HDPE装置黏壁原因分析及处理措施

高密度聚乙烯环管淤浆工艺生产过程中会出现黏壁现象,反应器的黏壁是普遍存在的问题,这也是多种因素相互作用造成的。低聚物的生成、聚合温度高、静电、共聚单体等都有可能使反应器产生黏壁现象。通过合理控制共聚单体浓度,控制反应温度,保持反应器内壁光洁度,控制反应器内固含量等方法,可有效减少反应器黏壁概率,延长装置的运行周期。     

乙烯聚合新工艺及产品特性

采用间歇聚合试验装置模拟了乙烯聚合新工艺(淤浆均聚合-离心分离-气相共聚合)的流程.考察了新工艺的可行性,研究了新工艺的技术特点及产品特性,并将采用新上艺制备的试样与工业生产PE80及PE100级双峰分布聚乙烯进行比较.结果表明:第一段淤浆聚合后脱除溶剂不影响第二段的气相共聚合活性,该工艺是可行的;通过模拟不同的工艺表...     

高密度聚乙烯淤浆环管工艺反应器黏壁原因及减缓措施

对高密度聚乙烯淤浆环管工艺反应器黏壁的原因进行了分析,并提出了相应的处理措施。反应器黏壁原因主要包括低聚物的产生,生成低密度及支化度大的产品,聚合温度过高,静电,设备性能差,转产时置换不彻底,反应器内的固相含量不合理等。通过减小催化剂浓度,合理控制共聚单体浓度,严格控制反应温度,采用Cr系催化剂生产,保证反应器的光洁度,抑制静电水平,转产时彻底置换出残留物,合理控制反应器内的固相含量等方式,可减缓反应器黏壁,延长装置运行周期。     

淤浆法HDPE装置低聚物不能结片原因探析

分析了淤浆法HDPE装置低聚物不能结片的原因,并提出了相应的工艺处理措施。     

PE100管材专用聚乙烯树脂的分子结构

通过基础性能测试、相对分子质量分布测试、力学性能测试、连续自成核退火分级测试和旋转流变测试,对3种PE100级管材专用树脂的分子结构进行了研究。结果表明:利用双釜串联淤浆工艺生产的PE100级树脂其低相对分子质量组分较多,相对分子质量较小,共聚单体含量高,短支链多,性能相对较差;利用多釜串联淤浆工艺生产的PE100级树脂与利用环管淤浆工艺生产的PE100级树脂性能较为优异,相对分子质量及其分布、支化程度以及片晶的厚度都较为合理。     

NT-1型高效乙烯聚合催化剂的工业试用

石油化工科学研究院针对淤浆法聚乙烯生产工艺开发了高效乙烯聚合催化剂NT-1。该催化剂在燕山石化公司化工一厂低压聚乙烯生产装置上的工业试用结果表明，该催化剂适合淤浆法聚乙烯生产工艺，其活性与原使用的BCH催化剂相当，氢调敏感性和共聚性优于BCH催化剂，并能够显著降低低聚物的生成。     

淤浆法聚乙烯低聚物的研究

对淤泺法聚乙烯（PE）的生产过程进行了分析，探讨了低聚物产生的原因和进入产品后对PE性能的影响，论述了降低产品低聚物含量和消除低聚物对产品性能影响的方法。     

HDPE生产工艺进展

分析了高密度聚乙烯(HDPE)生产工艺现状和技术特点,淤浆聚合工艺是我国HDPE最主要的生产技术。利用釜式淤浆法工艺特点可开发双峰或多峰产品以实现其机械性能和加工性能的平衡;利用环管淤浆法工艺特点开发高性能管材料和宽相对分子质量分布产品;利用气相法工艺单线生产能力大的特点稳定生产通用产品;利用溶液法工艺产品均一性好、切换容易的特点开发高附加值特色产品。建议结合装置特点开发高性能HDPE。     

淤浆催化剂喷雾过程影响THF含量因素的研究

适用于Unipol聚乙烯工艺的淤浆催化剂,因其活性比传统的固体干粉催化剂提高了4~6倍,树脂产品残留灰分少,产品性能得到提升,且用户可以根据不同牌号的树脂在线调节淤浆催化剂还原比例,应用非常方便。由于THF作为淤浆催化剂中一个重要参数,影响催化剂主要性能。主要探讨了淤浆催化剂在喷雾成型过程中影响THF含量的因素,以达到精确控制THF的目的,稳定和提升淤浆催化剂的产品质量。     

聚乙烯管材专用树脂生产技术开发

利用淤浆法串联聚合丁艺产品具有相对分子质量双峰分布的特点,结合管材专用树脂的物性及微观结构特点,确定了由第一聚合釜均聚合生产低相对分子质量产品、第二聚合釜共聚合生产高相对分子质量产品的生产工艺。通过对2个聚合釜聚合温度、聚合压力、共聚单体的加入量和氢气与乙烯比等工艺参数的分析和调整．得到适合高级别管材专用树脂的最佳生产条件,产品的最小要求强度超过8MPa,达到管材专用树脂PE80的等级。     

