy per kg of the fabric of a dosimeter placed at the surface of the linear, propylene polymer material being irradiated, whether in the form of a bed or layer of pellets, particles, or a film, or a sheet.

[0042] According to the present process, the semi-crystalline propylene polymer material, after having undergone irradiation, as described above, is subjected to the deactivation of free radicals still remaining therein.

[0043] After the irradiated polymer material has been heated in the first stage at T1, typically 40 to 140 C but preferably 80 to 120 C. Irradiated polymer is then exposed to a higher temperature T2to allow deactivation of any residual free radicals to occur. T2will be at least about 120°C, and preferably at least about 140°C. While temperatures as high as about 250°C can be used in the deactivation stage, it often will be preferred to select a T2which is below the melting point of the polymer, i.e., a maximum of about 160°C for propylene homopolymers and lower for propylene copolymers, and even lower for polyethylene-based polymers.

[0044] A preferred way of carrying out the heating process of the invention is to pass the irradiated polymer through the fluid bed assembly operating at T2. The fluidizing medium can be, for example, nitrogen or any other gas which is inert with respect to the free radicals present, e.g., argon, krypton, and helium. Unlike some techniques, such as melt extrusion methods, the fluidized bed method does not require the conversion of the irradiated polymer into the molten state and subsequent re-solidification and comminution back into the desired form.

[0045] Knowing the MFR of the starting material, the dose during the irradiation step, the oxygen level during the first treatment step, the time and temperature can be adjusted to obtain the desired MFR in the visbroken product prior to deactivating the free radicals. Degraded Polymer Recyclate

[0046] The method herein degrades the molecular weight of a polymer recyclate having a first weight average molecular weight (Mw1) to produce a degraded, lower viscosity polymer recyclatehaving a second molecular weight (Mw2) which is less than Mw1. In some embodiments, Mw2 / Mw1 is less than 1.0, and more typically less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1.

[0047] In some embodiments, a degraded polymer recyclate has a molecular weight distribution (MWD or Mw / Mn,Mz / Mwor Mz / Mn) or Polydisperisy Index (PI) of from about 1.5 to 100, more likely from 1.5 to 15, even more likely from 1.5 to about 7, from 1.5 to 4, from 1.5 to 3, or from 1.5 to 2.5.

[0048] In some embodiments, a degraded polypropylene recyclate has a melt flow rate in the range of from 1 dg / min. to 5,000 dg / min., from 50 dg / min. to 5,000 dg / min., from 100 dg / min. to 4,000 dg / min., from 150 dg / min. to 3,000 dg / min., or from 200 dg / min. to 2,000 dg / min. (2.16 kg, 230°C).

[0049] In some embodiments, a degraded polyolefin recyclate, when compared to the corresponding polyolefin recyclate, exhibits one or more of: a reduction in in volatile organic compounds (VOC) content from non-intentional added substances (NIAS), as measured by chromatography-mass spectrometry (GC-MS); a reduction in yellowness, as measured by Color Index Testing (CIT, L*a*b*); a reduced diameter swell (Ud) and / or weight swell (Uw), as measures by the Uniloy™ 5630 Dairy Mold Processability and Swell Test; a reduction in melt strength as measured by a Gottfoert Rheotens instrument; a reduction in melt viscosity / increase in melt flow rate as measured by ASTM D-1238; or a combination thereof.

[0050] In some embodiments, a polypropylene recyclate has a first melt flow rate (MFR1), a corresponding degraded polypropylene recyclate has a second melt flow rate (MFR2), and MFR2 is greater than MFR1. In some embodiments, MFR1 / MFR2is less than 1.0, is less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1.

