丙烯淤浆预聚合对聚丙烯产品性能的影响

研究了丙烯淤浆预聚合对聚丙烯（PP）性能的影响，试验过程中采用Ziegler-Natta催化剂，并使用三乙基铝作为助催化剂。结果表明，与不预聚相比，经过预聚PP的等规度、结晶度、熔点、结晶温度都有所提高，但熔体流动速率下降。预聚时加入外给电子体。可以提高PP的熔点和结晶度。在铝钛物质的量比为3／1～10／1范围内增加预聚合过程中的烷基铝用量。也可以提高PP的熔点和结晶度。提高预聚合温度。PP的结晶温度不下降。     

负载型非茂金属催化剂聚合制备UHMWPE

在淤浆聚合条件下采用新型负载型非茂金属催化剂(SSTU)制备了超高相对分子质量聚乙烯(UHMWPE),考察了聚合温度、预聚合、助催化剂用量等聚合条件对催化剂活性、UHMWPE堆密度、粒径分布、粘均相对分子质量、力学性能、结晶性能和微观形貌等的影响.结果表明,提高聚合温度和助催化剂用量有利于催化剂活性发挥,而降低聚合温度和不预络合时可以得到高粘均相对分子质量的UHMWPE.由SSTU聚合得到的UHMWPE粒径分布均匀,细粉含量低(质量分数小于0.5%),结晶性能和力学性能好,在微观形貌上与齐格勒-纳塔催化剂制备的UHMWPE有显著区别.     

丙烯预聚合工艺的研究进展

综述了有关丙烯预聚合的最新进展,包括新的预聚合工艺及其对聚合过程、聚丙烯(PP)产品性能等的影响以及在“超临界”聚合上的应用等。丙烯预聚合对于PP颗粒形态、主聚合阶段的聚合动力学以及聚合工艺都会产生影响。     

DQC-602型催化剂催化丙烯的聚合

以DQC-602型催化剂为主催化剂,三乙基铝为活化剂,环己基甲基二甲氧基硅烷为外给电子体,在5 L聚合釜中进行丙烯本体聚合,研究了不同聚合温度和预聚合温度条件下,DQC-602型催化剂和用其制备的聚丙烯(PP)的性能,考察了不同n(Al)/n(Si)的条件下用DQC-602型催化剂制备的PP的等规指数调节性能。结果表明:DQC-602型催化剂具有聚合活性高、立构定向性高的特点,用其所制PP的等规指数在96.5%~98.9%可调、粉料的细粉含量低;提高聚合温度,可提高DQC-602型催化剂的活性和PP的等规指数,PP的相对分子质量分布变窄;提高预聚合温度,可降低PP的细粉含量。     

DQC-700型催化剂催化丙烯聚合

采用仪器分析和化学分析法表征了DQC-700型催化剂的组成、结构及其颗粒形态。以环己基甲基二甲氧基硅烷为外给电子体,用DQC-700型催化剂催化丙烯本体聚合,评价了预聚合温度对预聚合倍数、预聚物等规指数和预聚物粉料粒径分布的影响,研究了催化剂的聚合性能和聚丙烯粉料中的细粉含量。结果表明:DQC-700型催化剂具有较窄的粒径分布(粒径分布跨度1.0)、较大的比表面积(300 m2/g)、较高的聚合活性[45 kg/(g·h)]和立构定向性(聚丙烯等规指数98%)。     

N催化剂在丙烯聚合反应中的应用Ⅰ.预聚与预络合对N催化剂聚合性能的影响

考察了丙烯预聚、预络合对N催化剂聚合性能的影响，结果表明，预络合有助于提高催化剂的聚合活性以及聚合物的表观密度，提高催化剂的抗杂质干扰能力，预聚除能够提高催化剂的活性外，对提高聚丙烯粉料的表观密度和等规指数，减少聚丙烯颗粒的破碎有显著影响。     

