ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412701

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412702

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe kinetics of chain growth and chain transfer processes in the stereospecific polymerization of propylene, using catalytic systems such as TiCl3Al(C2H5)3and TiCl3AlCl(C2H5)2, has been examined. The number of active centers present on the catalyst surface has been determined radiochemically by kinetic and adsorption measurements, using aluminum labeled with C14. The mean life of macromolecules was determined by radiochemical determination of terminal groups, and the relationships between intrinsic viscosity and number‐average molecular weight were found. Kinetic research into ethylene‐propylene copolymerization enableld us to determine the different reactivity ratios of t

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412703

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractMeasurements have been made on the kinetics of the polymerization of ethylene using Ziegler‐type catalysts made from zine di‐n‐butyl and titanium tetrchloride in hydrocarbon solvents. The rate of polymerization was proportional to the square of the ethylene pressure. At catalyst ratios (the molar ratio of zine butyl to titanium tetrachoride in the reaction mixture) less than 0.5, an initial, fast polymerzation was followed by a slower but more persistent polymerization. Both processes increased in velocity with increasing ratio up to 0.5; above this ratio the fast process was not observed while the rate of the slower one decreased with increasing ratio and was very small at unit ratio. At higher ratios the rate increased again as though to reach a limiting value when a very large excess of zine butyl was used. It has not been possible to devise more than speculative interpretations of these results. They suggest that at ratios greater than unity the reaction\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm TiCl}_4 + {\rm ZnBu}_2 \to {\rm TiCl}_3 + {\rm ZnBuCl} + ({\rm Bu radicals}) \to {\rm other products} $\end{document}may be completed and that the chain initiation step takes place between zine butyl and ethylene, both adsorbed equilibrium‐wise onto the solid, reduced titanium choloride. It is not yet known whether propagation of polymerization occurs along the catalyst surface or at single sites on the surface. If the former is the case and the mobile propagation center is an ion‐pair, the hydrocarbon end being negative and the positive charge lying in the surface, the mobility of this latter charge may limit the rate of propagation. It is possible to explain some of the results obtained most easily from th

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412704

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA study has been made of the influence of several variables on the performance of a Ziegler catalyst, prepared from triisobutylduminum and TiCl, in the polymerization of ethylene. Polymerizations were run at atmospheric pressure, with catalyst formedin situ, and with reaction rate unrestricted by gas‐liquid mass transfer rate. The influence of impurities on the catalyst performance has been minimized by a concerted effort to eliminate moisture, oxygen, etc., from the system as a whole; by the use of triisobutylaluminum scrubbers to purify the ethylene; and through the purification of the solvent, isooctane, by distillation in presence of triisobutylaluminum. Conditions leading to reproducible results and high catalyst efficiency have been established. A catalyst prepared in the absence of ethylene is relatively inefficient depending on Al/Ti ratio. Under the conditions studied, the most efficient catalysts were obtained by the addition of triisobutylaluminum to the TiCl4. The reverse mode of addition gave poor catalysts, particularly if the triisobutylaluminum was exposed to ethylene for a short time a t 50°C. However, under special conditions insuring complete mixing before significant reaction or aging of the catalyst components, the order of addition had no effect. A study of the performance of catalyst prepared by the rapid addition of triisobutylaluminum to TiC14, as a function of its components concentrations, at 50°C., revealed regions of maximum efficiencies. Maximum efficiency of 600 to 850 g. polyethylene/g. triisobutylaluminum was reached with Al/Ti ratios between 1.4 and 2.8. The efficiency with respect to TiCl4reached a plateau of 1800 g. polyethylene/g. TiCl4above an Al/Ti ratio of 2.8. The ratio of polymer yield to maximum polymerization rate was constant above an Al/Ti ratio of 1.4. The highest efficiency, 1500 g. polyethylene/g. triisobutylaluminum and 2100 g. polyethylene/g. TiCl, was obtained by incremental addition of triisobutylaluminum. These results have been interpreted consistently with a previously proposed mechanism of heterogeneous catalysis of polymerization. It appears that under conditions of rapid triisobutylaluminum addition, all intrinsic properties of the catalyst become constant above an Al/Ti ratio of 2.8. That is, the surface of the solid phase (presumably TiCL) is apparently a constant molar fraction of the total titanium content and is completely covered by adsorbed triisobutylaluminum. The same effect can be obtained a t a lower AI/Ti ratio of about 1.4 when triisobutylaluminum is added incrementally. Otherwise, a t AI/Ti ratios below 2.8, the adsorbed co‐catalyst is partly alkylaluminum chlorides, resulting in decreased activity per polymerization center. At a ratio of 0.7 the surface is less than completely covered with adsorbed aluminum compounds. It is indicated that the polyethylene obtained at high Al/Ti ratios is partially crosslinked. The physical nature of the polymer varies with operating conditions. A new, simple method for determining the quantity of catalyst poisons in the solvent is desc