[0051] In some embodiments, the visbreaking process disclosed herein starts with a polyolefin recyclate having a melt flow rate of between about 0.1 and 20 dg / min. Visbreaking such a polymer by conventional methods, such as treatment with peroxides, to achieve a polymer capable of producing high quality melt blown fabrics (e.g., melt flow rate=100-3500 dg / min) results in creation of excessive quantities of oligomers in degraded polymer product. The presence of oligomers in melt blown and other processes that utilize such degraded polymers can: cause smoking, thereby imparting undesirable color or odor to the final article formed from the degraded polymer; cause oil and wax build-up in processing machinery; and / or may shorten the useful lifeof the melt blown die tip. Furthermore, nonwoven fabrics made from such degraded polymers with excessive quantities of oligomers can have levels of extractables that exceed regulatory limits (e.g., those promulgated by the United States Food and Drug Administration) and may not meet FDA tertiary butyl alcohol (TBA) limits of < 100 ppm.

[0052] In some embodiments, a degraded polypropylene recyclate comprises an oligomer content of less than or equal to 1.5 wt. %, or less than or equal to 0.5 wt%, less than or equal to 0.4% wt%, less than or equal to 0.3% wt%, less than or equal to 0.2% wt%, or less than or equal to 0.1% wt%. Oligomer concentration in a propylene polymer composition may be measured using, among other tests known to those of skill in the art, a hexane extractables test (ASTM D5227-01).

[0053] In some embodiments, a degraded polypropylene recyclate has a reduced diameter swell (Ud) and / or weight swell (Uw), as measure by the Uniloy™ 5630 Dairy Mold Processability and Swell Test, a reduction in melt strength as measured by a Gottfoert Rheotens instrument, a reduction in melt viscosity / increase in melt flow rate as measured by ASTM D-1238; or a combination thereof. End-use Applications

[0054] The degraded polyolefin recyclate produced according to this invention can be converted into useful products by extrusion coating, including, but not limited to fabric coating and wire and cable coating; melt extrusion, including, but not limited to, sheet extrusion and coextrusion; profile extrusion; spinning operations to produce fibers, such as melt spinning, including, but not limited to, melt blowing and spun-bonding operations to produce fibers; stretching, uniaxially or biaxially, to form film, including, but not limited to, heat shrinkable film, strapping and slit-tape film; blow molding operations; foaming operations to produce foamed articles, including, but not limited to, high and low density foamed articles; synthetic pulp operations; molding operations, such as injection, and compression and roto molding; netting operations; and thermoforming operations. The propylene polymer material of this invention can also be blended with normally solid, isotactic, semi-crystalline, linear propylene polymer materials and with other polymeric materials, such as polyethylene, polyphenylene ethers, polyamides, homopolymers and copolymers (random and block) of styrene, polyurethanes, polycarbonates, ethylene-propylene copolymer rubbers, ethylene-propylene terpolymers rubbers and polyesters. Certain Embodiments

[0055] Disclosed is a method for degrading a polyolefin recyclate. The method comprises introducing into a reaction zone a polyolefin recyclate having a first weight average molecular weight (Mw1). The polyolefin recyclate is subjected to first reaction conditions comprising exposure to a dose of ionizing radiation in an atmosphere, having an active oxygen content of lessthan or equal to 15%, to form a first reaction product comprising free-radical polyolefin recyclate chain segments. The dose of ionizing radiation is sufficient for free-radical chain scission of an amorphous content of the polyolefin recyclate to occur but insufficient for gelation to occur. The first reaction product is subjected to second reaction conditions sufficient to deactivate the free radicals. A degraded polyolefin recyclate is recovered as a product, wherein the degraded polyolefin recyclate has having a second weight average molecular weight (Mw2), wherein Mw2is less than Mw1.

