Evidence for ethylene‐propylene block copolymer formation

Prabhu, P.; Schindler, A.; Theil, Michael H.; Gilbert, R. D.

doi:10.1002/pol.1980.130180512

Cited by 24 publications

(4 citation statements)

References 6 publications

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“…In most cases, claims of styrene/α-olefin copolymer formation with Ziegler−Natta catalytic systems have not been proven directly but instead inferred from physical properties and the method of synthesis. Experimental evidence has shown that many of these commercial claims are indeed nothing more than intimate blends of homopolymers which show enhanced properties due to the fine level of dispersion achieved by in situ polymerization …”

Section: Introductionmentioning

confidence: 99%

“…The discovery of homogeneous group 4 metallocene−methylaluminoxane catalysts that combine high activity with excellent stereoregularity in the stereospecific polymerization of α-olefins or styrene has led to a resurgence of interest in this field . It is believed that metallocene catalytic systems will open up the possibility of controlling stereospecificity in styrene or olefin polymerization/copolymerization at the molecular level and making use of it to produce polymers with new microstructure. 2b, This can be attributed to the following factors: first, to the versatility of these catalysts in controlling the tacticity (e.g. isotactic, stereoblock, syndiotactic) and the performance (including narrow molecular weight distribution, well-defined microstructure and near-uniform composition) of polymers formed by changing the structural characteristics of the ligand; second, to the universality of these catalysts in promoting isospecific or syndiospecific polymerization of not only α-olefins but also cyclic olefins, polar vinyl monomers, vinyl aromatics, and dienes; third, to the increased activity and the true “single-site” formation of the metallocene catalysts 7 compared with traditional Ziegler−Natta catalysts.…”

Section: Introductionmentioning

confidence: 99%

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Titanocene−Methylaluminoxane Catalysts for Copolymerization of Styrene and Ethylene: Synthesis and Characterization of Styrene−Ethylene Copolymers

Xu¹,

Lin²

1997

Macromolecules

105

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The copolymerization of styrene and ethylene has been performed using a titanocene-based catalytic system of cyclopentadienyltitanium triphenoxide (CpTi(OPh)3) and methylaluminoxane (MAO). The catalyst system exhibited a high catalytic activity of 104−105 g (mof Ti·h)-1 and was found to selectively (more than 90 wt %) give an elastoplastic and amorphous styrene−ethylene (S−E) copolymer with a well-defined random/alternating microstructure and a single glass transition (T g) as thoroughly characterized by solvent fractionation, GPC, 13C NMR, DSC, and WAXD. Under the reaction conditions employed, up to 54.5 mol % of styrene could be introduced into the copolymer chains. The composition, microstructure, molecular weight of the copolymers, and catalytic activity of the copolymerization are strongly dependent upon the comonomer feed ratio, polymerization temperature (T p), CpTi(OPh)3/MAO mole ratio, and trimethylaluminum (TMA) content or structure in MAO. For 300 ⩽ Al/Ti < 1000, the copolymerization product was essentially the random S−E copolymer. For 1000 < Al/Ti ⩽ 2000, the copolymerization product was significantly SPS homopolymer. The results showed that 24.5−28.2 mol % TMA content in MAO (oligomerization degree (n) ≈ 18−20) was optimum for the copolymerization, but 30.2−35.7 mol % TMA in MAO (oligomerization degree (n) ≈ 24−28) for styrene syndiospecific homopolymerization, even in the presence of ethylene feed monomer. The external addition of TMA or triisobutylaluminum (TIBA) inhibited the copolymerization but promoted the styrene homopolymerization. ESR spectroscopic analysis combined with copolymerization results suggests the presence of a Ti(IV) active center which is responsible for the formation of polyethylene, a Ti(III) species which is active in the syndiospecific polymerization of styrene, and, moreover, the presence of a third intermediate which contributes to promoting the copolymerization of styrene with ethylene to produce S−E copolymer.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Titanocene−Methylaluminoxane Catalysts for Copolymerization of Styrene and Ethylene: Synthesis and Characterization of Styrene−Ethylene Copolymers

Xu¹,

Lin²

1997

Macromolecules

105

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“…As noted above, the Sgb+ peak was found in the 13C-NMR spectrum of an (AB)zm block copolymer. 6 The spectrum is shown in Figure 8. No polyethylene was found by urea complexation.…”

