Ethylene-l-octene copolymer

The ability to control the polymer from the design of the catalyst, coupled with high catalytic efficiency has led to an explosion of commercial and academic interest in these catalysts. Exxon started up a 30 million lb/5rr ethylene copol3rmer demonstration plant in 1991 using a bis-cyclopentadienyl zirconium catalyst of structure 1. The Dow Chemical Company (Dow) began operating a 125 million Ib/yr ethylene/l-octene copolymer plant in 1993 and has since expanded production capacity to 375 million Ib/yr. This paper will focus on the structure / property relationships of the catalysts used by Dow to produce single-site ethylene a-olefin copolymers. 

For the production of ethylene/l-octene copolymers, metallocenes in combination with oligomeric methylalumoxanes or other compounds are now used [31, 63]. Half-sandwich transition metal complexes such as [(tetramethyl- / -cyclopentadienyl) (A-/-butylamido)dimethylsilyl]titanium dichloride are applied to synthesize linear low-density copolymers and plastomers, called constrained geometry catalysts [31]. Ethylene and styrene can be copolymerized to products ranging from semicrystalline mbber-like elastomers to highly amorphous rigid materials at room temperature [64]. 

Figure 6 Mole Percent 1-Olefin Versus Density for a Series of Ethylene-l-Butene, Ethylene-1-Hexene and Ethylene-l-Octene Copolymers...

Bovey et al.(3) also observed both H-links and Y branches in an NMR study of a normal alkane irradiated in vacuum in the molten state. The long chain Y branch was easy to recognize in the present study because of the presence of a methine resonance at 38.19 ppm, an a methylene resonance at 34.55 ppm and a P methylene resonance at 27.30 ppm. These assignments are in excellent agreement with those of Bovey et al. (3) and correspond closely to the methine and a, p methylene resonances observed for an ethylene-l-octene copolymer as shown below ... 

Chemical Shifts Backbone Chemical Shifts Y Branch (3) Ethylene-l-Octene Copolymer... 

Kilburn, D., Bamford, D., Liipke, T., Dlubek, G., Menke, T. J., and Alam, M. A., Free volume and glass transition in ethylene/l-octene copolymers positron lifetime studies and dynamic mechanical analysis, Polymer, 43, 6973-6983 (2002). 

Kolesov and Radusch prepared peroxide cross-linked binary and ternary blend SMPs from high density polyethylene and two ethylene-l-octene copolymers with medium and high degrees of branching [47]. The blends were prepared by a melt mixing and subsequently are cross-linked with 2 wt% of liquid peroxide 2,5-dimethyl-2,5-di-(tertbutylperoxy)-hexane at 190°C. The blends showed multiple shape memory behavior that appeared only at consequent stepwise application of convenient programming strains and temperatures. Obviously, that is caused by multiple melting behavior of these blends with many poorly separated peaks. 

The Jerome group made day nanocomposites containing ethylene/l-octene copolymers and ethylene/l-octene/l,9-decadiene terpolymers using the catalyst XX. To avoid... 

K. Surlya, S. Anantawaraskul, J.B.P. Soares, Cocrystallization of ethylene/l-octene copolymer blends during crystallization analysis fractionation and crystallization elution fractionation. J. Polym. Sci. B Polym. Phys. 49, 678-684 (2011)... 

While the range of the new metallocene-based polymers includes such specialty polymers as cyclo-olelin copolymers (COC), syndiotactic polystyrene, ethylene/ styrene copolymers, which are stiU in the developmental stage, commercially, the most prominent candidates are the elhylene/a-olefin copolymers such as ethylene/ butylene or hexene copolymers (Exxon s Exact ) or ethylene/l-octene copolymers (Dow s Engage and Affinity ). Depending on the comonomer content, these copolymers have been classified as plastomers or elastomers. At comonomer levels of >25 %, the copolymers exhibit the characteristics of thermoplastic elastomers such as high softness, toughness, flexibility, and resilience and hence been referred to as polyolefin elastomers (POE). CompositionaUy, these POEs usually contain 65 % ethylene and 35 % octene-1, hexene-1, or butene-1 as comonomers. 

Chang and co-workers (52,53) studied the large-scale deformation behavior and recovery behavior of semicrystalline ethylene-co-styrene polymers as a function of temperature, comonomer content, and crystallinity and compared them to the behavior of metallocene-produced ethylene/l-octene copolymers. Chen and co-workers (54) have provided an in-depth comparison of the morphological structure and properties of copolymers and confirmed that aspects of deformation that depended on crystallinity, such as yielding and cold drawing, were determined primarily by comonomer content for both sets of copolymers. 

Fig. 22. Comparison of Crystaf profiles and Stockmayer s distributions for a series of ethylene/l-octene copolymers. Experimental Crystaf curves are indicated with syrmbols and the solid curves are the respective Stockmayer s distributions. Sample A sample D A sample H. Molecular weights of samples A = 29 600 D = 38 000 H Mn =...

Ahzadeh, A. Richardson, L. Xu, J. McCartney, S. Maraud, H. Cheung, Y. W. Chum, S. Influence of structural and topological constraints on the crystallization and melting behavior of polymers. 1. Ethylene/l-octene copolymers. Macromolecules 1999, 32, 6221-6235. 

Fig. 39 Effect of comonomer type on cocrystallization at a cooling rate of 0.1 °C/min for blends with the same comonomer type. BPED blend of ethylene/1-dodecene copolymers, BPEO blend of ethylene/l-octene copolymers BPEH blend of ethylene/1-hexene copolymers, BPEP blend of ethjdene/propylene copolymers [67]...

Further work has resulted in ADMET copolymer models of ethylene/l-hexene [141], and ethylene/l-octene [142]. Commercial ethylene/1-octene copolymers represent a significant portion of the linear low-density PE market however, the ADMET model polymers, with hexyl branches on every 9th, 15th, or 21st carbon, displayed much better thermal profiles than those seen with ethylene/l-octene copolymers produced by other methods. Additionally, the thermal properties of these hexyl-branched ADMET polymers were similar to those of their methyl-branched ADMET polymer analogs. This observation points to the possible... 

Backbone Chemical Shifts Ethylene-l-Octene Copolymer... 

This technique was employed to visualize the morphology of polymer blends comprising HOPE and an ethylene/l-octene copolymer (EOC Tkffrnity EG 8150, a commercial product of the Dow Chemical Company) which had a relatively high 1-octene content [57]. The representative results are presented in Figure 17.2. 

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