[0056] In some embodiments of method for degrading a polyolefin recyclate, is further characterized by one or more of the following: a) Mw2 / Mw1 is less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1; b) the degraded polymer recyclate has a molecular weight distribution (MWD or Mw / Mn) of from about 1.5 to about 7, from 1.5 to 4, from 1.5 to 3, or from 1.5 to 2.5; c) the degraded polyolefin recyclate, when compared to the polyolefin recyclate, exhibits: i) a reduction in in volatile organic compounds (VOC) content from non-intentional added substances (NIAS), as measured by chromatography-mass spectrometry (GC-MS); ii) a reduction in yellowness, as measured by Color Index Testing (CIT, L*a*b*); iii) a reduced diameter swell (Ud) and / or weight swell (Uw), as measures by the Uniloy™ 5630 Dairy Mold Processability and Swell Test; iv) a reduction in melt strength as measured by a Gottfoert Rheotens instrument; v) an increase in hexane solubles; vi) a reduction in melt viscosity / increase in melt flow rate as measured by ASTM D-1238; or vii) or a combination thereof; and d) the degraded polyolefin recyclate comprises an oligomer content of less than or equal to 0.5 wt%, less than or equal to 0.4% wt%, less than or equal to 0.3% wt%, less than or equal to 0.2% wt%, or less than or equal to 0.1% wt%.

[0057] In some embodiments of method for degrading a polyolefin recyclate, the polyolefin recyclate is a polypropylene recyclate. In some embodiments, the polypropylene recyclate: a) comprises units derived from propylene and units derived one or more of ethylene and C4-C20 alpha-olefins or mixtures thereof; b) comprises a polypropylene impact copolymer, a polypropylene random copolymer, or a combination thereof;c) has a melt flow rate less than or equal to 2.0 dg / min. (2.16 kg, 230°C); or d) a combination thereof.

[0058] In some embodiments of method for degrading a polyolefin recyclate, the polyolefin recyclate is a polyethylene recyclate. In some embodiments, the polyethylene recyclate: a) comprises units derived from ethylene and units derived from one or more of C3-C20 alpha-olefins or mixtures thereof; b) comprises a high density polyethylene, a medium density polyethylene, a low density polyethylene, a linear low density polyethylene, or a combination thereof; c) has a melt index less than or equal to 1.0 dg / min. (2.16 kg, 190°C); or d) a combination thereof.

[0059] In some embodiments of method for degrading a polyolefin recyclate, in addition to the limitations of any one of the above embodiments, the dose of ionizing radiation is in the range of from 0.01 Gy to 100 Gy per minute.

[0060] In another aspect, disclosed is a degraded polyolefin recyclate produced by any one of the embodiments of the method as disclosed above.

[0061] In another aspect, disclosed is an article of manufacture comprising the product as disclosed above. Test Methods

[0062] Densities are determined in accordance with ASTM D-792 and ASTM D-1505 / ISO-1183.

[0063] 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, ^^∗, 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 190oC. 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.

[0064] 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 perfrequency 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 x 10-3) x 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.

[0065] Melt index (“I2”) was determined by ASTM D-1238-E (190°C / 2.16 kg).

[0066] Melt flow rate (“MFR”) was determined by ASTM D-1238-L (230°C / 2.16 kg).

[0067] Molecular weight distribution (“MWD”) as well as the molecular weight averages (number-average molecular weight, Mn weight-average molecular weight, Mw, and z-average molecular weight, Mz) 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. Mn, Mw, Mz,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]linwhere, [η] is the average intrinsic viscosity of the polymer that is derived by summation of the slices over the GPC profiles as follows: ∑c୧^η^୧where ci is the concentration of a particular slice obtained from IR detector, and ^η^୧is the intrinsic viscosity of the slice measured from the viscometer detector. [η]lin is obtained from the IR detectorusing Mark-Houwink equation (^η^୪୧୬ ൌ ∑KMୟ୪୮୦ୟ୧ ) for a linear high density polyethylene, where Miis the viscosity-average molecular weight for a reference linear polyethylene, K and ^ are Mark-Houwink constants for a linear polymer, which are K=0.000374, ^=0.7265 for a linear polyethylene and K=0.00041, ^=0.6570 for a linear polypropylene.

[0068] Oxygen gas transmission rate (OVTR) can be measured by ASTM D3985.

