KOBUNSHI RONBUNSHU
Online ISSN : 1881-5685
Print ISSN : 0386-2186
ISSN-L : 0386-2186
Volume 51, Issue 10
Displaying 1-8 of 8 articles from this issue
  • Hajime YASUDA, Eiji IHARA
    1994 Volume 51 Issue 10 Pages 637-646
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    Recent developments of olefin polymerization catalysts based on group III and IV metal complexes are described. Me2Si-bridged Cp rings with sterically bulky substituents were used as ligands for organolanthanide complexes and their reactivities to olefins were examined. As for the divalent Sm, racemic type complex Me2Si (2-Me3Si-4-t-Bu-C5H2) 2Sm (THF) 2 gave higher molecular weight polyethylene than Cp2Sm (THF) 2, and also showed catalytic activity to α-olefins, giving isotactic poly (α-olefin) s. A meso type Sm (II) complex with high activity for ethylene polymerization afforded relatively low molecular weight polyethylene. A C1 symmetric trivalent Sm complex Me2Si [2, 4- (Me3Si) 2C5H2] [3, 4- (Me3Si) 2C5H2] SmCH (SiMe3) 2 showed high activity for ethylene polymerization, but the same kinds of racemic and meso type complexes did not show it at all. The structures of the active complexes were revealed by the X-ray method. Atrivalent hydride complex [Me2Si (2-Me3Si-4-t-BuMe2Si-C5H2) 2H] 2 showed high activity for a-olefins, giving isotactic poly (1-pentene) and poly (1-hexene) in high yield. Furthermore, the complex catalyzed cyclopolymerization of 1, 5-hexadiene affording high molecular weight poly (methylene-1, 3-cyclopentane).
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  • Riichiro CHUJO, Eiji SAKAGUCHI, Mika HARKONEN, Jukka SEPPALA
    1994 Volume 51 Issue 10 Pages 647-651
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    The formulae for conditional probabilities are derived with the terms of NMR triad tacticities for the polymers whose polymerization process is described by the asymmetric Markovian process. The obtained formulae are applied to the polypropylenes polymerized by Ziegler-Natta catalysts with external alkoxysilane donors. For both of unfractionated samples and heptane-insoluble fractions, the followings were clarified: 1) the transformation from symmtric to (fluctuating) asymmetric centers the transformation of one (hereafter, L) site is much enhanced than that of Dsite, 2) the monotonous increase of isotacticity as a result of the increase of the concentration of the donors is due to the increase ofPLL, 3) aromatic donors are effective than aliphatic ones for the improvement of isotacticity, and 4) the improvement of isotacticity after an addition of the alkoxysilanes is not due to the contribution from both of L and D sites, but the positive contribution from the former is larger than the negative one from the latter.
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  • Kiyoshi ENDO, Koji MASAKI
    1994 Volume 51 Issue 10 Pages 652-656
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    Polymerization of styrene (St) with nickel acetylacetonate [Ni (acac) 2] and methylalumoxane (MAO) catalyst was investigated. It was found that the Ni (acac) 2-MAO catalyst showed a high catalytic activity for the polymerization of St. From a kinetic study, the polymerization rate (Rp) can be expressed by Rp=k [St] 2.0 [Ni (acac) 2-MAO] 0.75. The overall activation energy for the polymerization was determined to be 23.4 kJ/mol. The polymers were found to be rich in isotactic sequence. From ESR study, it was assumed that the active sites for the polymerization involve the Ni (I) complex.
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  • Shojiro KAITA, Isao SHIMOSATO, Eiichi KOBAYASHI, Sadahito AOSHIMA, Jun ...
