Bimodal Polypropylene Compositions and Method of Making Same
AssigneeExxonMobil Chemical Patents Inc.
InventorsYi Ping Ni, Rohan A. Hule, Sudhin Datta
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Abstract
The present invention relates to a bimodal polypropylene composition comprising a blend of a HMW polypropylene component and a LMW polypropylene component, where the high molecular weight (HMW) component of the bimodal composition has a z-average molecular weight Mz of more than 400,000 g/mole, and a process to make such composition. The composition is suitable for thermoformed articles and injection molded articles.
Claims24
A polypropylene composition comprising at least one high molecular weight (HMW) polypropylene component and at least one low molecular weight (LMW) polypropylene component, wherein the polypropylene composition has any one or more of the following features:
- a) an extensional viscosity of the polypropylene composition of more than 10,000 Pa·s, when measured on an extensional rheometer at a temperature of 172° C., and an extensional rate of 10 second−1 measured at 0.3 seconds;
- b) a zero shear viscosity of the polypropylene composition no less than the zero shear viscosity of the HMW polypropylene component alone, as determined in accordance with Small Angle Oscillatory Shear (SAOS) Rheology Test;
- and/or
- c) a relaxation time of the polypropylene composition of more than 0.9 seconds, as determined in accordance with Small Angle Oscillatory Shear (SAOS) Rheology Test;
- wherein the HMW polypropylene component has a z-average molecular weight Mz of more than 400,000 g/mole, as determined by Gel Permeation Chromatography (GPC), and is in an amount in the range of from 80.0 wt % to 99.9 wt %, based on the total weight of the composition.
A process to form a polypropylene composition comprising at least one HMW polypropylene component in the range of from 80.0 wt % to 99.9 wt %, based on the total weight of the composition, and at least one LMW polypropylene component, in at least one single pass extrusion, which process comprises:
- a) combining the HMW polypropylene component having a z-average molecular weight Mz of more than 400,000 g/mole with the LMW polypropylene component;
- b) melt blending in an extruder the components in step a) at a melt temperature within a range from 350° C. to 450° C.;
- c) isolating the blend produced in step b) to produce the polypropylene composition.
A polymerization process to form HMW polypropylene component having a z-average molecular weight Mz of more than 400,000 g/mole, comprising contacting propylene monomers with a catalyst system comprising a metallocene catalyst compound represented by the formula:
- where:
- M is a group 4 metal, preferably Hf or Zr;
- T is a bridging group;
- X is an anionic leaving group;
- each R2, R3, R5, R6, R7, R8, R9, R11, R12, and R13 is independently, a halogen atom, hydrogen, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl, substituted silylcarbyl, germylcarbyl, substituted germylcarbyl substituents or a —NR′2, —SR, —OR′, —OSiR′3 or —PR′2 radical, wherein R′ is one of a halogen atom, a C1-C10 alkyl group, or a C6-C10 aryl group;
- and
- R4 and R10 are phenyl groups substituted at the 3′ and 5′ positions.
Dependencies are inferred from the claim text.