[0069] Color Index Testing (CIT) L*a*b* is a method for measuring color differences between compositions and / or articles described herein using a standard defined by Commission Internationale d'Eclairage (CIE) L*a*b* color coordinates. L* indicates lightness, a* is the red / green coordinate, and b* is the yellow / blue coordinate. The system was designed to be perceptually uniform with respect to human color vision. The standards used for the color difference can include virgin HDPE. The space itself is a 3-dimensional real-number space; therefore, any color variation can be expressed in L*a*b* coordinates. Deltas for L* (ΔL*), a* (Δa*) and b* (Δb*) may be positive (+) or negative (−): ^ ΔL* (L* sample minus L* standard)=difference in lightness and darkness (+=lighter, −=darker) ^ Δa* (a* sample minus a* standard)=difference in red and green (+=redder, −=greener) ^ Δb* (b* sample minus b* standard)=difference in yellow and blue (+=yellower, −=bluer)

[0070] The total difference between the compositions and / or articles and the standard is defined as Delta E (ΔE*) and is calculated using the following: ^ΔE*=√∆^^ ∗ଶ^ ∆^^ ∗ଶ^ ∆^^ ∗ଶ

[0071] Uniloy™ 5630 processability: Bottle swell properties were determined using one gallon bleach-type bottles produced using a reciprocating Uniloy™ 5630 (single head) blow molder with the following heat settings: Feed 166°C °

[0072] The melt temperature under these conditions was 193°C. Screw speed was maintained at 26 rpm and the total cycle time was 15.4 seconds (10 seconds blow and 1.5 seconds parisondrop). High-shear processability and swell changes were determined from bottles produced on a Uniloy™ 5630 intermittent extrusion blowmolder - 1-gal milk / water bottles from homopolymers. Swell was measured by two methods. Weight swell was determined by the initial weight change observed for a test resin after transitioning from the control. Diameter swell was determined by measuring on an inlaid centimeter scale the distance of the flash down the handle of the bottle after the bottle weight had been reset at the target weight.

[0073] GC-MS for NIAS Volatiles are methods used to study the potential effects of reduced VOC emissions, yellowness, and gel count. Gas chromatography-mass spectrometry (GC-MS) is a powerful analytical technique used for the identification and quantification of volatile organic compounds (VOCs) in complex mixtures. GC-MS has been widely used for the analysis of non- intentionally added substances (NIAS) volatiles, which are chemical compounds that can be released from materials and products during their production, use, and disposal.

[0074] To perform GC-MS analysis, the sample is first injected into a gas chromatograph, which separates the different components of the sample based on their physical and chemical properties. The separated compounds are then directed to the mass spectrometer, where they are ionized and fragmented into smaller ions. The resulting mass spectra are used to identify the individual compounds based on their unique mass-to-charge ratios.

[0075] GC-MS, or gas chromatography-mass spectrometry, was used to identify and quantify volatile organic compounds (VOCs) in a wide range of samples. This technique is particularly useful for analyzing non-intentionally added substances (NIAS) volatiles, which are chemical compounds that are not intentionally added to a product or material, but can be present as impurities or byproducts of manufacturing processes. In the context of studying the potential effects of reduced VOC emissions, GC-MS can be used to identify the specific VOCs that are present in a sample and determine their concentrations. This information can be used to compare the VOC emissions of different materials or products and assess the effectiveness of strategies to reduce VOC emissions. In addition to VOC emissions, GC-MS can also be used to study the properties of materials and products, such as yellowness and gel count. Yellowness is a measure of the degree of yellow coloration in a material, which can be caused by the presence of certain chemical compounds. GC-MS can be used to identify these compounds and determine their concentrations, which can help to understand the factors contributing to yellowness and develop strategies to reduce it.

[0076] 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 anyother 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.

[0077] All documents and references cited herein, including testing procedures, publications, patents, journal articles, etc., are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted and to the extent such disclosure is consistent with the description of the present invention.