超临界溶液快速膨胀法制备二氯二茂钛微粒及催化乙烯聚合

为克服茂金属催化剂得到的聚合物形态难以控制、表观密度较低、易粘釜和不适于气相淤浆聚合等缺点,以超临界溶液快速膨胀过程为手段,以期制得颗粒分布均匀的细微催化剂颗粒,继而得到形态良好的聚合物.作为超临界流体技术的基础,首先测定了二氯二茂钛在超临界丙烷中的溶解度.在此基础上,用RESS方法制得了均匀的超细催化剂颗粒,且系统考察了溶液浓度、预膨胀温度、喷嘴结构和接收距离对沉析颗粒粒径的影响.最后,将RESS所制得的催化剂颗粒进行乙烯淤浆聚合,并分析聚合物形态结构.实验结果表明,在温度为383.15～408.15 K和压力为10～35 MPa范围内,溶解度随温度的增加而增加,随压力的升高而增加,说明在该操作范围内,不存在反向区.RESS操作的结果显示,二氯二茂钛颗粒粒径随溶液浓度的增大而减小,随预膨胀温度的升高而增大,而喷嘴直径的减小和喷嘴长度的增加将使得颗粒粒径增大,而收集距离的增加将使得颗粒粒径先增加后减缓,直至不再变化.通过对原始的催化剂颗粒和RESS制得的催化剂颗粒进行乙烯淤浆聚合表征发现,相比于原始催化剂,由于烯烃催化剂的复制原理,RESS制得的催化剂颗粒的聚合物具有良好的形态.     

新型TiCl_4/MgCl_2催化剂催化丙烯聚合——不同取代基的β-二酮类内给电子体对催化剂性能的影响

制备了一系列β-二酮类化合物作内给电子体的新型TiCl4/MgCl2负载型催化剂,研究了其对丙烯聚合的影响.该催化剂催化丙烯聚合淤浆反应的最佳条件:聚合温度为40℃、n(Al)/n(Ti)为100.给电子体2,4-戊二酮结构中3-位上有取代基的催化剂的催化活性及所得聚合物的等规指数都明显优于3-位上无取代基的催化剂:二酮类内给电子体中3-位上取代基的体积越大,所得催化剂的催化活性以及所得聚合物的等规指数越高.     

SPG聚丙烯工艺流程模拟研究和优化

采用ASPEN PLUS的Polymer Plus对SPG聚丙烯技术中本体淤浆聚合工段和气相卧釜工段的两个关键的技术进行了较深入的研究。模拟结果表明,淤浆聚合反应收率在52%～58%时,聚丙烯总收率最高。淤浆反应温度提高,聚丙烯总收率和淤浆反应收率都提高。随着气相反应温度提高,气相反应收率先下降随后缓慢提高。加入少量氢气可以使聚丙稀数均分子量快速下降,聚合物分散度快速增加,而当氢气超过一定量以后,这种变化趋缓。为了确保反应器体积的充分利用和催化剂活性基本消耗完,要确定淤浆反应器体积和气相釜的体积和反应温度的匹配关系。根据反应热分布相应采用非均匀冷凝回流的方法,可以解决采用均匀冷凝回流方式时卧釜温度控制比较困难的问题。最后,提出了一些优化卧釜气相聚合流程的建议。     

预接触温度对聚丙烯DQC球形催化剂聚合性能的影响

使用甲基环己基二甲氧基硅烷（C-donor）作为外给电子体，对聚丙烯DQC球形催化剂进行了预接触温度液相本体聚合研究。实验结果表明，预接触温度升高，DQC球形催化剂的聚合活性降低，得到聚合物的等规指数升高，熔融指数下降，得到的聚合物细粉含量增加。GPC测试结果表明，预接触温度升高，聚合物的分子量分布变宽，数均分子量和重均分子量降低。DSC测试结果表明，聚合物的熔融温度、熔融焓和结晶焓数值均有不同程度的提高，聚合物的结晶度提高。¹³C NMR测试结果表明，预接触温度升高，得到的聚合物全同立构三单元组mm序列结构和五单元组mmmm序列结构含量均增加。     

