The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Gerhard Luft - One of the best experts on this subject based on the ideXlab platform.
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kinetic investigations of the metallocene catalyzed Polymerization of ethylene at high pressure
Chemical Engineering & Technology, 2002Co-Authors: Alexander Rau, Stefan Schmitz, Gerhard LuftAbstract:Metallocene catalysts are already used for the industrial High-Pressure Polymerization of ethylene. The products form this process show a small molecular weight distribution and a uniform incorporation of the comonomer. Excellent properties, suitable for the industrial use of the polymers results from this special molecular structure. The aim of this experimental work is to evaluate the kinetic parameters numerically, that is the pre-exponential factor, the activation energy and the activation volume, which describes the pressure dependence. Therefore, Polymerization tests are performed varying the concentration of ethylene and catalyst, temperature and pressure.
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Kinetic Investigations of the Metallocene – Catalyzed Polymerization of Ethylene at High Pressure
Chemical Engineering & Technology, 2002Co-Authors: Alexander Rau, Stefan Schmitz, Gerhard LuftAbstract:Metallocene catalysts are already used for the industrial High-Pressure Polymerization of ethylene. The products form this process show a small molecular weight distribution and a uniform incorporation of the comonomer. Excellent properties, suitable for the industrial use of the polymers results from this special molecular structure. The aim of this experimental work is to evaluate the kinetic parameters numerically, that is the pre-exponential factor, the activation energy and the activation volume, which describes the pressure dependence. Therefore, Polymerization tests are performed varying the concentration of ethylene and catalyst, temperature and pressure.
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Influence of Aluminium Alkyl Compounds on the High‐Pressure Polymerization of Ethylene with Ternary Metallocene‐Based Catalysts. Investigation of Chain Transfer to the Aluminium
Macromolecular Materials and Engineering, 2002Co-Authors: Christian Götz, Alexander Rau, Gerhard LuftAbstract:The influence of aluminium alkyl compounds on metallocene-catalyzed high pressure Polymerizations of ethylene has been investigated at 150 MPa and 180°C in a continuously operated autoclave. The catalysts were based on the metallocenes bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) and diphenylmethylene (cyclopentadienylfluorenyl)zirconium dichloride (Ph2C-(CpFlu)ZrCl2), which were preactivated outside the reactor with triisobutylaluminium (TiBA) and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (DMAP, [PhNHMe2][B(C6F5)4]). The concentrations of triisobutylaluminium (TiBA) and triethylaluminium (TEA) in the reactor were varied over a wide range, using a separate dosing for these two aluminium alkyl compounds. Productivity and polymer properties strongly depended on the type and the concentration of the aluminium alkyl compound used. Highest productivities and molecular weights were obtained with low concentrations of TiBA in the reactor. Up to a concentration of 30 molppm Al in the reactor, unimodal polymers were formed with Mw/Mn between 2 and 3. With higher aluminium concentrations the products formed contained small amounts of waxes, due to oligomerization catalyzed by the aluminium alkyl compounds. The molecular weight distributions (MWDs) of these products could be described as a superimposition of two Schulz-Zimm distributions. All MWDs were analyzed with regard to the amount of waxes produced by ethylene oligomerization and with regard to the influence of chain transfer reactions to the aluminium. The rate constants of chain transfer to aluminium, in relation to the rate constants of insertion of ethylene, were estimated.
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9.5 – High-Pressure Polymerization with metallocene catalysts
High Pressure Process Technology: Fundamentals and Applications, 2001Co-Authors: Gerhard LuftAbstract:In recent years, metallocene catalysts have been introduced into low-pressure gas-phase-, solution-, and slurry-processes to manufacture polyethylene and polypropylene. The new technology extends not only the range of conventional materials but generates new speciality polymers. Some companies have also retrofitted High-Pressure reactors to make use of the advantages of metallocene catalysts. The advantages of the new process result from the excellent properties of metallocene-based polyethylene (mPE). One of the main features of mPE is the uniform molecular weight distribution. It is generated by the single-site metallocene catalyst. In contrast, polyethylenes from the Ziegler–Natta processes show a broad molecular weight distribution. Ziegler–Natta catalysts exhibit sites of different activity, which contribute to the broad range of molecular weights. These catalysts are known as multisite catalysts. The narrow molecular weight distribution and the uniform incorporation of co-monomers lead to improved product properties, such as high impact strength, transparency, and heat seal, together with less stickiness and blocking of films. mPE exhibits a smaller fraction of extractables. On the other hand, mPE suffers from a more difficult processibility, lower melt strength, and higher melt fracture.