C_2对称茂金属配合物催化丙烯均聚及丙烯与高级α-烯烃共聚

研究了C2对称的[Me2Si(2-Me-4-Ph-Ind)2]Zr Cl2双茂锆催化剂在不同条件下对丙烯均聚及丙烯与高级α-烯烃共聚反应的催化特性。研究结果表明:配合物的催化活性随着铝锆比、温度、压力的增加而提高;聚合物数均相对分子质量随着温度的提高而降低,在25℃、1 MPa丙烯压力下,可以获得数均相对分子质量高达40万的等规聚丙烯。该催化体系具有良好的共聚活性,共单体的侧链长度并不影响聚合活性。通过改变共单体的投料比,可控制共聚物中共单体的含量。     

大型中空容器级HDPE树脂的中试聚合研究

采用两段淤浆聚合工艺合成了由低摩尔质量的均聚物和高摩尔质量的共聚物组成的、具有宽峰或双峰摩尔质量分布的高密度聚乙烯大型中空容器级树脂。通过调节第一段和第二段聚合过程中聚合物的熔体质量流动速率来控制摩尔质量的大小及其分布;采用控制第二段共聚物中共聚单体数量来调节聚合物密度;控制第一段小分子数目,增加第二段摩尔质量或调整密度获得最大耐环境应力开裂性（ESCR）。随着共聚单体丁烯-1加入量的增加,反应釜共混物的密度、熔点、结晶度、拉伸屈服应力、断裂伸长率减少。随着高摩尔质量共聚物的含量增加,屈服应力、熔点、密度、结晶度减少,摩尔质量分布的双峰特性也增加,反应釜共混物的均聚物峰的高度减少,共聚物峰的高度增加。流变性能结果表明,通过改变共混物的组分可以获得力学性能和加工性能的平衡。     

丁二烯/苯乙烯阴离子连续溶液共聚反应模型化研究

针对n_BuLi引发剂引发的丁二烯／苯乙烯阴离子连续溶液共聚反应,结合共聚机理与反应器操作模式,建立了完全混合全混流模式下共聚单体转化率及分子量分布模型,并借助共聚单体转化率实验结果,对共聚单体转化率模型进行参数估计,求得了4个链增长速率常数。在此基础上,进行了分子量分布模型的模拟计算,并将模拟结果与共聚物分子量分布的实测结果进行了比较。研究结果表明,建立的模型能较为满意地描述丁二烯／苯乙烯阴离子连续溶液共聚反应的单体转化率和分子量分布。     

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

Ethylene/1-olefin copolymerization using vanadium and titanium complexes bearing tetradentate [O,N,N,O]-type ligand and EtAlCl₂ or MAO as a cocatalyst is carried out. In the presence of the vanadium complex activated with EtAlCl₂ is observed (a) negative “comonomer effect”, (b) high comonomer incorporation and narrow chemical composition distribution (CCD), (c) unexpected copolymer microstructure, and (d) increased molecular weight of copolymers when compared with the homopolymer. In contrast, titanium catalyst gives copolymers with lower 1-olefin content and broad CCD. Supported complexes show higher activity, lower 1-olefins incorporation and give copolymers with ultra high molecular weights.     

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

The relationship between the molecular structure and the thermal and rheological behaviors of metallocene‐ and Ziegler–Natta (ZN)‐catalyzed ethylene copolymers and high‐density polyethylenes was studied. Of special interest in this work were the differences and similarities of the metallocene‐catalyzed (homogeneous) polymers with conventional coordination‐catalyzed (heterogeneous) polyethylenes and low‐density polyethylenes. The short‐chain branching distribution was analyzed with stepwise crystallization by differential scanning calorimetry and by dynamic mechanical analysis. The metallocene copolymers exhibited much more effective comonomer incorporation in the chain than the ZN copolymers; they also exhibited narrower lamellar thickness distributions. Homogeneous, vanadium‐catalyzed ZN copolymers displayed a very similar comonomer incorporation to metallocene copolymers at the same density level. The small amplitude rheological measurements revealed the expected trend of increasing viscosity with weight‐average molecular weight and shear‐thinning tendency with polydispersity for the heterogeneous linear low‐density polyethylene and very‐low‐density polyethylene resins. The high activation energy values (34–53 kJ/mol) and elevated elasticity found for some of our experimental metallocene polymers suggest the presence of long‐chain branching in these polymers. This was also supported by the comparison of the relationship between low shear rate viscosity and molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1140–1156, 2002     

