丙烯聚合用齐格勒—纳塔催化剂的作用机理

讨论了丙烯聚合用齐格勒－纳塔催化剂的反应机理,论述了如何保持催化剂在活性与等规指数之间的平衡作用,特别研究了内给电子子体与外给电子体对催化剂活与等规指数的影响。     

丙烯超临界聚合研究取得重大突破

扬子石化公司研究院经过不断研究探索,目前在丙烯超临界聚合研究方面取得了重大突破。 超临界是介于液态和气态之间的一种状态,处于这种状态的物质被称为超临界流体。丙烯超临界聚合可以产生对聚合有利的许多因素,目前只有著名的北欧化工公司具有此项工艺技术,我国在这方面的研究相对落后。近年来,研究院科研人员在研     

丙烯超临界聚合研究取得重大突破

扬子石油化工股份有限公司研究院经过不断研究探索,日前在丙烯超临界聚合试验方面取得重大突破。 超临界是介于液态和气态之间的一种状态。处于这种状态的物质被称为超临界流体。丙烯超临界聚合可以产生许多对聚合反应有利的因素。目前,只有北欧化工公司具有此项工艺技术。 我国在这方面的研究相对落后。近年来,该     

助催化剂对负载型Ziegler-Natta催化剂催化丙烯高温聚合的影响

在低温下通过三乙基铝和水在不同的Al／H2O摩尔比下分别制备了EAO1（2：1），EAO2（3：2），EAO3（5：4）和EAO4（10：9）等一系列乙基铝氧烷，并将其作为助催化剂用于丙烯在不同温度下的聚合反应。通过对不同助催化剂的研究，发现助催化剂对负载型Ziegler—Natta催化剂催化丙烯聚合有显著的影响。在7O℃时，不同助催化剂所制备的聚合物的等规度相近，但聚合活性按AIEt3〉EAOl〉EAO2〉EAO3〉EAO4次序递减，而EAO制备的聚合物的分子量明显高于AIEt3；在100℃时，不同助催化剂（除EAO4外）的聚合活性相差不大，但聚合物的等规度和分子量都按AIEt3≈EAO1〈EAO2〈EAO3次序递增。结果表明助催化剂的反应性和体积大小影响活性中心的状态，进而影响聚合物的性质。     

NDQ催化剂催化丙烯聚合

采用以二醇酯为内给电子体合成的NDQ催化剂,在5 L高压釜中催化丙烯本体聚合,评价了NDQ催化剂的聚合性能.结果表明:NDQ催化剂具有较高聚合活性、立构定向性;NDQ催化剂在低氢气浓度下氢调不敏感,适宜生产低熔体流动速率的树脂;得到的聚丙烯具有相对分子质量分布宽的特点.     

扬子石化公司研究院丙烯超临界聚合研究取得重大突破

超临界是介于液态和气态之间的一种状态,处于这种状态的物质被称为超临界流体。试验证明,丙烯超临界聚合可以产生许多对聚合反应有利的因素,但目前只有著名的北欧化工公司具有此项工艺技术。目前,我国在这方面的研究相对落后。近年来,南京扬子石化公司研究院在丙烯超临界聚合研究方面取得了重大的突破,发现了一种催化剂配方体系能够适应高温丙烯聚合,     

SC型高效催化剂丙烯液相本体聚合

SC型高效催化剂是用无水MgCl_2、醇、蘸、TiCl_4以及添加剂制备的,SC型催化剂和A1Et_3助催化剂、Ph_2Si(OMe)_2外给电子体,用于丙烯液相本体聚合,丙烯在70℃聚合2h具有高效率(大于3万gPP/gCat),得到的聚丙烯等规度(大于98％)和堆密度(大于0.45g/cm~3)高,颗粒形态好,粒度分布窄,聚丙烯的MFR容易用氢调节。     

