多支化聚甲基丙烯酸甲酯-g-聚苯乙烯的合成研究

以α－溴代丙酸乙酯为引发剂引发ＭＭＡ和ＴＥＭＰＯ自由基发生ＡＴＲＰ活性共聚合,,制得带数个ＴＥＭＰＯ基团的ＰＭＭＡ预聚物,它能直接引发苯乙烯发生氮氧自由基下的ＡＴＲＰ,制得侧链相对分子质量可控的多支化ＰＭＭＡ－ｇ－ＰＳ。由于氮氧自由基容易夺得ＰＭＭＡ－ｇ－ＰＳ。由于氮氧自由基容易夺得ＰＭＭＡ预聚物中ＥＰＮＢｒ链端中的ω碳氢,导致引发效率下降,最终的ＰＭＭＡ－ｇ－ＰＳ。由于共聚物相对分子质量分布趋宽     

硅胶负载型烯烃聚合催化剂的研究：Ⅱ.TiCl4正己熔溶液与硅胶？…

研究了ＴｉｃＬ４正己烷溶液与硅胶表面基团的反应,着重讨论了活化温度对于硅胶表面烃基数的影响,以及活化温度,反应温度和ＴｉＣｌ４正己烷溶液浓度对于反应过程中硅胶表面载钛量的影响,最后提出了相应的操作策略以控制硅胶表面的改性。     

TiCl4/SiO2负载型催化剂用于丁二烯聚合Ⅰ .催化剂制备条件对聚合的影响

用球磨法制备的SiO_2负载TiCl_4催化剂进行丁二烯溶液聚合,考察了催化剂制备条件对催化效率的影响,分析了聚合物的结构。结果表明：球磨48 h,负载钛质量分数4％的催化剂具有较好的催化效率;SiO_2在负载TiCl_4前用适量Al(i－Bu)_3处理,或将球磨法制备的TiCl_4/SiO_2催化剂与适量Al(i－Bu)_2Cl 在100 ℃下反应1 h,均能大幅度提高催化剂的活性;在40～50 ℃下,聚合按溶液淤浆聚合形式进行,产物为低顺式聚丁二烯。     

TiCl4—C60Cln催化体系引发异丁烯正离子聚合

研究了碳笼烯非质子酸经体系引发异丁烯正离子聚合的反应规律,并与ＴｉＣｌ４正离子催体系进行了比较。ＧＰＣ的测试结果表明,ＴｉＣｌ４－Ｃ６０Ｃｌｎ催化体系中可能存在２种活性中心：（１）体系中的微量水与ＴｉＣｌ４配位形成的质子引发体系;（２）（ＴｉＣｌ５）－（Ｃ６０Ｃｌｎ－１）＾＋离子引对引发活性中心。     

TiCl4/SiO2负载型催化剂用于丁二烯聚合Ⅱ.聚合条件及聚合动力学

使用以球磨法制备的 SiO2负载 TiCl4催化剂进行丁二烯溶液聚合,考察了聚合条件对催化效率的影响以及在 20～ 60℃下的聚合动力学。确定了适宜的聚合条件：以加氢汽油为溶剂, Al/Ti摩尔比为 20, Ti/Bd摩尔比为 2× 10－ 4, 50℃聚合 10 h以上。溶液聚合动力学研究结果表明,本体系在低转化率下为稳态聚合,其稳态聚合速率方程为 Rp=kpf[Ti]0[Bd],聚合的表观活化能为 11.4 kJ/mol。     

C60和C70对聚苯乙烯耐紫外老化性能的影响

采用熔融共混法制得富勒烯C60和C70含量分别为1%,3%,5%(质量分数)的聚苯乙烯/C60和聚苯乙烯/C70复合膜,对其进行抗紫外光加速老化性能研究。采用乌氏粘度计、红外光谱仪和差热(DTA)仪分别对样品的特性粘度、分子链段结构和分解温度进行测定和表征。研究表明,C60和C70含量为5%的聚苯乙烯/C60和聚苯乙烯/C70复合膜经过紫外老化处理后,其特性粘度、分子链结构、热分解温度变化不大。因此,适当配比的C60和C70能够增强聚苯乙烯材料的耐紫外老化作用。并结合荧光光谱结果对C60和C70改善聚苯乙烯耐老化性能的作用机理进行初步探讨。     

TiCl4／SiO2负载型催化剂用于丁二烯聚合——I.催化剂制备条件对聚合的影响

用球磨法制备的SiO2负载TiCl4催化剂进行丁二烯溶液聚合,考察了催化剂制备条件对催化效率的影响,分析了聚合物的结构。结果表明：球磨48h,负载钛质量分数4%的催化剂具有较好的催化效率;SiO2在负载TiCl4前用适量Al(i-Bu)3处理,或将球磨法制备的TiCl4/SiO2催化剂与适量Al(i-Bu)2Cl在100℃下反应1h,均能大幅度提高催化剂的活性;在40～50℃下,聚合按溶液淤浆聚合形式进行,产物为低顺式聚丁二烯。     

