Preparation and characterization of high MFR polypropylene and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys

In this work, high melt flow rate (MFR) polypropylene (HF‐PP) and polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloys (HF‐PP/EPR) with MFR ≈ 30 g/10 min were synthesized by spherical MgCl₂‐supported Ziegler–Natta catalyst with cyclohexylmethyldimethoxysilane (CHMDMS) or dicyclopentyldimethoxysilane (DCPDMS) as external donor (De). The effects of De on polymerization activity, chain structure, mechanical properties, and phase morphology of HF‐PP and HF‐PP/EPR were studied. Adding CHMDMS caused more sensitive change of the polymers MFR with H₂ than DCPDMS, and produced PP/EPR alloys containing more random ethylene‐propylene copolymer (r‐EP) and segmented ethylene‐propylene copolymer (s‐EP). CHMDMS also caused formation of s‐EP with higher level of blockiness than DCPDMS. HF‐PP/EPR alloy prepared in the presence of DCPDMS exhibited higher flexural properties but lower impact strength than that prepared with CHMDMS. Toughening efficiency of the rubber phase was nearly the same in the alloys prepared using CHMDMS or DCPDMS as De, but stiffness of the alloy can be improved by using DCPDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42984.     

Effect of 1-allyl-3,4dimethoxybenzene on propene polymerization with the TICl4/DBP(dibutylphthalate)/MgCl2 catalyst

Summary Propene polymerization was carried out using the TiCl₄/DBP(dibutylphthalate)/MgCl₂-Al(C₂H₅)₃ catalyst combined with various kinds of aromatic ether compounds as external donor. Addition of o-dimethoxybenzene derivatives, especially, 1-allyl-3,4-dimethoxybenzene(ADMB), caused a marked increase in both yield and molecular weight of atactic polypropylene.     

几种高活性外给电子体工业应用评价

综合评价了环己基甲基二甲氧基硅烷CMMS、二环戊基二甲氧基硅烷DCPDMS、二异丙基二甲氧基硅烷DIPDMS、二异丁基二甲氧基硅烷DIBDMS在工业上使用CS-I聚丙烯主催化剂下对于聚丙烯等规度、聚合活性的影响,以及它们的氢调敏感程度.     

Control of molecular weight distribution for polypropylene obtained by a commercial Ziegler–Natta catalyst: Effect of a cocatalyst and hydrogen

The polymerization of propylene was carried out with an MgCl₂‐supported TiCl₄ catalyst (with diisobutyl phthalate as an internal donor) in the absence and presence of hydrogen (H₂) as a chain‐transfer agent. Different structures of alkylaluminum were used as cocatalysts. The effects of the alkyl group size of the cocatalyst, H₂ feed, and feed time on the propylene polymerization behaviors were investigated. The catalyst activity significantly decreased with increasing alkyl group size in the cocatalyst. The molecular weight and polydispersity index (PDI) increased with increasing alkyl group size. With the introduction of H₂, the catalyst activity increased significantly, whereas the molecular weight and PDI of polypropylene (PP) decreased. Additionally, the effect of the polymerization time in the presence of H₂ on the propylene polymerization was studied. The molecular weight distribution curve was bimodal at short polymerization times in the presence of H₂, and we could control the molecular weight distribution of PP by changing the polymerization time in the presence of H₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microstructure of isotactic polypropylene obtained using Ziegler–Natta catalyst at high polymerization temperature

The microstructure of the isotactic polypropylene obtained with various MgCl₂‐supported catalyst systems at high polymerization temperature of 70–100°C is investigated by discussing the intrinsic relation between the different types of active centers and the polymerization temperatures via gel permeation chromatography, temperature rising elution fractionation, and ¹³C NMR. For the MgCl₂/TiCl₄/di‐n‐butyl phathalate‐AlEt₃/external donor and MgCl₂/TiCl₄/2,2‐diisobutyl‐1,3‐dimethoxypropane‐AlEt₃ catalyst systems, the differences in the isotactic productivity of polymers obtained at different polymerization temperatures mainly result from the variation of both the activity of the different isospecific active centers and the stability constants of the complex of catalyst/donor. The reaction rate of high isotactic active centers reaches maximum at 85–90°C, and this effect contributes to both the highest isotacticity and the narrowest molecular weight distribution. For the MgCl₂/TiCl₄/phthalate ester‐AlEt₃ catalyst system, the isotacticity of polypropylene remains approximately constant in the temperature range of experiments, which could be ascribed to elution of phthalate ester after the activation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42487.     

