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1.
A novel self‐supported emulsion‐based catalyst and a conventional MgCl2‐supported Ziegler–Natta catalyst were used in the copolymerization of propylene and ethylene under industrial conditions using triethyl aluminium as cocatalyst and dicyclopentyl dimethoxy silane as external donor. The effects of the concentration of ethylene and hydrogen on the polymerization behaviors and polymer properties were investigated. The combined effect of both ethylene and hydrogen increased the relative activity of the novel catalyst more than for the conventional catalyst. This trend was consistent with our earlier observed higher degree of dormancy, due to 2,1 insertions, found with the novel catalyst. More importantly, the work has uncovered that the self‐supported catalyst incorporates ethylene in a more random fashion and produces copolymers with relatively narrow molecular weight distribution (MWD). These results in combination with polymer microstructure studies using Fourier transform infrared spectroscopy, 13C‐NMR spectroscopy, and differential scanning calorimetry all indicated that the novel catalyst has a narrower distribution of active site types than the conventional reference catalyst. The narrow composition of active site structures, the narrow MWD, and the random incorporation of ethylene into the polymer chain indicated that the emulsion‐based catalyst possesses features that to a certain degree tend to be more indicative for a single‐site‐like catalyst structure and behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
2.
A series of polypropylene (PP) alloys containing different ethylene contents have been prepared by the in situ sequential polymerization technique, using Ziegler–Natta catalyst (MgCl2/TiCl4/BMF; BMF is 9,9‐bis(methoxymethyl)fluorine, as an internal donor) without any external donor. The structure and properties of PP alloys obtained have been investigated by nuclear magnetic resonance, Fourier transform infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy (SEM). The results have suggested that PP alloys are the complex mixtures containing PP, the copolymer with long sequence ethylene chain, ethylene‐propylene rubber (EPR), and block copolymer etc. In the alloys, PP, EPR, and the copolymer with long sequence ethylene chain are partially compatible. The investigation of the mechanical properties indicates that notched Izod impact strength of PP alloy greatly increases at 16°C/?20°C in comparison with that of pure PP. The noticeable plastic deformation is observed in SEM photograph. The increase in the toughness, the mechanical strength of PP alloy decreases to a certain extent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4804–4810, 2006 相似文献
3.
The bisupported Ziegler–Natta catalyst system SiO2/MgCl2 (ethoxide type)/TiCl4/di‐n‐butyl phthalate/triethylaluminum (TEA)/dimethoxy methyl cyclohexyl silane (DMMCHS) was prepared. TEA and di‐n‐butyl phthalate were used as a cocatalyst and an internal donor, respectively. DMMCHS was used as an external donor. The slurry polymerization of propylene was studied with the catalyst system in n‐heptane from 45 to 70°C. The effects of the TEA and H2 concentrations, temperature, and monomer pressure on the polymerization were investigated. The optimum productivity was obtained at [Al]/[DMMCHS]/[Ti] = 61.7:6.2:1 (mol/mol/mol). The highest activity of the catalyst was obtained at 60°C. Increasing the H2 concentration to 100 mL/L increased the productivity of the catalyst, but a further increase in H2 reduced the activity of the catalyst. Increasing the propylene pressure from 1 to 7 bar significantly increased the polymer yield. The isotacticity index (II) decreased with increasing TEA, but the H2 concentration, temperature, and monomer pressure did not have a significant effect on the II value. The viscosity‐average molecular weight decreased with increasing temperature and with the addition of H2. Three catalysts with different Mg/Si molar ratios were studied under the optimum conditions. The catalyst with a Mg/Si molar ratio of approximately 0.93 showed the highest activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1177–1181, 2003 相似文献
4.
