冷凝技术使聚烯烃气相工艺生产能力成倍增长

最近,聚烯烃反应器工艺改进的重大进展——“第三代”反应器技术极为引人注目,据报道,它将大幅度地提高聚烯烃的产量而不必投资建设新的树脂生产装置。SRI国际部高级顾问Kenneth Sinclair认为,它可能使气相聚乙烯和淤浆聚丙烯的生产能力增加两倍。 在最近的有关专利中,新的工艺进展包括超冷凝气相工艺、球形反应器超临界淤浆工艺     

干法腈纶聚合系统稳定运行的改进

对干法腈纶聚合系统运行中的问题进行了分析,并针对影响因素进行了工艺改进:保持进入聚合釜各物料流量及含量稳定、合理分配盐水量、尽量使去与混合单体的水量最大,控制聚合釜搅拌转速为140～145 r/min,聚合釜二层搅拌浆叶角度由22°调整为45°;水封槽加碱改为2股,二道滤液全回用进入淤浆供给槽,安装淤浆供给槽底部滤网,提高气液分离效果,将气相管线及调节阀倾斜30°安装.改进后延长了聚合釜的运行周期,保证了聚合反应的连续性,能生产出高质量、高品位的聚合物.     

气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为

气相法聚乙烯工艺冷凝态操作模式由于显著提高了循环气移热能力和反应器时空产率,已成为流化床乙烯聚合工艺的主流操作模式。建立了气相法聚乙烯工艺冷凝态操作模式的数学模型,包括流化床反应器模型,多级换热器模型和反应温度、压力以及循环气组成的控制模型。基于此,采用流程模拟方法,计算了系统在反应器温度采用闭环控制时的稳态解;根据系统对小扰动的动态响应特点,定性判断了反应器温度采用开环控制和闭环控制时聚合反应系统的稳定性;考察了系统对1-己烯分压和催化剂进料速率的阶跃响应特性。结果表明,反应器温度采用闭环控制时,聚合反应系统在所考察操作条件下均是稳定的,而采用开环控制时,解曲线被分叉点分割为稳定区域和不稳定区域。反应器温度对1-己烯分压阶跃变化的动态响应表明聚合反应系统存在长、短周期两类振荡,表明冷凝态操作模式下乙烯聚合反应过程是一个多控制回路耦合的复杂过程。     

PVC生产中聚合温度异常原因探讨

在ＰＶＣ聚合期间根据生产牌号的需要，投用回流冷凝器，提高釜的传热能力，能较好地保证釜内反应物料温度的稳定。在生产末期，粘釜成为聚合反应后期温度高的主要因素。冷冻水的温度和流量直接影响着聚合釜的传热速率，要加强工艺操作技术管理和设备维护。     

丙烯超临界聚合中原生晶特征

通过广角X射线衍射(WAXD)对由丙烯超临界聚合和传统本体淤浆法制得的等规聚丙烯原生结晶特征进行了研究,并讨论了聚合工艺、预聚温度、粒径、分子量等对原生晶特征的影响。结果表明,超临界聚合法制备的等规聚丙烯(SC-iPP)呈现出α和γ的混合晶型,而采用传统淤浆法制备的等规聚丙烯(C-iPP)只含有单一α晶型,这是因为超临界的高温高压状态,使得体系传热传质阻力较小,更有利于原生晶型的发展。此外,预聚温度、粒径、分子量等因素也对丙烯超临界聚合所制得的SC-iPP结晶特征有显著影响。     

氯乙烯回流对悬浮聚合,微悬浮聚合及乳液聚合的影响

在聚合时氯乙烯单体的回流，与造成树脂大颗粒、表皮增厚、鱼眼增多、泡沫多、干燥困难、气相粘釜加重等有一定关系。为了减少季节变化对聚合的影响，采用在聚合釜中保留一定量的惰性气体或空气、釜顶部保温等措施，减少氯乙烯的回流。     

提高悬浮法PVC收率的研究

介绍了影响悬浮法PVC收率的主要因素，提出了提高聚合收率的方法：①采用压缩冷凝技术及无堰筛板塔，提高VCM的回收率；②引进先进的防粘釜技术、先进的清釜设备(用高压水清釜效果更好)，使用性能稳定的防粘釜液，加强设备管理，严防跑、冒、滴、漏的现象发生，提高防粘釜效果，减少“成品”料的损失。     

