Propene, copolymerization

The chain-end stereocontrol for olefin polymerizations leads generally to lower stereoselectivities (differences in activation energy for insertion of the two enantiofaces generally lower than 2 kcal/mol) than the chiral site stereo-control.18131132 For this reason, the corresponding catalytic systems have not reached industrial relevance for propene homopolymerization. However, some of them are widely used for propene copolymerization with ethene. 

Propen-l-ol. See Allyl alcohol 2-Propenal. See Acrolein 2-Propenamide. See Acrylamide Propene, copolymerizations of, 16 111 Propene homopolymerization, 16 104-110 Propene polymerization, 16 94, 99 2-Propenenitrile. See Acrylonitrile (AN) Propenoic acid, physical properties, 5 31t Propenoic acid nitrile. See Acrylonitrile (AN)... 

Fig. 5. Rate constant kp of the ethene/propene copolymerization as a function of the ethene concentration in the liquid phase at 37 °C (- -) calculated (-) measured...

Even dialkyl dicarbonates can be produced in the polymerizing medium. This technique was applied by Ravey and Waterman [87] for the initiation of vinyl chloride—propene copolymerization. 

In ethylene—propene copolymerization the former monomer is greatly favoured and a value for r, of 72 was found. Hydrogen is particularly active as a chain transfer agent for this catalyst, a value of fetr,H,/ tr,M 3.8 X 10 being quoted, some ten times greater than that for a conventional Ziegler system [133b]. The active species in both these systems was ascribed to a low valence Cr complex. 

A) Monomer feed and copolymer composition for ethylene/propene copolymerization with the catalyst VCl4/AlEt2Cl at —78°C have been shown to fit accurately empirical relationships [322]... 

Homogeneous vanadium-based catalysts formed by the reaction of vanadium compounds and reducing agents such as organoaluminum compounds [10-12] are used industrially for the production of elastomers by ethylene/propene copolymerization (EP rubber) and ethylene/propene/diene terpolymerization (EPDM rubber). The dienes are usually derivatives of cyclopentadiene such as ethylidene norbomene or dicyclopentadiene. Examples of catalysts are Structures 1-4. Third components such as anisole or halocarbons are used to prevent a decrease in catalyst activity with time which is observed in the simple systems. 

A conventional approach to fhe controlled formation of short-chain branches is ethene copolymerization wifh co-monomers such as propene, butene(l), 4-mefhyl-pentene(l), hexene(l) or octene(l). In the ethene/propene copolymerization example given below an increased number of methyl groups compared with vinyl end groups is consistent wifh a propene incorporation of approximately 6 mol% [Eq. (13)], fhe observed lower DSC melt temperatures and lower densities are typical for medium density (MDPE) and hnear low density polyethylene (LLDPE). 

Scheme 8.16 Some phosphorus-containing ligands (or their corresponding catalyst precursors) used for carbon monoxide-propene copolymerization.

Scheme 8.17 Attempted rationalization of the higher catalytic activity of the meso-vs. the rac-ligand for carbon monoxide-propene copolymerization.

Galimberti, M., Mascellani, N., Piemontesi, R, et ak, 1999. Random ethene/propene copolymerization from catalyst system based on a constrained geometry half-sandwich complex. Macromok Rapid Commun. 20 (4), 214-218. 

Galimberti, M., Piemontesi, F., Fusco, O., Camurati, L, and Destro, M., Ethene/ Propene Copolymerization with High Product of Reactivity Ratios from a Single Center, Metallocene-Based Catalytic System, Macromolecules, 31, 3409 (1998). 

Leclerc, M. K. Waymouth, R. M. Alternating ethene/propene copolymerization with a metallocene catalyst. Angew. Chem., Int. Ed. Engl. 1998, 37, 922-925. 

Schneider, M. J. Mulhaupt, R. Influence of indenyl ligand substitution pattern on metallocene-catalyzed propene copolymerization with 1-octene. Macromol. Chem. Phys. 1997,198, 1121-1129. 

The ranges of the reactivity ratios obtained at the lowest [N]/[E] feed ratio are ri = 2.34-4.99 and r2 = 0.0-0.062. The r2 values are in general smaller than those obtained for propene copolymerization. The highest r x 2 values found for the copolymers prepared with catalyst 1-4 confirmed its tendency to give more random copolymers. The values of ri, r2, and ri x r2 for the E-N copolymers obtained with catalysts IV-1 and 1-5 are comparable with those of alternating ethene-propene copolymers with metallocene catalysts. The results of the second-order Markov model also showed that all rn values, as r, are similar to those found for ethene and propene copolymerization with metallocene catalysts with low reactivity ratios. Differences in ri2 and in r22 are illuminating, since they clearly show the preference of the insertion of ethene or norbomene into E-N-Mt (Mt = Metal) and N-N-Mt, respectively. Parameter ri2 increases in the order IV-1 < 1-5 I-l < 1-2, opposite to the tendency to alternate the two comonomers [88]. 

The copolymers produced possessed high molecular weights and narrow molecular weight distribution with high Tg values irrespective of the Ti complex used. The activities of norbomene-propene copolymerization were too high to evaluate monomer reactivity ratios. Thus, the copolymerization abilities of each Ti complex were investigated with norbomene-l-octene copolymerization by changing the monomer feed ratio. 

Table 5 Activities of the cyclopentene/propene copolymerization by different cyclopentene concentration and temperature with rao(Et(lnd)2)ZrCl2...

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