Polymerization of propylene was carried out by using a MgCl2–EtOH–TiCl4–ID–TEA–ED catalyst system in n‐heptane, where ID (internal donor) was an organic diester, ED (external donor) was a silane compound, and TEA (triethyl aluminum) was the activator. The influences of temperature, pressure, time, hydrogen, and the molar ratios of Al/Ti and ED/Ti on polymer isotacticity and catalyst activity were studied by solubility in boiling n‐heptane and measuring the polymer produced, respectively. The morphology of the polymers was evaluated through scanning electron microscopy and particle size distribution. The rheological properties of the poly(propylene) were determined by the melt flow index. It was found that the catalyst showed good morphology and high activity and also the produced polymers were characterized by high isotacticity and globulelike shapes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1744–1749, 2005 相似文献
5.
The effects of alkylaluminum and polymerization temperature on propylene polymerization without an external donor in the use of a TiCl4–MgCl2–diether(BMMF) catalyst were investigated. The results indicated that with increasing polymerization temperature the concentrations of [mmmm] of heptane‐insoluble poly(propylene) (PP) fraction increased. Crystallization analysis fractionation (CRYSTAF) results showed the fractions of different crystallization temperatures were changed according to various polymerization temperatures. The activity with Et3Al as cocatalyst at 100°C was much lower than that at 70°C. However, the activity with i‐Bu3Al at 100°C was as high as that at 70°C. The fraction of high‐crystallization temperature of PPs obtained with i‐Bu3Al increased with increasing polymerization temperature, which was opposite to that with Et3Al, thus implying that the copolymerization of propylene with the monomer arising from Et3Al led to the lower crystallization ability of PPs obtained with Et3Al. The terminal groups of PP suggested that the chain‐transfer reaction by β‐H abstraction was the main chain‐transfer reaction at 120°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3980–3986, 2003 相似文献
6.
This work aims to study the effects of high loading (total 50 wt %) of inorganic calcite, zeolite particulates, and calcite/zeolite mixture with structurally different copolymer [CoPP; poly(propylene‐co‐ethylene)] and terpolymer [TerPP; poly(propylene‐co‐ethylene‐co‐1‐butene)] systems. Melt processing is the sole mode of mixing particulates with polymer for making master batch sample throughout this work. Mechanical properties, like the modulus and yield stress, continuously increase up to a critical zeolite ratio in calcite/zeolite mix and then decrease after exceeding the critical concentration. The impact strength of the composites is not improved by replacing the calcite portion from the mix with zeolite. Morphological study was carried out for matrix–filler dispersion observation. The complex melt viscosity, increased for both systems with increasing zeolite content, indicates extra processing difficulties because of high filler volume. Burning properties and thermal stability of CoPP and TerPP composites with 50 wt % filler systems were also studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
7.
Antonio Marigo Valerio Causin Carla Marega Paolo Ferrari 《Polymer International》2004,53(12):2001-2008
Wide‐angle X‐ray scattering and differential scanning calorimetry measurements have been conducted on seven random copolymers of propylene with ethylene in order to study the γ phase formation as a function of the comonomer content. The lamellar morphology of the samples was also investigated by small‐angle X‐ray scattering. The content of the γ phase was found to go through a maximum with crystallization temperature and to increase with comonomer concentration, up to a point (ethylene ≥6.5 wt%) where the latter parameter became less influential. The multiple melting endotherms behaviour of the samples was studied by DSC and temperature‐controlled diffractometric techniques. The attribution of the DSC peaks to the different isotactic polypropylene polymorphs that form in these conditions was confirmed. The results obtained permitted us to ascertain that, in the experimental conditions chosen, some further formation of crystallites takes place during the quenching to room temperature after the crystallization isotherm. In this phase, the chains organize themselves in stacks with thin lamellae, forming a distinct population with respect to those formed on isothermal crystallization. The melting of the thinner lamellae determines a convergence of the two populations into just one, still retaining an organization in stacks, that gradually disappears until complete melting of the material. Copyright © 2004 Society of Chemical Industry 相似文献
8.
