不同钛催化体系引发异戊二烯聚合

初步考察了不同的催化体系以及聚合条件对异戊二烯聚合催化效率的影响,并通过红外和核磁共振谱图表征了聚合产物的微观结构。结果表明,采用负载钛和钛酸酯催化剂并用双组分体系引发异戊二烯聚合时,聚合产物中3,4-结构含量较高。其它3种负载催化剂引发生成的聚异戊二烯大部分为1,4-结构,3,4-结构含量甚微。     

钼基开环移位催化剂催化双环戊二烯聚合研究

分别用对甲基苯酚、壬基酚、2,6-二叔丁基-4-甲基苯酚、2,4,6-三溴苯酚和2,4-二硝基苯酚与五氯化钼(MoCl5)反应,制备出系列用于双环戊二烯(DCPD)开环移位聚合的钼-酚催化剂。考察了不同结构催化剂的活性及其在不同条件下对催化DCPD开环聚合的影响。以红外光谱和示差扫描量热分析表征了聚合产物的结构和性能。结果表明,产物中钼-对甲基苯酚的活性最高,其催化DCPD聚合的单体转化率为98.07%,交联度为90.44%。同时发现钼-酚催化剂催化DCPD聚合的凝胶时间随着Mo、Et2AlCl物质的量的增加和温度的升高而减小,而单体转化率和交联度则先增大后减小。     

Synthesis and properties of naphthalene oligomers polyalkylated with 1-octadecene and 1-hexadecene

Summary A one-pot method is described for the synthesis of naphthalene oligomers polyalkylated with 1-octadecene and 1-hexadecene. The synthesis involves two steps: 1) oligomerization of naphthalene using an AlCl₃/CuCl₂ catalyst/oxidant system, and 2) polyalkylation with a 1-olefin. Characterization studies include¹H- and¹³C-NMR spectroscopy, GPC and testing methods for lubricants. The degree of alkylation, variations in the alkyl groups, and the position of the substituent on the naphthalene ring were established by¹³C NMR spectroscopy. The purified products possess excellent properties for being suitable as a lubricant base stock, lubricant additives and functional fluids.     

Ethylene polymerization with heterogeneous Ziegler-Natta catalysts

Summary TiCl₄/SiO₂, Ti(OC₄H₉)₄/SiO₂, MgCl₂/TiCl₄/SiO₂ and MgCl₂/Ti(OC₄H₉)₄/SiO₂ catalysts were prepared by treating silica gel with TiCl₄, Ti(OC₄H₉)₄, MgCl₂/TiCl₄ or MgCl₂/Ti(OC₄H₉)₄ in tetrahydrofuran (THF) solution. Ethylene polymerization was performed with these catalysts activated by common alkylaluminum compounds. The influence of magnesium dichloride on catalyst performance was investigated. MgCl₂ has enhanced the catalyst activity for both titanium compounds. In addition, all catalyst systems were only active when they were washed with AlCl(C₂H₅)₂ (DEAC).     

1-丁烯聚合用Ziegler-Natta催化剂的性能评价

考察了6种用于1-丁烯本体聚合的Ziegler-Natta(Z-N)催化剂的性能,并采用凝胶渗透色谱仪、差示扫描量热仪研究了催化剂对聚1-丁烯微观结构调控的影响。结果表明:有5种Z-N催化剂反应活性高、立构定向性强;调整反应体系H₂分压,催化剂活性可提高1倍以上,Cat5活性最高可达40.1 kg/(g?h);催化剂氢调敏感性好,所制聚1-丁烯具有良好的结晶性能;Cat5的综合性能较好。     

Advances in the polymerization of polyolefins with coordination catalysts

A historical survey about the development of Ziegler-Natta catalysts for polymerization of propylene is given. After having employed catalysts based on titaniumtrichloride for several years, in the 70's catalysts of the so-called second generation were introduced, which are more effective and yield products of higher crystallinity. Catalysts of the so-called third generation and their morphological properties are extensively dealt with. These catalysts give high yields and highly stereoregular polymers and enable simplification of polypropylene technology and energy saving. In the future polypropylene manufacturing will probably consist only of the polymerization steps with no need for centrifuging, extruding or another post-treatment.     

