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Polymerization processes low pressure

Conventionally, HAS are blended with PO during processing. 2-(Diethy-lamino)-4,6-bis[butyl(l,2,2,6,6-pentamethyl-4-piperidyl) amino]-l,3,5-triazine may be fed with an olefin directly into the low pressure polymerization process catalyzed with a modified MgCl2 supported Ziegler-Natta catalyst [142]. The catalytic activity was not impaired [143], Tetramethylpiperidine was reported to be a useful component in MgC -supported Ziegler-Natta catalysts as well. Very high stereospecificity of the synthesised PO was achieved. A complex of HAS with the alkyl aluminium activator was envisaged without interaction with the catalytically active alkyl titanium compound [144],... [Pg.125]

During the late 1970s, Union Carbide developed a low-pressure polymerization process (Unipol process) capable of producing polyethylene in the gas phase that required no solvents. The process employed a chromium based catalyst. In this process (Figure 4.1) ethylene gas and solid catalysts are fed continuously to a fluidized bed reactor. The fluidized material is polyethylene powder which is produced as a result of polymerization of the ethylene on the catalyst. The ethylene, which is recycled, supplies monomer for the reaction, fluidizes the solid, and serves as a heat-removal medium. The reaction is exothermic and is normally run at temperatures 25-50°C below the softening temperatures of the polyethylene powder in the bed. This operation requires very good heat transfer to avoid hot spots and means that the gas distribution and fluidization must be uniform. [Pg.384]

The low-pressure polymerization processes were originally used in a single reactor configuration, but since the 1970s more complex polymerization systems have been developed that utilize two or more reactors that are in parallel and/or in series. Consequently, the polymerization conditions in each reactor may be varied over a wide range so that the final polyethylene material manufactured has a complex molecular structure, which is designed to provide various premium-grades of polyethylene that are suited for specific markets and applications. [Pg.227]

With the combined capabilities of high and low pressure production facilities it became possible to produce polyethylene resins with densities in a range of 0.91-0.96 g/cm This increased the range of products over those available prior to 1955 and permitted polyethylene to penetrate new markets and increase its utilization in existing ones. Research and development continued on both the high and low pressure polymerization processes with the goal of tailoring resins to meet the requirements of more specialized markets. [Pg.38]

Polyethylene. Low pressure polymerization of ethylene produced in the Phillips process utilizes a catalyst comprised of 0.5—1.0 wt % chromium (VI) on siUca or siUca-alumina with pore diameter in the range 5—20 nanometers. In a typical catalyst preparation, the support in powder form is impregnated with an aqueous solution of a chromium salt and dried, after which it is heated at 500—600°C in fluid-bed-type operation driven with dry air. The activated catalyst is moisture sensitive and usually is stored under dry nitrogen (85). [Pg.203]

A more recent development in ethylene polymerization is the simplified low pressure LDPE process. The pressure range is 0.7—2.1 MPa with temperatures less than 100°C. The reaction takes place in the gas phase instead of Hquid phase as in the conventional LDPE technology. These new technologies demand ultra high purity ethylene. [Pg.432]

PE produced by a high-pressure polymerization process (pressure 1000-3000 atm) using a free radical initiator is a highly branched material that contains both LCBs and SCBs. The polymer so produced is a low-density material (density up to about 0.925 g/cc) and is known as high-pressure low-density PE (HP LDPE). The LCBs are formed via intermolecular hydrogen transfer [19], whereas SCBs are formed by intramolecular hydrogen abstraction [16]. [Pg.278]

The main use of propylene is for polymerization to polypropylene, a process similar to the manufacture of high-density polyethylene (i.e., a low-pressure, catalytic process). Textile hhers made from polypropylene are relatively low-cost and have particularly good properties, such as high resistance to abrasion and soiling for use in furniture upholstery and indoor/outdoor carpeting. [Pg.127]

In many cases, the linear low-density polyethylene (LLDPE) produced in low-pressure processes competes for the same market as LDPE. For this reason, in Figure 8.2-7 capital- and operation costs of the high-pressure polymerization are compared with those of a low-pressure solution process having the same capacity. Also, the production costs of the low-pressure process are dominated by the costs of the monomer, but some differences can be noted which are typical for the economics of low- and high-pressure processes. [Pg.458]

Above all, the total costs of the low-pressure solution process are 1,393 DM/t compared to 1,491 DM/t of the high-pressure polymerization, which is a difference of 7%. However, it must be mentioned that the average European sales prices of standard film-grades LDPE in recent years have been higher by 100 to 200 DM/t than those of LLDPE [3]. [Pg.459]

What happens in a low-pressure plasma process cannot be determined in an a priori manner based only on the nature of the plasma gas or on the objective of the process. The plasma sensitivity series of elements involved, in both the luminous gas phase and the solids, that make contact with the luminous gas phase seems to determine the balance between ablation and polymerization by influencing the fragmentation pattern of molecules in the luminous gas environment. [Pg.199]

Although low-pressure plasma treatment and plasma polymerization are the main tool of the interface engineering described in this book, SAIE does not necessarily require low-pressure plasma processes. Some excellent corrosion... [Pg.582]

The revolutionary discoveries by Ziegler and Natta, relating to the low pressure polymerization, respectively, of ethylene and of propylene and other a-olefins onto the previously unknown crystalline polymers, opened a new era in science and technology. Since then, remarkable progress has been made in the fields of coordination catalysis, macromolecular science and stereochemistry. With the discovery and development of the new generation catalytic systems for polyethylene in the late 1960 s, and more recently for polypropylene, enormous progress was made in terms of polymerization process as to economics and product quality Further process simplification and, above all, ever more accurate product quality control by taylor made catalytic systems is the aim of the 1980 s. [Pg.103]

Although the low-pressure polymerization of ethylene in the presence of a Ziegler catalyst is a catalytic process, the growth reaction of aluminum hydride or a corresponding alkylaluminum with ethylene occurs as an organometallic synthesis 29 at 60-80° aluminum hydride reacts with ethylene to yield tri-ethylaluminum ... [Pg.851]

A. von Grosse, J. M. Mavity, J. Org. Chem. 5, 106 (1940). Recent pressure processes for aluminumtrialkyls starting with Al, Ha and olefins, as well as their applications to the low-pressure polymerization of ethylene, are given in K. Ziegler et al., Angew. Chem. 67 424 (1955). [Pg.810]

Low-pressure polymerizations were initiated by ultraviolet radiation in the presence of di-iert-butyl peroxide in bulk, dimethyl sulfoxide, or /ert-butanol solution at — 20°C to -I- 30°C. While the polymer precipitated out of solution at low conversion, in dimethyl sulfoxide, this precipitate was a gel which was partially transparent to light. At low conversions, the reaetion kinetics were treated as pseudohomogeneous processes [15]. [Pg.348]

Most importantly the development of gas-phase processes allowed the energy-intensive high-pressure polymerization process to be replaced by the far more energy-efficient low-pressure process. The gas-phase processes offer the greatest versatility of products in terms of resin density and melt index of polyethylenes. From an environmental standpoint the gas-phase reaction is of particular interest and offers several advantages over the conventional technology as recently summarized by Joyce [9]. [Pg.90]


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Low Processing

Low pressure

Low pressure polymerization

Low pressure processing

Low-pressure process

Pressure process

Pressures processing

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