超临界聚合生产高附加值PE

论述了用丙烷代替异丁烷作稀释剂的超临界环管反应器生产聚乙烯的最新工艺,介绍了该工艺的设计基础及技术特点。     

丙烯聚合工艺技术介绍和进展

介绍了聚丙烯的主要工艺技术、技术进展和发展方向。     

马来酸酐/苯乙烯多单体接枝低等规聚丙烯

低等规聚丙烯（LIPP）是由等规立构和间规立构组成的嵌段共聚物，具有低的结晶性能，良好的粘接性和加工性能，在胶粘剂领域有着广阔的应用前景。然而LIPP的非极性和低的机械性能限制了它的应用。本文采用溶液法，以过氧化二异丙本（DCP）为引发剂，以苯乙烯（St)作为共聚单体，将马来酸酐（MAH）接枝到低等规聚丙烯（LIPP）大分子链上，采用化学滴定法测定产物（LIPP－g-MAH-St)的接枝率（GR），并系统地研究了加料方式，单体用量，引发剂用量，反应时间等因素对GR的影响，结果表明，采用先加入引发剂的加料方式有利于马来酸酐对低等规聚丙烯的接枝反应，反应的最佳条件是：反应时间7h，MAH的加入量为9份（以100份LIPP计），引发剂DCP的加入量为0．45份。     

Isothermal crystallization behavior of metallocene‐catalyzed isotactic polypropylene

Isothermal crystallization behavior of isotactic polypropylene (iPP) synthesized using metallocene catalyst was investigated in this work. The isotacticity of the polypropylene was characterized by ¹³C‐NMR spectroscopy. It was found that the melting temperature (T_m) of the iPP is 123.51°C and the crystallization temperature (T_c) is 93°C. The iPP synthesized in this work did not show a general increase of T_m with an increase of crystallization temperature T_c, due to the short crystallization time of 20 min and low molecular weight (number average molecular weight = 6,300). The iPP showed a tendency of increasing heat of fusion (ΔH_f) with decreasing crystallization temperature. All the spherulites of iPP samples showed negative birefringence. For the iPP sample crystallized at the highest T_c (= 123°C, just below T_m), the spherulite showed a pronounced Maltese Cross and a continuous sheaf‐like texture aligning radially, which suggests that R‐lamellaes are dominant in this spherulite. The crystalline structure of the iPP was also investigated by X‐ray diffraction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 231–237, 2005     

Morphology,crystallization, and thermal behavior of isotactic polypropylene/propylene‐g‐styrene blends

Optical microscopy, differential scanning calorimetry, and small angle X‐ray scattering techniques were used to study the influence of the crystallization conditions on morphology and thermal behavior of samples of binary blends constituted of isotactic polypropylene (iPP) and a novel graft copolymer of unsaturated propylene with styrene (uPP‐g‐PS) isothermally crystallized from melt, at relatively low undercooling, in a range of crystallization temperatures of the iPP phase. It was shown that, irrespective of composition, no fall in the crystallinity index of the iPP phase was observed. Notwithstanding, spherulitic texture and thermal behavior of the iPP phase in the iPP/uPP‐g‐PS materials were strongly modified by the presence of copolymer. Surprisingly, iPP spherulites crystallized from the blends showed size and regularity higher than that exhibited by plain iPP spherulites. Moreover, the amount of amorphous material located in the interspherulitic amorphous regions decreased with increasing crystallization temperature, and for a given crystallization temperature, with increasing uPP‐g‐PS content. Also, relevant thermodynamic parameters, related to the crystallization process of the iPP phase from iPP/uPP‐g‐PS melts, were found, composition dependent. The equilibrium melting temperature and the surface free energy of folding of the iPP lamellar crystals grown in the presence of uPP‐g‐PS content up to 5% (wt/wt) were, in fact, respectively slightly lower and higher than that found for the lamellar crystals of plain iPP. By further increase of the copolymer content, both the equilibrium melting temperature and surface free energy of folding values were, on the contrary, depressed dramatically. The obtained results were accounted for by assuming that the iPP crystallization process from iPP/uPP‐g‐PS melts could occur through molecular fractionation inducing a combination of morphological and thermodynamic effects. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2286–2298, 2001     

低等规聚丙烯的研制Ⅴ.粘性聚合物的分离技术

采用液相本体法生产的粘性低等规聚丙烯在排放输送和分离回收时易堵塞阀门和管道。模试结果表明：控制聚合时丙烯转化率为20％～50％,同时预先在闪蒸釜中加人表面分散剂质量分数约0．3％的液体介质及预先充人丙烯单体可以有效地解决这一问题。介绍了采用乙醇-水溶液作为分散介质的分离技术特征,并可用深度冷冻法或吸附极性分子法从回收体系中除去乙醇。     