乙烯淤浆聚合反应器的模型与模拟

建立了乙烯淤浆聚合反应器的多相全混流模型,描述了包括乙烯共聚合反应动力学、气液和液固传质、反应器传热在内的物理化学过程。通过模拟计算分析了聚合过程的控制步骤,得到了反应器生产能力与有关操作变量之间的关系,对某工业反应器的模拟结果表明计算值与生产数据具有很好的一致性。     

乙烯淤浆聚合用Ziegler-Natta催化剂的制备及催化性能

通过加入新型给电子体制备了适用于乙烯淤浆聚合工艺的Ziegler-Natta催化剂。采用激光粒径分析仪、扫描电子显微镜、比表面吸附仪及X射线衍射仪分析和表征了催化剂的粒径、形态和物理结构等。采用乙烯淤浆聚合法研究了该催化剂的乙烯淤浆聚合性能,并与进口参比催化剂进行了比较。结果表明:在氢气分压为0.28 MPa、乙烯分压为0.45 MPa、反应温度为80℃、反应时间为2 h的条件下,催化剂活性达到21.3 kg/(g·h),聚合物堆密度达到0.34 g/cm3,粒径小于100μm的细粉含量为1.87%,催化剂的综合指标优于参比催化剂。     

关于我国聚丙烯技术及市场发展的思考

本文主要阐述了聚丙烯工艺技术,重点分析了聚丙烯的主要生产工艺:本体聚合工艺、气相聚合工艺以及淤浆工艺,并从催化剂开发、反应装置的大型化等方面,对我国未来聚丙烯技术与市场的发展方向做了一系列分析和探讨。     

工业聚合反应装置：Ⅷ.聚烯烃装置

简介了低密度聚乙烯、高密度聚乙烯和聚丙烯生产工艺及其聚合反应器。     

丙烯聚合用BCZ型催化剂的开发

在MgCl2溶解过程中加入内给电子体,开发了一种新型丙烯聚合用BCZ型催化剂,并在5 L聚合釜中进行了本体聚合考核评价,在12 m3小本体工艺装置上进行工业应用试验,在25 kg/h的连续法Innovene气相工艺装置进行中试试验。研究表明:用BCZ型催化剂制备聚丙烯(PP)时,催化剂活性高出国产同类催化剂近50%,氢调敏感性好,同样氢气用量下,PP的熔体流动速率可提高25%左右;所制PP的相对分子质量分布大于7.5,等规指数高;BCZ型催化剂可用于小本体法工艺、连续法气相工艺装置制备均聚和共聚PP。     

Preparation of chelating fabrics by radiation‐induced grafting of itaconic acid and acrylonitrile onto polypropylene nonwoven fabrics and subsequent amination of graft copolymer

A mixture of acrylonitrile (AN) and itaconic acid (IA) was cografted onto polypropylene (PP) nonwoven fabrics by preirradiation method. The effects of graft polymerization conditions such as temperature, reaction time, Mohr's salt concentration, solvent mixture ratio, and comonomer composition on the total grafting yield were investigated. The addition of AN as a comonomer increased the amount of IA that reacted with PP fabrics. An increase in the temperature from 40 to 60°C increased the grafting rate, but the final grafting yield decreased at high temperature. The addition of 0.01 wt % Mohr's salt to the reaction medium leaded to a sharp increase of grafting yield. The accelerative effect of solvent medium on the grating yield was higher in dimethylformamide (DMF) and methanol mixtures, when compared with DMF or methanol. Chelating fabrics was synthesized by subsequent amination of grafted fabric with ethylene diamine (EDA) and phenylhydrazine (PH). The conversion yield reached maximum value at about 90% for 80% PP‐g‐AN‐IA fabrics at 90°C. At same amination conditions, the conversion yield is higher when PP‐g‐AN‐IA fabrics react with EDA compared with PH. FT‐IR data indicate that amine groups were introduced onto PP‐g‐AN‐IA fabric through amide linkage between grafted AN or IA and EDA or PH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reactor design and operation for gas-phase ethylene polymerization using ziegler-natta catalysts