Effect of isotacticity distribution on crystallization kinetics of polypropylene

The crystallization kinetics of isotactic polypropylene (iPP) depends not only on the undercooling but also on its microstructure characteristics. In this paper the effect of isotacticity distribution on the isothermal kinetics of iPPs in the crystallization regime III was examined by differential scanning calorimetry. The microstructure features of two commercial film grade iPPs were characterized with temperature rising elution fractionation and size exclusion chromatography. The results indicated that, although the overall isotacticities and molecular weights of two iPPs were similar, their isothermal crystallization kinetics displayed marked differences due to the disparity in isotacticity distributions. With increasing molecular weight of components containing crystallizable units, the isothermal crystallization rate exhibited a higher temperature dependence. When the isotactic defects in polypropylene chains increase with the molecular weight of components, both the fold surface free energy σ_e and the work of chain folding q decreases, in spite of the higher molecular weight. © 2002 Society of Chemical Industry     

负载型茂金属催化剂用于乙烯淤浆聚合的研究

在烯烃催化聚合领域,茂金属催化剂显示出比传统Ziegler-Natta催化剂更高的活性。以苯甲酸催化三甲基铝（TMA）受控水解生成甲基铝氧烷（MAO）,经热解过程后合成了一种不溶形式的固体聚甲基铝氧烷（sMAO）。以合成的sMAO为载体负载茂金属催化剂,并将该催化剂应用于乙烯淤浆聚合反应中,系统探究了聚合条件对催化行为的影响,同时对聚乙烯产品mPE的粒度、堆密度、分子量及分布和熔体流动速率等基本理化性能进行了分析表征。实验结果表明,制备的催化剂颗粒形态较好,粒子分布均匀,在5 L釜中催化淤浆反应,乙烯/1-己烯共聚活性最高可达15 302.6 g·g^-1,并得到了相对分子质量分布均匀的中、高密度聚乙烯产品。     

An electron microscope study of the microstructure of some rubber-reinforced polystyrenes

Rubber-reinforced polystyrenes were prepared by graft copolymerization using various butadiene polymers and copolymers. Electron microscopy showed that variations in the pre-polymerization temperature, composition of the rubber, and molecular weight of the rubber influenced the size and structure of the dispersed rubber particles. Microstructures and impact strengths comparable to those of commercial materials were obtained from a limited range of conditions. Solution styrene-butadiene copolymers and a polybutadiene of low molecular weight gave unusual microstructures although polystyrenes of inferior impact strength were obtained. A particle size of 2 μm or greater was required to obtain reasonable improvements in impact strength. The particle size increased with an increase in the initial viscosity of the rubber in styrene solution provided that rubber type and concentration, and pre-polymerization temperature were constant. The effects of these three variables on particle size could not be related to viscosity changes.     

烯烃聚合过程的分形演化及其生长模型

The surface morphology of Ti-Mg supported catalyst and the polyethylene particles are studied using scanning electron microscope(SEM) technology.The results show that either the catalyst‘s surface or polymer particle‘s surface is irregular and has fractal characteristics,which can be described by fractal parameter.The more interesting discovery is that the surface fractal dimension values of the polymer particles vary periodically with the polymerization time.We call this phenomenon fractal evolution,which can be divided into the “revolution“ stage and the “evolution“ stage,And then we present polymerization fractal growing model(PFGM),and successfully describe and /or predict the whole evolving process of the polyethylene particle morphology under the different slurry polymerization(including pre-polymerization) conditions without H2.     