Section: C Nmr Spectroscopymentioning

confidence: 99%

Synthesis and properties of ABA propylene‐ethylene block copolymers

Prabhu

Schindler

Theil

et al. 1981

J. Polym. Sci. Polym. Chem. Ed.

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SynopsisExperimental data, which includes catalyst lifetimes, thermal analyses, fractionation by urea complexation, x-ray diffraction, and 13C-NMR spectroscopy, are presented to confirm the successful synthesis of ABA propylene-ethylene block copolymers. A dry catalyst system of DEAC-TiC13(AA) and a gas-phase polymerization technique was used to prepare the copolymers. PRP-and ERE-type copolymers (P-isotactic polypropylene, E-polyethylene, and R-random propylene-ethylene copolymer block) were prepared. Some preliminary physical property data are given which indicate that PRP-type copolymers can behave as elastomeric fibers. The stress-strain behavior also indicates block copolymer formation. EXPERIMENTALThe preparation of the active dry catalyst from Et2AlCl and TiC13(AA) and the technique for sequential addition of propylene and ethylene has already been d e~c r i b e d .~?~ Experimental conditions for the various copolymers are summarized in Table 1. The random B blocks were synthesized by admitting both monomers simultaneously, in various ratios, to the reaction vessel. The end A

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“…In addition, Doi et al (1972bDoi et al ( , 1973Doi et al ( ,1980 made kinetic studies of the gas-phase polymerizations of propene with several conventional Ziegler-Natta catalysts based on TiCl3 and showed that there is no appreciable difference in the number of active centers in the gas-phase and slurry polymerizations. Prabhu et al (1980Prabhu et al ( , 1981 studied the block copolymerization of ethylene and propene in the gas-phase process using TiCl3-Al(C2H5)2Cl catalyst. The BASF gas-phase process for the polymerization of propene has been outlined by Wisseroth (1969,1977).…”

Section: Introductionmentioning

confidence: 99%

Gas-phase polymerization of propene with the supported Ziegler catalyst: TiCl4/MgCl2/C6H5COOC2H5/Al(C2H5)3

Doi¹,

Murata²,

Yano³

et al. 1982

Ind. Eng. Chem. Prod. Res. Dev.

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The gas-phase polymerization of propene with the MgCI,-supported Ti CI , / C, H, COOC, H, catalyst in conjunction with AI(C2H,), has been investigated. The rate of polymerization depends on both titanium content and surface area of the MgCITsupported catalyst and decreases with the polymerization time. The number of active centers in the catalyst at different polymerization times is estimated by the inhibition method using carbon monoxide. As a result, the number of active centers decreasesjuring the course of polymerization, but the mean propagation rate constant k , remains constant. The value of k , is one order of magnitude larger than that in the conventional TiCI, catalyst.Potassium-graphite intercalation compounds were shown to catalyze the addition of ethylene to C, to C, n-olefins to give a preponderance of linear olefinic products. Addition of ethylene to 2-pentenes with KC, -KC, , mixtures made from pure graphite gave 57% linear 3-heptenes and 37% 3-ethyI-1-pentene compared to 19% 3-heptenes and 54 % 3-ethyl-1-pentene produced at similar conditions with catalyst prepared from potassium metal dispersion.With catalysts varying from KC8 to KC24, the rate of reaction was proportional to the amount of KC, and not to the amount of potassium. Varying the reaction temperature had only a small effect on reaction rates. Olefin isomerization was catalyzed by potasslum-graphite catalysts made from graphite containing a significant amount of ash. A new method of preparing potassium-graphite intercalation compounds by reaction of graphite with molten potassium dispersions in liquid hydrocarbon is described.

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Evidence for ethylene‐propylene block copolymer formation

Cited by 24 publications

References 6 publications

Titanocene−Methylaluminoxane Catalysts for Copolymerization of Styrene and Ethylene: Synthesis and Characterization of Styrene−Ethylene Copolymers

Titanocene−Methylaluminoxane Catalysts for Copolymerization of Styrene and Ethylene: Synthesis and Characterization of Styrene−Ethylene Copolymers

Synthesis and properties of ABA propylene‐ethylene block copolymers

Gas-phase polymerization of propene with the supported Ziegler catalyst: TiCl4/MgCl2/C6H5COOC2H5/Al(C2H5)3

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