Synthesis of well‐defined comblike hydroxy‐functionalized atactic polystyrene promoted by metallocene/tin/poly(phenyl glycidyl ether)‐co‐formaldehyde

Well‐defined comblike atactic polystyrene functionalized with hydroxyl groups was synthesized via living/controlling radical polymerization promoted by metallocene complexes in the presence of poly(phenyl glycidyl ether)‐co‐formaldehyde as the initiator and Sn as a reducing agent. The effect of the polymerization conditions, such as the ratio of initiator to monomer, temperature, and polymerization time, and the structure of the metallocene complex on the polymerization process were investigated. The resulting polymers were characterized by gel permeation chromatography, multiangle laser light scattering, ¹H‐NMR, and ¹³C‐NMR. The results show that the polymer had a narrow molecular weight distribution in the range 1.1–1.4 and the number‐average molecular weight of the polymer linearly depended on the monomer conversion within the polymerization timescale, which confirmed that living radical polymerization characteristics prevailed in the polymerization process. Both the number of arms and the number of hydroxyl groups in each polymer molecule were about four, which suggested that they arose from the epoxy functional groups of the initiator. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Syndiotactic poly(propene-co-norbornene): Synthesis and properties at low norbornene incorporation

Copolymerizations of propene with norbornene were carried out using a syndiotactic metallocene catalyst at low initial comonomer concentrations for different polymerization times. The influence of the norbornene concentration on the catalytic activity and on the resulting material properties has been analyzed. The copolymer molecular weight decreased drastically when small amounts of norbornene were added in reactions which lasted 30 min. When longer reaction times were used the molecular weight increased with time, however living polymerization was ruled out because the polydispersity was ca. 2. The DSC measurements showed copolymers with low crystallinity or which were completely amorphous.     

Progress in the catalyst for ethylene/α-olefin copolymerization at high temperature

Ethylene/α-olefin copolymers are one of the most widely-used polyolefin materials. With the continuous improvement of polyolefin catalysts, high-performance polyolefin materials were synthesized by adjusting the chain microstructure, changing the comonomer type and comonomer insertion amount, among which the ethylene/α-olefin random copolymer elastomer (POE) and olefin block copolymer elastomer (OBC) are the most famous and well accepted by the market. The excellent properties of POE and OBC first depend on their polymer chain microstructure. The chain microstructure of polyolefins is fundamentally determined by the catalysts, polymerization conditions, comonomer feed policies, and reaction engineering. High-performance ethylene/α-olefin copolymer elastomers are currently prepared by high-temperature solution polymerization process, which needs to be carried out at a temperature above the melting point of the polymer and is beneficial to speed up the polymerization reaction rate and control the polyolefin chain microstructure. However, the high-temperature solution polymerization process launched more stringent requirements for the olefin coordination polymerization catalyst. Systematic reports on catalysts for high-temperature solution copolymerization of ethylene and α-olefins are lacking. In this review, we screened some catalysts suitable for the controllable copolymerization and high-temperature solution copolymerization of ethylene/α-olefin based on the catalyst's heat resistance, copolymerization activity, comonomer insertion ability, molecular weight, and distribution of the copolymer, including traditional Z–N catalysts, metallocene catalysts, and post-metallocene catalysts. And the future development of catalysts for high-temperature solution copolymerization of olefins, catalysts for precise control of polyolefin chain microstructures, and catalysts for olefin copolymerization with polar monomers at high temperature are envisaged.     

Copolymerization of ethylene/α‐olefins using bis(2‐phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution

Catalysts have a major role in the polymerization of olefins and exert their influence in three ways: (1) polymerization behaviour, including polymerization activity and kinetics; (2) polymer particle morphology, including bulk density, particle size, particle size distribution and particle shape; and (3) polymer microstructure, including molecular weight regulation, chemical composition distribution and short‐ and long‐chain branching. By tailoring the catalyst structure, such as the creation of a bridge or introducing a substituent on the ligand, metallocene catalysts can play a major role in the achievement of desirable properties. Kinetic profiles of the metallocene catalyst used in this study showed decay‐type behaviour for copolymerization of ethylene/α‐olefins. It was observed that increasing the comonomer ratio in the feedstock affected physical properties such as reducing the melting temperature, crystallinity, density and molecular weight of the copolymers. It was also observed that the heterogeneity of the chemical composition distribution and the physical properties were enhanced as the comonomer molecular weight was increased. In particular, 2‐phenyl substitution on the indenyl ring reduced somewhat the melting point of the copolymers. In addition, the copolymer produced using bis(2‐phenylindenyl)zirconium dichloride (bis(2‐PhInd)ZrCl₂) catalyst exhibited a narrower distribution of lamellae (0.3–0.9 nm) than the polymer produced using bisindenylzirconium dichloride catalyst (0.5–3.6 nm). The results obtained indicate that the bis(2‐PhInd)ZrCl₂ catalyst showed a good comonomer incorporation ability. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and type of substituent in the catalyst. Copyright © 2010 Society of Chemical Industry     

