A commercially viable solution process to control long-chain branching in polyethylene

• 成果类型: Article
• 署名作者: Froese, Robert D.; Arriola, Daniel J.; den Doelder, Jaap; Hou, Jianbo; Kashyap, Teresita; Lu, Keran; Martinetti, Luca; Stubbert, Bryan D.
• 署名单位: Dow Chemical Company; Dow Chemical Company
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-9997
• DOI: 10.1126/science.adn3067
• 发表日期: 2024-03-15
• 页码: 1223-1228
• 关键词: constrained-geometry; molecular-weight; polymerization; density; ethylene; catalyst; hafnium; polypropylene; polyolefins; activation

摘要

In polyolefins, long-chain branching is introduced through an energy-intensive, high-pressure radical process to form low-density polyethylene (LDPE). In the current work, we demonstrated a ladder-like polyethylene architecture through solution polymerization of ethylene and less than 1 mole % of alpha,omega-dienes, using a dual-chain catalyst. The ladder-branching mechanism requires catalysts with two growing polymer chains on the same metal center, thus enchaining the diene without the requirement of a steady-state concentration of pendant vinyl groups. Molecular weight distributions lacking a high-molecular weight tail, distinctive Mark-Houwink signatures, nuclear magnetic resonance characterization, and shear and extensional rheology consistent with highly branched polyethylene architectures are described. This approach represents an industrially viable solution-polymerization process capable of producing controlled long-chain branched polyethylene with rheological properties comparable to those of LDPE or its blends with linear low-density polyethylene (LLDPE).