用Cp*TiCl3/MAO催化体系合成间规聚苯乙烯

介绍了以Cp TiCl3 为主催化剂、MAO为助催化剂组成催化体系制备间规聚苯乙烯的实验室方法 ,研究了试验条件变化对聚合反应的影响。合适的聚合反应条件是 :反应温度 5 0℃ ,Al/Ti摩尔比在 5 0 0～ 30 0 0之间 ,催化剂浓度 0 .5× 1 0 - 4 ～ 1 .5× 1 0 - 4 mol·L- 1 ,反应时间 1～2h,催化剂有较高的活性 ,聚合反应能平稳进行。得到间规度大于 97%以上的聚苯乙烯 ,并有很高收率     

TiCl4/SiO2负载型催化剂用于丁二烯聚合Ⅲ.聚合物的结构与性能

用以球磨法制备的TiCl4/SiO2负载型催化剂进行丁二烯溶液聚合,考察了聚合条件对聚合物溶解性及结构的影响,测试了聚合物的基本力学性能。结果表明,Ti/Bd、聚合温度、溶剂类型对聚合物的溶解性影响较大。随着聚合温度升高,聚合物的反式-1,4-结构摩尔分数增加,顺式-1,4-结构摩尔分数降低。聚合物生胶具有较高强度和邵尔A型硬度,但扯断伸长率低,其硫化胶具有较好的耐磨性能和回弹性。     

MgCl2-BuOH/TiCl4催化剂催化乙烯聚合

研究了自制MgCl2-BuOH/TiCl4催化剂在不同条件下用于乙烯均聚合和共聚合的性能,考察了不同的氢气分压、铝钛摩尔比和共聚单体浓度对催化剂活性和聚合反应动力学的影响,测试了聚合产品的熔体流动速率、堆密度及拉伸性能等,表征了聚合产品的相对分子质量及其分布、分子链结构,得出了聚合条件对MgCl2-BuOH/TiCl4催化剂及其产品性能影响的一般规律.     

Ethylene-propylene copolymers by a supported Ziegler-Natta catalyst based on TiCl4/MgCl2

Ethylene-propylene copolymers have been prepared by using Ziegler-Natta catalysts based on TiCl₄, MgCl₂, PCl₃ and (n-Bu)₃PO₄. The catalysts TiCl₄/MgCl₂/PCl₃ and TiCl₄/MgCl₂/(n-Bu)₃PO₄ were prepared by reacting TiCl₄ with pretreated MgCl₂. The support was prepared by ball milling of MgCl₂ with varied amounts of PCl₃ or (n-Bu)₃PO₄. The addition of PCl₃ has remarkably increased the MgCl₂ surface area in comparison with (n-Bu)₃PO₄. The effects of PCl₃ and (n-Bu)₃PO₄ on ethylene homopolymerization, ethylene-propylene copolymerization and on copolymer properties were evaluated. The catalyst system containing PCl₃ permitted to synthesize propylene-ethylene copolymers with up to 75% (w/w) of propylene and provided control of copolymer crystallinity. The reduction of the copolymer molecular weight distribution suggested that PCl₃ acted as an internal donor, poisoning some active catalytic sites. Received: 2 April 1997/Revised: 6 June 1997/Accepted: 18 June 1997     

TiCl4/MgCl2催化剂载体掺杂的研究进展

综述了用于烯烃配位聚合的MgCl_2载体掺杂负载型Ziegler-Natta(Z-N)催化剂的研究进展,讨论了此类催化剂用于烯烃聚合的催化活性、活性中心分布、聚合产物的相对分子质量分布及立构规整性的变化等。掺杂MgCl_2负载的Z-N催化剂比常规负载的Z-N催化剂生产的聚烯烃的相对分子质量分布宽,催化活性也有一定的改变。     

Homo- and copolymerization of ethylene with highly active catalysts based on TiCl4 and grignard compounds

In this paper, the synthesis of different catalytic systems based on the reduction of TiCl₄ by Grignard compounds has been systematically studied. The catalysts exhibited the highest activities when used in the copolymerization of ethylene with n-hexene. The profile of the kinetic curves also changed when the comonomer was present during polymerization. By thermal analysis and scanning electron microscopy techniques, it could be found that the incorporation of the comonomer to the polymer chain brings about a decrease in the polymer crystallinities and an increase in the porosities of the growing particles. Due to that, the diffusion of the monomer to the catalytic active centers takes place more easily, consequently increasing the polymerization rate. In addition, catalysts control better the morphology (size and shape) of the nascent polymer particles when used for copolymerization.     

Polymerization of propylene by highly active catalysts synthesized with Mg(OEt)2/benzoyl chloride/TiCl4

Summary Active centers have been studied in the polymerization of propylene using highly active Mg(OEt)₂/Benzoyl chloride/TiCl₄ catalysts activated with AlEt₃. The method for the measurement of active centers is based on the inhibiting effect of CO on polymerization. The activity of the present catalysts, which is higher than that of TiCl₃ or MgCl₂-supported catalyst, is mainly due to the higher concentration of active centers by one order of magnitude. In order to investigate the stability of active centers during polymerization the number of active centers are compared at various polymerization times.     