Tao Jiang Wei Chen Feng Zhao Yuexiang Liu Ruen Wang Hongbin Du Tianyi Zhang 《应用聚合物科学杂志》2005,98(3):1296-1299
The MgCl2/SiO2 complex support was prepared by spray drying using alcoholic suspension, which contained MgCl2 and SiO2. The complex support reacted with TiCl4 and di‐n‐butyl phthalate, giving a catalyst for propylene polymerization. The catalyst was spherical and porous with high specific surface area. TEA was used as a cocatalyst, and four kinds of alkoxysilane were used as external donors. The bulk polymerization of propylene was studied with the catalyst system. The effect of the reaction conditions and external donor on the polymerization were investigated. The results showed that the catalyst had high activity, high stereospecificity, and sensitive hydrogen responsibility. Polypropylene has good grain morphology because of duplicating the morphology of the catalyst. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1296–1299, 2005 相似文献
9.
A coupled‐single‐particle and Monte Carlo model was used to simulate propylene polymerization. To describe the effects of intraparticle transfer resistance on the polymerization kinetics, the polymeric multilayer model (PMLM) was applied. The reaction in each layer of the PMLM was described with the Monte Carlo method. The PMLM was solved together with the Monte Carlo model. Therefore, the model included the factors of the mass‐ and heat‐transfer resistance as well as the stochastic collision nature of the polymerization catalyzed with single‐site‐type/multiple‐site‐type catalysts. The model presented results such as the polymerization dynamics, the physical diffusion effect, and the polymer molecular weight and its distribution. The simulation data were compared with the experimental/actual data and the simulation results from the uniform Monte Carlo model. The results showed that the model was more accurate and offered deeper insight into propylene polymerization within such a microscopic reaction–diffusion system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
10.
New polymer blends of polypropylene random copolymer (PP‐R) and poly(ethylene‐octene) (POE) were prepared by melt‐blending process using a corotating twin‐screw extruder. The POE content was varied up to 35%. The toughening efficiency of POE for PP‐R was evaluated by the mechanical properties of the resulted PP‐R/POE blends. The crystallization behavior and morphology of the blends were also studied. Results show that POE acts as nucleation agent to induce the crystallization of PP‐R matrix at higher crystallization temperature. Super‐toughened PP‐R/POE blends (Izod impact strength more than 500 J/m) can be readily achieved with only 10 wt % of POE. The high toughness of PP‐R/POE is attributed to cavitation and shear yielding of matrix PP‐R, as revealed by the morphology studies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
11.
12.
Ali Dashti Ahmad Ramazani SA Yuichi Hiraoka Sang Yull Kim Toshiaki Taniike Minoru Terano 《Polymer International》2009,58(1):40-45
BACKGROUND: Kinetic and morphological aspects of slurry propylene polymerization using a MgCl2‐supported Ziegler–Natta catalyst synthesized from a Mg(OEt)2 precursor are investigated in comparison with a ball‐milled Ziegler–Natta catalyst. RESULTS: The two types of catalyst show completely different polymerization profiles: mild activation and long‐standing activity with good replication of the catalyst particles for the Mg(OEt)2‐based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball‐milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl4 on the outermost part and inside of the catalyst particles. CONCLUSION: The Mg(OEt)2‐based Ziegler–Natta catalyst is believed to show highly stable polymerization activity and good replication because of the uniform titanium distribution all over the catalyst particles. Copyright © 2008 Society of Chemical Industry 相似文献
13.
The initial state polymerization of propylene with Ziegler–Natta catalysts has been investigated and discussed at very low polymerization yields under adiabatic industrial prepolymerization conditions in diluted slurry regarding the effects of significant process parameters like monomer pressure, aluminum alkyl, and donor kind and concentration including the morphology of the catalyst/polymer particles formed. A sharp temperature increase in the first minutes of the initial state polymerization is followed by a temperature maximum and a slow decrease. With cocatalyst triethyl aluminum (TEAL), high prepolymerization yields were already achieved at a molar ratio TEAL/Ti of 3.0, remaining about constant until ratios of at least 300. The external donor dicyclopentyl dimethoxy silane leads to higher polymerization yields than the donor cyclohexyl dimethoxymethyl silane in the initial state polymerization too; however, both show a remarkable decreasing effect on polymerization yield above a specific molar ratio donor/Ti obviously correlated with the bulkiness of the alkyl groups. The particle size of the catalyst and the catalyst/prepolymer particles is increasing with polymerization yield until about 22 g PP/g Cat with particles almost perfectly spherical. The particle size distribution is rather broad at lower prepolymerization stages but unifying with lower polymerization rates at higher polymerization times. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
14.
