CN-122003451-A - Multimodal ethylene-based copolymer composition and method of production

Abstract

The present invention provides a process for preparing a multimodal ethylene-based copolymer. The methods include adding ethylene, at least one olefin monomer, at least a first catalyst system, and less than 0.3mol% hydrogen to a solution polymerization reactor at a reactor temperature greater than or equal to 100 ℃ to produce an effluent feed. The effluent feed and the second catalyst system are fed to a second reactor in the absence of fresh feed and in the absence of hydrogen. At least one of the first catalyst system and the second catalyst system has a chain transfer constant of 0.005 to 1.0. The multimodal ethylene-based copolymer comprises from 8% to 50% of the high molecular weight fraction, i.e. fraction having a molecular weight of more than 500,000g/mol, based on the total percentage of the multimodal ethylene-based copolymer.

Inventors

• M S Ross
• P.P. Fontaine
• J. Closey
• E.M. Kanahan
• WANG YONG
• Y. A. Dasa
• F.G. Hamad
• P. Balding
• JOSE ANTONIO PEREIRA

Assignees

• 陶氏环球技术有限责任公司

Dates

Publication Date

20260508

Application Date

20240613

Priority Date

20230628

Claims (19)

1. 1. A process for preparing a multimodal ethylene-based copolymer, the process comprising: Adding ethylene, at least one olefin monomer, at least a first catalyst system, and less than 0.3 mole percent hydrogen to a solution polymerization reactor at a reactor temperature of greater than or equal to 150 ℃ to produce an effluent feed, wherein mole percent hydrogen is based on moles of ethylene in the feed; feeding the effluent feed and a second catalyst system to a second reactor in the absence of fresh feed and in the absence of hydrogen; Wherein: The first catalyst system comprises a first procatalyst and a first activator, and the second catalyst system comprises a second procatalyst and optionally a second activator; At least one of the first catalyst system and the second catalyst system has a chain transfer constant of 0.005 to 1.0, and Wherein the multimodal ethylene-based copolymer comprises a high molecular weight fraction of from 8% to 50% based on the total percentage of the multimodal ethylene-based copolymer, the high molecular weight fraction being calculated by measuring the area fraction of the molecular weight chromatogram obtained from the absolute molecular weight of low angle light scattering of more than 500,000 g/mol.
2. 2. The method of claim 1, wherein one of the first catalyst system and the second catalyst system is capable of producing a polymer having a primary molecular weight greater than 100,000g/mol, wherein the polymer primary molecular weight is measured in a single 1 gallon reactor containing an ethylene pressure of 320psi, a 60g 1-octene amount, 0H 2 , in the presence of 1250 grams ISOPAR-E, and at a reactor temperature of at least 150 ℃.
3. 3. The method of claim 2, wherein the other of the first catalyst system and the second catalyst system is capable of producing a polymer having a primary molecular weight of less than 150,000g/mol, wherein the polymer primary molecular weight is measured in a single 1 gallon reactor containing an ethylene pressure of 320psi, a 60g 1-octene amount, 0H 2 , in the presence of 1250 grams ISOPAR-E, and at a reactor temperature of at least 160 ℃.
4. 4. The method of claim 1, wherein the first catalyst system is capable of producing a first polymer having a virgin molecular weight and the second catalyst system is capable of producing a second polymer having a virgin molecular weight that differs from the virgin molecular weight of the first polymer by at least 80,000 g/mol.
5. 5. The process of any of the preceding claims, wherein the solution polymerization reactor is a continuous stirred tank reactor, a loop reactor, or a plug flow reactor.
6. 6. The process of any of the preceding claims, wherein the second polymerization reactor is a non-stirred reactor.
7. 7. The method of claim 4, wherein the non-stirred reactor is a plug flow reactor.
8. 8. The process of any of the preceding claims, wherein at least one of the first catalyst and the second procatalyst has a reactivity ratio of less than 20, wherein the reactivity ratio of the catalysts is measured in a single 1 gallon reactor containing a solution having an ethylene mole fraction of 0.709, 60g 1-octene, and having only the catalyst system, in the presence of 1250 grams ISOPAR-E, and at a reactor temperature of at least 150 ℃.
9. 9. The method of any of the preceding claims, wherein the multimodal ethylene-based copolymer further comprises a low molecular weight fraction of greater than or equal to 50% based on the total percentage of the multimodal ethylene-based copolymer, the low molecular weight fraction calculated by measuring the area fraction of a molecular weight chromatogram obtained from absolute molecular weights of low angle light scattering of less than 500,000 g/mol.
10. 10. The method of any of the preceding claims, wherein the multimodal ethylene-based copolymer further comprises a high molecular weight fraction of greater than or equal to 10% to 50% based on the total percentage of the multimodal ethylene-based copolymer, the high molecular weight fraction calculated by measuring the area fraction of a molecular weight chromatogram obtained from the absolute molecular weight of low angle light scattering of greater than 500,000 g/mol.
11. 11. The method of any of the preceding claims, wherein the multimodal ethylene-based copolymer further comprises a high molecular weight fraction of 20% to 50% based on the total percentage of the multimodal ethylene-based copolymer, the high molecular weight fraction calculated by measuring the area fraction of a molecular weight chromatogram obtained from absolute molecular weights of low angle light scattering of greater than 500,000.
12. 12. The process of any of the preceding claims, wherein the multimodal ethylene-based copolymer has a density of from 0.900g/cc to 0.940g/cc measured according to ASTM D792.
13. 13. The process of any of the preceding claims, wherein the multimodal ethylene-based copolymer has a melt strength of at least 5cN and a melt index (I 2 ) of at least 0.5g/10 min measured according to ASTM 1238 at 2.16kg and 190 ℃.
14. 14. The method of any of the preceding claims, wherein the multimodal ethylene-based copolymer has a Melt Strength (MS) that satisfies the following equation: Wherein x is equal to 15, y is equal to 1, and I 2 is the melt index of the copolymer measured according to ASTM 1238 at 2.16kg and 190 ℃.
15. 15. The method of any one of the preceding claims, wherein the V 0.1 /V 100 value as determined by dynamic mechanical analysis is greater than 10.
16. 16. The process of any one of the preceding claims, wherein the first reactor temperature is from 160 ℃ to 200 ℃.
17. 17. The method of any one of the preceding claims, wherein the first procatalyst is selected from one of the following: 。
18. 18. The method of any one of the preceding claims, wherein the second procatalyst is selected from one of the following:
19. 19. The method of any one of the preceding claims, wherein the method further comprises a third catalyst system.

