Copolymerization ethene/propene

The water-soluble palladium complex prepared from [Pd(MeCN)4](Bp4)2 and tetrasulfonated DPPP (34, n=3, m=0) catalyzed the copolymerization of CO and ethene in neutral aqueous solutions with much lower activity [21 g copolymer (g Pd) h ] [53] than the organosoluble analogue in methanol. Addition of strong Brpnsted acids with weakly coordinating anions substantially accelerated the reaction, and with a catalyst obtained from the same ligand and from [Pd(OTs)2(MeCN)2] but in the presence of p-toluenesulfonic acid (TsOH) 4 kg copolymer was produced per g Pd in one hour [54-56] (Scheme 7.16). Other tetrasulfonated diphosphines (34, n=2, 4 or 5, m=0) were also tried in place of the DPPP derivative, but only the sulfonated DPPB (n=4) gave a catalyst with considerably higher activity [56], Albeit with lower productivity, these Pd-complexes also catalyze the CO/ethene/propene terpolymerization. 

An interesting effect is observed for the polymerization with ethylene(bisin-denyl) zirconium dichloride and some other metallocenes (Fig. 5). Although the activity of the homopolymerization of ethene is very high, it increases when copolymerizing with propene [66]. 

The measured data of the polymerization rate using a molar ratio of ethene/ propene = 1 1 are four times higher than the calculated data. A clear increase in activity by the comonomer is observed. The results of the sequence analysis of the copolymer samples suggest no change in the mechanism of copolymerization. One explanation for this effect lies in the increase in the insertion rate due to an electronic influence of the comonomer. 

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...

The excellent performance of metallocenes in copolymerizations also offer improvements in impact copolymers. In the wide variety of properties of impact copolymers, the stiffness of the material is determined by the matrix material, while the impact resistance largely depends on the elastomeric phase. While conventional catalysts show some inhomogeneities in the ethene/propene rubber phase due to crystalline ethene rich sequences, the more homogenous comonomer distribution obtained with metallocene catalysts results in a totally amorphous phase [153]. 

Mw/M = 2, highly linear Copolymerization random distribution, LLDPE co-monomers propene, 1-butene, 1-octene Elastomers, Terpolymers of Ethene, Propene and Diene low transition metal concentration in the polymer, narrow molecular weight distribution Polymerization to ... 

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). 

This review covers the homopolymerization of propene with group 4 metallocene catalysts, and special emphasis is dedicated to isotactic polypropene. Reference to other poly(l-olefins) and copolymerization between propene and minor amounts of ethene will be done only when relevant to the discussion. 

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). 

Processes of ethene/a-olefin copolymerization are of great practical importance. Copolymerization of ethene with small amounts of highest a-olefins (1-butene, 1 -hexene, 1 -octene) allows one to produce linear low density polyethylene (LLDPE), which is one of the most widely used large-scale polyolefin products. Polypropylene, modified with small amounts of ethene, exhibits higher impact strength compared to isotactic homopolypropylene. Copolymerization of propene with large amounts of ethene and terpolymerization of ethene/propene/diene result in amorphous elastomer materials (rubbers) [103]. 

Stevens, J. C. Boone, H. VanderLende, D. Boussie, T Diamond, G M. Goh, C. HaU, K. et al. New high activity group 4 Cj-symmetric catalysts for isotactic-selective high temperature solution polymerization of propene, and copolymerization of propene with ethene. 1-Synthesis, process and products. Abstract of Papers, European Polymer Conference on Stereospedfic Polymerization and Stereoregular polymers. Milano, Italy, June 8-12, 2003 pp 79-80. 

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

Important for the copolymerization are the different ractivities of the olefins. The principal order of monomer reactivities is well known [187] ethene > propene > 1-butene > linear a-olefins > branched a-olefins. Normally propene reacts 5 to 100 times slower than ethene, and 1-butene 3 to 10 times slower than propene. Table 8 shows the reactivity ratios for the copolymerization of ethene with other olefins. The data imply that the reactivity of the polymerization center is not constant for a given transition metal compound but depends on the structure of the innermost monomer unit of the growing polymer chain and on the cocatalyst. 

Copolymerization of ethene with ethene/propene macromers ... 

Long-chain branched polyethylenes can be also obtained by copolymerization of ethene with ethene oligomers by tandem polymerization in one step [100] or with ethene/propene oligomers in two steps [101]. In the latter case, polymers are obtained with crystalline polyethylene backbone chains and amorphic ethene/ propene copolymer side chains [102]. 

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]. 

Hence, homo- and copolymerizations with propene or ethene and co-halo-a-olefins were also carried out on a zirconocene/MAO catalytic system. First copolymerization experiments of 11-chloroundec-l-ene with 1-hexene using a rac-Et(Ind)2ZrCl2/MAO catalyst system in methylene chloride and toluene show a complete deactivation with the former solvent because of fast side reactions however, in the case of... 

High pressiffe copolymerization (100- 150 MPa). [Monomer]/[Comonomer] ratio varied. The cited r-values hold only for a Not determined. selected ratio of [Ethene]/[Propene], ... 

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. 

Water-soluble l,3-bis(di(hydroxyalkyl)phosphino)propane derivatives were thoroughly studied as components of Pd-catalysts for CO/ethene (or other a-olefins) copolymerization and for the terpolymerization of CO and ethene with various a-olefins in aqueous solution (Scheme 7.17) [59], The ligands with long hydroxyalkyl chains consistently gave catalysts with higher activity than sulfonated DPPP and this was even more expressed in copolymerization of CO with a-olefins other than ethene (e.g. propene or 1-hexene). Addition of anionic surfactants, such as dodecyl sulfate (potassium salt) resulted in about doubling the productivity of the CO/ethene copolymerization in a water/methanol (30/2) solvent (1.7 kg vs. 0.9 kg copolymer (g Pd)" h" under conditions of [59]) probably due to the concentration of the cationic Pd-catalyst at the interphase region or around the micelles which solubilize the reactants and products. Unfortunately under such conditions stable emulsions are formed which prevent the re-use... 

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