Study of the effect of the monomer pressure on the copolymerization of ethylene with 1-hexene

The effect of ethylene pressure on the copolymerization of ethylene with 1-hexene was studied. The results show an increasing of productivities (g of polymer/n_Zr h) with pressure. This tendency was not observed for the activity (g of polymer/n_Zr h bar) that decreases when pressure is raised. When varing the pressure, the characteristics and properties of the formed copolymers are in accordance with the expectation for changes in the monomer concentration; increasing the pressure causes a decrease in comonomer incorporation. At higher ethylene pressure, the polymer is more crystalline due to less incorporation of 1-hexene and the molecular weight is higher. The density of the copolymers also decreases with comonomer incorporation into the copolymer © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2567–2574, 1997     

Comonomer effects in copolymerization of ethylene and 1‐hexene with MgCl2‐supported Ziegler‐Natta catalysts: New evidences from active center concentration and molecular weight distribution

In this article, comonomer effects in copolymerization of ethylene and 1‐hexene with four MgCl₂‐supported Ziegler‐Natta catalysts using either ethylene or 1‐hexene as the main monomer were investigated. It was found that no matter which monomer was used as the main monomer, the polymerization activity was significantly enhanced by introducing small amount of comonomer. In copolymerization with ethylene as the main monomer, the strength of comonomer effects was much stronger in active centers producing low‐molecular‐weight polymer than those producing high‐molecular‐weight polymer. In copolymerization with 1‐hexene as the main monomer, the number of active centers ([C*]/[Ti]) was determined, and the propagation rate constants (k_p) were calculated. Deconvolution of the polymer molecular weight distribution into Flory components were made to study the active center distribution. Introduction of small amount of ethylene caused marked increase in the number of active centers and decrease in average chain propagation rate constant. Introducing internal electron donor in the catalyst enhanced not only the number of active centers but also the chain propagation rate constant. In copolymerization of 1‐hexene with small amount of ethylene, the internal donor weakened the comonomer effects to some extent and changed the distribution of comonomer effects among different types of active centers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41264.     

Modification of cellulose acetate with oligomeric polycaprolactone by reactive processing: Efficiency,compatibility, and properties

Oligomeric polycaprolactone (oPCL) was used for the modification of cellulose acetate by reactive processing in an internal mixer at 180°C, 50 rpm, 60 min reaction time, and 45 wt % caprolactone (CL) content. The product of the reaction was characterized by several analytical techniques and its mechanical properties were determined by dynamic mechanical thermal analysis and tensile testing. The synthesized oPCL contained small and large molecular weight components. The small molecular weight fraction plasticized cellulose acetate externally and helped fusion. Although composition and structure did not differ considerably from each other when CL monomer or polycaprolactone oligomer was used for modification, the grafting of a few long chains had considerable effect on some properties of the product. The large molecular weight chains attached to CA increased the viscosity of the melt considerably and resulted in larger deformability. oPCL homopolymer is not miscible with cellulose acetate and migrates to the surface of the polymer. Exuded polycaprolactone oligomers crystallize on the surface but can be removed very easily. More intense conditions may favor the grafting of long chains leading to polymers with advantageous properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Progress in the catalyst for ethylene/α-olefin copolymerization at high temperature

Ethylene/α-olefin copolymers are one of the most widely-used polyolefin materials. With the continuous improvement of polyolefin catalysts, high-performance polyolefin materials were synthesized by adjusting the chain microstructure, changing the comonomer type and comonomer insertion amount, among which the ethylene/α-olefin random copolymer elastomer (POE) and olefin block copolymer elastomer (OBC) are the most famous and well accepted by the market. The excellent properties of POE and OBC first depend on their polymer chain microstructure. The chain microstructure of polyolefins is fundamentally determined by the catalysts, polymerization conditions, comonomer feed policies, and reaction engineering. High-performance ethylene/α-olefin copolymer elastomers are currently prepared by high-temperature solution polymerization process, which needs to be carried out at a temperature above the melting point of the polymer and is beneficial to speed up the polymerization reaction rate and control the polyolefin chain microstructure. However, the high-temperature solution polymerization process launched more stringent requirements for the olefin coordination polymerization catalyst. Systematic reports on catalysts for high-temperature solution copolymerization of ethylene and α-olefins are lacking. In this review, we screened some catalysts suitable for the controllable copolymerization and high-temperature solution copolymerization of ethylene/α-olefin based on the catalyst's heat resistance, copolymerization activity, comonomer insertion ability, molecular weight, and distribution of the copolymer, including traditional Z–N catalysts, metallocene catalysts, and post-metallocene catalysts. And the future development of catalysts for high-temperature solution copolymerization of olefins, catalysts for precise control of polyolefin chain microstructures, and catalysts for olefin copolymerization with polar monomers at high temperature are envisaged.