Rheology modified relatively high melt strength polyethylene compositions and methods of making pipes, films, sheets, and blow-molded articles

摘要

A polymer composition comprises a low-molecular-weight (LMW) ethylene polymer component and a high-molecular-weight (HMW) ethylene polymer component coupled with a polysulfonyl azide. Preferably, the LMW polyethylene component and the HMW polyethylene component co-crystallize in the composition such that it exhibits a single or substantially single peak in a lamella thickness distribution (LTD) curve. The ethylene polymer for the LMW and the HMW polyethylene components can be either homopolymer or ethylene copolymer. Preferably, both components are an ethylene copolymer of the same, or different, composition (that is, with the same or different comonomers). A method of making a pipe that includes selecting a polymer composition having a substantially single peak in the LTD curve is described. Compositions comprising a chromium-catalyzed ethylene polymer, coupled with a polysulfonyl azide are also described herein.

主权项

1. An azide-modified composition, comprising the reaction product of:
(a) a first composition comprising a LMW polyethylene component; and a HMW polyethylene component, and (b) a second composition comprising a coupling amount of at least one polysulfonyl azide, and
wherein the first composition has a substantially single peak in an LTD (Lamellar Distribution Thickness) curve, and has an I5 from 0.01 to 0.5 g/10 min; andwherein the concentration of polysulfonyl azide is up to 200 μg/g, and wherein the azide-modified composition has a PENT (Pennsylvania Notch Test) value of greater than 1,000 hours at 80° C., and at an applied stress of 2.4 MPa, and wherein the azide-modified composition has a density greater than 0.940 g/cc, a flow rate ratio (I21/I5) from 15 to 50, and a viscosity at 0.01 sec−1, 190° C., from 272,000 to 340,000 Pa·s, and
wherein the LMW polyethylene component has a density from 0.955 to 0.980 g/cc, and is an ethylene homopolymer or an ethylene/C3-C10 aliphatic alpha-olefin copolymer; andwherein the HMW polyethylene component has a density from 0.920 to 0.932 g/cc, and is an ethylene homopolymer or an ethylene/C3-C10 aliphatic alpha-olefin copolymer, andwhere the HMW polyethylene component and the LMW polyethylene component are made in-situ, in one or more polymerization reactors, in the presence of one or more Ziegler-Natta catalyst systems.