Patent application number | Description | Published |
20080300370 | Preparation of polyethylene - A process for preparing a polyethylene in a multi-stage process is described. The process comprises pre-treating a Ziegler catalyst in a first stage in the presence of a 1-olefin/ethylene mixture or a 1-olefin to produce a LLDPE or VLDPE, which have the characteristics of a polymer prepared with a single-site catalyst, e.g. high levels of short-chain branching that are uniformly distributed. The contents of the first stage are then transferred to a second stage where an ethylene or an ethylene/1-olefin mixture is polymerized in the presence of the pre-treated catalyst to form a polyethylene with good processability. | 12-04-2008 |
20090048402 | Preparing multimodal polyethylene having controlled long chain branching distribution - A process to prepare a multimodal polyethylene with controlled LCB distribution is disclosed. In the first stage, ethylene is polymerized in the presence of a Ziegler catalyst that results in a homopolyethylene component having a higher LCB concentration. In the second stage, ethylene is copolymerized with a 1-olefin in the presence of the Ziegler catalyst and a lower concentration of hydrogen resulting in a copolymer component with a lower LCB concentration. The homopolyethylene component and the copolymer component are combined to form a novel multimodal polyethylene. | 02-19-2009 |
20100113715 | Olefin polymerization process - A multi-reactor solution process for polymerizing ethylene is disclosed. Ethylene is polymerized in a first reaction zone in two parallel reactors and the polyethylene is transferred to a second reaction zone to continue or complete the polymerization. Ethylene is contacted with a mixture of a titanium halide and a vanadium halide in the first parallel reactor and with a magnesium-titanium based Ziegler-Natta catalyst at a lower temperature in the second parallel reactor. The process gives improved catalyst activity. | 05-06-2010 |
20100129581 | Process for making ethylene homopolymers - A process for making an ethylene homopolymer in the presence of an oxide-supported chromium catalyst is disclosed. A small amount of an α-olefin contacted with the catalyst before polymerizing ethylene or introduced into an ethylene homopolymerization unexpectedly boosts process productivity. When used at part per million levels, the α-olefin improves productivity while maintaining desirable polymer properties. The invention is particularly valuable for making HDPE resins useful for blow molding applications. | 05-27-2010 |
20120116022 | PROCESS FOR MAKING ETHYLENE POLYMER BLENDS WITH CONTROLLED LONG-CHAIN BRANCHING - A high-temperature solution process for making an ethylene polymer blend having a controlled degree of long-chain branching is disclosed. Ethylene is polymerized in the presence of a first Ziegler-Natta catalyst comprising titanium, magnesium, and aluminum in the absence of hydrogen to produce a first ethylene polymer component having substantial long-chain branching. A second ethylene polymer component having little or no long-chain branching is also prepared. Both polymerizations are performed at a temperature from 140° C. to 250° C. The first and second ethylene polymer components are combined to give a polymer blend. The degree of long-chain branching in the blend is controlled by adjusting the relative amounts of the first and second ethylene polymer components. The invention enables the preparation of valuable products having a pre-determined degree of long-chain branching using readily available Zeigler-Natta catalysts, commercially practiced techniques, and conventional equipment. | 05-10-2012 |
20120232230 | PROCESS FOR MAKING ETHYLENE HOMOPOLYMERS - A process for making an ethylene homopolymer in the presence of an oxide-supported chromium catalyst is disclosed. A small amount of an α-olefin contacted with the catalyst before polymerizing ethylene or introduced into an ethylene homopolymerization unexpectedly boosts process productivity. When used at part per million levels, the α-olefin improves productivity while maintaining desirable polymer properties. The invention is particularly valuable for making HDPE resins useful for blow molding applications. | 09-13-2012 |
20130172499 | PROCESS FOR THE PREPARATION OF OLEFIN POLYMERS IN THE PRESENCE OF CHROMIUM CATALYSTS - A process for the polymerization of olefin carried out in the presence of a Cr-oxide supported catalyst and a cocatalyst the improvement comprising polymerizing in the presence of an effective amount of hydrogen thereby obtaining an increased catalyst activity. | 07-04-2013 |
20150141592 | BIMODAL POLYMERIZATION PROCESS UTILIZING CHROMIUM/SILICA CATALYSTS - The present invention relates to novel methods for producing a bimodal or broad distribution of molecular weight polyolefin polymers using Cr/silica catalysts. In some aspects the methods utilize different pressures of hydrogen to tailor the properties of the polymer. In particular aspects, a method of preparing a polyolefin having a bimodal molecular weight distribution, comprising:
| 05-21-2015 |