[0078] 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

CLAIMS What is claimed is:

1. A method for degrading a polyolefin recyclate, the method comprising: introducing into a reaction zone a polyolefin recyclate having a first weight average molecular weight (Mw1); subjecting the polyolefin recyclate to first reaction conditions comprising exposure to a dose of ionizing radiation in an atmosphere, having an active oxygen content of less than or equal to 15%, to form a first reaction product comprising free-radical polyolefin recyclate chain segments, wherein the dose of ionizing radiation is sufficient for free-radical chain scission of an amorphous content of the polyolefin recyclate to occur but insufficient for gelation to occur; subjecting the first reaction product to second reaction conditions sufficient to deactivate the free radicals; and recovering a degraded polyolefin recyclate having a second weight average molecular weight (Mw2), wherein Mw2 is less than Mw1.

2. The method of claim 1, wherein Mw2 / Mw1is less than or equal to 0.

5.

3. The method of claim 1 or 2, wherein the degraded polymer recyclate has a molecular weight distribution (MWD or Mw / Mn) of from about 1.5 to about 7.

4. The method of any one of the preceding claims, wherein the degraded polyolefin recyclate, when compared to the polyolefin recyclate, exhibits: a reduction in in volatile organic compounds (VOC) content from non-intentional added substances (NIAS), as measured by chromatography-mass spectrometry (GC-MS); a reduction in yellowness, as measured by Color Index Testing (CIT, L*a*b*); a reduced diameter swell (Ud) and / or weight swell (Uw), as measures by the Uniloy™ 5630 Dairy Mold Processability and Swell Test; a reduction in melt strength as measured by a Gottfoert Rheotens instrument; an increase in hexane solubles; a reduction in melt viscosity / increase in melt flow rate as measured by ASTM D-1238; ora combination thereof.

5. The method of any one of the preceding claims, wherein the degraded polyolefin recyclate comprises an oligomer content of less than or equal to 0.5 wt%.

6. The method of any one of the preceding claims, wherein the polyolefin recyclate is a polypropylene recyclate.

7. The method of claim 6, wherein the polypropylene recyclate comprises units derived from propylene and units derived one or more of ethylene and C4-C20alpha-olefins or mixtures thereof.

8. The method of claim 6 or 7, wherein the polypropylene recyclate comprises a polypropylene impact copolymer, a polypropylene random copolymer, or a combination thereof.

9. The method of any one of claims 6 through 8, wherein the polypropylene recyclate has a melt flow rate less than or equal to 2.0 dg / min. (2.16 kg, 230°C).

10. The method of any one of claims 6 through 9, wherein the polypropylene recyclate has a melt flow rate in the range of from 1 dg / min. to 5,000 dg / min.

11. The method of any one of claims 1 through 5, wherein the polyolefin recyclate is a polyethylene recyclate.

12. The method of claim 11, wherein polyethylene recyclate comprises units derived from ethylene and units derived from one or more of C3-C20alpha-olefins or mixtures thereof.

13. The method of claim 11 or 12, wherein the polyethylene recyclate comprises a high density polyethylene, a medium density polyethylene, a low density polyethylene, a linear low density polyethylene, or a combination thereof.

14. The method of any one of claims 11 through 13, wherein the polyethylene recyclate has a melt index less than or equal to 1.0 dg / min. (2.16 kg, 190°C).

15. The method of any one of the preceding claims, wherein a dose of ionizing radiation is in the range of from 10 kGy to 120 kGy.

16. The method of any one of the preceding claims, wherein a dose rate of ionizing radiation is in the range of from 1 kGy to 1×105kGy per minute.

17. A product produced by the method of any one of the preceding claims.

18. An article of manufacture comprising the product of claim 17.

19. The article of manufacture of claim 18, wherein the product of claim 17 is incorporated into the article of manufacture by one or more of extrusion coating, melt extrusion, profile extrusion, spinning operations to produce fibers, stretching to form film, blow molding operations, foaming operations to produce foamed articles, molding operations, and thermoforming operations.

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