Preparation of ultra high molecular weight polyethylene with MgCl<Subscript>2</Subscript>/TiCl<Subscript>4</Subscript> catalyst: effect of internal and external donor on molecular weight and molecular weight distribution

Ultra high molecular weight polyethylene (UHMWPE) was prepared by using MgCl₂-supported TiCl₄ catalyst in conjunction with triethylaluminium (TEA) cocatalyst. The effects of internal and external donor on polydispersity index (PDI) of UHMWPE were investigated. The catalyst activity with various kinds of internal donor decreased in the following order: none > succinate > phthalate > diether, while the catalyst activity was less influenced by the structure of external donor. The PDI of UHMWPE was examined by using gel permeation chromatography (GPC) analysis and/or rheometry measurements. The PDI obtained by rheometer was matched with the results obtained by GPC within an error of max. 20%. The highest molecular weight and PDI of UHMWPE were obtained by the catalyst of succinate as internal donor. It was also observed that the molecular weight and PDI of UHMWPE were less affected by the introduction of external donor.     

Preparation of bimodal polypropylene in two‐step polymerization

Polymerization of propylene was carried out by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system in n‐heptane, where MgCl₂, EtOH, TiCl₄, DIBP (diisobutyl phthalate), TEA (triethyl aluminum), and cHMDMS (cyclohexyl methyl dimethoxy silane) were support, ethanol for alcoholation, catalyst, external donor, cocatalyst (activator), and internal donor, respectively. The catalyst activity and polymer isotacticity were studied by measuring the produced polymer and its solubility in boiling n‐heptane, respectively. The molecular weight and molecular weight distribution of the polymers were evaluated by gel permeation chromatography. Hydrogen was used for controlling the molecular weight. For producing the bimodal polypropylene, the polymerization was carried out in two steps (i.e., in the presence and absence of hydrogen). It was found that the catalyst showed high activity and stereoselectivity, on the other hand, bimodal polymer could simply be produced in two‐step polymerization by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system. Meanwhile, the effect of the step of the hydrogen adding on propylene polymerization was investigated. It was shown that the addition of hydrogen in the second step was more suitable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1456–1462, 2006     

A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition

New data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40658.     

Dimethylsilylbis(1‐indenyl) zirconium dichloride/methylaluminoxane catalyst supported on nanosized silica for propylene polymerization

A dimethylsilylene‐bridged metallocene complex, (CH₃)₂Si(Ind)₂ZrCl₂, was supported on a nanosized silica particle, whose surface area was mostly external. The resulting catalyst was used to catalyze the polymerization of propylene to polypropylene. Under identical reaction conditions, a nanosized catalyst exhibited much better polymerization activity than a microsized catalyst. At the optimum polymerization temperature of 55°C, the former had 80% higher activity than the latter. In addition, the nanosized catalyst produced a polymer with a greater molecular weight, a narrower molecular weight distribution, and a higher melting point in comparison with the microsized catalyst. The nanosized catalyst's superiority was ascribed to the higher monomer concentration at its external active sites (which were free from internal diffusion resistance) and was also attributed to its much larger surface area. Electron microscopy results showed that the nanosized catalyst produced polymer particles of similar sizes and shapes, indicating that each nanosized catalyst particle had uniform polymerization activity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Propylene polymerization over supported Ziegler–Natta catalysts: Effect of internal and external donors on distribution of active sites according to stereospecificity

Data on the content of fractions with different microtacticities for polypropylene (PP) samples produced over three catalysts [the “donor‐free” titanium–magnesium catalyst and catalysts with dibutyl phthalate and 1,3‐diether(fluorene) used as internal donors] upon polymerization in the absence/presence of an external donor (ED) have been obtained by preparative temperature rising elution fractionation method. The effect of internal and EDs on the distribution of PP fractions with different microtacticity is discussed. Data on molecular weight and thermophysical characteristics were obtained for individual fractions with different microtacticities. Correlations were found between microtacticity, molecular weight, and the melting points of these fractions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46291.     