A well-instrumented, semi-batch reactor has been constructed for studying the gas-phase polymerization of ethylene using solid Ziegler—Natta type catalysts. This reactor can be operated over the entire range of temperatures and pressures used in the commercial production of linear low, and high density polyethylenes. Successful operation of the reactor depends on careful control of the reaction temperature which in turn is mainly dependent on the total rate of polymerization. If this rate is too large, then the reaction temperature increases uncontrollably (thermal runaway) until catalyst deactivation occurs when melting polymer encapsulates the catalyst particles. Operating conditions are described which resulted in precise and reproducible kinetic measurements for a δ-TiCl₃ δ 1/3AlCl₃ catalyst (Stauffer AA Type 2.1) with diethylaluminum chloride (DEAC) as the co-catalyst. This system displayed first-order kinetic behavior over the temperature range 20 to 90°C with an activation energy of 32.6 kJ/mol.     

原位螯合制备含镁聚磷酸铵的工艺研究

采用一步投料法,将磷铵、尿素和硫酸镁充分混合后粉碎,再加入反应器中原位螯合制备含镁元素的水溶性聚磷酸铵（APP）肥料。研究镁添加量、尿素/磷铵物质的量比、反应温度、反应器搅拌转速对产品聚合度及聚合度分布的影响。结果表明：当镁添加量＜5%（质量分数）时,可以促进磷铵与尿素的聚合反应,提高产品聚合度;增加尿素比例、提高反应温度,可显著提高产品聚合度;随着反应器搅拌转速增加,含镁APP产品聚合度增加,而纯APP产品聚合度降低。各实验因素对APP聚合度的影响由大到小顺序为尿素/磷铵物质的量比、反应温度、搅拌转速、镁添加量。     

N型催化剂在连续法PP装置的工业应用

N型催化剂在立式釜液相本体与卧式釜气相本体组合的三釜工艺(SPG)连续法聚丙烯(PP)装置的工业应用数据表明,该催化剂完全适应SPGT艺PP装置。由此催化剂生产的PP产品的内在质量优异,特别是屈服拉伸强度可达36．1MPa,弯曲模量达1481MPa,断裂伸长率达656％。对于生产纺丝料极为有利。     

Preparation of thermal‐responsive poly(propylene) membranes grafted with n‐isopropylacrylamide by plasma‐induced polymerization and their water permeation

Poly(propylene) (PP) membrane grafted with poly(N‐isopropylacrylamide) (PNIPAAm), which is known to have a lower critical solution temperature (LCST) at around 32°C, was prepared by the plasma‐induced graft polymerization technique. Graft polymerization of PNIPAAm onto a PP membrane was confirmed by microscopic attenuated total reflection/Fourier transform IR spectroscopy. The grafting yield of PNIPAAm increased with the concentration of N‐isopropylacrylamide monomer and the reaction time of graft polymerization. The average pore size of the PP membrane also affected the grafting yield. From the field emission scanning electron microscopy (FE‐SEM) measurement, we observed a morphological change in the PP‐g‐PNIPAAm membrane under wet conditions at 25°C below LCST. The permeability of water through the PP‐g‐PNIPAAm membrane was controlled by temperature. The PP‐g‐PNIPAAm membrane (PN05 and PN10) exhibited higher water permeability (L_p) than the original PP substrate membrane below LCST. As the temperature increased to above LCST, L_p gradually decreased. In addition, the graft yield of PNIPAAm and the average pore size of the PP substrate influenced water permeability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1168–1177, 2002; DOI 10.1002/app.10410     

外给电子体对DQ-Ⅳ催化剂催化丙烯聚合反应的影响

采用DQ-Ⅳ催化剂,在4 L丙烯聚合反应釜进行聚合实验,考察了C-Donor和D-Donor对聚合反应及产品性能的影响。结果表明,其他条件相同时,采用D-Donor作为助催化剂与使用C-Donor相比,催化剂平均活性提高20％～30%,聚丙烯等规度提高平均约1%,催化剂的氢调敏感性降低,聚丙烯结晶温度和熔点显著提高,分子量提高,分子量分布基本未变。     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999