悬浮聚合法制备磁性微球的粒度分布特性

本文研究了含有微细铁黑颗粒的混合单体悬浮聚合产物的粒度分布特性。分析了分散剂、超声预分散和无机铁黑颗粒对形成粒度多峰分布的影响。结果表明,分散剂是体系中形成小颗粒的主要因素;超声波的预分散作用使悬浮体系的液滴破裂以“腐蚀破碎（erosive breakage)”为主;无机铁黑颗粒由于其表面亲水性,倾向于分布在油性单体液表面,不仅有利于悬浮液滴的“磨蚀破碎”,同时也对分散液滴具有良好的稳定作用。上述因素的共同作用使得聚合产物的粒度呈三峰分布。     

Comparison of RAFT polymerization of methyl methacrylate in conventional emulsion and miniemulsion systems

In this study, we have conducted the reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) in two heterogeneous systems, i.e. conventional emulsion and miniemulsion, with identical reaction conditions. The main objective is to compare the living character in both systems according to the nucleation mechanism, the latex stability, the particle sizes and particle size distributions of latexes, the molecular weights and molecular weight distributions (or polydispersity index, PDI) of PMMA, and the kinetics of the RAFT polymerization. The RAFT agent used in both systems was 2-cyanoprop-2-yl dithiobenzoate (CPDB). The effects of an oil-soluble initiator 2,2′-azobisisobutyronitrile (AIBN) and a water-soluble initiator kalium persulfate (KPS) on the RAFT/emulsion and RAFT/miniemulsion polymerizations were investigated. Methyl-β-cyclodextrin (Me-β-CD) was used as a solubilizer. The average molecular weights and molecular weight distributions (PDIs) of dried PMMA samples were characterized by gel permeation chromatography (GPC). The experimental results showed that the RAFT/miniemulsion polymerization of MMA exhibited better living character than that of RAFT/emulsion polymerization under the conditions of our experiment. The PDI of PMMA in RAFT/miniemulsion polymerization was decreased with the addition of Me-β-CD. However, Me-β-CD did not have influence on the PDI of PMMA prepared in RAFT/emulsion polymerization.     

超浓乳液及其应用

介绍了超浓乳液的制备方法、形成条件以及在各领域的应用.讨论了超浓乳液的相行为与稳定性及各自的影响因素,比较了超浓乳液聚合与本体聚合、传统乳液聚合的区别.超浓乳液聚合存在聚合物分子量大,聚合速率快,乳胶粒子粒径可控等优点.     

Nascent morphology of syndiotactic polystyrene synthesized over silica-supported metallocene catalyst

The nascent morphology of semi-crystalline syndiotactic polystyrene (sPS) polymerized over silica-supported pentamethyl cyclopentadienyl titanium trimethoxide (Cp^∗Ti(OCH₃)₃) catalyst in a liquid slurry polymerization has been investigated under various reaction conditions. The scanning electron microscopic analysis of nascent polymers reveals that sPS molecules grow as long nanofibrils of 30-50 nm diameter and X-ray diffraction analysis shows the co-crystalline phases including both sPS and low molecular weight guest molecules of monomer and diluent. The energy dispersive X-ray spectroscopy also shows that the disintegration of silica primary particles occurs during the polymerization as evidenced by the uniform dispersion of silicon and aluminum in a polymer particle. The fibrous growth of the polymer inside a polymer particle leads to the shape replication of the original silica particles.     

甲基丙烯酸甲酯的RAFT微乳液聚合

该文合成了一种双官能团的RAFT试剂——S,S'-二(α,α'-二甲基-α″-乙酸)三硫代碳酸酯(BDAT)。以其为链转移剂,在微乳液体系中进行了甲基丙烯酸甲酯的RAFT聚合。分别讨论了聚合反应温度和链转移剂浓度对聚合反应的影响,并对相关的聚合反应动力学常数进行了计算。研究结果表明,在微乳液中进行的RAFT聚合具有显著的活性聚合的特征。聚合产物的相对分子质量(简称分子量,下同)随着转化率的提高而线性增加,同时聚合产物具有较窄的分子量分布,聚合过程随着链转移剂浓度的增加而逐渐可控。另外,利用透射电子显微镜对链转移剂浓度对微乳液粒子尺寸的影响也进行了考察,扫描电镜照片表明,微乳液聚合所得乳液粒子呈现单分散性状态,并且粒子尺寸随着链转移剂浓度的增加而逐渐增加。