共查询到17条相似文献,搜索用时 140 毫秒
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以碱土金属氨钙为催化剂,经环氧乙烷的开环聚合得到聚氧化乙烯(PEO),考察了陈化温度和催化剂用量对聚合反应的影响。结果表明,陈化温度对聚合收率的影响较小,但影响聚合物分子量的波动程度;陈化温度为60℃的催化剂表现最为稳定,不仅聚合收率保持在99%以上,不同批次间聚合物的分子量波动程度(以变异系数表示)也降至最低,达7.3%。通过改变催化剂用量,可以在保持高聚合收率的情况下稳定地合成不同分子量级别(39万~86万)的PEO。SEM、XRD和DSC表征结果进一步表明,所得PEO粉末是一种具有层状结构的部分结晶性聚合物,且结晶度随分子量的增加而增大。 相似文献
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聚氧化乙烯的性质及其合成 总被引:3,自引:0,他引:3
介绍了聚氧化乙烯的主要性质,采用有机金属化合物为主体的多组分催化剂进行环氧乙烷的聚合试验,探讨了聚合收率,聚合物分子量与聚合时间的关系,催化剂浓度,聚合温度,催化剂贮存时间对环氧乙烷聚合的影响。在较佳的工艺条件下制得分子量主同于500万的白色粒状聚氧化乙烯,聚合收率大于95%(重量)。 相似文献
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本文采用三乙基铝、乙酰丙酮、水系催化剂使环氧乙烷聚合。探讨了水与三乙基铝的摩尔比、乙酰丙酮与三乙基铝的摩尔比、聚合温度、催化剂浓度、稀释剂用量、环氧乙烷质量同聚氧化乙烯平均分子量及聚合收率之间的关系。在较好的条件下,制得分子量达300万的白色块状聚氧化乙烯。考察了一些样品的降解情况,大多数样品存放半年后,平均分子量仍高于200万。 相似文献
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以丁二酸(SA),1,4-丁二醇(BDO)为原料,通过熔融聚合法合成聚丁二酸丁二醇酯(PBS)。通过对催化剂筛选及用量、缩聚反应温度、总反应时间和酸醇比等因素对产品粘均分子量影响的探讨,优化出了熔融法合成PBS的最佳工艺条件:选择SnCl2做催化剂,用量在2%(以催化剂加入SA的质量比表示),缩聚反应温度在230℃,总反应时间5h,在酸醇配比为1∶1.1时,反应得到的PBS产品的粘均分子量最大,粘均分子量为5.14×104g/mol,产品颜色为白色。用IR、TG、1H-NMR等表征证明产品合成成功。 相似文献
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以烯丙醇和固体KOH为原料制得烯丙醇钾,再在常压下与环氧乙烷反应制得高纯度的烯丙基聚醚,讨论了反应时间、反应温度、原料配比、投料方式等因素对反应的影响。当KOH与烯丙基的摩尔比为1:1.25时,加热回流下可以得到高收率的烯丙醇钾,开环反应依据所需的聚醚分子量调节环氧乙烷的用量,产品收率达到98%以上。 相似文献
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制备了四苯基卟啉、四-4-甲氧基苯基卟啉、四-4-氟苯基卟啉及3种卟啉相对应的钴、锰、铁金属卟啉,并利用Cary紫外可见分光光度计(UV-vis)和傅里叶变换红外光谱仪(FTIR)对金属卟啉进行了表征;以制备的不同金属卟啉为催化剂,丙烯为原料,氧气为氧化剂,仿生催化丙烯氧化合成环氧丙烷。考察了金属卟啉催化剂类型、金属卟啉催化剂浓度、反应压力、反应温度、反应时间对反应的影响,结果发现上述因素对反应收率、转化率、选择性均有显著影响,且都有一个最佳值,获得的最优化反应条件为:选取四-4-氟苯基铁卟啉为催化剂,催化剂浓度为1.35×10-5mol/L,反应压力1.75MPa,反应温度100℃,反应时间为2h。在最优化的反应条件下,环氧丙烷的收率达到了40.38%,丙烯转化率达到了47.09%,环氧丙烷选择性达到了85.75%。 相似文献
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A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition 下载免费PDF全文
New data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40658. 相似文献
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以甲醇为溶剂,以环氧树脂为引发剂,乙酸乙烯酯与甲醇的质量比为25∶3.96,反应温度为(65±2)℃,引发剂用量为0.080 2 g,反应4.5 h,以溶液聚合法制备粘均相对分子质量为1.95×105的聚醋酸乙烯酯,经醇解得到无毒的聚乙烯醇,产品经UV,FTIR,1H NMR谱进行确认和结构分析。讨论了反应温度、反应时间、引发剂用量、原料质量比对醋酸乙烯酯相对分子质量的影响。 相似文献
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Reactor blends of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and low‐molecular‐weight polyethylene (LMWPE) were synthesized by two‐step polymerization using a hybrid catalyst. To prepare the hybrid catalyst, styrene acrylic copolymer (PSA) was first coated onto SiO2/MgCl2‐supported TiCl3; then, (n‐BuCp)2ZrCl2 was immobilized onto the exterior PSA. UHMWPE was produced in the first polymerization stage with the presence of 1‐hexene and modified methylaluminoxane (MMAO), and the LMWPE was prepared with the presence of hydrogen and triethylaluminium in the second polymerization stage. The activity of the hybrid catalyst was considerable (6.5 × 106 g PE (mol Zr)?1 h?1), and was maintained for longer than 8 h during the two‐step polymerization. The barrier property of PSA to the co‐catalyst was verified using ethylene polymerization experiments. The appearance of a lag phase in the kinetic curve during the first‐stage polymerization implied that the exterior catalyst ((n‐BuCp)2ZrCl2) could