CpTi(dbm)Cl_2/MgCl_2-SiO_2/MAO催化乙烯聚合及与其它α-烯烃共聚的研究

研究开发了一种新型非茂负载聚烯烃催化剂——CpTi(dbm)Cl2/MgCl2-SiO2/MAO,并考察了该催化剂的乙烯均聚、乙烯和1-己烯共聚及乙烯和苯乙烯共聚性能。结果表明,该催化剂具有较好的热稳定性,80℃时活性可达4.68×106g/(mol·h)。不同助催化剂对活性的影响规律为MAO>MMAO>TiBA>TEA。乙烯和1-己烯共聚时,催化活性提高,聚合温度70℃,1-己烯体积分数为8％时,活性可达3.61×106 g/(mol·h),共聚物的熔点、结晶度、相对分子质量、密度和堆密度随1-己烯含量增加而下降。乙烯和苯乙烯共聚时,随着苯乙烯含量的增加,共聚活性下降,共聚物的熔点、结晶度和相对分子质量都有较大幅度的下降。     

Gas‐phase olefin polymerization over supported metallocene/MAO catalysts: influence of support on activity and polydispersity

Three catalysts obtained by supporting bis(n‐butylcyclopentadienyl)zirconium dichloride/methylaluminoxane on: (1) porous crosslinked poly(2‐hydroxyethylmethacrylate‐co‐styrene‐co‐divinylbenzene) particles (CAT1); (2) swellable crosslinked poly(styrene‐co‐divinylbenzene) particles (CAT2); and (3) by evaporating the catalyst precursors solution to dry powder, CAT3 were used in gas‐phase polymerization of ethylene, and ethylene/1‐hexene in a 2 L semi‐batch reactor at 80 °C and 1.4 MPa. The average polymerization activities of the three catalysts were 12.3–15.5, 4.2–10.1, and 14.3–62.9 ton PE (mol Zr h)^?1 respectively. CAT1 and CAT3 produced polyethylenes with a polydispersity range of 2.3–2.7, while that of CAT2 was 3.5–6.4. The supported catalysts produced polyolefin particles with bulk density of 0.36–0.43 g ml^?1, and essentially no fines. Ethylene/1‐hexene co‐polymerization (7 mol m^?3 initial 1‐hexene concentration in the reactor) increased polymerization activities and produced lower‐molar‐mass co‐polymers. At 21 mol m^?3 1‐hexene the polymerization activities decreased, but the relative amount of the low‐molar‐mass co‐polymer for CAT2 increased, leading to higher polydispersity. Copyright © 2006 Society of Chemical Industry     

Synthesis of polyethylene using ultrasonic energy with a metallocene catalyst

Ethylene polymer was synthesized by the treatment of a metallocene catalyst Zr(CP)₂Cl₂ solution with ultrasonic energy. Ultrasonic energy irradiation was used to change the polymer structure of the formed polymer. Different ultrasonic energy irradiation times were applied to the metallocene catalyst solution. The ultrasonic energy had an effect on the average molecular weight, molecular weight distribution, and polymer productivity. A lower average molecular weight and a narrower molecular weight distribution were produced with a longer ultrasonic irradiation time. The polymer productivity was almost constant when the metallocene catalyst was treated with ultrasonic energy. Finer polyethylene particles were produced with longer ultrasonic irradiation times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 756–759, 2006     

茂金属催化剂用于乙烯聚合的研究和开发

在研究开发适合于浆液法聚乙烯生产工艺的茂金属催化剂的实验研究中，深入研究了桥链和非桥链，不同中心金属和茂环引入取代基等催化剂对乙烯聚合的影响。     

Ziegler-Natta/茂金属复合催化剂聚合性能的研究

制备了Ziegler-Natta/茂金属复合(Z-M)催化剂,用SEM技术对其形貌进行了表征,在10L丙烯液相本体聚合模试装置上对Z-M催化剂的氢调敏感性进行了评价。通过一段丙烯本体均聚、二段乙烯-丙烯近恒温恒压气相共聚模拟Spheripol-Ⅱ工艺制备了系列聚丙烯(PP)釜内合金;考察了二段共聚时的聚合反应动力学、乙烯与丙烯配比(n(C3)∶n(C2))对PP釜内合金性能的影响。实验结果表明,在一段均聚时Z-M催化剂具有较好的氢调敏感性,得到的均聚PP粒子具有较好的流动性;在二段共聚时,Z-M催化剂能在较长的共聚时间内保持较平稳、较高的共聚活性,改变n(C3)∶n(C2)时PP釜内合金中乙丙橡胶的质量分数可调(7.19%~10.75%),熔体流动速率(10min)可调(14.0~26.5g);n(C3)∶n(C2)对合金弯曲模量的影响不大;当n(C3)∶n(C2)=1.7时制备的PP釜内合金具有最大的冲击强度(92.9J/m)。     

五甲基环戊二烯三苄氧基钛/甲基铝氧烷/三异丁基铝催化合成的间规聚苯乙烯的结构与性能

对五甲基环戊二烯三苄氧基钛/甲基铝氧烷/三异丁基铝催化苯乙烯聚合得到的间规聚苯乙烯(sPS)的结构和性能进行了研究。采用13C核磁共振谱、傅里叶变换红外光谱、宽角X射线衍射、差示扫描量热法、热重分析方法对聚合得到的sPS进行表征,研究其微观结构、结晶行为、分子链结构和热性能。实验结果表明,得到的聚苯乙烯为全反式结构的sPS,间规度大于96%,熔点高于271.0℃,结晶度达46.85%,起始失重温度为291.6℃,失重5%的温度高于350.0℃,热稳定性好,灰分含量低。