加氢条件下球形MgCl2载体催化剂催化乙烯聚合

为开发可控制形态的催化剂并表征其在乙烯聚合过程中对氢气的响应,测定了不同氢气加入量条件下球形MgCl_2载体催化剂在乙烯聚合过程中的活性及聚合物的相对分子质量等。研究发现,随着氢气加入量的增加。氢气对第二活性中心的化学毒化加剧,催化剂活性明显降低。通过对聚合物相对分子质量和氢气分压的关联,认为氢气是通过吸附解离形成原子氢,利用氢气可对聚合物的熔体流动速率在0.2～10.0g/10min进行调节。     

基于相对分子质量分布指标的HDPE生产过程模拟

提出一种以相对分子质量分布为指标,关联熔体流动速率(MFR)的高密度聚乙烯(HDPE)工业生产过程流程模拟方法。基于Innovene S HDPE装置工业生产中的聚合过程,采用流程模拟软件Aspen Plus Polymers建立基于严格过程机理的HDPE过程框架模型,结合工业操作参数及实验数据,计算聚合物相对分子质量、相对分子质量分布指数,并关联MFR,利用TableCurve软件拟合得到HDPE的MFR模型。通过相对分子质量和MFR随氢气用量变化的灵敏度分析,在乙烯用量一定的条件下,氢气流量为0.20~0.45 kg/h,生产的相对分子质量分布呈双峰的管材专用HDPE PN049-030-122为优等品。     

BOPP薄膜专用树脂的工业试生产

采用DQ-3催化剂,在液相本体双环管反应器中试生产了双向拉伸聚丙烯薄膜专用树脂T28C。生产中发现,催化剂氢调敏感性差、给电子体难计量、粒料和粉料熔体流动速率(MFR)偏差较大等问题。采用关闭第1环管反应器的氢气注入阀、只在第2环管反应器中加入氢气来合理分配氢气浓度;稀释给电子体浓度;在测试粉料MFR时适当加入抗氧剂,密切监控反应工况等方法解决了问题,生产出合格产品,且产品各项性能指标与国内同类产品相当。     

21．6kg负荷熔体流动速率的测定及其影响因素

采用德国Zwick/ROell熔体流动速率仪,进行熔体流动速率(MFR)的测定,考察了影响结果精密度的一些因素,如温度、切样间隔、切样位置、料筒内的加料量.指出规范操作可以获得高精密度的测试结果.     

加料方式对钒系催化剂MAV-01聚合性能的影响

制备了钒系聚乙烯催化剂MAV-01,以三异丁基铝(TIBA)为助催化剂,研究了淤浆聚合体系中催化剂加料方式对其聚合性能的影响。优选了较佳的加料方式为:先将助催化剂加入氮气保护的反应系统中,加入定量氢气,然后加入乙烯到接近反应压力0.9MPa,将钒系催化剂加入聚合体系,之后补充乙烯至反应压力1.0MPa。在此条件下,钒系催化剂MAV-01的聚合活性较高,制备的聚合物具有较高的熔体流动速率和较宽的相对分子质量分布。     

聚丙烯环管工艺生产高MFR产品

采用聚丙烯(PP)环管工艺,通过提高加氢量来控制产品的熔体流动速率(MFR),提高给电子体用量来保证产品的等规指数,用氢调法生产出高MFR注塑料(PPH-MM45-S)。总结了MFR与氢气加入量、催化剂活性、产品物理性能的关系,及生产高MFR产品时压缩机和造粒机工艺参数调整操作。通过和同类产品进行比较以及下游生产商的使用效果,都表明该产品具有透明度高、光泽度好、韧性优异、加工流动性好等优点。     

乙烯气相聚合工艺参数优化及反应过程的数学模型建立北大核心

利用典型的限制几何构型催化剂催化乙烯与1-丁烯或1-己烯的共聚合,研究了聚合温度、共聚单体含量以及氢气用量对催化剂活性、聚乙烯熔体流动速率和密度的影响。结果表明:随着聚合温度升高,催化剂活性先升高后降低;聚合温度的提高、共聚单体含量及氢气用量的增加均会导致聚乙烯的熔体流动速率升高;随着共聚单体含量的增加,所制聚乙烯的密度逐渐降低。另外,建立了乙烯聚合过程的数学模型,并利用数学模型指导了乙烯聚合过程的研究和质量控制。     

乙烯气相聚合工艺参数优化及反应过程的数学模型建立

利用典型的限制几何构型催化剂催化乙烯与1-丁烯或1-己烯的共聚合,研究了聚合温度、共聚单体含量以及氢气用量对催化剂活性、聚乙烯熔体流动速率和密度的影响。结果表明:随着聚合温度升高,催化剂活性先升高后降低;聚合温度的提高、共聚单体含量及氢气用量的增加均会导致聚乙烯的熔体流动速率升高;随着共聚单体含量的增加,所制聚乙烯的密度逐渐降低。另外,建立了乙烯聚合过程的数学模型,并利用数学模型指导了乙烯聚合过程的研究和质量控制。     

三种铬系催化剂的聚合性能及其动力学行为

考察了三种铬系催化剂的聚合行为，研究了反应温度、反应压力对催化剂聚合性能的影响，并对其聚合动力学进行了研究；在优化的反应温度和反应压力下，研究了三种催化剂随反应时间的变化规律。结果表明：随着反应温度升高，聚乙烯黏均分子量降低，熔体流动速率增大；随着反应压力增大，聚乙烯黏均分子量增大，熔体流动速率降低；催化剂在10～25 min时达到最大聚合反应速率，随着反应时间的延长，聚合反应速率缓慢衰减。     

气相法聚乙烯牌号过渡优化策略

介绍了气相法聚乙烯工艺以熔体流动指数和密度为状态变量，以氢气和共聚单体的进料速率、反应温度、系统排放量、催化剂加料速率及床层料位为控制变量的产品过渡优化模型，讨论了利用该模型在最短的切换时间内生产最少数量不合格品的策略，以实现多牌号生产中经济效益的最大化。     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。     

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.     

基于ATRP法制备的触角状亲水性羟胺树脂的吸硼性能的研究

以大分子引发剂氯乙酰化聚苯乙烯微球(PS-acyl-Cl)经原子转移自由基聚合(ATRP)法引发丙烯酰胺(AM)和甲基丙烯酸缩水甘油酯(GMA)单体的共聚接枝,制得一种触角状亲水性环氧载体(PS-acyl-g-P(AM-co-GMA)),再经二乙醇胺(DEA)的环氧基开环胺化反应,得到一种含多个-NCH2CH2OH螯合配基的多齿-五元螯合环的触角状亲水性羟胺树脂(PS-acyl-g-P(AM-co-GMA)-DEA)。将此树脂用于硼吸附研究,结果表明,PS-acyl-g-P(AM-co-GMA)-DEA树脂对硼的吸附满足Langmuir方程,为单分子层吸附;饱和吸附量约为37.7 mg·g-1,且树脂5 min即可达到吸附平衡,与其它已报道的吸硼树脂相比,该树脂具有更高的吸附量和吸硼速率。吸附动力学研究表明,树脂吸附硼的过程主要由颗粒扩散过程控制。重复使用5次后该树脂的吸附量基本不变,解吸率均在90%以上,重复使用性能良好。