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412705

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractA mechanism is proposed for the polymerization of aliphatic diazo compounds catalyzed by boren trifluoride and similar boron derivatives which satisfactorily accounts for the observed kinetic and molecular weight results. The final polymer molecule is shown to be a baron alkyl of the type . Such molecules are catalysts for the polymerization of fresh diazo compounds and in this manner it has been possible to prepare block copolymers of the typeThe mechanism of polymerization is shown to be similar to the polymerization of ethylene catalyed by aluminum alkyls and possibly to the Ziegler‐type polymerization of α‐ole

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412706

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThe molecular weight of polymethacrylonitrile obtained in the system lithiumammonia‐methacrylonitrile at −75° increased with decreasing concentrations of lithium and increasing concentrations of methacrylonitrile, and in addition was found to be proportional to [methacrylonitrile]/[lithium]. On the basis of this and additional evidence, a one‐electron transfer from lithium to methacrylonitrile to give an anion radical is postulated. In addition, the structure of the colored polymer obtained is discussed on the basis of the infrared s

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412707

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractHigh polymers with a regular chain structure have been produced by polymerization of ethylene with complexes containing crystalline organolithium compounds and titanium tetrachloride in organic solvents. For this purpose RLi compounds have been prepared, R being methyl, ethyl, butryl, dodeeyl, tolyl, mesityl, naphthyl, benzyl, and other aliphatic and aromatic groups. The investigation of the polymerization has led to the elucidation of the influence of the nature of the organic radical bound with lithium on the properties of polythene formed. Thermomechanical data, infrared and X‐ray spectra, as well as viscometric molecular weight determination, have shown all specimens of polyethylene to be highly crystalline and of a regular chain structure. The polymers obtained have mechanical properties characteristic of polyethylenes of this type but with elongations that strongly differ in polymers produced using organolithium complexes with different radicals at the lithium. With some specimen, elongation has been found to reach extremely high values. Some suggestions have been made as to the causes of influence of different organic radicals in RLi on the properties of polymer

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412708

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractThis article gives experimental data concerning the dependence of polymerization efficiency of chromium oxide catalyst upon the methods of preparation and reports on the character of the polymerization efficiency. The polyethylene and polypropylene obtained in this process of polymerization is characterized by high quality. Besides chromium oxide catalyst, molybdenum oxide catalyst with added lithium hydride was studied.

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412709

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY

摘要:

AbstractKinetic measurements have been made on the polymerization of ethylene to low molecular weight products using a soluble catalyst formed by the interaction ofsec‐butyl titanate and aluminum triethyl. A maximum in catalyst activity occured at ratio Al:Ti = 2.5:1 and a scheme is proposed to explain this observation. An interesting feature of the polymerization is the existence of a well‐defined cut‐off pressure of ethylene below which no polymerization occ

ISSN:0022-3832    

DOI:10.1002/pol.1959.1203412710

出版商:Interscience Publishers, Inc.    

年代:1959

数据来源: WILEY