Fuyong Bi Aihua He Huayi Li Youliang Hu Zhiyuan He Charles C Han 《Polymer International》2011,60(8):1167-1172
MgCl2/TiCl4/diether is a fifth‐generation Ziegler–Natta catalyst for the commercial polymerization of propylene. The outstanding features of this catalyst are the high activity and high isotacticity for propylene polymerization without using an external electron donor. In this study, we explored the copolymerization of propylene and 1‐octene with MgCl2/TiCl4/diether catalyst. It was found that MgCl2/TiCl4/diether catalyst showed higher polymerization activity and led to greater 1‐octene content incorporation, compared with a fourth‐generation Ziegler–Natta catalyst (MgCl2/TiCl4/diester). With an increase in 1‐octene incorporation in polypropylene chains, the melting temperature, glass transition temperature and crystallinity of the copolymers decreased distinctly. The microstructures of the copolymers were characterized using 13C NMR spectroscopy, and the copolymer compositions and number‐average sequence lengths were calculated from the dyad concentration and distribution. This result is very important for the in‐reactor polyolefin alloying process, especially for the case of a single catalyst and two‐step (or two‐reactor) process. Copyright © 2011 Society of Chemical Industry 相似文献
15.
The structure, processing, morphology, and property relationships of biaxially drawn isotactic polypropylene (BOPP) film of mixed metallocene isotactic PP (m‐iPP) and Ziegler–Natta iPP (ZN‐iPP) homopolymer compositions are developed. The DSC and film drawing behavior show cocrystallization of the ZN‐iPP and m‐iPP components. The structure, processing, morphology, and property relations of ZN‐iPP/m‐iPP blends are compared with ZN‐iPP of varying isotacticities. The ZN‐iPP/m‐iPP blends exhibit reduced biaxial yield stress [σy(T)]. A fractional crystallinity model collapses the σy(T) data into a common normalized form over a range of draw temperatures, ZN‐iPP tacticities, and blend compositions. The simplified model is extended to define the interrelationships of yield activation and strain hardening behavior into regimes differentiated by characteristic draw stress (crystallinity) levels. Structure–property models are developed to explain the effect of draw temperature and resin–blend microstructure on the draw behavior, film stiffness, barrier, elongation, and synergies of the BOPP film processing–property balance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2400–2415, 2001 相似文献
16.
Shohjiroh Tanase Kiyokazu Katayama Susumu Inasawa Fumio Okada Yukio Yamaguchi Takehito Konakazawa Tadanori Junke Nobuhide Ishihara 《Applied Catalysis A: General》2008,350(2):197-206
Images from scanning electron microscopy, transmission electron microscopy and X-ray diffraction profiles of typical magnesium diethoxide (MGE) particles obtained by the reaction of ethanol, metal magnesium and iodine showed the round MGE particle (tertiary particle) had a layer structure consisting of many crystalline fragments (secondary particles) comprising many minute crystals (primary particles). It was clearly shown that each precipitated secondary particle had not agglomerated, but had repeatedly grown and combined with others. From the investigation of the course of a reaction, it was suggested the MGE crystals grown on Mg metal exfoliated as “lump-like” seeds, and crystal growth on seeds proceeded such that the shapes of the final MGE particles were more spherical than those of their seeds. It was presumed from a model reaction that the enhancement of MGE solubility by I2 addition to form the quasi-stable complex nMg(OEt)2·MgI2·mEtOH was the key process in the formation of plate crystals. The relationship between the size of crystalline fragments and crystallization rate (reaction rate, MGE solubility) was discussed.The catalyst, when prepared using MGE as the carrier material, exhibited exceptionally high polymerization activity than when it was prepared with MgCl2 alcohol complex (MgCl2·ROH). We presume that this is because particles of the MGE-based catalyst are porous, and because the formation of active species of the supported Ti and monomer diffusion progressed adequately from the surface of the particle to its internal parts. 相似文献
17.
