The present invention relates to a catalyst for olefin polymerization. Specifically, the present invention relates to a hybrid catalyst comprising different transition metal compounds and capable of preparing a polyolefin, particularly a linear low-density polyethylene, which has excellent processability, impact strength, and haze.

Catalyst systems and methods for making and using the same. A method of polymerizing olefins to produce a polyolefin polymer with a multimodal composition distribution, includes contacting ethylene and a comonomer with a catalyst system. The catalyst system includes a first catalyst compound and a second catalyst compound that are co-supported to form a commonly supported catalyst system. The first catalyst compound includes a compound with the general formula (C.sub.5H.sub.aR.sup.1.sub.b)(C.sub.5H.sub.cR.sup.2.sub.d)HfX.sub.2. The second catalyst compound includes at least one of the following general formulas:

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In both catalyst systems, the R groups can be independently selected from any number of substituents, including, for example, H, a hydrocarbyl group, a substituted hydrocarbyl group, or a heteroatom group, among others.

Provided are an ethylene-based polymer having excellent long-term pressure resistance characteristics and a pipe using the ethylene-based polymer. The ethylene-based polymer satisfies the balance of mechanical characteristics and excellent molding processability, as compared with a conventional ethylene-based polymer. Also provided are an ethylene-based polymer having a wide molecular weight distribution and a small lamellar thickness, thereby increasing tie molecules and obtaining excellent long-term pressure resistance characteristics, and a pipe using the same.

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems.

This invention relates to a method for producing multimodal polyolefin using multistage continuous polymerization process for producing multimodal polyolefin having superior melt-strength, moldability, mechanical strength, processability, and appearance. A method for producing multimodal polyolefin using multistage polymerization process, comprising the steps of: polymerizing a high molecular weight bimodal polymer by introducing a monomer in the presence of a catalyst composition including two or more different catalysts in a first reactor; and continuously introducing the high molecular weight bimodal polymer produced in the first reactor into a second reactor, and polymerizing a low molecular weight bimodal polymer by introducing a monomer in the presence of the catalyst composition, wherein the multimodal polyolefin includes the high molecular weight bimodal polymer and the low molecular weight bimodal polymer at the same time.

To provide a method for producing a styrene resin having a syndiotactic structure, including performing addition polymerization of one or more of a vinyl aromatic monomer in the presence of a catalyst containing a half metallocene transition metal compound (A) having at least one kind selected from metals of groups 3 to 5 of the periodic table and lanthanoid transition metals as a central metal, a compound (B) represented by the general formula (1), and a compound (C) selected from at least one kind of an oxygen-containing compound (c1) and a compound (c2) capable of forming an ionic complex through reaction with a transition metal compound, the styrene resin produced having a transition metal content derived from the half metallocene transition metal compound (A) of 1.5 to 12 ppm by mass.

A door assembly. The door assembly may include at least one door panel and a door frame having a plurality of frame members including a header and a pair of side jambs. The invention may also be considered a frame member. The frame member may include a core; and a two-piece top piece adjoining the core to form a structural member. The core and the top piece may be a composite of cellulosic material and at least one other material. The door assembly may further include at least one adjacent panel. Also disclosed are door jamb frame members and mullion frame members.

Techniques are provided for catalyst preparation. A system for catalyst preparation may include an agitator disposed inside a polymerization catalyst tank and configured to mix a polymerization catalyst and a solvent to generate a polymerization catalyst solution. The system may also include a heating system coupled to the polymerization catalyst tank and configured to maintain a temperature of the polymerization catalyst solution above a threshold. The system may also include a precontactor configured to receive feed streams comprising an activator and the polymerization catalyst solution from the polymerization catalyst tank to generate a catalyst complex. The system may also include a transfer line configured to transfer the catalyst complex from an outlet of the precontactor to a reactor.

Provided herein are polyethylene compositions suitable in the fabrication of PE-RT pipes for use in cold and hot water plumbing in accordance with ISO 22391-2, and processes for making the same.

A process for copolymerizing ethylene and at least one C3 to C8 alpha olefin to obtain an ethylene-C3 to C8 alpha olefin copolymer, the process comprising a) copolymerizing ethylene and at least one C3 to C8 alpha olefin in a solvent in a solution polymerization reactor to obtain an intermediate polymer solution, b) discharging an effluent stream from the intermediate polymer solution into a heat exchanger, c) setting the temperature of the effluent stream in the heat exchanger to obtain a heated effluent stream, d) feeding the heated effluent stream to a flash separation, e) separating at least a part of the ethylene-C3 to C8 alpha olefin copolymer in the flash separation, characterized by feeding an inert hydrocarbon fulfilling 90 C.<T(BP)<130 C. to the solution polymerization reactor; and/or accumulating an inert hydrocarbon fulfilling 90 C.<T(BP)<130 C. during the polymerization reaction; and/or feeding an inert hydrocarbon fulfilling 90 C.<T(BP)<130 C. to the discharged effluent stream of step b).