High-pressure copolymerization

One of the simplest polymers containing the ketone group can be synthesized by the high pressure copolymerization of ethylene and carbon monoxide ... 

Section 4.6.2 illustrates the experimental procedures that have recently been applied toward the study of high-pressure free-radical polymerization processes. Section 4.6.3 presents results of propagation, termination, chain-transfer (to monomer and to polymer), and P-scission rate coefficients for ethene homopolymerization. Recent results from experiments and modeling investigations into high-pressure copolymerizations (with ethene being one of the monomers) are reported in Section 4.6.4, together with information on homopolymerization rate coefficients of the comonomer species. 

It goes without saying that modeling of ethene high-pressure copolymerizations requires a significant number of additional reaction steps to be included. 

Ethylene Acrylic Acid Copolymer Specialty thermoplastic created by high-pressure copolymerization of ethylene (E), methacrylic acid (MAA), or acrylic acid (AA). Also called EAA. 

High-pressure copolymerization of ethylene with acrylic acid esters and with (meth)acrylic acid are other important technical processes that are run under supercritical conditions close to those of high-pressure ethylene polymerization (6, 6b). 

E/CO is produced commercially by the high-pressure copolymerization of ethylene and carbon monoxide using techniques similar to those used to make high-pressure, low-density polyethylene homopolymer (LDPE). The monomers undergo random copolymerization under well-controlled temperatures and pressures in either tubular or stirred autoclave reactors ... 

Ethene high-pressure copolymerization smdies have also been carried out for the systems E-MMA, E-BMA, E-acrylic acid, and E-methacrylic acid. Whereas the comonomer reactivity ratios turn out to be slightly different, the ethene reactivity ratios for the entire set of (meth)acrylates and for (meth) acrylic acid are remarkably close to each other. The similarity of rE = feEE/ Ex is probably due to the crosstermination propagation rate coefScient rate ftEx being dominated by the highly reactive ethene-terminated radical. ... 

When r and ri should be calculated for high-pressure copolymerization, following Alfrey and Price, the pressure dependence of Q, e data must be taken into account. Some values of Q and e for high pressures are collected in Section G. The dependence of the e data of two monomers on pressure is given by the equation... 

Polyethylene can be chlorinated in solution in carbon tetrachloride or in suspension in the piescnce ot a catalyst. Below 55-60% chlorine, it is more stable and more compatible with many polymers, especially polyvinyl chloride, to which it gives increased impact strength. The low pressure process copolymerizes polyethylene with propylene and butylene to increase its resistance to stress cracking. Copolymerization with vinyl acetate at high pressure increases flexibility, resistance to stress cracking, and seal ability of value to the food industry. 

Ionomers are made in a two-stage process. In the first step, we copolymerize ethylene with small amounts of an organic acid containing a vinyl group, such as acrylic or methacrylic acid, in a high pressure reactor. In the second step, we neutralize the acid comonomers to form metal salts. We can create ionomers with a variety of metal salts, including sodium, calcium, and zinc. 

Coordination copolymerization of ethylene with small amounts of an a-olefin such as 1-butene, 1-hexene, or 1-octene results in the equivalent of the branched, low-density polyethylene produced by radical polymerization. The polyethylene, referred to as linear low-density polyethylene (LLDPE), has controlled amounts of ethyl, n-butyl, and n-hexyl branches, respectively. Copolymerization with propene, 4-methyl-1-pentene, and cycloalk-enes is also practiced. There was little effort to commercialize linear low-density polyethylene (LLDPE) until 1978, when gas-phase technology made the economics of the process very competitive with the high-pressure radical polymerization process [James, 1986]. The expansion of this technology was rapid. The utility of the LLDPE process Emits the need to build new high-pressure plants. New capacity for LDPE has usually involved new plants for the low-pressure gas-phase process, which allows the production of HDPE and LLDPE as well as polypropene. The production of LLDPE in the United States in 2001 was about 8 billion pounds, the same as the production of LDPE. Overall, HDPE and LLDPE, produced by coordination polymerization, comprise two-thirds of all polyethylenes. 

Tphis paper is concerned with the effect of ionizing radiation on the physical and mechanical properties of copolymers of ethylene with alkyl acrylates, such as ethyl acrylate, butyl acrylate, and 2-ethvlhexyl acrylate (J, 2, 3). These polymers are made by the free radical copolymerization of ethylene under high pressure with alkyl esters of acrylic acid (9). They are more flexible than polyethylene and because of the polar nature of the comonomer, they are more compatible with fillers and with other polymers than is polyethylene. 

Because of its commercial importance, the polymerization of ethylene at high pressure has been extensively studied.204-209 Free-radical polymerization is characteristic of ethylene and vinyl compounds. Simple alkenes, such as 1-butene, however, do not give high-molecular-weight polymers, but they, as well as internal alkenes, can copolymerize with polymerizable monomers. 

Loss prevention of polyethylene plants is outlined in Chapter 7.2. The major hazard that can occur is the runaway of the high-pressure reactor and decomposition of ethylene besides fire and disintegration of high-pressure separators, pipes, and compressors. The critical conditions for runaway and ethylene decomposition during homo- and copolymerization are revealed together with the influence of decomposition sensitizers. Relief devices and venting systems are described. 

Vinylene carbonate is one of the few 1,2-disubstituted ethylenes that is known to undergo facile radical initiated homopolymerization. Initiation may be by oxygen, peroxides or cobalt-60 y-radiation. Such polymers are reportedly useful as coatings and films. Vinylene carbonate also copolymerizes with ethylene under high pressure to yield a material with about 10% vinylene carbonate content. This polymer, when blended with polyvinyl chloride, is suitable for injection molding. 

Besides the performance of metallocene catalysts in the homopolymerization of ethylene also their ability for copolymerization under high pressure was proofed. As comonomers a number of 1-olefins and dienes were used. In Figure 5 the change of the productivity with the concentration of the comonomer in the feed is shown for the copolymerization of ethylene with... 

Historically, high-pressure free radical copolymerization has been used to produce highly branched, ill-defined copolymers of ethylene and various polar monomers. Although these materials are in production and extensively used throughout the world, the controlled incorporation of polar functionality coupled with linear polymer structure is still desired to improve material properties. Recent focus in this area has led to the development of new transition metal catalysts for ethylene copolymerization however, due to the electro-philicity of the metal centers in these catalysts, polar functional groups often coordinate with the metal center, effectively poisoning the catalyst. There has b een some success, but comonomer incorporation is hard to control, leading to end-functionalized, branched polyethylenes [44, 46]. These results are undesirable due to low incorporation of polar monomer into the polymer as well... 

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