Abstract:
A method for preparing a titanium-containing Ziegler-Natta catalyst is disclosed. A dialkyl magnesium compound, a trialkyl aluminum compound, and a polymethylhydrosiloxane are first combined in a hydrocarbon solvent. That product is then combined with dry, alcohol-free magnesium chloride. A solid product from the reaction with the magnesium chloride component is isolated and washed with a hydrocarbon solvent. The washed solid product is then combined with an alkyl aluminum dichloride or a dialkyl aluminum chloride to give the catalyst. The catalyst is suitable for both slurry and gas-phase olefin polymerizations. Polyolefins produced with the catalyst have broad molecular weight distributions and narrow distributions of relatively large particles.
Abstract:
Bimodal polyethylene resins having reduced long-chain branching and suitable for use in pipe resin applications as a result of their improved SCG and RCP resistance are provided. The improved resins of the invention are produced in a two-reactor cascade slurry polymerization process using a Ziegler-Natta catalyst system and wherein an alkoxysilane modifier is present in both reactors.
Abstract:
The invention relates to supports comprising inorganic oxide particles coated with magnesium chloride and a method for making them. The inorganic oxide has a mean particle diameter of less than 5 microns and is used as a seed to crystallize magnesium chloride from solution. The magnesium chloride-coated inorganic oxide is useful for supporting transition metal compounds; the supported transition metal compounds are used as catalysts for polymerizing olefins.
Abstract:
A method of modifying a polyethylene is disclosed. In the method ethylene or a mixture of ethylene and a C3-C10 α-olefin is polymerized in an organic solvent with a Ziegler or single-site catalyst to form an initial polyethylene solution. The initial polyethylene solution is then reacted with a free radical initiator to produce a modified polyethylene. The modified polymer has an enhanced melt elasticity and increased long chain branching index, and is essentially free of gel.
Abstract:
An improved two-step polymerization process wherein ethylene homopolymer is produced in a first reactor and ethylene copolymer having narrowed short-chain branching distribution is prepared in a second reactor. Narrowed short-chain branching distribution of the copolymer is achieved by including specific silane modifiers in the second reactor.
Abstract:
A process for polymerizing ethylene is disclosed. A magnesium chloride-alcohol is used to support an organometallic complex comprising a Group 3 to 10 transition metal and an indenoindolyl ligand. The supported organometallic complex is mixed with an activator and ethylene and the ethylene is polymerized. Use of magnesium chloride containing an alcohol as the support provides an unexpected boost in catalyst activity and improves polymer rheological properties.
Abstract:
A clay-filled polyolefin composition and process for making it are disclosed. The process involves treatment of a non-acid-treated smectite clay with a Ziegler-Natta catalyst in the presence of a hydrocarbon and subsequent polymerization of an olefin in the presence of the treated clay and an organoaluminum cocatalyst. Results indicate that filled compositions produced by this process contain exfoliated clay.
Abstract:
The present invention relates to a novel catalyst component for ethylene polymerization comprising vanadium and titanium. Moreover, when the vanadium/titanium containing catalyst of the present invention is employed with an aluminum-containing cocatalyst enhanced activity as well as melt index is obtained.The present invention is directed to a novel halosilane cocatalyst component which, when used in conjunction with an aluminum containing cocatalyst, is effective in increasing the activity of a silica supported titanium/vanadium containing solid catalyst component in the polymerization of ethylene and/or .alpha.-olefins. In addition to the increased catalytic activity, the polymers produced by the present invention exhibit improved melt index values compared with melt index values typically obtained using prior art catalyst systems. Thus, the catalyst system of the instant invention represent an advancement in the art in view of the combination of increased activity, i.e., yield of polymer produced, and physical properties of the polyolefin product.In another aspect of the present invention, a process for polymerizing ethylene and/or .alpha.-olefins is disclosed. In this process at least one olefin is polymerized under olefin polymerization conditions utilizing the catalyst system of the present invention, which includes the solid catalyst component of the present invention, along with the first cocatalyst, an aluminum-containing compound, and the second cocatalyst, a halosilane.
Abstract:
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.
Abstract:
Bimodal polyethylene resins having reduced long-chain branching and suitable for use in pipe resin applications as a result of their improved SCG and RCP resistance are provided. The improved resins of the invention are produced in a two-reactor cascade slurry polymerization process using a Ziegler-Natta catalyst system and wherein an alkoxysilane modifier is present in both reactors.