    1994 Volume 51 Issue 10 Pages 657-662
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    Copolymerization of Styrenes was carried out with Gd (OCOCCl3) 3- (iso-Bu) 3Al-Et2AlCl in hexane at 50°C under N2. As monomers styrene (St), p-chlorostyrene (PCS), p-methylstyrene (PMS), and p-methoxystyrene (PMOS) were used. The copolymer composition was analyzed by 13C NMR to examine the monomer reactivity ratios by the Fineman-Ross method. The values of the monomer reactivity ratios were r1=0.72 and r2=1.25 for the St (M1) /PCS (M2), r1=0.38 and r2=0.51 for St (M1) /PMS (M2), and r1=0.55 and r2=1.07 for St (M1) /PMOS (M2). Hammett plot of r2 showed a positive line slope of ρ=2.15. Comequently, this result suggests that the mechanism of polymerizatio is apparently different from that by the Ziegler catalyst based on titanium where ρ=-0.95. An orbital level of Gd (OCOCCl3) 3 may control polymerizability of styrenes through the donatio and back-donation processes. Steric hindrance of asubstituted styrenes may decrease the polymerizability.
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  • Takeshi SHIONO, Toshiya UOZUMI, Kazuo SOGA
    1994 Volume 51 Issue 10 Pages 663-669
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    Propene polymerization was conducted with ethylenebis (tetrahydroindenyl) zirconium dichloride combined with methylalumoxane at O, 20, and 40°C. The activity increased linearly with an increase in propene pressure regardless of polymerization temperature. The molecular weights of the polymers obtained at 0°C were independent of the propene pressure, while those at 20 and 40°C slightly increased with an increase in the propene pressure. The polymers obtained at 40°C contained vinylidene end groups addition to a small amount of an internal olefin group, The amount of the vinylidene groups decreased with increasing the propene pressure of decreasing polymerization temperature. On the other hand, the amount of the internal olefins was independent of the propene pressure. The copolymerization of propene with ethylene was also conducted with this catalyst system at 0, 20, and 40°C. The produced polymers had a vinylidene end group exclusively. Moreover, the propene unit also existed at the saturated initiation end. From these results, it was concluded that the chain transfer reaction with this catalyst system was caused mainly by propene monomer when the propagation proceeded via 1, 2-addition.
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  • Seiji MAEHAMA, Akihiro YANO, Satoru YAMADA, Akira AKIMOTO
    1994 Volume 51 Issue 10 Pages 670-675
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    Stability of various fluorinated BPh4 anions in ion-pair metallocene catalyst systems has been studied. XPS measurement shows that the incorporation of electron-withdrawing fluorine substiuents decreases the electron density of boron drastically. The anions can be classified into three types according to the reactivity associated with its Lewis basisity, i. e., the number of fluorine substituents: (1) the anion without any fluorine substituent that reacts with Cp2ZrR with phenyl group transfer, (2) those with 1-3 fluorine substituents that react with trialkyl aluminium, and (3) those with 4 and 5 fluorine substituents that undergo no side reactions. Practically, the stability of the anion is one of the most important requirements for the application of the ion-pair (non-MAO) metallocene catalyst.
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  • Akira AOKI, Nobuhiko NAKAYAMA, Tetsuo HAYASHI, Tetsuo ASAKURA
    1994 Volume 51 Issue 10 Pages 676-684
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    13C NMR chemical shift assignments of comonomer sequences in an ethylene-propylene-1-butene terpolymer were obtained from mainly 13C two dimensional INADEQUATE NMR experiment and the calculated chemical shifts on the basis of the 13C NMR γ-effect. By tracing carbon-carbon connectivities in the 2D INADEQUATE spectrum, two kinds of peaks, which were not separated in the 1D-INEPT spectrum, were assigned clearly. In addition, the chemical shift differences among comonomer sequences longer than tetrad were predicted by chemical shift calculation. Further, the conformational states of the side chain in the 1-butene unit were evaluated through the chemical shift calculation.
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  • Koichiro ISHII, Teruo MORI, Takashi FUJITA
    1994 Volume 51 Issue 10 Pages 685-687
    Published: October 25, 1994
    Released on J-STAGE: March 15, 2010
    JOURNAL FREE ACCESS
    NMR was used to study the interaction between alkoxysilane compounds and a MgCl2-supported Ziegler-Natta catalyst (MgCl2/TiCl4/dibutyl phthalate). 29Si NMR data indicated the interaction of alkoxysilane compounds with MgCl2 on the solid-catalyst, but not with TiCl4. Moreover, we found a correlation between the 29Si chemical shift of the alkoxysilane compounds and isotactic or atactic polymerization rate in the propylene polymerization.
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