The effect of light on the cationic polymerisation of isobutene by TiCl4 some comments on two papers by Kennedy and Diem

Summary Several objections are raised regarding the mechanistic conclusions drawn by Kennedy and Diem in two recent papers dealing with the effect of light on the polymerisation of isobutene and its dimer by titanium tetrachloride. In particular, the process of photogenerated cocatalysis and the attempted explanation of condensation polymerisation by that mechanism are critically discussed.     

Effect of carbon coating on low temperature electrochemical performance of LiFePO4/C by using polystyrene sphere as carbon source

Carbon perfectly coated LiFePO₄ cathode materials are synthesized by carbon-thermal reduction method using polystyrene (PS) spheres as carbon source. The PS spheres with diameters of 150–300 nm used for the pyrolysis reaction not only inhibit the particle growth but also lead to uniform distribution of carbon coating on the surface of LiFePO₄ particles. Rate capability and cycling stability of LiFePO₄/C with the carbon contents ranging from 1.4 wt% to 3.7 wt% are investigated at −20 °C. The LiFePO₄/C with 3.0 wt% C exhibits excellent electrochemical capability at low temperature, which delivers 147 mAh g⁻¹ at 0.1 C. After 100 cycles at a charge–discharge rate of 1 C, there is still 100% of initial capacity retained for the LiFePO₄/C electrode at −20 °C. According to the transmission electron microscope analysis and cyclic voltammetry measurement, this can be attributed to the good carbon coating morphology and optimal carbon coating thickness.     

Preparation of soluble TiCl3 catalysts by reduction of TiCl4 with Grignard reagents and their use for copolymerization of ethylene with propylene

Summary Preparations of soluble TiCl₃ catalysts by reduction of TiCl₄ with some types of Grignard reagents were carried out in halogenated hydrocarbon solvents by using appropriate ethers as donor. The soluble TiCl₃·MgX₂·ether complex catalysts and triisobutylaluminum as co-catalyst showed high activities for the copolymerization of ethylene with propylene. It was first found that the soluble TiCl₃·MgX₂·ether complex catalysts enhance the activities for the copolymerizations in the same manner as solid titanium catalysts supported on MgCl₂ which show high activities for homopolymerizations of olefin monomers. The copolymers obtained possessed low crystallinities. Also, the copolymers seem to contain microblock sequences and have outstandingly high tensile strength and elongation at break compared to copolymers by the conventional VOCl₃/Al(Et)_1.5Cl_1.5 catalyst system.     

Comonomer enhancement effect of 1-hexene in ethylene copolymerization catalyzed over MgCl2/THF/TiCl4 catalysts

Homo- and copolymerization of ethylene were performed by using a catalyst system composed of TiCl₄/THF/MgCl₂ complex activated with AlEt₃ at 70°C and 3 atm. To investigate the effect of the compositional difference of the catalyst on the rates of homo- and copolymerization and on the reactivity in ethylene–hexene copolymerization, a series of six catalysts with different compositions (Mg/Ti = 0.4–16.5) were prepared by coprecipitation. The catalytic activity in ethylene polymerization increased sharply with the Mg/Ti ratio from 21 (Mg/Ti = 0.4) to 1477 kg PE/g-Ti h (Mg/Ti = 16.5). The activity in copolymerization with 1-hexene also increased with Mg/Ti ratio. The values of r₁ were 120, regardless of Mg/Ti ratios within the experimental error range. Enhancement of the polymerization rate by the addition of 1-hexene in the reaction medium was observed only for the catalysts of low Mg/Ti ratio. This unusual effect of 1-hexene on the polymerization rate was explained by chemical and physical processes that occurred during polymerization. © 1993 John Wiley & Sons, Inc.     

Studies on highly active coordination catalysts for polymerization of α-olefins: 3. Polymerization of propylene with MgCl2/TiCl4/AlEt3 or MgCl2/PhCOOC2H5/TiCl4/AlEt3 systems

Activity and stereospecificity of the $\text{MgCl}{}_2\text{TiCl}{}_4$ catalyst in the polymerization of propylene follow curves showing maxima with grinding time of the MgCl₂ support. Using MgCl₂/PhCOOC₂H₅/TiCl₄ catalysts, no decrease in activity and stereospecificity was observed presumably because of complex formation between MgCl₂ support and ethyl benzoate.     

The influence of aluminum alkyls on the polymerization of ethylene with SiO2/MgCl2-supported TiCl4 catalysts

The influence of different aluminum alkyls (diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and isoprenylaluminum) on the ethylene polymerization activity of a laboratory prepared high-activity SiO₂/MgCl₂-supported TiCl₄ catalyst has been investigated. A slurry reactor (decane diluent) was used for measuring rates of polymerization. The average molar mass, the breadth of the molar mass distribution, the polymerization activity, and the shapes of the activity-time profiles, were strongly dependent on the nature of the aluminum alkyl. For several of the cocatalysts used, the catalytic activity approached a constant value after a certain amount of time under reaction conditions. In this constant activity region, a first-order dependence of the polymerization rate on the monomer concentration was found for all of the systems examined. However, the activation energy of the polymerization reaction was found to depend strongly on the type of cocatalyst which was used.