聚乙烯催化剂溶剂回收吸附解吸技术研究

针对聚乙烯催化剂制备过程中产生的废气采用高浓度回收工艺后的尾气中含有低浓度、多组分有机溶剂的问题,采用不同种类的活性炭对异戊烷、戊烷、四氢呋喃、甲苯4种溶剂进行吸附、解吸性能试验,筛选出性能较好的活性炭后并在搭建的模试装置上进行验证.试验结果表明:椰壳活性炭的吸附性能较好,在150℃、空速6 000 h-1的热氮气吹扫...     

VOC膜回收技术在聚乙烯装置中的应用

VOC膜回收在聚乙烯低压气相法的应用中如何有效的回收乙烯单体。回收后的富乙烯气流返回到压缩机入口,然后进入反应器进一步反应。从而达到减少排放及乙烯回收利用的目的。     

分离二元有机共熔混合物的复合结晶方法

利用结晶分离共熔有机混合物,从原理上看,尽管具有只需一个步骤的优点,但是结晶物的产率却受到共熔混合物限制。为避免采用造成较大能耗和引入杂质的操作来分离共熔混合物,于是提出复合结晶方法     

支化与功能化聚乙烯

综述了近年来制备支化和功能化聚乙烯的研究进展。采用Ziegler-Natta催化剂和茂金属催化剂催化乙烯与α-烯烃共聚合得到支化聚乙烯,但由于金属中心的亲电性和亲氧性强,加入极性单体会使催化剂严重失活。采用后过渡金属催化剂可通过调节反应条件得到不同拓扑结构的支化聚乙烯,且可催化乙烯与极性单体共聚合制备各种新颖的功能化聚乙烯。     

异戊烷发泡剂在聚氨酯硬泡中的应用

戊烷作为发泡剂具有良好的物理和工艺性能及合适的环境数据，适合于我国聚氨酯泡沫市场。本文将详细讨论异戊烷发泡聚酯硬泡的生产和泡沫性能及安全控制。     

戊烷发泡体系在冰箱聚氨酯泡沫中的应用

概述了冰箱用聚氨酯泡沫发泡剂CFC—11的主要替代路线,重点论述了纯环戊烷、环戊烷-异戊烷和正戊烷-异戊烷等3种戊烷发泡体系的泡沫体物性和工艺特点,同时对3种戊烷发泡技术进行了综合比较。     

尤尼维因在华建聚乙烯催化剂厂

美国尤尼维因（Univation）技术公司日前宣布,将在张家港新建聚乙烯催化剂工厂,计划于2011年开工投产。这座新工厂将生产UCATJ高产率催化剂,并留有扩能空间。这种催化剂可应用于生产各类线型低密度聚乙烯和高密度聚乙烯产品。     

乙烯和丙烯在低聚物-正己烷溶液中的溶解度及体积传质系数测定

在高压搅拌釜中,利用气体间歇物理吸收技术,在温度343～393 K、压力0.2～1.45 MPa下,测定了乙烯-正己烷、丙烯-正己烷、乙烯-正己烷-低聚物（低分子量聚乙烯）和丙烯-正己烷-低聚物的气体平衡溶解度与液相体积传质系数k_La,并回归出表观溶解热,使用PC-SAFT状态方程关联了汽液平衡数据,拟合得到乙烯/丙烯-正己烷-低聚物的k_La经验关联式,与实验结果吻合良好。实验系统考察了压力、温度和低聚物浓度对平衡溶解度和k_La的影响,结果表明：压力升高,气体溶解度增大,符合亨利定律,k_La略有降低;温度升高,气体溶解度减小,乙烯在正己烷中的k_La增大,丙烯在正己烷中的k_La则减小;低聚物浓度增加,气体溶解度与k_La均降低。     

新型线性低密度聚乙烯催化剂的研制

制备出新型线性低密度聚乙烯催化剂,考察了催化剂及其聚合物的性能,包括催化活性,聚合反应动力学,聚乙烯堆密度,聚合物粒度分布,加氢聚合物融熔指数及与己烯共聚物的性能等。     