be activated prior to the interior catalyst (M‐1). Furthermore, the melting temperature, crystallinity, degree of branching, molecular weight and molecular‐weight distribution of polyethylene obtained at various polymerization times showed that the M‐1 catalyst began to be activated by MMAO after 40 min of the reaction. The activation of M‐1 catalyst led to a decrease in the molecular weight of UHMWPE. Finally, the thermal behaviors of polyethylene blends were investigated using differential scanning calorimetry. Copyright © 2011 Society of Chemical Industry 相似文献
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He-xin Zhang Young-joo Lee Joon-ryeo Park Dong-ho Lee Keun-Byoung Yoon 《Polymer Bulletin》2011,67(8):1519-1527
Polymerization of propylene was carried out by using MgCl2-supported TiCl4 catalyst in conjunction with triethylaluminium (TEA) as cocatalyst. The effect of polymerization temperature on polymerization
of propylene was investigated. The catalyst activity was influenced by the polymerization temperature significantly and the
maximum activity of the catalyst was obtained at 40 °C. With increasing the polymerization temperature, the molecular weight
of polypropylene (PP) drastically decreased, while the polydispersity index (PDI) increased. The effect of the two-stepwise
polymerization procedure on the molecular weight and molecular weight distribution of PP was studied and the broad PDI of
PP was obtained. It was also found that the PDI of PP could be controlled for propylene polymerization through regulation
of polymerization temperature. Among the whole experimental cases, the M
w of PP was controlled from 14.5 × 104 to 75.2 × 104 g/mol and the PDI could be controlled from 4.7 to 10.2. 相似文献
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四种乳酸聚合方法的比较 总被引:1,自引:1,他引:0
以乳酸为原料,辛酸亚锡为催化剂,采用乳酸直接聚合(一步法)、丙交酯开环聚合(两步法)、熔融-固相聚合、溶剂回流脱水等不同的实验方法分别合成出了不同相对分子质量的聚乳酸。实验结果表明:实验方法不同,所得聚合物的相对分子质量不同,其中丙交酯开环聚合(两步法)所得聚合物的相对分子质量最大,可达80万左右,溶剂回流脱水法的可达24000左右,熔融-固相聚合的为10800,乳酸的直接聚合(一步法)的只有5000。 相似文献
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Francisco Lpez María P. Calcagno Jesús M. Contreras Zulay Torrellas Katania Felisola Franco M. Rabagliati Issa A. Katime 《Polymer International》1991,24(2):105-112
The diphenylzinc-butanone system was used as polymerization catalyst for some oxiranes in benzene solution at 60°C. This system is greatly influenced by the molar ratio of butanone to diphenylzinc, and the maximum catalytic activity for propylene oxide and ethylene oxide was found for a ratio of unity. GPC results strongly suggest the presence of more than one active species for the system. 13C NMR analysis indicates that the resulting poly(propylene oxide) has a head-to-tail arrangement. For the polymerization of propylene oxide with butanone/diphenylzinc = 1, after an initial induction period, the reaction was first-order with respect to monomer with k = 2·51 × 10?5 s?1. Ethylene oxide polymerizations using butanone/diphenylzinc = 1 and 5 were also first-order with respect to monomer after an initial induction period with k = 7·80 × 10?6 s?1 and k = 5·71 × 10?6 s?1, respectively. The diphenylzinc-butanone system was not an effective catalyst for styrene oxide polymerization. 相似文献