Ethylene-hexene copolymers

This new family of polyolefin copolymers hcis a significantly different chain microstructure than conventional LLDPE.The single site characteristics of metallocenes, with the catalyst site being identical, are known to produce materials having the most probable molecular weight distribution /M 2.0), with essentially a random comonomer distribution and narrow composition distribution. The comonomers most frequently used commercially are butene, hexene, and octene. Copolymerization of ethylene with 4-methyl-l-penetene (4-MP-l) and cyclic and bicylic groups has been also reported in the literature. Several terpolymers are also commercially available.Exxon Chemical Company manufactures ethylene-butene copolymers, ethylene-hexene copolymers, and terpolymers of butene and hexene comonomers. Exxon markets these mLLDPEs under the trademark name of... 

Rytter et al. reported polymerizations with the dual precatalyst system 14/15 in presence of MAO [30]. Under ethylene-hexene copolymerization conditions, 14/MAO produced a polymer with 0.7 mol% hexene, while the 15/MAO gave a copolymer with ca. 5 mol% hexene. In the mixed catalyst system, the activity and comonomer incorporation were approximate averages of what would be expected for the two catalysts. Using crystallization analysis fractionation (CRYSTAF) and differential scanning calorimetry (DSC) analysis, it was concluded in a later paper by Rytter that the material was a blend containing no block copolymer [31],... 

C are given in Table IV. The relatively greater proportion of 1-butene from ethylene-hexene copolymers indicates that there are two mechanisms for the formation of the butenes, one involving the butyl branches and that this pathway yields a much higher proportion (perhaps 100%) of 1-butene. The C4 hydrocarbons are apparently also formed by fragmentation of chain ends in the polymers. These are probably formed mainly by radiation-induced scission. 

The second polymer (sample E) was an ethylene-hexene copolymer which Is slightly branched, and had an My of 211,000 and a nominal density of 0.955 g/cm. Specimens approximately one millimeter thick were prepared from both polymers by molding flat sheets from which dumbbell-shaped bars were cut with a die. The sheets were molded by heating the polymer for ten minutes at 440K In a press at which time the heat was turned off and pressure applied. The polymer was then cooled In the press over... 

As in the case of the linear polyethylene, a quite similar behavior was found for the branched ethylene-hexene copolymer. 

Lower activation temperatures are usually preferred in commercial operations, despite the lower activity. The corresponding redistribution of sites results in improved polymer physical properties. An example is shown in Table 12, which is a list of the ESCR values, the resistance to chemical attack, of several ethylene-butene and ethylene-hexene copolymers. These copolymers were made at constant MI and density with Cr/ silica catalysts activated at various temperatures. The measured ESCR value decreases as the activation temperature is raised. This change results in part because the MW distribution is narrowed, but more so because the longest chains contain less branching.13... 

As noted in Section 6.9, when added to the reactor in trace amounts, some polar compounds can selectively inhibit some sites in preference to others. In addition to affecting the MW distribution, they sometimes have an influence on the branch content and distribution as well. An example of this behavior is shown in Figure 44. Ethylene-hexene copolymers were produced with a Cr/silica-titania catalyst activated at 850 °C. Methanol was added to the polymerization reactor in incrementally greater amounts to "titrate" the activity of the catalyst. As expected, the activity declined as methanol was added, reaching nearly zero at about three CH3OH molecules/Cr atom. The average polymer MW increased as methanol was added. The results imply that some sites, those more... 

SCHEME 19 Block- versus isolated branching in ethylene-hexene copolymer. 

Fig. 13. Load-extension curves for ethylene-Hexene. 1 copolymers A 4 butyl/103C B 1 butyl/10 0 C homopolymer...

Yamaguchi et al. subsequently investigated the mechanical properties of blends of polypropylene with ethylene-hexene copolymers (110,111). Interestingly... 

As discussed earlier, ethylene propylene rubber (EPR or EPM) has been blended with PP and PE to improve the impact strength and to render the materials softer. Recently, metallocene catalysts or postmetallocene catalysts provide new pathways to generate elastic copolymers that can replace EPR. These pathways possess cheaper manufacturing cost and generate new materials with better compatibility to PP or PE. Such new materials included ethylene-propylene random copolymers with dominant ethylene component (33-34) or propylene-dominant component (35 1), propylene-ethylene block copolymer (42), ethylene-octene copolymer (43), poly(propylene-co-ethylene) (44), ethylene-hexene copolymer (45), ethylene-butene copolymer (46), low isotactic PP (47), and stereoblock PP (48). These materials are generally compatible with PP or PE, thus can be used to tailor the toughness (or the softness) of... 

DO1 Dorr, H., Kinzl, M., and Luft, G., The influence of inert gases on the high-pressure phase equilibria of EH-copolymer/l-hexene/ethylene-mixtuies, Fluid Phase Equil, 178, 191, 2001. 

Elston from DuPont Canada Ltd. patented Advanced SCLAIRTECH technology with a single-site catalyst, which produced a bimodal ethylene-hexene copolymer for films or injection moldings... 

Compositions comprised 10-80 wt% low-MW polyethylene, HOPE [p > 940 kg m ], and 20-90 wt% high-MW ethylene-hexene copolymer, LLDPE [p < 955 kg m ]. The blends had a MFI > 0.05 g/10 min. The blend showed improved optical and physical properties, resulting in better blow- molded products ... 

Six companies currently market metallocene plastomers. Exxon Chemical manufactures and markets ethylene-butene and ethylene-hexene copolymers under the EXACT tradename. Dex-Plastomers, a joint venture of Exxon Chemical and DSM, manufactures ethylene-octene copolymers under the EXACT tradename, which are sold by both partners. Dow Chemical and DuPont Dow Elastomers offer ethylene-octene copolymers. Their tradenames are, respectively, AFFINITY and ENGAGE. Japan Polychem manufactures and markets ethylene-hexene copolymers under the KERNEL tradename. Mitsui Petrochemical manufactures propylene, butene, and octene copolymers sold under the TAFMER tradename, along with nonmetallocene plastomers. 

L. Jasinska-Walc, M.R. Hansen, D. Dudenko, A. Rozanski, M. Bouyahyi, M. Wagner, R. Graf, R. Duchateau, Topological behavior mimicking ethylene-hexene copolymers using branched lactones and macrolactones, Polym. Chem. 5 (2014) 3306-3310. 

The miscibility of PP with other hydrocarbon polymers has also been studied recently. Yamaguchi et al. [7] examined blends of PP with ethylene-hexene and ethylene-butene copolymers by microscopy and thermal analysis. The copolymers that had large amounts of the... 

Figure 4.4 C-NMR spectrum of ethylene-hexene-1 copolymer showing chemical shift assignments. Reproduced with permission from H.N. Cheng and M. Kakugo, Macromolecules, 1991, 24, 1724. 1991, ACS...

De Footer and co-workers [19] applied C-NMR spectroscopy at sample temperatures of 130 "C to branching studies of copolymers ethylene with 1-10 mole% of propylene, butene-, hexene-1, octene-1 and 4 methyl pentene-1. C-NMR spectra were recorded with proton noise decoupling to remove unwanted scalar... 

Figure 10.7 Single branched fragments (Cjo) from ethylene-hexene-1 copolymer. Reproduced with permission from M. Seeger and E.H. Barrall,/oz/m/j/ of Polymer Science, Polymer Chemistry Edition, 1975,13, 7,1515. 1975, Wiley...

Table 10.14 Areas of the main iso-alkane peaks in the pyrograms of linear polyethylene, ethylene - butene-1, ethylene - hexene-1 and ethylene - octene-1 copolymers. ...

---