再生聚乙烯制备3PE防腐聚乙烯专用料

以再生聚乙烯为主要原材料制备了管道防腐聚乙烯。通过优化基体树脂及其配比,添加少量乙烯-辛烯共聚物后,制备出力学性能合乎要求的管道防腐聚乙烯专用料。通过力学性能测试,发现聚乙烯及聚乙烯专用料的拉伸断裂均发生在应力应变上升阶段。     

Experimental and theoretical investigation of solubility and diffusion of ethylene in semicrystalline PE at elevated pressures and temperatures

The solubility and diffusivity of ethylene in semicrystalline polyethylene were experimentally measured using a magnetic suspension microbalance. The sorption measurements were carried out at temperatures up to 80°C and pressures up to 66 atm. The experimentally measured solubilities were found to decrease with increasing temperature and increased with ethylene pressure in good agreement with the predictions of the Sanchez–Lacombe lattice‐fluid model. The diffusivity of ethylene in semicrystalline polyethylene films was estimated from the reduced sorption curves using the half‐time method. The experimentally determined diffusivities were compared with theoretical values predicted by a new molecular hybrid model, which combines the characteristic features of the Pace–Datyner diffusion model with those of the Kulkarni–Stern free‐volume model. The ethylene diffusion coefficient was found to increase with temperature and/or the ethylene‐sorbed concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 953–966, 2003     

Solubility of polyethylene in n-pentane at high pressures

The high pressure solubility of polyethylene standards (M_w = 2100, 16400, 108000 and 420000 and M_w/M_n = 1.14, 1.16, 1.32 and 2.66, respectively) in n-pentane has been studied. Concentrations of up to 15 wt% polymer have been investigated. For each polymer sample and concentration, pressures that are required to achieve single-phase solutions have been determined over a range of temperatures. The solutions are found to all show lower critical solution temperatures. Demixing pressures are observed to depend strongly on the molecular weight of the polymer.     

Improvement in processability of metallocene polyethylene by ultrasound and binary processing aid

The effect of ultrasonic vibration and binary processing aid in improving the processability of metallocene linear low‐density polyethylene (mLLDPE) was investigated. During extrusion, ultrasonic vibration clearly reduced the die pressure and apparent viscosity of mLLDPE but had only a slight effect on its melt fracture. The effect of diatomite/PEG binary processing aid (BPA) was excellent in reducing the viscosity and eliminating the sharkskin fracture of mLLDPE. The effect of ultrasonic vibration and binary processing aid in improving the processability of mLLDPE was synergetic. With a combination of ultrasonic vibration and a small amount of processing aid, the flowability of mLLDPE was further improved, and the critical shear rate for the onset of sharkskin fracture was increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1927–1935, 2007     

Measurement of solubility and diffusion coefficients of ethylene in solid and molten low-density polyethylene with different melt indices

The diffusion behavior of ethylene in polyethylene is of great importance for the polymerization and degassing of polyethylene (PE) industry. Based on the gravimetric sorption and desorption measurement approach, an intelligent gravimetric analyzer is applied to obtain the solubility and diffusion coefficients of ethylene in solid low-density PE (LDPE) with different melt indices at 30°C to 70°C, 0 to 4 atm and in molten LDPE at 160°C to 230°C, 0 to 4 atm, respectively. Results indicate that both the solubility and diffusion coefficients of ethylene in solid LDPE are smaller than those in molten LDPE, while the dissolution enthalpy and diffusion activation energy of ethylene in solid LDPE are higher. In addition, one- and two-dimensional diffusion models are built and the effects of particle size, polymer properties, and operation conditions are systematically investigated on the diffusion behaviors of ethylene in solid and molten LDPE.     