Effect of an external donor upon chain-transfer reactions in propylene polymerization with a MgCl2-supported titanium catalyst system

The chain-end groups of the polypropylene (PP) polymerized without addition of molecular hydrogen over a MgCl₂·TiCl₄·dioctylphthalate/Et₃Al catalyst system consisted of n-butyl, n-propyl, vinylidene and vinyl groups in addition to ethyl and i-butyl groups which were detected in the PP prepared under the same polymerization conditions except for the addition of diphenyldimethoxysilane (DPDMS) as an external donor. The newly detected chain-end groups indicate that the additional chain-transfer reactions were brought about by Et₃Al at 2,1-inserted sites and by β-hydrogen elimination at both 1,2- and 2,1-inserted sites. These chain-transfer reactions could account for the observed drops of the activity and the molecular weight in the absence of DPDMS. In addition, the detected chain ends in the PP polymerized with addition of molecular hydrogen over this catalyst system having no DPDMS suggest that the molecular hydrogen addition leads not only to the conversion of the dormant 2,1-inserted sites into the active sites, but also to a decrease in the frequency of 2,1-insertion.     

MgCl2‐supported catalyst containing mixed internal donors for propylene polymerization

A MgCl₂‐supported catalyst containing diisobutyl phthalate (DIBP) and 2,4‐pentadiol dibenzoate (PDDB) as internal donors was prepared. Propylene polymerizations were carried out using the catalyst in the absence or presence of an external donor. The resulting polymers were characterized by ¹³C‐NMR, crystallization analysis fraction (CRYSTAF) and gel permeation chromatography (GPC). The performance of the catalyst was compared with that of other catalysts containing donor‐free, DIBP and PDDB as internal donors respectively. The results demonstrated that the catalyst containing mixed internal donors not only had high activity and stereospecificity but also produced the polymer with relatively broad molecular weight distribution and the highest [mmmm] value. ¹³C‐NMR analysis results indicated that strongly coordinating donors gave more stereoregular polymers, which was further confirmed by CRYSTAF data. The effects of mixed internal donors on the catalyst properties were discussed systematically. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Organometallics in ethylene polymerization with a catalyst system TiCl4/Al(C2H5)2Cl/Mg(C6H5)2: 2. Polymerization process in pseudo-solution

A study has been made of ethylene polymerization in pseudo-solution with a catalyst system TiCl₄/Al(C₂H₅)₂Cl/Mg(C₆H₅)₂ in the presence of hydrogen as a regulator of polyethylene molecular weight. The polymerization process in pseudo-solution by adjustment of hydrogen makes it possible to produce polyethylene having a wide range of molecular weights. For this purpose melt indices between 0°–50°C/min are desirable and these values are not reached with a suspension type of ethylene polymerization with a catalyst system TiCl₄/Al(C₂H₅)₂Cl/Mg(C₆H₅)₂. The effect of the molar ratio cocatalyst/catalyst (Al/Ti and Mg/Ti) on the catalyst activity and on the polyethylene molecular weight was studied, together with the content of hydrogen as a regulator of the molecular weight. The catalyst productivity increased to some limiting molar ratio Mg/Ti and Al/Ti and further increase of organometallics in the catalyst system did not influence the polymer molecular weight. In the case of ethylene polymerization with this catalyst combination in the presence of hydrogen, some activation of the catalyst was observed. Two mechanisms, which may account for the activation effect of the hydrogen are discussed.     

