Ziegler-Natta催化体系中影响聚丙烯等规度的因素

Ziegler-Natta(Z-N)催化剂是生产等规聚丙烯的最主要的催化剂,其不同组分对Ti活性中心立构选择性都有不同的影响,本文详细论述了MgCl₂载体、给电子体和烷基铝助催化剂以及它们之间的相互作用对Z-N催化剂立构选择性的影响。     

丙烯聚合用Ziegler-Natta催化剂的内给电子体研究进展

综述了丙烯聚合用Ziegler-Natta(Z-N)催化剂中内给电子体的研究进展,并对各类内给电子体的应用实例进行了评价。其中,以1,3-二醚、琥珀酸酯和1,3-二醇酯类化合物为内给电子体制备的Z-N催化剂具有活性高、立体定向性高,用该催化剂制备的聚丙烯具有特征相对分子质量分布等特点。分析具有代表性的内给电子体所制催化剂的活性中心模型发现,单酯体系的等规和无规活性中心在Lewis酸作用下存在可逆平衡,二醚体系中醚氧原子电子云的转移和二醚的空间结构影响钛活性中心的性能。     

助催化剂和外给电子体对丙烯聚合性能的影响

考察助催化剂加入量(Al/Ti摩尔比)和外给电子体加入量(Si/Ti摩尔比)变化对MgCl2负载的Ziegler-Natta催化体系催化丙烯聚合时的聚合性能的影响.发现A1/Ti摩尔比增大会使催化剂活性增加,并存在最佳的助催化剂用量.同时,Ai/Ti摩尔比增大还会使聚丙烯的等规度下降,但当存在外给电子体时,下降速度稍缓.而外给电子体的加入通常在提高聚合物等规度的同时会使催化剂的活性降低.     

不同催化剂体系对聚丙烯性能的影响

研究了不同内给电子体的Z-N催化剂对聚丙烯性能的影响。研究结果表明,在相同的聚合条件下,二醚类内给电子体Z-N催化剂和酯类内给电子体Z-N催化剂相比,具有良好的氢调敏感性和催化剂活性。采用二醚类内给电子体Z-N催化剂生产的聚丙烯样品和酯类内给电子体Z-N催化剂生产的聚丙烯样品相比,具有窄的分子量分布和高的等规度,在纺丝加工应用中,可获得更高的取向度。采用二醚类内给电子体Z-N催化剂生产的聚丙烯样品具有相对较低的灰分和挥发份以及良好的聚合物形态,可满足挤出加工工艺长周期的运行要求。     

丙烯/丁烯无规共聚聚丙烯小试研究

以工业上现有高效齐格勒-纳塔(Z-N)聚丙烯催化剂为基础,通过优化外给电子体种类及用量,进行了丙烯/丁烯无规共聚的小试研究。研究了烷基铝和催化剂之比(Al/Ti)、给电子体和催化剂之比(Si/Ti)和共聚单体加入量等聚合条件对催化剂共聚活性、共聚产物形态和性能的影响;通过差示扫描量热仪(DSC)、红外光谱分析、X射线衍射、扫描电镜(SEM)和核磁共振波谱法等方法对共聚产物结构进行了分析表征。结果表明,选择环己基甲基二甲氧基硅烷(CHMMS)为外给电子体,控制共聚单体加入量,共聚产物中丁烯含量在0.56%～12.0%范围可控;当共聚产物中丁烯含量为3.35%时,产物的拉伸强度36.4 MPa、冲击强度11.8 kJ/m²、断裂伸长率为596%,各项性能均明显优于均聚产物。     

新一代聚丙烯催化剂内给电子体的研究

综述了丙烯聚合物Z-N催化剂内给电子体的研究进展,讨论了内给电子体在丙烯聚合中的作用及机理.介绍了最新的内给电子体,通过对内给电子体在近年来发展的分析,对丙烯聚合物Z-N催化剂的发展进行了展望.     

Z-N催化剂内给电子体作用机理的研究进展

综述了内给电子体对齐格勒-纳塔丙烯聚合催化剂作用机理的研究进展。从内给电子体在催化剂体系中的作用方式及机理、内给电子体的种类与催化剂性能的关系以及内给电子体的结构与催化剂性能的关系三方面．讨论了内给电子体对催化剂活性中心的区域选择性和立体选择性的影响。内给电子体的引入影响了催化剂的活性、氢调敏感性和产物的相对分子质量及其分布。     

几种Ziegler-Natta催化剂催化丙烯聚合的反应动力学

研究了4种Ziegler-Natta催化剂在淤浆聚合条件下,助催化剂和外给电子体对其催化丙烯聚合反应动力学行为的影响。结果表明:4种催化剂都有一个短暂的活性中心形成阶段,聚合动力学曲线均为上升-衰减型;4种催化剂活性均随烷基铝用量的增加而降低;所制聚丙烯的等规指数均随烷基铝用量的增加而降低,随外给电子体用量的增加而升高;助催化剂为三乙基铝[n(Al)∶n(Ti)=100],外给电子体为二环戊基二甲氧基硅烷[n(Si)∶n(Ti)=5]时,4种催化剂都具有较高的活性及较慢的聚合反应速率衰减;用催化剂4制备的聚丙烯的等规指数受助催化剂及外给电子体的影响较小。     

二醚类Ziegler-Natta催化剂催化1-丁烯聚合

采用相同的工艺,制备了含有不同内给电子体[2-甲基-2-丙基-1,3-二甲氧基丙烷、2,2-二异丁基-1,3-二甲氧基丙烷(BIBIMP)、邻苯二甲酸二异丁酯]以及不含内给电子体的MgCl2负载型Ziegler-Natta催化剂,研究了给电子体结构对催化剂活性的影响以及用该催化剂合成的聚1-丁烯(PB)的等规指数、熔点、相对分子质量及其分布。结果表明:未加入外给电子体时,加入BIBIMP的催化剂活性最高,用其所制PB的等规指数最高,分别为539 g/g和84%;加入氢气可进一步提高催化剂活性和PB等规指数;加入外给电子体后,催化剂的活性均降低,二醚类Z-N催化剂活性降低最多,而使用二异丙基二甲氧基硅烷为外给电子体更有助于提高PB的等规指数。     

Ziegler-Natta催化剂催化1-丁烯聚合

采用9,9-双(甲氧基甲基)芴(BMMF)作为内给电子体,制备了聚1-丁烯高效载体型Ziegler-Nana催化剂.研究了催化剂浓度、n(Al)/n(Ti)、聚合温度、外给电子体种类及用量对该催化剂催化1-丁烯聚合的影响,并将该催化剂与无内给电子体及以邻苯二甲酸酯(DNBP)为内给电子体的聚1-丁烯催化剂进行对比.结果...     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。