Atactic polybutene

Metallocenes are far more versatile in controlling polymer stereochemistry compared to Ziegler-Natta catalysts, as extensively demonstrated in the case of PP. Also in 1-butene polymerization, all kinds of chain microstructures can be obtained with different metallocenes. The 13C NMR pentad analysis of polybutene is somewhat less immediate than that of PP, and has been reported for both ZN 886,887 and metallocenes.180 The 13C NMR spectrum of atactic polybutene, with pentad assignments of the C(3) methylene region, is shown in Figure 37. 

Isotactic poly(butene-l) is produced commercially with three-component coordination-type catalysts. It is manufactured by a continuous process with simultaneous additions to the reacticMi vessel of the monomer solution, a suspension of Ti l2-Al l3, and a solution of diethyl aluminum chloride [84], The effluent containing the suspension of the product is continually removed from the reactor. Molecular weight control is achieved through regulating the reaction temperature. The effluent contains approximately 5-8% of atactic polybutene that is dissolved in the liquid carrier. The suspended isotactic fractions (92-98%) are isolated after catalyst decomposition and removal. The product has a density of 0.92 g/cnf and melts at 124—130° . 

Almost all PP blends are immiscible the only miscible ones are those with aPP, some sPP, EPR containing la s 10% of ethylene, and atactic polybutene-1 (PB-1) [4]. However, the isotactic PB-1 was reported immiscible with PP [5]. In immiscible blends, the interfacial adhesion in both molten and solid states is usually poor, thus compatibilization is advisable. However, as for any immiscible polymer pair, there are three cases where acceptable product is obtained without compatibilization (1) at low concentration of either component, i.e., at < ) = 1 - s 0.1 (2) blends with phase co-continuity, e.g., = < >inversion/ (3) for applications not requiring high strength. 

MOR Moraglio, G., Gianotti, G., and Danusso, F., Unpertnrbed molecular dimensions of atactic polybutene-1 at different temperatures, Eur. Polym. J., 3, 251, 1967. 

DEL Delmas, G. and Tancrede, P., Heats of mixing of atactic polybutene-1 and of a model molecule with normal alkanes order in long alkanes, Eur. Polym. J., 9,199,1973. 

The unperturbed dimensions and their temperature coefficients are evaluated for poly n-pentene-1), poly(n-butene-l), and PS with the RIS model. The calculated values of the unperturbed dimensions for atactic and isotactic chains are in good agreement with the experimental data. The measured temperature coefficients, however, are described satisfactorily by the model for atactic polypentene and polybutene only. 

The above elastomeric polybutene might be similar in properties, if not in constitution, to the one produced with Al2C>3-supported tetrabenzyl and tetraneophyl metals (Ti, Zr, Hf), which is a blend of atactic PB and isotactic-atactic stereoblock PB,902 that can be fractionated by diethyl ether extraction. 

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