二、氯乙烯聚合

研究了氯乙烯(Ⅰ)聚合的动力学。发现了聚合速率和自由基生成速率间的差距使自由基变少,引起在转化时动力学链长度的增加。生成的PVC的表面面积不是自动加速的主要因素。由于链转移剂的自由基较单体自由基具有较低的渗透速率和较大的粒子,所以,四溴化碳链转移剂造成较高的初始聚合速率和较慢的自动加速作     

引发剂对氯乙烯微悬浮聚合转化率和聚氯乙烯粒径分布的影响

分别采用水溶性过硫酸铵(APS)和油溶性偶氮二异庚腈(ABVN)引发剂进行氯乙烯(VC)微悬浮聚合,并与APS引发的VC乳液聚合以及ABVN引发的VC悬浮聚合情况进行比较,考察了引发剂类型对聚氯乙烯(PVC)乳胶粒子粒径分布和增塑糊流变特性的影响。结果表明:引发剂浓度相同时,VC微悬浮聚合转化率大于悬浮聚合,而小于VC乳液聚合;APS引发微悬浮聚合得到的PVC乳胶粒子存在数目较多的纳米级粒子,而ABVN引发微悬浮聚合得到的PVC基本不存在纳米级粒子;引发剂和分解产生的初级自由基在水相/油相/胶束中的分配和成核机理不同是导致上述差异的主要原因。ABVN引发微悬浮聚合得到的PVC树脂成糊后呈剪切增稠特性,而APS引发微悬浮聚合得到的PVC树脂成糊后呈剪切变稀特性,且糊黏度较大。     

世界PVC生产技术新进展(待续)

介绍了近年来世界PVC生产技术在原料、清洁生产、聚合方法、助剂等方面的发展,包括：①以可再生资源甲烷为原料制备氯乙烯、氯乙醇脱水制氯乙烯,完全摆脱汞催化剂;②充分利用氯乙烯生产过程中精馏塔塔顶、塔釜流出物热量,节省10％－20％的能量;③用单电子转移－退化链转移活性自由基聚合技术进行氯乙烯的活性自由基聚合,实现了氯乙烯常温聚合、聚合物分子质量可控,且加工时不需要加入增塑剂;④在氯乙烯微悬浮聚合体系中,加入一种水溶性过渡金属盐和一种络合剂,可以明显提高聚合早期的反应速度,同时改善PVC树脂的热稳定性,降低单体残留量;⑤少量马来酸酯与醋酸乙烯共聚然后水解制得的改性聚乙烯醇用作氯乙烯聚合的分散剂,用量少、粘釜轻,并可提高PVC树脂的表观密度、降低“鱼眼”数;⑥以不对称环多元酸酯和丙酮衍生物作环保增塑剂,可全面替代有毒的苯甲酸酯增塑剂,性能优越、成本低廉。     

世界PVC生产技术新进展(续完)

介绍了近年来世界PVC生产技术在原料、清洁生产、聚合方法、助剂等方面的发展,包括:(1)以可再生资源甲烷为原料制备氯乙烯、氯乙醇脱水制氯乙烯,完全摆脱汞催化剂;(2)充分利用氯乙烯生产过程中精馏塔塔顶、塔釜流出物热量,节省10%~20%的能量;(3)用单电子转移-退化链转移活性自由基聚合技术进行氯乙烯的活性自由基聚合,实现了氯乙烯常温聚合、聚合物分子质量可控,且加工时不需要加入增塑剂;(4)在氯乙烯微悬浮聚合体系中,加入一种水溶性过渡金属盐和一种络合剂,可以明显提高聚合早期的反应速度,同时改善PVC树脂的热稳定性,降低单体残留量;(5)少量马来酸酯与醋酸乙烯共聚然后水解制得的改性聚乙烯醇用作氯乙烯聚合的分散剂,用量少、粘釜轻,并可提高PVC树脂的表观密度、降低"鱼眼"数;(6)以不对称环多元酸酯和丙酮衍生物作环保增塑剂,可全面替代有毒的苯甲酸酯增塑剂,性能优越、成本低廉。     

汽巴精化PVC行业用新型添加剂

PVC是最重要的热塑性聚合物之一,每年的产量和加工量接近2500万t。PVC的应用范围广,能和多种聚合物共混改进自身的物理机械性能。酚类产品,特别是受阻酚广泛用于PVC行业。新近开发的高效光稳定剂和其他功能性添加剂(抗菌、抗静电、防雾和荧光增白剂等)增强了PVC制品的品质,因此强化了PVC应用在市场中的地位。1受阻酚抗氧剂1.1PVC聚合中的链终止剂和抗氧剂理想的链终止剂必须能完全终止聚合反应,猝灭任何催化剂残留(自由基) ,以防止在生产中的过度聚合。从而,减少了停机清理的时间,提高了生产率。IRGANOX1141是两种受阻酚的协效复…     