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Synthesis and application in High-Pressure Polymerization of a titanium complex with a linked cyclopentadienyl-phenoxide ligand
Journal of Organometallic Chemistry, 2000Co-Authors: Alexander Rau, Stefan Schmitz, Gerhard LuftAbstract:Abstract The ansa half-sandwich complex [η 5 :η 1 -C 5 H 4 -C(CH 3 ) 2 -2-C 6 H 4 O]TiCl 2 ( 1 ) has been prepared using two different ways, a ‘one-pot’ synthesis and a synthesis via thermolysis of the Ti trichloride precursor [η 5 -C 5 H 4 -C(CH 3 ) 2 -2-C 6 H 4 OCH 3 ]TiCl 3 ( 3 ). When activated with methylaluminoxane ( 4 ) or the cocatalyst system triisobutyl aluminum/[Me 2 PhNH] + [B(C 6 F 5 ) 4 ] − ( 5 ), complex 1 could be used as a catalyst in High-Pressure, high-temperature Polymerization. The productivity of the catalyst system 1 / 4 in High-Pressure Polymerization of ethene is 400 t polymer mol −1 Ti, while the productivity of catalyst system 1 / 5 is only 6 t polymer mol −1 Ti. In ethene/1-hexene coPolymerizations productivity and molecular weights decrease with increasing 1-hexene in the feed. The Polymerization results were discussed and compared to results of High-Pressure Polymerization with the catalyst system Me 2 Si[IndH 4 ] 2 ZrCl 2 / 4 .
Osamu Fukunaga - One of the best experts on this subject based on the ideXlab platform.
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New High Pressure Polymerization and Simultaneous Processing for Polyaminoimide from Aromatic Diamine and Bismaleimide
Polymer Journal, 1993Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Yoshihiro Kumagai, Masami Kanamaru, Hidetsugu Sawada, Osamu FukunagaAbstract:The simultaneous Polymerization and processing under high pressure was carried out by using a piston-cylinder type hot pressing apparatus. Before the polymer synthesis, the Michael addition of aniline to N -phenylmaleimide was performed under high pressure as a model reaction, giving N , N ′-diphenylaspartimide. The Michael-type polyaddition of 4,4′-methylenedianiline to 4,4′-bismaleimidodiphenylmethane under 150–820 MPa at 180–300°C for 20–40 h afforded the linear polyaminoimide having inherent viscosities in the range of 0.2–0.8 dl g^−1. When the Polymerization was carried out at higher temperature, the closslinked polymer was produced. The Polymerization under higher pressure required higher temperature. The closslinked polymer synthesized under high pressure was very hard resin with Vickers hardness of 330–360 MPa and high modulus (>1.5 GPa), compared with the polymer obtained under ordinary pressure.
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High Pressure Solid-State Synthesis of Poly(p-phenylene-1,2,4-oxadiazole) through 1,3-Dipolar Cycloaddition Polymerization of p-Cyanobenzonitrile N-Oxide
Polymer Journal, 1992Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Osamu FukunagaAbstract:Poly( p -phenylene-1,2,4-oxadiazole) was synthesized by the solid-state 1,3-dipolar cycloaddition Polymerization of p -cyanobenzonitrile N -oxide under high pressure. The high pressure Polymerization was carried out by using a piston cylinder type hot-pressing apparatus. Pressure and temperature accelerated the Polymerization, and higher pressure (up to 750 MPa) and higher temperature (up to 150°C) afforded the polymer with an inherent viscosity around 0.5 dl g^−1. The crystallinity and thermal behavior of the polymer were discussed in connection with the Polymerization conditions.
Kazuo Itoya - One of the best experts on this subject based on the ideXlab platform.
