Second Generation Ziegler Catalysts

However, in the early 1970s, Ti-based Ziegler catalysts were significantly improved after it was foxmd that the incorporation of magnesium chlorides 

A solution polymerization process was especially useful to commercially produce LLDPE products for the market, while the Phillips loop reactor was somewhat limited in producing LLDPE with relatively lower levels of comonomer in order to avoid process problems, as the solubility of the LLDPE increased in the slurry solvent. The LLDPE became commercially more important in 1977 when Union Carbide developed a high-activity, silica-supported Ziegler catalyst that was utilized to manufacture LLDPE in a gas-phase, fluidized-bed process. 

by the early 1980s, the global polyethylene business consisted of three basic polymer types LDPE, HDPE and LLDPE, as summarized in Table 1.3. 

Since about 1980, each type of polyethylene has xmdergone significant growth because high-pressure produced LDPE and low-pressure produced HDPE and LLDPE each address different markets because of the differences in polymer engineering properties due to the differences in the molecular structure associated with each type of polyethylene. 

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The result of the early work led to development of second-generation Ziegler catalysts (23-29). These are discussed in the next section and include (i) nonsupported trivalent titanium compounds, (ii) products of treating magnesium compounds with titanium compounds, and (iii)... 

Second Generation Ziegler Catalyst for the Manufacture of Polyethylene... 

The activity of these second generation Ziegler catalysts is 10-100 times more active on a titanium basis than the first-generation Ziegler catalysts, which created significant growth opportxmities in the polyethylene industry. 

Table 2.3 Titanium-based activity of various second generation Ziegler catalysts.

Polyethylene manufactured with a single-site catalyst possesses several advantages relative to a similar material produced with a titanium/magne-sium-containing, second-generation Ziegler catalyst. These include ... 

The majority of the research summarized in this chapter will pertain to second-generation, magnesium-containing Ziegler catalysts due to their importance to the polyethylene industry today. However, a brief summary of first generation catalysts will be included due to the historical importance of these early ethylene polymerization catalysts from an academic and industrial perspective (see Appendix 2.1 for review references on first generation Ziegler catalysts). 

Therefore, suitable supports for second generation Ziegler-Natta catalyst systems must meet similar requirements in order to perform satisfactorily. 

Second generation Ziegler-Natta catalysts of high activity also employ particle-form technology. Therefore, the particle size, the particle size distribution and the porosity of supported second generation Ziegler-Natta catalysts needed to be controlled over a certain range. Such requirements... 

TABLE 8.3. Second Generation Ziegler-Natta Catalyst (1970). 

Karl Ziegler and Erhard Holzkamp liom Kaiser Wilhehn Institute. Starting in the mid-1960s a series of patents was issued for the second generation of Z-N catalyst It was later found that addition of Mg compound tenfold increased the catalyst activity... 

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