Ethylene/1-olefin

Ethylene-1-butene copolymers, 20 180 Ethylene-1-olefin copolymerization, 26 525 Ethylene-acrylic elastomers, 10 696-703 commercial forms of, 10 697-698 dynamic mechanical properties of,... 

The high-temperature solution process is state-of-the-art for the production of ethylene homopolymers as well as ethylene/1-olefin copolymers with a wide range of average molecular mass and copolymer composition [15]. This process is performed in a CSTR or in a cascade of two reactors, like the low-temperature process. Only the downstream equipment is different. The diluent is an aliphatic hydrocarbon such as cyclohexane, n-hexane, or a Cg-Cio alkane fraction. Homogeneous catalyst and co-catalyst are fed into the polymerization reactor mixed with solvent. Ethylene, hydrogen to regulate average molecular mass, and the comonomer are injected either as a gas or as a liquid. Temperature can be con-... 

Keywords Living polymerization, Living copolymerization, Rare earth metal complexes, Alkyl methacrylate, Alkyl acrylates, Lactones, Ethylene, 1-Olefins, Conjugated dienes, Acetylene... 

Organo rare earth metal initiators also show good activity towards non-polar monomers such as ethylene, 1-olefins, styrene, conjugated dienes, and acetylene... 

There is other useful information that can be determined from an n-ad distribution, for example how well a secondary comonomer is dispersed among the primary repeat units. Two approaches are commonly used to indicate the degree of clustering of ethylene units in an ethylene-1-olefin copolymer [4]. One involves a direct empirical measurement of clustering, the monomer dispersity (MD), and the other utilizes the Bernouillian distribution as a reference point for establishing the degree of clustering and is denoted the cluster index (Cl). These numbers are... 

Recently, Ni- and Pd-based catalysts have been developed in order to copolymerize nonpolar ethylene, 1-olefins or cycloolefins with polar comonomers, such as carbon monoxide and methyl acrylate or 1-olefins, containing polar groups which are separated by at least two methylene... 

For ethylene/1-olefin copolymers, chain crystaUizabihty is mainly controlled by the fraction of noncrystalhzable comonomer imits in the chain. Consequently, the differential Crystaf profile shown in Fig. 1, together with an appropriate cahbration curve, can be used to estimate the copolymer chemical composition distribution (CCD), also called the short-chain branch distribution. The CCD of a copolymer describes the distribution of the... 

Comonomer content significantly affects Tref profiles. This is to be expected, as the comonomer units are known to reduce chain regularity, thus lowering chain crystallizability [26,27]. Linear relationships between average comonomer contents (CC) and elution peak temperatures are generally observed for ethylene/1-olefin copolymers [5,6]. It is important that these relationships reflect only the influence of comonomer content because they are used as calibration curves to convert Tref profiles into CCDs. 

Perhaps one of the greatest contributions of Tref to the understanding of olefin polymerization was the elucidation of the natiue of active sites present on heterogeneous Ziegler-Natta catalysts. The systematic apphcation of Tref to ethylene/1-olefin copolymers made with heterogeneous Ziegler-Natta catalysts in different polymerization processes has shown that aU these resins have a signature bimodal Tref peak that can only be explained by the presence of two or more distinct types of active sites on the catalyst [34]. In contrast, low-density polyethylene (LDPE) made with the free-radical mechanism has a much narrower and unimodal Tref profile (Fig. 18), as expected from a free-radical polymerization mechanism. 

In P-Tref/SEC cross-fractionation, copolymer chains are first fractionated according to comonomer composition into a series of fractions using P-Tref. Each fraction is then analyzed using SEC to obtain its MWD. P-Tref/SEC is a very powerful cross-fractionation technique because it provides information on the bivariate comonomer composition and MWD. Although the process is still time-consuming, the information obtained with P-Tref/SEC crossfractionation provides an almost complete map of chain microstructures. This cross-fractionation technique has been used for various ethylene/1-olefin copolymers (1-butene, 1-hexene, 1-octene, and l-pentene-4-methyl). 

Because of the complexity of the fractionation mechanism, not many mathematical models have been proposed to describe separation with Tref. Soares and Hamielec [47] used Stockmayer s distribution (Eq. 7) to simiflate the CCD of Hnear binary copolymers synthesized with miflti-site-type catalysts. Under the assumption that the fractionation process of Tref was controlled only by comonomer composition, the CCD was directly converted into the Tref profile using a calibration curve. For the case of ethylene/1-olefin copolymers made with multiple-site catalysts, the CCD of the whole polymer is described as the weighted summation of the CCDs of the copolymers produced by each active site ... 

More recent work by the same research group [60] has investigated the effect of comonomer type using a series of ethylene/1-olefin copolymers (1-decene, 1-tetradecene, and 1-octadecene). Notice that ethylene instead of propylene was used in this particular study. Once more, they reported that Crystaf peak temperatures were practically independent of comonomer type (Fig. 35). 

