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.

The polypropylene copolymer according to the present invention has a low melting point and also is excellent in the low temperature heat sealing effect, transparency and strength, and the film prepared therefrom can be effectively used as a sealing layer of the non-stretched polypropylene-based film.

A system and method of producing polyethylene, including: polymerizing ethylene in presence of a catalyst system in a reactor to form polyethylene, wherein the catalyst system includes a first catalyst and a second catalyst; and adjusting reactor conditions and an amount of the second catalyst fed to the reactor to control melt index (MI), density, and melt flow ratio (MFR) of the polyethylene.

Catalyst systems and methods for making and using the same are described. A method includes selecting a catalyst blend using a blend polydispersity index (bPDI) map. The polydispersity map is generated by generating a number of polymers for at least two catalysts. Each polymer is generated at a different hydrogen to ethylene ratio. At least one catalyst generates a higher molecular weight polymer and another catalyst generates a lower molecular weight polymer. A molecular weight for each polymer is measured. The relationship between the molecular weight of the polymers generated by each of the catalysts and the ratio of hydrogen to ethylene is determined. A family of bPDI curves for polymers that would be made using a number of ratios of a blend of the at least two catalysts for each of a number of ratios of hydrogen to ethylene. A ratio for the catalyst blend of the catalysts that generates a polymer having a bPDI that matches a polymer fabrication process is selected, and the product specific polyolefin is made using the catalyst blend.

Methods for preparing metallocene-based catalyst compositions include the steps of contacting an alcohol compound and an organoaluminum compound for a first period of time to form a precontacted mixture, and contacting the precontacted mixture with an activator-support and a metallocene compound for a second period of time to form the catalyst composition. Such catalyst compositions can contain an activator-support, a metallocene compound, an organoaluminum compound, and a dialkyl aluminum alkoxide, and these catalyst compositions have increased catalytic activity for the polymerization of olefins.

The polypropylene copolymer according to the present invention has a low melting point and also is excellent in the low temperature heat sealing effect, transparency and strength, and the film prepared therefrom can be effectively used as a sealing layer of the non-stretched polypropylene-based film.

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: ##STR00001##
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.

A styrene resin having a syndiotactic structure, with an endothermic amount in a range of 175 to 260? C. of less than 30% based on the total endothermic amount, and a styrene resin composition containing 50 to 95% by mass of a thermoplastic resin composition and 5 to 50% by mass of a glass filler, the thermoplastic resin composition containing 100 parts by mass containing 80 to 100% by mass of a styrene resin having a syndiotactic structure and 0 to 20% by mass of a rubbery elastic material, 0.2 to 2.0 parts by mass of at least one kind of an antioxidant selected from a phenol-based antioxidant and a sulfur antioxidant, 1.5 to 5.0 parts by mass of at least one kind of a compound selected from a polyphenylene ether or a modified polyphenylene ether, and at least one kind selected from a nucleating agent or a release agent.

Provided are use of organosilane, and polyolefin resin and preparation method thereof. The method of preparing the polyolefin resin comprises: conducting olefin polymerization of olefin monomers in the presence of a catalyst, and adding organosilane to a polymerization system before the olefin polymerization and/or during the olefin polymerization, wherein the organosilane is represented by a general formula of R.sup.1.sub.mSiX.sub.n(OR.sup.2).sub.k, wherein R.sup.1 is a C.sub.2-C.sub.20 alkyl, and a terminal of R.sup.1 has an -olefin double bond, a norbornene group, a cycloalkene group, or a dicyclopentadiene group; X is a halogen element; R.sup.2 is a C.sub.1-C.sub.20 straight chain, a C.sub.1-C.sub.20 branched chain, or an isomerized alkyl group; m is an integer from 1-3; n is an integer from 1-3; k is an integer from 0-2; and m, n, and k satisfy the following condition: m+n+k=4. The polyolefin resin obtained by the above method has higher melt strength and mechanical strength.

In the present disclosure, there are provided a polyethylene having improved low-temperature sealing properties with an increase in the content and molecular weight of a low crystalline polymer, and a method for preparing the same.