Polyethylene production,

High density polyethylene (HDPE) is defined by ASTM D1248-84 as a product of ethylene polymerisation with a density of 0.940 g/cm or higher. This range includes both homopolymers of ethylene and its copolymers with small amounts of a-olefins. The first commercial processes for HDPE manufacture were developed in the early 1950s and utilised a variety of transition-metal polymerisation catalysts based on molybdenum (1), chromium (2,3), and titanium (4). Commercial production of HDPE was started in 1956 in the United States by Phillips Petroleum Company and in Europe by Hoechst (5). HDPE is one of the largest volume commodity plastics produced in the world, with a worldwide capacity in 1994 of over 14 x 10 t/yr and a 32% share of the total polyethylene production. 

By the mid-1990s capacity for polyethylene production was about 50 000 000 t.p.a, much greater than for any other type of plastics material. Of this capacity about 40% was for HDPE, 36% for LDPE and about 24% for LLDPE. Since then considerable extra capacity has been or is in the course of being built but at the time of writing financial and economic problems around the world make an accurate assessment of effective capacity both difficult and academic. It is, however, appeirent that the capacity data above is not reflected in consumption of the three main types of material where usage of LLDPE is now of the same order as the other two materials. Some 75% of the HDPE and LLDPE produced is used for film applications and about 60% of HDPE for injection and blow moulding. 

Mention may also be made of an application in which careful control of polymer morphology has led to the production of novel materials. By treatment of solutions of high-density polyethylene, products are obtained with a celluloselike morphology and which are known as, fibrides or synthetic wood pulp. They are used for finishing paper and special boards to impart such features as sealability and improved wet strength. They are also reported to be used for such diverse applications as tile adhesives, thixotropic agents, battery separators and teabags ... 

S. S. Mindlin and N. N. Samosatsky, Production of Polyethylene Products by the Extrusion Method, Goschimizdat Publishers (1959). 

Polyethylene is an inexpensive thermoplastic that can be molded into almost any shape, extruded into fiber or filament, and blown or precipitated into film or foil. Polyethylene products include packaging (largest market), bottles, irrigation pipes, film, sheets, and insulation materials. 

A number of highly active ethylene polymerisation catalysts have resulted from the combination of functionalised NHC ligands with Ti, the first of these was the bis(phenolate)carbene ligated complex 3 [8], Upon activation with modified MAO (MMAO), this species gave an activity of 290 kg-mol bar h in the one test reported, making it one of the most active carbene-based olefin polymerisation catalysts known. In later work the same complex was evaluated with straight MAO activation, and activities of up to ca. 100 kg mol -bar" -h" were reported for linear polyethylene production [9],... 

A proposed expansion of the corporation s polyethylene production capacity will require additional ethylene monomer as a feedstock. It is suggested that the ethylene be produced by the pyrolysis of a propane stream that is available at axrate of 7000 lb/hr. 

The release occurred in the polyethylene product takeoff system, as illustrated in Figure 1-12. Usually the polyethylene particles (product) settle in the settling leg and are removed through the product takeoff valve. Occasionally, the product plugs the settling leg, and the plug... 

Polyethylene polymers history of, 17 701-702 simulations of, 16 747 Polyethylene products, Ziegler-Natta catalysts for, 26 540-543 Polyethylene resins, 17 700-703 applications for, 17 703 Polyethylenes, classification of, 17 701t. 

In 1971, LDHs containing different metal cations (such as Mg, Zn, Ni, Cr, Co, Mn and Al) with carbonate as interlayer anions, calcined at 473-723 K and partially or completely chlorinated, were reported to be effective as supports for Ziegler catalysts in the polymerization of olefins [8], with the maximum catalytic activity of polyethylene production observed for Mg/Mn/Al - CO3 LDH calcined at 473 K. Even earher, calcined Mg/Al LDHs were used to support Ce02 for SO removal from the emissions from fluidized catalytic cracking units (FCCU) [9,10]. Some transition metal oxides have also been... 

The catalyst preparation area is positioned between the two polyethylene production units with 60 feet separating each one. The aluminum alkyls storage canopy and isopentane horizontal storage tank are located at a remote area at an approximate distance of 250 feet away from the production and utility areas. The isopentane is transported to the catalyst preparation area through a 3-inch pipeline. A remote actuated isolation valve on this supply line that fails closed is located at the isopentane storage tank. This control valve and an associated isopentane feed pump are managed by the operator in the control room. 

A somewhat different type of polyethylene is low density polyethylene (LDPE). This oldest member of the polyethylene product family differs structurally from the linear polyethylenes by being highly branched and... 

The discovery of the Ni effect led to the invention of polyethylene production catalysed by TiCI4 combined with Et3Al, the so-called the Ziegler catalyst, in 1953. Soon after, the process for isotactic polypropylene was invented by Natta using a slightly modified catalyst prepared from TiCl3 and Et3Al, which is called the Natta catalyst (eq. 1.7) [7],... 

From a practical point of view, one of the most challenging applications to date has been in the experimental fluidised bed shown in Figure 3, which is a scaled-down version of a polyethylene production unit, of overall height approximately 2 m, with a conical expansion section 1 m above the distributor the diameter of the lower section is 0.154 m. The bed is constructed of 316 stainless steel and is placed within a gas circulation loop allowing operation at pressures up to 20 bars. 

Supported CrC>3 catalysts, referred to as Phillips catalysts, are important industrial catalysts and are employed in high-density polyethylene production. Phillips catalysts polymerise ethylene with an induction period, which has been ascribed to the slow reduction of Cr(VI) by the monomer and to the displacement of oxidation products (mainly formaldehyde) from the catalytic species [226]. The prereduction of the catalyst with the use of H2 or CO enables the induction period to be eliminated. Active sites thus formed involve surface low-valence Cr(II) and Cr(III) centres, which can appear as mononuclear (formed from chromate species) and binuclear (formed from dichromate species) [227-232],... 

In contrast to polyethylene production, solution polymerisation at high temperature is rarely applied for isotactic polypropylene, but some special-purpose polypropylene grades are manufactured (Figure 3.57) [51]. However, the solution process, which yields isotactic polypropylene with a very low level of impurities, is characterised by high overall costs. The solution process is being used to make atactic polypropylene, to which it seems more suited [43],... 

LC2) or b) the reaction temperature T2 (if allowed), which affects the rate constant k. Figure 4.4(b) shows that, whenever Da < 2, this strategy requires moderate changes of the manipulated variables. We note that there are many situations when a large reactor cannot be used. For example, in the polyethylene production, the high operating pressure requires a small reactor. In addition, the molecular weight distribution of the final product and difficult heat transfer due to the gel effect favor low conversion, and thus small reactors. 

Polyolefin Production Plastic Resin Polypropylene Production Polyethylene Production... 

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