Patent attributes
Pellet-stable olefinic copolymer bimodal rubber is made using parallel reactors, with one reactor synthesizing higher molecular weight (MW) rubber with dual catalysts, with an improved molecular weight split ratio and an improved composition distribution of the moderate and ultra-high MW components, while another reactor synthesizes random isotactic polypropylene copolymer (RCP). The effluents are reactor-blended and result in pellet-stable bimodal rubber (P-SBR), which may be pelletized. When making thermoplastic vulcanizates (TPVs) with P-SBR, the need to granulate rubber bales and subsequently use talc, clay, or other anti-agglomeration agents to prevent granulated rubber crumbs from agglomerating are eliminated. TPVs made with P-SBR have vulcanized rubber particles that are smaller and more uniform in size, resulting in TPVs with higher particle counts and more thermoplastic “ligaments” between the particles, with such ligaments being made stronger by the added RCP. Such thus-produced TPVs have a lower hysteresis and flexural modulus, and better elastic properties.
