Ziegler-Natta catalyst high-density polyethylene

Polymerization with Complex Catalysts. High density polyethylene reached a domestic production of 1.25 billion pounds in 1968. It is made either with a stereospecific Ziegler-Natta catalyst or on a supported chromium oxide catalyst. The latter forms a complex with the silica-alumina and is activated by treatment with air and steam at elevated temperature. The mechanism is such that electrons are donated to the catalyst in order to be returned under polymerizational-promoting conditions, consequently lowering the energy of the system ... 

High density polyethylene produced by a low-pressure low-temperature process involving Ziegler-Natta catalysts. This creates low levels of branching and hence a high degree of crystallinity. 

A small number of companies use metal oxide catalysts, such as the example shown in Fig. 18.6, to make high density polyethylene. The polyethylene made with this catalyst generally has a narrower molecular weight distribution than high density polyethylene made with Ziegler-Natta catalysts. 

Ziegler-Natta catalysts are used commercially for the production of stereoregular polymers, especially isotactic polypropylene and high-density linear polyethylene. The resultant polymers have number and weight average molecular weights (Mn and Mw, respectively) that are defined as... 

High-density polyethylene (HDPE) is a commodity chemical that is produced on a very large scale in one of two catalytic processes the Ziegler-Natta and the Phillips process. The latter accounts for about one third of all polyethylene. It uses a catalyst consisting of small amounts of chromium (0.2-1.0 wt% Cr) on a silica support, developed by Hogan and Banks at the Phillips Petroleum Company in the early 1950s [84,85]. 

The Ziegler-Natta catalysts have acquired practical importance particularly as heterogeneous systems, mostly owing to the commercial production of linear high- and low-density polyethylenes and isotactic polypropylene. Elastomers based on ethylene-propylene copolymers (with the use of vanadium-based catalysts) as well as 1,4-cz s-and 1,4-tran.y-poly(l, 3-butadiene) and polyisoprene are also produced. These catalysts are extremely versatile and can be used in many other polymerisations of various hydrocarbon monomers, leading very often to polymers of different stereoregularity. In 1963, both Ziegler and Natta were awarded the Nobel Prize in chemistry. 

Application The Innovene G (gas phase) process produces linear-low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) using either Ziegler-Natta, chromium or metallocene catalysts. 

Application The SCLAIRTECH1 technology (PE) process can produce linear-low-density, medium-density and high-density polyethylene (PE) with narrow to broad molecular weight distribution using either Ziegler-Natta (ZN) or proprietary single-site catalyst (SSC). 

Using Ziegler-Natta catalysts to make high-density polyethylene (Section 30.4)... 

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