固相氯化法氯化等规聚丙烯结构分析

借助ＤＳＣ,ＩＲ,＾１Ｈ－ＮＭＲ方法对搅拌式固相氯化制备的氯化等规聚丙烯的宏观氯原子分布和微观氯原子分布进行了分析。结果表明,搅拌式固相氯化法能够迅速破坏等规聚丙烯的结晶,从而得到宏观氯原子分布均匀的ＣＩＰＰ。此方法制备的ＣＩＰＰ主要为等丙烯分子链上的仲氢原子被取代的产物。     

Influences of copolymerization conditions on the structure and properties of isotactic polypropylene/ethylene–propylene random copolymer in situ blends

A spherical TiCl₄/MgCl₂‐based catalyst was used in the synthesis of in situ isotactic polypropylene/ethylene–propylene random copolymer blends by propylene bulk polymerization and subsequent gas‐phase copolymerization of ethylene with propylene. Different copolymerization conditions, such as the reaction time, monomer pressure, and composition, were investigated, and their influences on the structure and properties of the products were studied. Raising the monomer pressure was the most effective way of speeding up the copolymerization, but it caused more increases in the random copolymer than the block copolymer fractions. Increasing the ethylene content of the monomer feed also resulted in higher reaction rates and copolymer contents, but the ethylene contents of both the random and block copolymer fractions were also raised. In situ blends that contain more than 50 wt % copolymer were prepared. The mechanical properties of the blends, including the impact strength and flexural modulus, were regulated in a rather broad range with changes in the copolymerization conditions. The properties were highly dependent on the amount, distribution, and chain structure of the copolymer fractions. The impact strength was influenced by both the random copolymer and block copolymer portions in a complicated way, whereas the flexural modulus was mainly determined by the amount of random copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 445–453, 2002; DOI 10.1002/app.10415     

The morphology of irradiated isotactic polypropylene

The research in this article explores the response of semicrystalline isotactic polypropylene to gamma radiation in air, and relates the morphological changes of the polymer to corresponding changes in mechanical properties. The effect of the initial morphology of the polymer on its response to irradiation is considered using infrared spectroscopy (FTIR), small‐ and wide‐angle X‐ray scattering, dynamic mechanical thermal analysis (DMTA), and mechanical testing. The extent of chain scission and crosslinking is dependent on the dose but not the initial starting morphology. These chemical changes cause the crystallinity to increase slightly, and the glass transition temperature to rise by a few degrees in all samples, but the overall morphology is only subtly changed. In contrast, a major deterioration in mechanical properties is caused. The effects of the irradiation observed under these conditions are similar in each material and the ultimate properties determined by the properties seen in the original material. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2234–2242, 1999     

Cavitation during isothermal crystallization of isotactic polypropylene

Cavitation during isothermal crystallization of thin films of isotactic polypropylene was investigated systematically by light microscopy. Cavitation results from the negative pressure buildup due to density change during crystallization in the pockets of melts occluded by impinging spherulites. The morphology of such areas was also studied by SEM. The value of the negative pressure at the moment of cavitation was calculated from the drop of the spherulite growth rate. It was shown that the process of cavitation and the value of the negative pressure causing cavitation depend on the crystallization temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2439–2448, 2001     

Orientated crystallization in discontinuous aramid fiber/isotactic polypropylene composites under shear flow conditions

Melt blends of short aramid fibers (AF) and isotactic polypropylene (iPP) are subjected to shear at 145°C and the structural evolution and final morphology are examined by in situ synchrotron X‐ray scattering/diffraction and high‐resolution scanning electron microscopy, respectively. The results indicate that the presence of short AFs significantly enhances the crystallization of iPP. It is argued that shear flow in this system exerts a twofold orientating action, namely, on the bulk iPP molecules and on the short AFs. The resultant crystalline morphology reflects the combined effects of crystallization on orientated iPP molecules to facilitate a shish kebab morphology and at the interface of the aligned fibers, to form transcrystallinity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1113–1118, 2005     

等规聚丙烯-丙烯酸接枝共聚

详细研究了等规聚丙烯细粒子在丙烯酸水溶液中,以过氧化苯甲酰为引发剂的液－固相接枝共聚反应和十氢化萘乙醇溶液对等规聚丙烯的膨化预处理作用,检测了等规聚丙烯－聚丙烯酸的某些性质,发现随接枝率提高,其吸湿性和碱性染料染色性均提高,熔点略有降低,但熔体流动性下降,按本研究获得的最佳膨化预处理条件和最佳接枝共聚反应条件,接枝产物等规聚丙烯－聚丙烯酸的接枝率可超过13％。