Kinetic study on propylene polymerization with MgCl2/TiCl4-AlEt3/PhCO2Et System — the role of ethyl benzoate

Summary A kinetic study on propylene polymerization with the catalyst system of MgCl₂-supported TiCl₄ catalyst(MgCl₂/TiCl₄) in conjunction with AlEt₃ and PhCO₂Et (EB) has been made to elucidate the role of ethyl benzoate (EB) which is known to increase stereospecificity of produced polypropylene. It has been found that a part of added EB was fixed on the supported Ti catalyst and that EB modified the isotactic specific centers to increase the k_p (iso) value. Thus the productivity of isotactic polymer and the molecular weight of the isotactic polymer(2·10⁴(¯Mn) to 6·10⁴ at 60°C) were increased.     

超高分子量聚丙烯的制备

超高分子量聚丙烯（UHMWPP）是一种黏均分子量百万以上,具有超高的强度、超高的耐磨性、较强的抗氧化能力的热塑性工程塑料,可用于制备高强度、高模量、耐腐蚀、抗冲击、耐应力开裂的聚丙烯产品。本工作的目的在于制备出分子量超过200万的聚丙烯,将其用作3D打印材料来解决由于分子链较长引起高熔体黏度和低流动性而导致加工难成型问题。本工作基于传统的Ziegler-Natta催化剂,对主催化剂进行金属离子和有机物的负载,通过控制丙烯的链转移来控制聚丙烯的分子量,并且在聚合反应过程中不加入氢气（带有活性氢的物质）,以防止其成为聚合反应的终止剂。研究了聚合反应温度、聚合反应时间、助催化剂和外给电子体对聚丙烯分子量的影响。采用黏度法、升温淋洗分级法等表征了制备的聚丙烯分子量。通过聚合工艺优化,在聚合反应温度70℃、聚合反应时间60min、助催化剂三异丁基铝、外给电子体P Donor下,最终制备出了黏均分子量超过204万的超高分子量聚丙烯。     

Effect of prepolymerization on propylene polymerization

Polymerization of propylene was performed using MgCl₂. EtOH.TiCl₄.ID.TEA.ED catalyst system in hexane, where internal donor (ID) was an organic diester and external donor (ED) was a silane compound and also triethyl aluminum (TEA) as activator. A new method called isothermal/nonisothermal method (INM), a combination of isothermal and nonisothermal methods, was applied to produce the spherical polymer particles. The effects of the INM method and prepolymerization temperature on the final polymer morphology, M_w, and catalyst activity were also investigated. The morphology of the polymers was evaluated through scanning electron microscopy (SEM) images. GPC results were used for molecular weight (M_w) evaluation. It was found that the polymers had a better morphology when they were prepared using INM method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

On the Correlation of Rheology and Morphology of Bimodal Polypropylene Reactor Blends Synthesized by Homogeneous Binary Metallocene/Metallocene Catalysts

In this study, morphological and rheological characteristics of bimodal polypropylene reactor blends synthesized by binary catalysts based on I: rac-Me₂Si(2-Me-4-PhInd)₂ZrCl₂ and II: (2-PhInd)₂ZrCl₂ at different molar ratios were investigated. Gel permeation chromatography, scanning electron microscopy, and rheometry analysis were performed to evaluate the effect of molar ratio of catalyst II, responsible for the formation of elastomeric stereoblock polypropylene with low molecular weight, to catalyst I, responsible for production of high molecular weight isotactic (i) polypropylene, on the molecular weight, molecular weight distribution, morphological characteristics and rheological behavior of the synthesized products. The gel permeation chromatography results indicated that once a hybrid of the two catalysts is used, a broad and bimodal molecular weight distribution would be obtained, and the molar ratio of the catalysts governs the values of molecular weight and molecular weight distribution. ¹³C NMR results suggest that the different polypropylene tacticity resulting from the two catalysts (stereoblock vs. isotactic) is hardly influenced using a binary system. The effect of molecular weight enhancement and molecular weight distribution broadening was confirmed through the linear rheological data (G′ at lower frequencies, crossover modulus and crossover frequency) due to the impeded molecular motions of chains with high molecular weights which play an important role in the elasticity of chains. The zero shear rate viscosity and relaxation time, determined by fitting the Carreau–Yasuda model, are in great conformity with the experimental data at low-frequency region. Likewise, the miscibility and increased level of heterogeneity of microstructure, which is a result of changing the molar ratios of catalysts II/I, are confirmed through the Cole–Cole and Han plots and were further corroborated through the obtained scanning electron microscopy results.     