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A new high pressure Polymerization and simultaneous processing technique for the preparation of aromatic polycyanurates from aromatic dicyanate monomers
Polymer, 1994Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio ImaiAbstract:Abstract The high pressure Polymerization of aromatic dicyanates was carried out by using a piston cylinder type hot-pressing apparatus, which led to the formation of crosslinked polycyanurate resins. In a model compound study, aromatic cyanates were found to cyclotrimerize under high pressure to give aromatic cyanurates, with the application of high pressure accelerating the cyclotrimerization process. Aromatic dicyanates polymerized at 150–280°C under pressures of 200–450 MPa, affording polycyanurates through a cyclotrimerization reaction. Polymerization under higher pressure required both higher temperatures and longer reaction times. After further curing of these crosslinked polymers, very hard resins were produced, with Vickers hardness values of 330–530 MPa and with a high modulus (> 2 GPa), when compared with the same polymers synthesized under normal atmospheric pressure.
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New High Pressure Polymerization and Simultaneous Processing for Polyaminoimide from Aromatic Diamine and Bismaleimide
Polymer Journal, 1993Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Yoshihiro Kumagai, Masami Kanamaru, Hidetsugu Sawada, Osamu FukunagaAbstract:The simultaneous Polymerization and processing under high pressure was carried out by using a piston-cylinder type hot pressing apparatus. Before the polymer synthesis, the Michael addition of aniline to N -phenylmaleimide was performed under high pressure as a model reaction, giving N , N ′-diphenylaspartimide. The Michael-type polyaddition of 4,4′-methylenedianiline to 4,4′-bismaleimidodiphenylmethane under 150–820 MPa at 180–300°C for 20–40 h afforded the linear polyaminoimide having inherent viscosities in the range of 0.2–0.8 dl g^−1. When the Polymerization was carried out at higher temperature, the closslinked polymer was produced. The Polymerization under higher pressure required higher temperature. The closslinked polymer synthesized under high pressure was very hard resin with Vickers hardness of 330–360 MPa and high modulus (>1.5 GPa), compared with the polymer obtained under ordinary pressure.
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High Pressure Solid-State Synthesis of Poly(p-phenylene-1,2,4-oxadiazole) through 1,3-Dipolar Cycloaddition Polymerization of p-Cyanobenzonitrile N-Oxide
Polymer Journal, 1992Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Osamu FukunagaAbstract:Poly( p -phenylene-1,2,4-oxadiazole) was synthesized by the solid-state 1,3-dipolar cycloaddition Polymerization of p -cyanobenzonitrile N -oxide under high pressure. The high pressure Polymerization was carried out by using a piston cylinder type hot-pressing apparatus. Pressure and temperature accelerated the Polymerization, and higher pressure (up to 750 MPa) and higher temperature (up to 150°C) afforded the polymer with an inherent viscosity around 0.5 dl g^−1. The crystallinity and thermal behavior of the polymer were discussed in connection with the Polymerization conditions.
Yoshio Imai - One of the best experts on this subject based on the ideXlab platform.
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A new high pressure Polymerization and simultaneous processing technique for the preparation of aromatic polycyanurates from aromatic dicyanate monomers
Polymer, 1994Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio ImaiAbstract:Abstract The high pressure Polymerization of aromatic dicyanates was carried out by using a piston cylinder type hot-pressing apparatus, which led to the formation of crosslinked polycyanurate resins. In a model compound study, aromatic cyanates were found to cyclotrimerize under high pressure to give aromatic cyanurates, with the application of high pressure accelerating the cyclotrimerization process. Aromatic dicyanates polymerized at 150–280°C under pressures of 200–450 MPa, affording polycyanurates through a cyclotrimerization reaction. Polymerization under higher pressure required both higher temperatures and longer reaction times. After further curing of these crosslinked polymers, very hard resins were produced, with Vickers hardness values of 330–530 MPa and with a high modulus (> 2 GPa), when compared with the same polymers synthesized under normal atmospheric pressure.
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New High Pressure Polymerization and Simultaneous Processing for Polyaminoimide from Aromatic Diamine and Bismaleimide
Polymer Journal, 1993Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Yoshihiro Kumagai, Masami Kanamaru, Hidetsugu Sawada, Osamu FukunagaAbstract:The simultaneous Polymerization and processing under high pressure was carried out by using a piston-cylinder type hot pressing apparatus. Before the polymer synthesis, the Michael addition of aniline to N -phenylmaleimide was performed under high pressure as a model reaction, giving N , N ′-diphenylaspartimide. The Michael-type polyaddition of 4,4′-methylenedianiline to 4,4′-bismaleimidodiphenylmethane under 150–820 MPa at 180–300°C for 20–40 h afforded the linear polyaminoimide having inherent viscosities in the range of 0.2–0.8 dl g^−1. When the Polymerization was carried out at higher temperature, the closslinked polymer was produced. The Polymerization under higher pressure required higher temperature. The closslinked polymer synthesized under high pressure was very hard resin with Vickers hardness of 330–360 MPa and high modulus (>1.5 GPa), compared with the polymer obtained under ordinary pressure.
