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Results from an experimental study of propylene polymerization in heptane diluent over a high activity Mg-supported Ti catalyst are presented. The study provides an examination of the effect of operating conditions on polymerization rate, product melt index, and powder bulk density. Among the findings are that product bulk density decreases with increasing operating temperature and decreasing operating pressure while prepolymerization increases the bulk density. The results support the hypothesis that polymer morphology is closely linked to mass transfer limitations within the growing polymer particle during the early stages of polymerization. 相似文献
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介绍了20kt/aPA6聚合装置前聚合器的结构及工艺特点;分析了生产中前聚合工艺存在的问题,提出了解决措施;验证了前聚合器结构的设计参数。指出生产中由于前聚合器底部出料温度波动大,波动值达±8.08℃,影响了PA6切片的可纺性。通过降低前聚合反应的压力及加热联苯炉的温度,调整前聚合器顶部冷凝器的排汽温度,前聚合器底部出料温度的波动值可控制在±2.5℃,有效提高了PA6切片的质量。 相似文献
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A mathematical model for the continuous prepolymerization of BHET to PET, carried out in a series of stirred tank reactors, has been developed. The influence of process and operational variables on productivity, as well as the side-product formation (which controls the product quality), have been studied in a range as close to industrial practice as possible. The overall conclusions concerning the productivity profile, as well as some side products, appear to be substantiated from the available data in the open literature. The results of the mathematical model have been used to highlight the key process and operational variables that are likely to give the best productivity and product quality in industrial practice. 相似文献
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The initial state polymerization of propylene with Ziegler–Natta catalysts has been investigated and discussed at very low polymerization yields under adiabatic industrial prepolymerization conditions in diluted slurry regarding the effects of significant process parameters like monomer pressure, aluminum alkyl, and donor kind and concentration including the morphology of the catalyst/polymer particles formed. A sharp temperature increase in the first minutes of the initial state polymerization is followed by a temperature maximum and a slow decrease. With cocatalyst triethyl aluminum (TEAL), high prepolymerization yields were already achieved at a molar ratio TEAL/Ti of 3.0, remaining about constant until ratios of at least 300. The external donor dicyclopentyl dimethoxy silane leads to higher polymerization yields than the donor cyclohexyl dimethoxymethyl silane in the initial state polymerization too; however, both show a remarkable decreasing effect on polymerization yield above a specific molar ratio donor/Ti obviously correlated with the bulkiness of the alkyl groups. The particle size of the catalyst and the catalyst/prepolymer particles is increasing with polymerization yield until about 22 g PP/g Cat with particles almost perfectly spherical. The particle size distribution is rather broad at lower prepolymerization stages but unifying with lower polymerization rates at higher polymerization times. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
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以钛酸四乙酯(TET)为催化剂,聚四氢呋喃醚二醇(PTMG)和1,6-六亚甲基二氨基甲酸甲酯(HDC)为原料,1,4-丁二醇为扩链剂,酯交换缩聚合成了聚醚型聚氨酯(PEPU)弹性体。以二丁基氧化锡(DBTO)催化合成的PEPU为参考,通过红外光谱(FTIR)、凝胶色谱(GPC)、热重分析(TGA)、力学性能与光学性能测试表征TET的催化效果。通过一系列单因素实验探讨了缩聚温度、缩聚时间、预聚温度、预聚时间对PEPU特性黏度的影响规律。结果表明,TET比DBTO催化制得的PEPU热性能更好,力学性能更优。较佳的制备工艺为:预聚阶段温度为110℃,压力为0.070MPa,时间为20min;160℃下高真空缩聚110min. 相似文献
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以TiCl4/Al(i-Bu)3为引发体系,用本体预聚合法引发1-十二烯聚合,制备高减阻性能的油溶性减阻剂。研究了二苯基二甲氧基硅烷(DDS)、预聚与后聚单体体积比、预聚温度和预聚时间对聚合物减阻性能的影响。结果表明,在优化的合成工艺条件下,能够合成减阻率为50.67%,增输率为48.1%的聚合物(添加量为10 mg/L)。通过IR、GPC和1H-NMR分析表明:转化率接近100%,重均相对分子质量Mw为3.58×106、相对分子质量分布宽度指数Mw/Mn为4.44。采用预聚工艺较本体直接聚合可以节省主催化剂用量达40%以上。 相似文献
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Suphan Kovenklioglu 《Polymer Engineering and Science》1980,20(12):816-822
Thermal bulk polymerization of styrene in the plate and frame batch reactor i.s simulated with a mathematical model which accounts for chain transfer to monomer and gel effect. The design parameters are: the frame thickness, the temperature policy, and the level of prepolymerization in the feed. The recommended frame thickness with 27% prepolymerization is 5 in. The resulting polydispersities and number average chain lengths range from 2.2–2.3 and 2000–2100 respectively. The implementation of temperature policy, particularly the timing of the application of the coolant, is critical to obtain satisfactory polymer quality. When pure styrene feed is used the reactor displays thermal ignition unless the frame thickness is less then 2 in. For a 5 in. frame prepolymerization should be at least 25 percent to permit adequate temperature control. 相似文献
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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。 相似文献
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对乙二醇和对苯二甲酸预缩聚反应过程进行了分析,把该过程分解为反应动力学和反应器内各种传质,对预缩聚反应过程的反应动力学进行了实验研究。得到了不同温度下的反应速率及其参数 相似文献