不同催化体系所得聚酯的等温结晶研究

用DSC法对三氧化二锑 (Sb2 O3)、氟钛酸钾 (K2 TiF6 )、钛酸四丁酯 (Ti(OC4 H9) 4)及乙二醇锑(S -2 4) 4种催化体系所得聚酯进行等温结晶研究 ,求得了结晶速率常数 (k)和Avrami指数 (n)。结果表明 ,锑系催化剂所得聚酯的结晶速度总体大于钛系催化剂所得聚酯 ,其中以Sb2 O3催化所得聚酯结晶速度最快 ,而Ti(OC4 H9) 4催化所得聚酯结晶速度最慢。DTA结果表明锑系催化剂所得聚酯冷结晶温度低于钛系催化剂所得聚酯 ,与结晶速度测试结果相一致。     

Study on the volumetric expansion of benzoxazine curing with different catalysts

A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1107–1113, 2002; DOI 10.1002/app.10267     

Ring-opening polymerization of tetrahydrofuran with rare earth-contained catalysts

Rare earth trifluoroacetates, Ln(CF₃CO₂)₃ (Ln=thirteen rare earth elements), combined with R_nAlH_3?n (R=methyl, octyl, n=3; R=ethyl, i-Butyl, n=2,3) were used as catalysts for the polymerization of tetrahydrofuran (THF). The activity increased by adding propylene oxide (PO), as a promoter, to the polymerization system, producing high molecular weight polytetrahydrofuran (PTHF). The effects of Ln, PO/Ln, and Al/Ln, and others on the polymerization of THF were also studied. © 1993 John Wiley & Sons, Inc.     

不同催化体系下L-丙交酯的合成及表征研究

以乳酸为单体,采用先缩聚后解聚的方法制备了L-丙交酯。首先通过正交实验较系统的研究了合成工艺,包括三种不同催化剂(锌粉、乙酸铜及辛酸亚锡)用量、脱水温度及裂解温度对产物收率的影响；进而考察了提纯方法对丙交酯最终产率及杂质(乳酸、水)含量的影响,并利用红外、热分析及核磁共振技术对产物结构进行了详细表征。结果表明,在辛酸亚锡催化下,脱水及裂解温度分别为130℃及190℃时,L-丙交酯单体的产率达到80%；通过多次重结晶可以得到较高纯度产物。     

锑系催化剂聚酯的熔融及固相聚合

对锑系催化剂中常用的醋酸锑(Sb(AC)3)、三氧化二锑(Sb2O3)和乙二醇锑(Sb2(EG)3)进行熔融及固相聚合试验,结果表明,三氧化二锑的有效锑含量比醋酸锑及乙二醇锑低;乙二醇锑在固相聚合时的催化作用略低于醋酸锑和三氧化二锑;3种锑系催化剂相比,乙二醇锑催化剂聚酯固相聚合速度略慢,但特性粘数增幅最为平稳;220℃下的反应速率常数以醋酸锑制得的聚酯最大。     

Syndiospecific oligomerization and polymerization of norbornene with titanium catalysts

Norbornene (NB) has been polymerized with TiCl₄-AlR₂Cl (R = Et, Me, iBu) at various NB/TiCl₄ molar ratio. The products obtained at low ratio (from ca. 5 to 12, depending on the mode of catalyst preparation) are a mixture of oligomers, from which it has been possible to isolate a crystalline heptamer having a 2,3-exo-disyndiotactic structure by single crystal X-ray analysis. The products obtained at higher NB/TiCl₄ ratio have a higher molecular weight (up to ca. 5000 for the soluble products) and consist of amorphous and crystalline polymers. The crystalline polymers, characterized by X-ray and ¹³C NMR, are a new type of stereoregular polynorbornene (PNB), having a 2,3-exo-disyndiotactic structure. Mechanistic aspects are examined and a precise assignment of some resonances in the ¹³C NMR spectrum of vinyl-type PNBs is reported.     