EVA改性硅烷交联聚乙烯绝缘料

使用乙烯-乙酸乙烯共聚物(EVA)对硅烷交联聚乙烯电力电缆绝缘料进行了改性。结果表明,EVA对绝缘料的熔体流动速率(MFR)、介电强度、热延伸性能影响较小,使其介电常数、热稳定性提高,体积电阻率、结晶度、交联度、拉伸强度下降。EVA的添加量在10phr之内,绝缘料的MFR、介电强度、热延伸性能、断裂伸长率、体积电阻率、交联度满足技术指标要求;EVA的添加量超过6phr时,绝缘料的拉伸强度和介电常数不能满足要求。     

木质素填充LDPE、EVA对复合物性能的影响

以木质素为填充剂分别与低密度聚乙烯(LDPE)、乙烯-乙酸乙烯酯共聚物(EVA)共混,经双螺杆造粒机共混挤出造粒,再经吹塑成膜。研究了木质素/LDPE、木质素/EVA共混物薄膜的表面形貌、力学性能、热性能和红外光谱。热分析表明木质素与EVA共混物的热稳定性比木质素与LDPE的共混物热稳定性好;红外光谱分析表明木质素与EVA分子间产生了强烈的相互作用,扫描电镜分析表明木质素与EVA共混的相容性较好,力学性能分析表明低于30%的木质素与LDPE、EVA共混力学性能较好。     

Study on the morphology and properties of metallocene polyethylene and ethylene/vinyl acetate blends

Two commercial polymer materials, metallocene linear low density polyethylene (m‐LLDPE) and ethylene/vinyl acetate copolymer (EVA) have been used to form binary blends of various compositions. The mechanical properties, morphology, rheological behavior, dynamic mechanical properties, and crystallization of m‐LLDPE/EVA blends were investigated. It was found that with the addition of EVA, the fluidity and processability of m‐LLDPE were significantly improved, and the introduction of polar groups in this system showed no significant changes in mechanical properties at lower EVA content. As verified by morphology observation and differential scanning calorimetry analysis, miscible blends were formed within certain weight ratios. Dynamic mechanical property studies showed that flexibility of the blends was enhanced in comparion with pure m‐LLDPE, where the peak value of loss modulus shifted to lower temperature and its intensity was enhanced as EVA content increased, indicating the existence of more amorphous regions in the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 905–910, 2004     

Thermal and crystallization behaviors of polyethylene blends synthesized by binary late transition metal catalysts combinations

A series of reactor blends of linear and branched polyethylenes have been prepared, in the presence of modified methylaluminoxane, using a combination of 2,6‐bis[1‐(2,6‐dimethyphenylimino) pyridyl]‐cobalt(II) dichloride ( 1 ), known as an active catalyst for producing linear polyethylene, and [1,4‐bis(2,6‐diidopropylphenyl)] acenaphthene diimine nickel(II) dibromide ( 2 ), which is active for the production of branched polyethylene. The polymerizations were performed at various levels of catalyst feed ratio at 10 bar. The linear correlation between catalyst activity and concentration of catalyst 2 suggested that the catalysts performed independently from each other. The weight‐average molecular weights , crystalline structures, and phase structures of the blends were investigated, using a combination of gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, and small angle X‐ray scattering techniques. It was found that the polymerization activities and MWs and crystallization rate of the polymers took decreasing tendency with the increase of the catalyst 2 ratios, while melting temperatures (T_m), crystalline temperatures (T_c), and crystalline degrees took decreasing tendency. Long period was distinctly influenced by the amorphous component concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4188–4198, 2007     

Modeling the solubility of ternary mixtures of ethylene,iso‐pentane,n‐hexane in semicrystalline polyethylene

The coabsorptions of ethylene and iso‐pentane, and ethylene and n‐hexane were measured by the use of a pressure decay method. The solubility data of ethylene‐iso‐pentane and ethylene‐n‐hexane in semicrystalline polyethylene (PE) of crystallinity of 48.6% were obtained at temperatures 70, 80, and 90 °C, and the total pressure 2 MPa, iso‐pentane partial pressure 80–190 KPa, n‐hexane partial pressure 20–90 KPa. The presence of iso‐pentane or n‐hexane in the corresponding ternary system leads to increase the solubility of ethylene, while the solubility of iso‐pentane or n‐hexane remains unchanged with an increase of the ethylene partial pressure, even slightly decreases. Assumed that the presence of iso‐pentane or n‐hexane decreases the crystallinity of the polymer sample, a coabsorption model was built to model the solubility of each gas in the ternary systems. The relative root mean square errors of the coabsorption model for ethylene‐iso‐pentane‐PE system and ethylene‐n‐hexane‐PE system are 5.13% and 4.64%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3654–3662, 2007