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AssigneeExxonMobil Chemical Patents Inc.
InventorsAspy K. Mehta, Michael C. Chen, James J. McAlpin, Anthony N. Speca, Kelly Tormaschy, Chon Y. Lin
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This invention relates generally to crystalline propylene polymers, to methods for their production and to methods for their use in film applications. Specifically, this invention relates to crystalline propylene polymers comprising both propylene homopolymer and propylene copolymer. The compositions are prepared using metallocene catalyst systems comprising at least two metallocenes in a polymerization process that involves the sequential or parallel polymerization of propylene homopolymer and copolymer using propylene with a small amount of comonomer, preferably ethylene. The polymerization is catalyzed by a dual metallocene catalyst system. The resulting polymers have a broad, bimodal molecular weight distribution. The resulting polymers are excellent for use in the production of biaxially oriented films or non-oriented films. Films prepared with these propylene polymers have a significantly broader processability range and can be evenly stretched at lower temperature compared to films prepared from traditional propylene polymer.
An isotactic propylene polymer composition comprising a reactor blend comprising at least four propylene/ethylene copolymers, the composition comprising from 0.05 to 15 wt % comonomer units based on the total weight of the composition the composition having a Mz value of from 400,000 to 2,000,000, a Mn value of from 65,000 to 130,000, and a MWD value of less than 3.0.
An isotactic propylene polymer composition comprising a reactor blend of at least four propylene/ethylene copolymers, the composition comprising from 0.05 to 15 wt % comonomer units based on the total weight of the composition, wherein the composition is generated from at least two polymerization steps conducted in the presence of a catalyst system comprising at least two different metallocene catalysts, and wherein the molecular weight distribution of the polymer is characterized as being bimodal, the composition having a Mz value of from 400,000 to 2,000,000, and an Mn value from 65,000 to 130,000.
A crystalline isotatic propylene polymer composition comprising a reactor blend comprising at least four propylene/ethylene copolymers, the composition comprising from 0.05 to 15 wt % comonomer units based on the total weight of the composition, wherein the composition is generated from at least two polymerization steps conducted in the presence of a catalyst system comprising at least two different metallocene catalysts, and the composition has a Mz value from 500,000 to 1,500,000 molecular weight units, and an Mn value from 65,000 to 130,000.
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