NT-1和BCH催化剂在乙烯淤浆聚合中的催化性能

利用XRD和BET测试技术对BCH和NT-1两种工业催化剂进行了物相表征和结构分析,研究了两种催化剂的结构对其催化乙烯淤浆聚合活性的影响。结果表明,BCH催化剂较多的大孔有利于单体的扩散,使得其初始活性较高,随着部分活性中心的被包埋导致中后期活性低于NT-1催化剂。采用NT-1催化剂聚合得到的产品粉末平均粒径大,粒径分布集中,但堆密度略低;产品的力学性能略优于用BCH聚合得到的产品。NT-1催化剂的氢调敏感性和共聚性能优于BCH催化剂。     

Vinyl polymerization by Ziegler catalysts

Summary Methylmethacrylate and styrene were polymerized with Co(acac)₃-AlEt₂ Br catalyst system in benzene at 40°C. Rate of polymerization is linear to monomer concentrations. Maximum percent conversion of polymer was obtained when Al/Co2 with styrene and Al/Co3 with methylmethacrylate. With increase in aging time catalytic activity decreases. Activation energy was found to be 60 KJ mol^–1. with styrene and 40 KJ mol^–1. with methylmethacrylate.The authors arc thankful to the UGC, INDIA for the financial support.     

单茂金属化合物催化烯烃聚合

综述了单茂金属化合物催化烯烃聚合的机理及研究进展，指出IVB族元素钛、锆、铪的单茂金属化合物催化烯烃及α－烯烃的均聚和共聚的活性很好，并通过改变配体结构及聚合条件可得到立构规整性的聚合物，桥联的单茂金属化合物催化乙烯，丙烯聚合的活性相当高，可得到高间规度的聚丙烯和支化的超低密度聚乙烯，但催化苯乙烯的活性很低，VB族元素钒，铌、钽的单茂金属化合物作为烯烃催化剂可得到分子量分布相当窄（1．05）的聚烯烃，另外，单茂铬化合物在很低的Al/Cr(45-100)下具有相当高的催化活性，单茂镍化合物由于其亲氧性小，可催化极性单体（如甲基丙烯酸甲酯等）聚合。     

The influence of cocatalysts on 1-hexene polymerization with various supported magnesium – titanium catalysts

Summary The influence of various cocatalysts on the activity and stereospecificity of a supported magnesium–titanium catalyst, generated by in situ reduction of titanium (IV) chloride using a Grignard reagent (MgCl₂/TiCl₃) or prepared by the recrystallization method (MgCl₂/2M2P/ED/TiCl₄, 2M2P= 2-methyl-2-pentanol, ED= dibutyl phthalate or ethyl benzoate), in the 1-hexene polymerization was investigated. The MgCl₂/TiCl₃ catalyst showed the highest activity but the lowest stereospecificity in the 1-hexene polymerization with all investigated cocatalysts. The MgCl₂/2M2P/ED/TiCl₄ catalyst with dibutyl phthalate as an internal electron donor was characterized by the highest stereospecificity and led to the polymers with high molecular weight. All catalysts showed the highest activity and stereospecificity when triisobutylaluminium was used as a cocatalyst. The addition of a small amount of ethyl benzoate as an external electron donor ([Al]/[ED] 10:1) led to considerable improvement of the stereospecificity of the MgCl₂/TiCl₃ catalyst in comparison with the catalysts prepared by the recrystallization method.     

Supported catalysts for the polymerization of 1,3-butadiene

Summary Highly dispersed supported catalysts were prepared by supporting various complexes of CoCl₂, CoBr₂and NiCl₂ on SiO₂, MgO, Al₂O₃ and MgCl₂ in n-heptane, followed by evacuating at room temperature. The catalysts combined with AlEt₂Cl or Al₂Et₃Cl₃ showed very high activities for cis-1,4-polymerization of 1,3-butadiene.