Polymerization of propylene by using MG(OEt)2–DNBP–TiCl4 catalyst with alkoxy disilanes as external donor

The effect of different external silane donors on the activity and isotacticity of polypropylene prepared by using Mg(OEt)₂–phthalate ester–TiCl₄‐AlEt₃–alkoxy disilane catalyst systems has been investigated. In the case of catalyst systems containing (trimethylsilyl)methylalkyldimethoxysilanes [Me₃SiCH₂Si(OMe)₂R] as external donors, the bulky Me₃SiCH₂‐ group was effective in converting aspecific sites into isospecific ones, followed by the increase of activity and isospecificity of the obtained polymer. Catalyst activity and isotacticity of the polymer increased with the decrease of the number of alkoxy groups in the substituted alkoxy disilanes. The effect of alkoxy groups between alkoxy disilanes and alkylaluminum as cocatalyst on the active sites of the catalyst and the influence of the size of alkoxy groups in disilane compounds were examined, respectively. Some correlation between molecular weight, molecular weight distribution, and isospecificity was also observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 293–301, 1999     

A study of the effect of styrene concentration on the molecular weight of polypropylene produced using metallocene catalysts

It has been observed in the production of polypropylene nanocomposites containing silicate materials that the molecular weight of the polymer used can have a significant effect on the final quality of the composites. The availability of polypropylene over a range of molecular weights with similar material properties (e.g. melting temperature and tacticity) is limited. Therefore, the ability to use a single catalyst system to generate polypropylene with a range of molecular weights is an attractive goal. In this contribution the use of styrene as a chain‐terminating agent is explored, in order to produce materials with a range of molecular weights from a single catalyst system. It is found that the molecular weight of the polypropylene produced can be varied in the range from 120 000 to 9000 g mol^?1 using the Me₂Si(Ind)₂ZrCl₂/methylaluminoxane catalyst system. Copyright © 2011 Society of Chemical Industry     

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

This paper reviews a new family of olefin polymerization catalysts. The catalysts, named FI catalysts, are based on non‐symmetrical phenoxyimine chelate ligands combined with group 4 transition metals and were developed using “ligand‐oriented catalyst design”. FI catalysts display very high ethylene polymerization activities under mild conditions. The highest activity exhibited by a zirconium FI catalyst reached an astonishing catalyst turnover frequency (TOF) of 64,900 s ^–1 atm ^–1, which is two orders of magnitude greater than that seen with Cp₂ZrCl₂ under the same conditions. In addition, titanium FI catalysts with fluorinated ligands promote exceptionally high‐speed, living ethylene polymerization and can produce monodisperse high molecular weight polyethylenes (M_w/M_n<1.2, max. M_n>400,000) at 50 °C. The maximum TOF, 24,500 min ^–1 atm ^–1, is three orders of magnitude greater than those for known living ethylene polymerization catalysts. Moreover, the fluorinated FI catalysts promote stereospecific room‐temperature living polymerization of propylene to provide highly syndiotactic monodisperse polypropylene (max. [rr] 98%). The versatility of the FI catalysts allows for the creation of new polymers which are difficult or impossible to prepare using group 4 metallocene catalysts. For example, it is possible to prepare low molecular weight (M_v∼10³) polyethylene or poly(ethylene‐co‐propylene) with olefinic end groups, ultra‐high molecular weight polyethylene or poly(ethylene‐co‐propylene), high molecular weight poly(1‐hexene) with atactic structures including frequent regioerrors, monodisperse poly(ethylene‐co‐propylene) with various propylene contents, and a number of polyolefin block copolymers [e.g., polyethylene‐b‐poly(ethylene‐co‐propylene), syndiotactic polypropylene‐b‐poly(ethylene‐co‐propylene), polyethylene‐b‐poly(ethylene‐co‐propylene)‐b‐syndiotactic polypropylene]. These unique polymers are anticipated to possess novel material properties and uses.