US-12623392-B2 - Polymer recyclate processes and products

US12623392B2US 12623392 B2US12623392 B2US 12623392B2US-12623392-B2

Abstract

Methods for processing LDPE recyclates including, but not limited to, polyethylene and polypropylene and compositions therefrom are provided. LDPE recyclate can be visbroken to improve processing characteristics and/or devolatilized to remove waste byproducts to produce processed LDPE recyclates. Processed LDPE 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 LDPE recyclate and/or pre-consumer polyolefins.

Inventors

Harilaos Mavridis
Diana Doetsch
KATHARINA ELSAS
Mick C. Hundley
Sameer D. Mehta
Marco Consalvi
Gerhardus Meier
Lindsay E. Corcoran
Andreas Maus
Timo Hees
Pascal Rebmann

Assignees

EQUISTAR CHEMICALS, LP

Dates

Publication Date: 20260512
Application Date: 20220621

Claims (14)

1 . A method for processing low density polyethylene (LDPE) recyclate comprising: a. providing a LDPE recyclate feedstock having: i) a first density in the range of from 0.910 g/cm 3 to 0.940 g/cm 3 ; ii) a first melt index (12; 2.16 kg, 190° C.) less than or equal to 5.0 g/10 min; iii) a first molecular weight distribution (M w /M n ) greater than 4.0; iv) a first weight average molecular weight (“M w1 ”) greater than or equal to 85,000 daltons; and v) a first melt elasticity (“ER”) greater than or equal to 1.0; b. adding the LDPE recyclate to a first extruder to produce a first LDPE recyclate melt; c. subjecting the first LDPE recyclate melt to visbreaking conditions to produce a second LDPE 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 in the range of from 0.60 to 0.99; iv) a second weight average molecular weight (“M w2 ”), wherein M w2 /M w1 is in the range of from 0.60 to 0.99; and v) a second melt elasticity, wherein the ratio of the second melt elasticity to the first melt elasticity is in the range of 0.30 to 0.90; wherein a LDPE recyclate product is formed by withdrawal of the second LDPE recyclate melt from the first extruder, and further processing or pelletizing of the second LDPE recyclate melt d. adding the LDPE recyclate product and a first polyolefin blend component to a second extruder; and e. effecting compounding conditions in the second extruder to form a polyolefin product comprising the melt-blended mixture of the LDPE recyclate product and the first polyolefin blend component.
2 . The method of claim 1 , wherein the LDPE 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 subjecting the first LDPE recyclate melt to devolatilization conditions to produce the second LDPE recyclate melt wherein: the LDPE recyclate feedstock has a first volatile organic compound content; the first LDPE 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 LDPE recyclate feedstock has a first high load melt index (I 21 ; 21.6 kg, 190° C.), the second LDPE 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 2.0; ii) the LDPE recyclate feedstock has a first melt index ratio (I 21 /I 2 ), the second LDPE recyclate melt has a second melt index ratio, and the ratio of the second melt index ratio to the first melt index ratio is in the range of 0.50 to 0.75, wherein I 21 is the first high load melt index of the LLDPE recyclate feedstock; iii) the LDPE recyclate feedstock has a first long chain branching parameter (g′) in the range from 0.40 to 0.75, the second LDPE recyclate melt has a second g′, and the ratio of the second g′ to the first g′ is greater than or equal to 1.0; iv) the LDPE recyclate feedstock has an overall polydispersity measure (“PDR”), the second LDPE recyclate melt has a second PDR, and the ratio of the second PDR to the first PDR is less than or equal to 0.5; v) the LDPE recyclate feedstock has a first complex viscosity ratio, the second LDPE 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 0.40, and/or the second complex viscosity is less than or equal to 12; and vi) the LDPE recyclate feedstock has a first intrinsic viscosity, the second LDPE 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 0.85.
8 . The method of claim 1 , wherein the first polyolefin blend component comprises a virgin polyolefin, a polyolefin recyclate feedstock, a processed polyolefin recyclate, or a combination thereof.
9 . The method of claim 8 , 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 second processed LDPE recyclate, a processed LLDPE recyclate, a processed HDPE recyclate, a processed MDPE recyclate, a processed polypropylene recyclate, or a combination thereof.
10 . The method of claim 9 , wherein the first polyolefin blend component comprises a virgin LDPE, a LDPE recyclate feedstock, a processed LDPE recyclate, or a combination thereof.
11 . The method of claim 1 , wherein the LDPE recyclate product is added in an amount in the range of from 5 wt. % to 90 wt. % based on the combined weight of the LDPE recyclate product and the first polyolefin blend component.
12 . The method of claim 1 , wherein the compounding conditions include a temperature less than or equal to 300° C.
13 . The method of claim 1 , 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.
14 . The method of claim 13 , wherein the second blend component comprises a virgin LDPE, a LDPE recyclate feedstock, a processed LDPE recyclate, or a combination thereof.

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 LDPE 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 LDPEs 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. This disclosure provides—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 LDPE portion—processes to produce polyolefin compositions comprising recycled LDPE, such polyolefin compositions having a useful combination of properties. Such 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 low density polyethylene (“LDPE”) recyclates. Such processing includes implementing in an extruder visbreaking conditions to convert a LDPE recyclate into a visbroken LDPE recyclate having a reduced weight average molecular weight. In some embodiments, the LDPE recyclate is also subjected to devolatilization conditions to convert the LDPE recyclate into a visbroken LDPE 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 LDPE 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 s