关于氯乙烯悬浮聚合反应的机理及其动力学

本文作者认为乙烯悬浮聚合反应的机理是:PVC 及其大分子自由基不溶解于单体,但能被单体溶胀成为粘胶体,沉析出的处于粘胶体中孤立状态的大分子自由基很难有彼此相遇形成双基链终止(偶合或歧化)的机会,因此 PVC 大分子自由基与粘胶体中的单体发生的链转移反应便成为其唯一的或起主导作用的链终止过程。通过链转移反应,在大分子自由基链终止的同时,形成了单体自由基,后者仍可与粘胶体中的单体发生链的引发、增长及转移等过程。另一方面,由于初级自由基、单体自由基、大分子自由基及单体等的极性与空间位阻作用的影响,使得聚合形成的 PVC 大分子为自由单体首尾相接的链节结构。本文作者按照上述机理进行了一系列高转化率的氯乙烯悬浮聚合反应动力学方程的推导,所推导的动力学方程经过科学实验和生产实践数据的反复验证,证明其是符合客观实际的。     

水相原子转移自由基聚合制备PVC-g-BA共聚物

以不同不稳定氯含量的聚氯乙烯(PVC)为大分子引发剂,CuCl2/三(2-吡啶甲基)胺(TPMA)为催化体系,抗坏血酸(AA)为还原剂,通过水相电子转移催化再生原子转移自由基聚合(ARGETATRP)制备PVC接枝丙烯酸丁酯(BA)共聚物(PVC-g-BA),研究聚合条件对BA聚合转化率和接枝率的影响。发现其它聚合条件相同时,采用不稳定氯含量高的PVC为大分子引发剂制备的PVC-g-BA的接枝PBA的平均分子量较低;随着BA单体用量增加,聚合转化率和接枝率增大;随着催化剂CuCl2用量和聚合温度的增加,转化率和接枝率先增加后减小;当PVC为1.589 g,BA为2.70 g,CuCl2用量为0.0048 g,AA/TPMA/CuCl2(mol)=15/5/1,聚合温度为70℃,可获得BA转化率为56.06%、接枝率为95.14%的PVC-g-BA产物;由于PVC仅部分溶胀于BA,导致PVC接枝不均匀,PVC-g-BA分子量分布出现双峰现象,接枝PBA的分子量大于理论分子量。     

石墨烯/纳米碳酸钙杂化材料对PVC的稳定作用

制备了氧化还原石墨烯/纳米碳酸钙杂化材料,将其与氯乙烯进行原位聚合制得了改性PVC树脂。该改性PVC树脂的刚果红试纸完全变色时间可达到28 min,采用液相电导法测得的热分解诱导时间超过80 min,加热后其多烯结构数量明显降低,自由基浓度与普通PVC树脂相比呈指数级降低,分子链结构上部分碳原子的结合能明显提高。     

PVC聚合釜技术特性及全流通PVC聚合釜

介绍了国内外PVC聚合釜的发展状况,对比分析了传统PVC聚合釜与全流通PVC聚合釜的结构特性、生产强度及防粘釜技术等。指出大型聚合釜的正常运转是以很高的控制水平为前提的。     

PVC聚合釜的技术进展与开发应用

概述了PVC聚合釜的基本结构,指出了其发展特点是大型化、生产强度高及安全性能好。介绍了国内PVC聚合釜的生产状况：13、30、48、70m^3聚合釜可批量生产,110、136、160、200m^3聚合釜现处于开发及待开发阶段。详细介绍了LF-30Ⅳ型、LF-70型及RLF-48型PVC聚合釜的技术特性。同时还指出国内大型PVC聚合釜设计及制造的关键技术问题现已解决．70m^3以上PVC聚合釜的成功开发指日可待。     

Structural heterogeneities of suspension poly(vinyl chloride). II. Formation of compact glassy particles and the cause of their difficult processing

By modifying the polymerization process of suspension polymerization of vinyl chloride, poly(vinyl chloride) (PVC) samples were prepared containing various amounts of compact glassy particles. It was found that these particles probably arise by a different polymerization mechanism than usual suspension particles, namely, as a result of the nonhomogeneous distribution of initiator in vinyl chloride drops of the polymerization system. It was proved experimentally that the lower heat stability of difficultly processible particles is due to a side reaction between the initiator radical and the PVC polymer chain which causes dehydrochlorination of PVC already under polymerization conditions. This reaction may also explain the yet unknown mechanism of formation of internal double bonds in PVC produced by the radical polymerization of vinyl chloride. In conclusion, the difficult processibility of compact glassy particles is discussed as a consequence of the insufficient drying of these particles in the usual drying process.     