Description

Multimodal ethylene-based copolymer composition and method of production Cross Reference to Related Applications The present application claims the benefit of U.S. provisional application Ser. No. 63/510,779, filed on 6/28 of 2023, the contents of which are incorporated herein in their entirety. Technical Field Embodiments of the present disclosure relate generally to polymer compositions, and more particularly, to multimodal ethylene-based copolymer compositions and methods of producing the same. Background The use of polyolefin compositions in industries such as packaging applications is well known. Such polyolefin compositions can be produced by a variety of conventional methods. Various polymerization techniques using different catalyst systems have been used to produce such polyolefin compositions suitable for packaging applications. However, despite efforts in some embodiments to develop compositions suitable for packaging applications, there remains a need for improved polyethylene compositions suitable for packaging applications that can have a good balance of physical properties and melt strength at the desired polymer composition density. Disclosure of Invention Melt strength and processability are relevant properties of polyethylene resins. Generally, higher melt strength provides polyethylene resins with improved processability. In addition, conventional polyethylene resins produced by conventional methods typically compromise between mechanical properties and melt strength of the resin. For example, detrimental conventional free radical processes are known to produce Low Density Polyethylene (LDPE), which generally exhibits high melt strength but has poor mechanical properties. In contrast, linear Low Density Polyethylene (LLDPE) produced via solution or gas phase processes generally has poor melt strength but excellent mechanical properties. Thus, to improve processability, an amount of LDPE may be blended with LLDPE to improve the processability and melt strength of the LLDPE resin. Unfortunately, the addition of LDPE results in reduced mechanical properties of the resulting blend when compared to pure LLDPE resins. Thus, there is a need for a solution polymerization process for producing polyethylene resins that can have melt strength comparable to polyethylene resins produced via a free radical process. In particular, there is a need for a solution polymerization process for producing polyethylene resins that can have melt strength comparable to LDPE resins produced via a free radical process. Thus, there is a need to produce High Molecular Weight (HMW) polyethylene copolymers and Low Molecular Weight (LMW) polyethylene copolymers to produce multimodal ethylene-based copolymers. These multimodal ethylene-based copolymers having a HMW ethylene-based copolymer component have a higher melt strength than a polyethylene having a similar melt index without the HMW polyethylene component. Embodiments of the present disclosure meet those needs by providing a multimodal ethylene-based copolymer comprising a bulk Low Molecular Weight (LMW) ethylene-based component prepared by one or more catalysts and a High Molecular Weight (HMW) ethylene-based component prepared by a different one or more catalysts. The multimodal ethylene-based copolymers described herein may have long chain branching that, together with the HMW ethylene-based component, allows achieving melt strengths comparable to or higher than various LDPEs produced via conventional processes. Thus, the multimodal ethylene-based copolymers described herein can be used as a blending component with LLDPE in amounts less than required for conventional LDPE resins, resulting in improved mechanical properties of the resulting LLDPE blend when compared to the mechanical properties in conventional LLDPE/LDPE blends. In embodiments, the multimodal ethylene-based copolymer is produced via a solution polymerization process. Embodiments of the present disclosure include methods that utilize low levels of H 2. Controlling the level of H 2 in the reactor may allow for adjusting the molecular weight of the ethylene-based copolymer. If the H 2 level is too high, the molecular weight difference between the polymers made with the two catalysts may be reduced to the point that no HMW ethylene-based copolymer component is present (and both catalysts will produce LMW PE) and no improvement in melt strength is obtained. Embodiments of the present disclosure include methods of preparing multimodal ethylene-based copolymers. In an embodiment, the process includes adding ethylene, at least one olefin monomer, at least a first catalyst system, and less than 0.3mol% hydrogen to a solution polymerization reactor at a reactor temperature greater than or equal to 150 ℃ to produce an effluent feed, feeding the effluent feed and a second catalyst system to a second reactor in the absence of fresh feed and in the absence of hydrogen, wherein the first catalyst system compris