In our recent work [67], we investigated the effect of comonomer type on CO crystallization using a series of ethylene/1-olefin copolymers with four comonomer types propylene, 1-hexene, 1-octene, and 1-dodecene. Four blends, one for each copolymer type, were prepared such that they crystallized at the same temperature range and had similar ATq to ehminate the effect of similarity of chain crystalHzabihties. The Crystaf results of these blends indicated that the comonomer type of the parent samples did not appreciably influence their cocrystalHzation behavior, as illustrated in Fig. 39. 

Fig. 40 Calibration curves reported for ethylene/1-olefin copolymers (see Table 2 for details of applicable range and conditions)...

We proposed a modified Monte Carlo model [57] based on the distribution of average ethylene sequence lengths, which was found to better represent the Crystaf profiles for a wider range of ethylene/1-olefin copolymers. Figiu e 49 compares the experimental Crystaf profiles with results from the proposed... 

DesLauriers, P.J., Rohlfing, D.C., Hsieh, E.T., Quantifying short chain branching microstructures in ethylene 1-olefin copolymers using size exclusion chromatography and Fourier transform infiared spectroscopy (SEC-FTIR), Polymer 2002,43 159-170. 

This section reviews copolymerization studies and aims to give an overview of research on ethylene-1-olefin copolymerization, the role of ligand substitution in copolymerization and the polymerization mechanisms involved. The copolymerization behavior of a group of siloxy-substituted complexes is discussed because they have the ability to be activated at low MAO ratios and some of them provide excellent comonomer respraise. 

Table 1 Ethylene and 1-olefin reactivity ratios (rg) for selected metallocenes in ethylene/1-olefin copolymerization...

Using a similar polymerization filling process, metallocenes such as Bu2Cp2ZrCl2 were supported by Anselm and Mtilhaupt on FG/MAO in order to copolymerize ethylene with 1-octene (cf. Fig. 11) [177]. As a function of the ethylene/1-olefin feed ratio, varied by increasing the 1 -olefin content from 5 to 50 vol.-% at constant ethylene pressure of 5 bar, the catalytic copolymerization on FG/MAO/ Bu2Cp2ZrCl2... 

These data explain the relatively heterogeneous branching distribution of ethylene/1-olefin copolymers prepared with Ti/Mg Ziegler catalysts. For example, the catalyst prepared without silica contained at least five active sites that exhibited a range of r values from 19 to -180, which varies by a... 

The xmiform branching distribution found in this new type of polyethylene, and the relatively high reactivity of these catalysts with higher 1 -olefins, has allowed the manufacture of ethylene/1-olefin copolymers containing very high levels of comonomer such as 1-butene and 1-hexene, i.e., 5-20 mol% comonomer. Consequently, the density range of the polyethylene... 

This patent disclosed a series of single-site, vanadium-based coordination catalysts for the preparation of ethylene/1-olefin copolymers with an intermolecular uniform branching distribution. The patent describes this preferred branching distribution as a homogeneous branching distribution in which the comonomer is randomly distributed within a given molecule, while the copolymer molecules contain the same ethylene/comonomer ratio. In addition, the copolymers produced with these coordination catalysts possess a narrow molecular weight distribution. 

Elston used copolymer melting point values to determine the branching homogeneity of copolymers noting that ethylene/1-olefin copolymers with a heterogeneous branching distribution show crystalline melting... 

Although ethylene/1-olefin copolymers were well documented in the late 1950s with the discovery of the chromium-based Phillips catalyst and the titanimn-based Ziegler catalyst, it was the discovery of metallocene-based single-site catalysts and the constrained geometry catalyst system that significantly increased the various types of new ethylene-based copolymers that are available for commercial applications. These new catalysts created new products, applications and markets for the polyethylene industry. 

These copolymers behave in a similar manner to ethylene/1-olefin copolymers as the amount of styrene is increased over the range of 20-50 wt%. Melting point temperatures and copolymer crystallinity decrease with increasing amounts of styrene, with the copolymer becoming an amorphous material at about 50 wt% (21 mol%) styrene. 

On February 28,1978, A. W. Anderson and G. S. Stamatoff received US. Patent 4,076,698. It was assigned to DuPont de Nemours and Company and provided DuPont the composition of matter on ethylene/1-olefin copolymers in which the 1-olefin contained 5 to 18 carbons. The original patent was filed on January 4, 1957. After a series of court proceedings that took place in the early 1980s, the court awarded DuPont the composition of matter claim on these copolymers. Hence, any polyethylene producer that offered ethylene/1-hexene or ethylene 1-octene copolymers from approximately 1978-1995 was obligated to pay DuPont a royalty. The copolymers produced by Anderson and coworkers were prepared with the solution... 

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