Equistar Chemicals, LP

Paula L Nygard

Philip J Garrison

Lawrence R Wallace

Mark P Mack

Leonard V Cribbs

Jean A Merrick-Mack

James H Meas

James H Meas, Jr

Danny L Wise

Bradley P Etherton

Charles S Holland

Linda N Winslow

James Ronald Clark

Everett O Lewis

Donnie W Jordy

Travis W Knight

Dale A Vedder

An ethylene polymerization process is disclosed. Ethylene is polymerized in two slurry reaction zones with a C-Calpha-olefin in the presence of a single-site catalyst capable of making a high molecular weight polyolefin. The process yields medium density and linear low density polyethylene having a bimodal molecular weight distribution and a melt index from about 0.10 to about 0.80. Films from the polyethylene have superior impact properties.

Polyethylene process

A process for preparing polyethylene thin films is disclosed. The process comprises extruding a blend that comprises a linear low density polyethylene (LLDPE) and a high molecular weight, high density polyethylene (HMW-HDPE) or high molecular weight, medium density polyethylene (HMW-MDPE). The blend has an LLDPE/HMW-HDPE or HMW-MDPE weight ratio at least 50/50. The blend is extruded through an annular die to form a molten material tube. The molten material tube is then pulled around a flexible internal orientation device (FIOD) to form the film. The FIOD makes it possible to prepare polyethylene thin films from LLDPE-rich LLDPE/HMW-HDPE or HMW-MDPE blends on a high stalk film line. The films have increased machine-direction (MD) tears.

Preparation of polyethylene films

A high molecular weight, medium density polyethylene (HMW, MDPE) is disclosed. The polyethylene comprises from about 85 to about 98 wt % of recurring units of ethylene and about 2 to about 15 wt % of a C &agr;-olefin. It has a density from about 0.92 to about 0.944 g/cc, a melt index MI from about 0.01 to about 0.5 dg/min, and a melt flow ratio MFR from about 50 to about 300. It has a multimodal molecular weight distribution comprising a high molecular weight component and a low molecular weight component. The low molecular weight component has an MI from about 50 to about 600 dg/min and a density from about 0.94 to about 0.97 g/cc. A process for making the medium density polyethylene is also disclosed. The process uses a Ziegler catalyst and applies multiple reaction zones.

High molecular weight, medium density polyethylene

A high molecular weight, medium density polyethylene (HMW, MDPE) is disclosed. The polyethylene comprises from about 85 to about 98 wt % of recurring units of ethylene and about 2 to about 15 wt % of a C -C &agr;-olefin. It has a density from about 0.92 to about 0.944 g/cc, a melt index MI from about 0.01 to about 0.5 dg/min, and a melt flow ratio MFR from about 50 to about 300. It has a multimodal molecular weight distribution comprising a high molecular weight component and a low molecular weight component. The low molecular weight component has an MI from about 50 to about 600 dg/min and a density from about 0.94 to about 0.97 g/cc. A process for making the medium density polyethylene is also disclosed. The process uses a Ziegler catalyst and applies multiple reaction zones.

A process for producing a polyethylene film composition, comprising melt extruding a linear copolymer of ethylene and at least one other olefin having from 3 to 8 carbon atoms, said linear copolymer having a bimodal distribution comprising a high molecular weight fraction having a weight average molecular weight of at least 600,000 and a low molecular weight fraction having a weight average molecular weight of less than 20,000 at a temperature of from 195 to 285.degree. C. in the presence of oxygen in an amount of from about 0.5 to about 6% by volume to improve bubble stability without any significant reduction in tear strength of film produced from said melt extruded linear copolymer.

Process for producing polyethylene film composition having broad

A polyethylene film composition characterized as having a broad molecular weight distribution, Mw/Mm 15, a density of 0.920 to 0.970 g/cc, a melt flow index (190.degree. C./2.16 kg) of 0.01 to 0.2 g/10 min., the polyethylene film composition being produced by melt extruding a linear copolymer at a temperature of at least 180.degree. C. in the presence of an amount of a free radical initiator sufficient to improve bubble stability without any significant reduction in the tear strength of film produced from the composition as compared with film produced from the linear copolymer that has not been treated with the free radical initiator.

Growing community of inventors

Bay City, TX, United States of America

Paula L Nygard