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High Pressure Solid-State Synthesis of Poly(p-phenylene-1,2,4-oxadiazole) through 1,3-Dipolar Cycloaddition Polymerization of p-Cyanobenzonitrile N-Oxide
Polymer Journal, 1992Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Osamu FukunagaAbstract:Poly( p -phenylene-1,2,4-oxadiazole) was synthesized by the solid-state 1,3-dipolar cycloaddition Polymerization of p -cyanobenzonitrile N -oxide under high pressure. The high pressure Polymerization was carried out by using a piston cylinder type hot-pressing apparatus. Pressure and temperature accelerated the Polymerization, and higher pressure (up to 750 MPa) and higher temperature (up to 150°C) afforded the polymer with an inherent viscosity around 0.5 dl g^−1. The crystallinity and thermal behavior of the polymer were discussed in connection with the Polymerization conditions.
Masa-aki Kakimoto - One of the best experts on this subject based on the ideXlab platform.
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A new high pressure Polymerization and simultaneous processing technique for the preparation of aromatic polycyanurates from aromatic dicyanate monomers
Polymer, 1994Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio ImaiAbstract:Abstract The high pressure Polymerization of aromatic dicyanates was carried out by using a piston cylinder type hot-pressing apparatus, which led to the formation of crosslinked polycyanurate resins. In a model compound study, aromatic cyanates were found to cyclotrimerize under high pressure to give aromatic cyanurates, with the application of high pressure accelerating the cyclotrimerization process. Aromatic dicyanates polymerized at 150–280°C under pressures of 200–450 MPa, affording polycyanurates through a cyclotrimerization reaction. Polymerization under higher pressure required both higher temperatures and longer reaction times. After further curing of these crosslinked polymers, very hard resins were produced, with Vickers hardness values of 330–530 MPa and with a high modulus (> 2 GPa), when compared with the same polymers synthesized under normal atmospheric pressure.
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New High Pressure Polymerization and Simultaneous Processing for Polyaminoimide from Aromatic Diamine and Bismaleimide
Polymer Journal, 1993Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Yoshihiro Kumagai, Masami Kanamaru, Hidetsugu Sawada, Osamu FukunagaAbstract:The simultaneous Polymerization and processing under high pressure was carried out by using a piston-cylinder type hot pressing apparatus. Before the polymer synthesis, the Michael addition of aniline to N -phenylmaleimide was performed under high pressure as a model reaction, giving N , N ′-diphenylaspartimide. The Michael-type polyaddition of 4,4′-methylenedianiline to 4,4′-bismaleimidodiphenylmethane under 150–820 MPa at 180–300°C for 20–40 h afforded the linear polyaminoimide having inherent viscosities in the range of 0.2–0.8 dl g^−1. When the Polymerization was carried out at higher temperature, the closslinked polymer was produced. The Polymerization under higher pressure required higher temperature. The closslinked polymer synthesized under high pressure was very hard resin with Vickers hardness of 330–360 MPa and high modulus (>1.5 GPa), compared with the polymer obtained under ordinary pressure.
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High Pressure Solid-State Synthesis of Poly(p-phenylene-1,2,4-oxadiazole) through 1,3-Dipolar Cycloaddition Polymerization of p-Cyanobenzonitrile N-Oxide
Polymer Journal, 1992Co-Authors: Kazuo Itoya, Masa-aki Kakimoto, Yoshio Imai, Osamu FukunagaAbstract:Poly( p -phenylene-1,2,4-oxadiazole) was synthesized by the solid-state 1,3-dipolar cycloaddition Polymerization of p -cyanobenzonitrile N -oxide under high pressure. The high pressure Polymerization was carried out by using a piston cylinder type hot-pressing apparatus. Pressure and temperature accelerated the Polymerization, and higher pressure (up to 750 MPa) and higher temperature (up to 150°C) afforded the polymer with an inherent viscosity around 0.5 dl g^−1. The crystallinity and thermal behavior of the polymer were discussed in connection with the Polymerization conditions.