世界聚氯乙烯工业技术进展(1998～1999)

介绍了１９９８～１９９９年世界主要国家和地区聚氯乙烯市场动态,分析了氯乙烯合成和聚合工艺技术的发展趋势,叙述了聚氯乙烯加工应用技术的发展,针对国内聚氯乙烯工业的具体情况,提出了发展我国聚氯乙烯工业的建议。     

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

Poly(vinyl chloride) (PVC) samples were synthesized by a living radical polymerization (LRP) method and compared with commercial PVC prepared by the conventional free radical polymerization (FRP). The differences were assessed, for the first time, in terms of viscosimetry parameters and thermal analysis. The LRP method used to prepare the PVC‐LRP samples is the only one available to obtain this polymer free of structural defects, being of commercial interest in a view of preparing a new generation of PVC‐based polymer with outstanding performance. The polymerization temperature selected (35°C) to prepare the LRP samples is currently used in the industry to prepare PVC‐FRP grades with moderate to high molecular weight. Since the thermal stability is a direct consequence of the polymer structure, this study is of vital importance to understand the potential of new PVC‐LRP. The thermoanalytical measurements demonstrate an enhanced thermal stability of PVC‐LRP when compared with its FRP counterpart. The PVC‐LRP sample with very low molecular weight reveals a higher thermal stability than the most stable PVC‐FRP sample. It is the first report dealing with thermal analysis of PVC prepared by LRP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photografting of PVC containing N,N‐diethyldithiocarbamate groups with vinyl monomers

Poly(vinyl chloride) (PVC) with pendent N,N‐diethyldithiocarbamate groups (PVC–SR) was prepared through the reaction of PVC with sodium N,N‐diethyldithiocarbamate (NaSR) in butanone and used as a photoinitiator for the grafting polymerization of three vinyl monomers [styrene (St), methyl methacrylate (MMA), and acrylamide (Am)]. The effects of ultraviolet (UV) irradiation time, PVC–SR amount, and the monomer amount on grafting and grafting efficiency were investigated. The results showed that PVC–SR could initiate the polymerization of three vinyl monomers effectively and obtained crosslinked copolymers. The grafting and grafting efficiency of styrene and methyl methacrylate were higher than those of acrylamide. The polymerization activity of three monomers was acrylamide > methyl methacrylate > styrene. By analyzing the UV spectrum of PVC–SR with a different irradiation time, it was confirmed that PVC–SR was dissociated mainly into macromolecular the sulfur radical PVC–S · and the small molecular carbon radical · C(S)N(C₂H₅)₂; the grafting polymerization mechanism was discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2569–2574, 2000     

Zum einfluß hochdispersen polyvinylchlorids auf die polymerisation aminhaltiger monomerer der acrylreihe

The radical polymerization of amine-containing acrylic monomers is accelerated in presence of PVC as filler. To clarify this effect the influence of PVC concentration on the polymerization kinetics of acrylic monomers with or without amino-groups has been estimated. The immobilization of monomers on the filler has been investigated by viscosimetric and swelling measurements. The results confirm the conception of a specific chemical interaction between PVC and amine-containing monomers.     

特种聚氯乙烯树脂生产概况

简述了国内外主要特种聚氯乙烯树脂(包括高聚合度PVC树脂、消光PVC树脂、PVC掺混树脂、氯乙烯一醋酸乙烯共聚树脂和氯化PVC树脂)的生产情况。并列举了主要特种PVC树脂的生产厂商、牌号和技术规格。     

Synthesis of amphiphilic PVC‐b‐poly(hydroxypropyl acrylate) (PHPA)‐b‐PVC block copolymers with low PHPA contents and different molecular weights by (Single Electron Transfer)—(Degenerative Chain Transfer) living radical polymerization

The aim of this work was to synthesize new amphiphilic block copolymers, based on poly(vinyl chloride) (PVC) and containing poly(hydroxypropyl acrylate) (PHPA), by using the controlled/“living” radical polymerization (CLRP) method. Various block copolymers containing a small proportion of PHPA were prepared, each having a different molecular weight. The technique used was the same as that employed in the production of commercial PVC made by free‐radical polymerization. The materials were characterized in terms of their molecular structure, morphology, particle size, and surface and thermal properties. The CLRP preparation of block copolymers that are based on PVC and have low contents of other monomer units opens the possibility of synthesizing new materials whose properties are close to those of PVC but have new properties that may considerably enhance their performance. The incorporation of small amounts of PHPA into PVC block copolymers provided greater surface hydrophilicity and improved thermal stability while maintaining relevant processing properties, such as particle size and average molecular weight, so that they close to those of conventional PVC homopolymers. J. VINYL ADDIT. TECHNOL., 19:157‐167, 2013. © 2013 Society of Plastics Engineers     

两种制备疏松PVC树脂的新型聚合方法

介绍了制备疏松PVC树脂的两种新聚合方法——以正丁烷为反应介质分散聚合和悬浮态乳液聚合，并对树脂颗粒的特性进行了简述。结果表明：以正丁烷为反应介质的非均相VC分散聚合所得树脂的粒径和颗粒形态与聚合体系VC／But比例和转化率等有关，由于存在向But的链转移，PVC分子质量小于相同聚合温度下生产的悬浮PVC树脂。悬浮态乳液聚合所得树脂粒径分布和颗粒形态与水油比、转化率和添加剂品种有关。     

影响氯乙烯悬浮聚合生产能力的主要因素及提高措施

根据氯乙烯悬浮聚合生产PVC树脂的工艺特点,分析了影响聚合生产能力的主要因素,并提出通过缩短聚合反应时间、聚合辅助时间,提高单釜产量等措施来提高聚合釜的生产能力。