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A mathematical model has been developed for the direct, continuous esterification process. Influence of process and operational variables, including temperature distribution, residence time distribution, bis(hydroxyethyl)terephthalate recycle, pressure, and ethylene glycol (EG) to terephthalic acid ratio on the reactor performance have been investigated in a range as close to industrial practice as possible. The variables influencing the amount of EG reflux (which governs the energy economy) and side products (which govern the product quality) have been discussed. This investigation provides an analysis of a continuous, direct esterification process, and the results indicate strategies for optimizing productivity and product quality. 相似文献
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采用化学分析方法研究了羟基氯醋树脂微粉存在下的聚醚N-220、蓖麻油等聚醚多元醇混合物与甲苯二异氰酸酯(TDI-80)的预聚合反应动力学,获得了聚氨酯预聚体合成反应动力学参数及反应表观速率常数表达式k=0.049exp(-23.95/RT),并通过反应初期的实验数据对反应级数进行了验证。结果表明,在该体系下的预聚体合成反应中,氨酯化反应的表观速率常数随反应温度的升高而增大,合成反应以氨酯化反应为主,总反应级数为1.74~1.88,为近二级反应。该合成反应机理具有一定的复杂性。实验结果对相关聚氨酯弹性体预聚物合成及改性反应具有一定的理论价值和指导意义。 相似文献
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Won Jung Yoon 《Korean Journal of Chemical Engineering》1996,13(1):88-96
Free radical solution polymerization of styrene in two stage polymerization process has been studied using a binary mixture
of symmetrical bifunctional initiators. The continuous reactor system was composed of two reactor units; a prepolymerization
reactor (e.g. stirred tank reactors) and a filled tubular reactor packed with static mixers. When the stirred tank reactor
was used as a prepolymerizer, a feed stream to the filled tubular reactor was more viscous than the monomer/solvent mixture.
It was of interest to investigate how the performance of the filled tubular reactor has been investigated by the feed of viscous
prepolymer solution. A dynamic model of the continuous two stage polymerization process was presented by experimental data
and model simulation. A reasonably good agreement between the model and the experimental data was obtained without using any
adjustable parameters. The experimental results of the two stage polymerization were compared with the results without prepolymerization
reactor. It was found that the addition of a prepolymerization reactor has almost no effect on the performance of the filled
tubular reactor. 相似文献
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The bulk polymerization of propylene in liquid monomers with Ziegler‐Natta catalyst at 95°C is studied, using alkyl aluminum as the cocatalyst and dicyclopentyldimethoxysilane as the external donor. The highest catalyst activity is shown at the cocatalyst/Ti molar ratio of 300, which keeps relatively constant with the molar ratio increasing from 300 to 800. Besides, the catalyst activity is up to 65 kgPP/(gCat*h) in the range of cocatalyst/donor molar ratio from 12 to 16. The polymerization reaction rate curves with and without catalyst precontacting are similar, while the activity with catalyst precontacting are higher than that without precontacting. Furthermore, the kinetics of polymerization with and without prepolymerization are investigated in the range of the polymerization temperature from 70 to 95°C. It shows that at the high temperature, the polymerization rate increases with prepolymerization. Finally, the influence of prepolymerization at 95°C on the polymerization kinetics and particle properties is also described. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41816. 相似文献
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This work experimentally and theoretically investigates the use of bifunctional initiators in the synthesis of high-impact polystyrene (HIPS). The experimental design involved a series of nonisothermal bulk polymerizations of styrene (St) in the presence of polybutadiene (PB). The performance of three commercial initiators [2,5-dimethyl −2,5 bis(2-ethylhexanoyl peroxy] hexane or L–256; 2,5 bis(benzoyl peroxy) hexane or L–118; and ethyl 3,3 di(t-butyl peroxide) butirate or L–233] were compared to the performance of a standard monofunctional initiator (terbutylperoctoate or TPBO), and to the blank case (i.e., without initiator). From samples taken along the prepolymerization period, the phase inversion point and the 30% conversion point were estimated. For the final product, the free polystyrene (PS) molecular weights and the St grafting efficiency were measured. A mathematical model was developed that predicts the evolution of the MWDs for the free PS the residual PB, and the graft copolymer, together with the chemical composition distribution for the total graft copolymer. Compared to the monofunctional case, the L–256 initiator induces phase inversion and rubber grafting at low conversions. Also, it shortens the prepolymerization times by around 38%, without affecting the molecular characteristics of the final product. L–118 also shortens prepolymerization time with respect to TBPO; but is not as effective as L–256 or TBPO in promoting rubber grafting. At the polymerization end, the final molecular characteristics are practically independent of the initiator type because most of the polymerization in induced by monomer initiation. Due to its slow decomposition rate, the L–233 initiator is less effective that TBPO for reducing prepolymerization times and for promoting phase inversion. © 1996 John Wiley & Sons, Inc. 相似文献
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通过对预缩聚反应器流动模型分析,结合缩聚反应化学平衡,反应动力学和反应器内传质的研究,建立了适用于工业装置的预缩聚反应过程的数学模型 相似文献