The adsorption behavior of various poly(ethylene oxide)–polystyrene–poly(ethylene oxide) (PEO‐PS‐PEO) triblock copolymer (TBC) s on acrylic latex particles in propylene glycol was studied. The composition of the PEO‐PS‐PEO triblock polymers varied from 41 to 106 in each PEO block length and from 18 to 41 in the PS block length. The location of the PEO‐PS‐PEO TBC was determined by analyzing for the physically adsorbed amount on the latex surface, the anchored mount on the surface, the entrapped amount inside the particle, and the “free” PEO‐PS‐PEO TBCs in the propylene glycol. A contour graph technique was applied to analyze the experimental data, which showed that a minimum existed for the physically adsorbed portion at a PS block length of about 30 units. When the PS block length was less than 30 units, the adsorption decreased with increasing PS block length, indicating rearrangement of mixed PEO brush and adsorbed PS block. When the PS block was greater than 30 units, the adsorption increased with increasing block length because of the poor solvency of the PS block in the propylene glycol medium, resulting in a collapse of the PS chain. Considering the binding energy between the PS block and the latex particle surface, which governs adsorption, it was hypothesized that a lower block length limit exists, below which no adsorption takes place. The solubility of the PS block in propylene glycol guides the important upper block length limit. The anchored fraction of the block copolymer increased continuously with increasing PS block length in the entire region investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1963–1975, 2001 相似文献
18.
In this work, the effect of two antifouling materials on the activity of catalyst used to produce polyethylene in a 1‐L slurry reactor and on the titanium oxidation state of the catalyst was investigated. Armostat 300 with the formula alkyl C14‐C18 bis(2‐hydroxyethyl)amine is an antistatic agent that reduces static electricity of the polymer particles. It was found that within the concentration of 0.16–1.32 g/mmol Ti, Armostat 300 helps to increase the catalyst activity to 1.3–2 times. The variation of the titanium oxidation state of the catalyst in the presence of Armostat 300 at 80°C with Al/Ti molar ratio of 100 showed that Ti (III) species increased. The effect of Armostat 300 on Tm, % Xc, density, bulk density, and MFI of polymer was insignificant. In this work, Zonyl FSN‐100 with the formula Rf(CH2CH2O)xH, Rf = F(CF2CF2)y, y = 1–9, x = 1–26 was used as antifouling agent in copolymerization of ethylene with 1‐butene. It was found that Zonyl FSN‐100 at the concentration range of 5–20 ppm reduces the catalyst activity to 1.11–1.9 times. It was also shown that Ti (III) species in the presence of Zonyl FSN 100 decreased. This antifouling agent slightly decreased the properties of polymer including % Xc, density, and Mw. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 257–260, 2006 相似文献
19.
Propylene was polymerized in gas phase and liquid phase by using a novel nonporous Ziegler–Natta‐catalyst system. The polymer particles formed at different polymerization times were used for sorption measurements. In both cases it was found that the effective diffusion coefficient is increasing with increasing size of polymer particles and the effective diffusion coefficients of polymer particles formed by liquid‐phase polymerization are larger than those of polymer particles produced by gas‐phase polymerization. The effective diffusion coefficients of polymer particles are in the range of 2 × 10?11 to 1.6 × 10?10 m2/s with activation energies from 34 to 22 kJ/mol. The analyzed polymer particles have average diameters between 250 and 875 μm. The solubility of propylene in polypropylene particles can be described by the law of Henry at conditions studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2642–2648, 2006 相似文献