Catalysts and process developments propel polyolefins growth

With consumption of almost 88 million tons in 2002, polyolefins dominate the plastics family. They continue to grow at about 5-6%, not only because of the overall economic growth, but their capability of widening applications and thereby eating into some volumes of other materials including the other plastics.

This has been made possible because of continuing developments in catalysts as well as processes. Most of these Polyolefins are about 50 years old and have seen 5 distinct generations of catalysis developments. Developments have been in the field of Ziegler catalysts required for all Polyolefins except high pressure LDPE and some other products like EVA.

The fifth generation Ziegler catalysts enhance productivity as well as widen molecular structural capabilities required to widen the application spectrum. Single site catalysts have opened other areas of controlled addition of comnomer as well as characteristics like molecular weight distribution and significant reduction of lower molecular weight species. While the single site Metallocene catalysts brought significant enhancements on LLDPE, the Ziegler catalysts have developed significant improvements in the morphological as well as molecular architecture of the polymer.

Basell Polyolefins, the largest producer of PP has recently introduced another component in the form of internal donor, considered to broaden the MWD of PP produced by gas phase process. This new catalyst system would improve the processability of film grades required for very high capacity modern film equipments.
The new component Ethyl Benzoate is used in place of the earlier internal donors like Phthalates, Diether and Succinates. This internal donor also increases the bulk density of the polymer powder. The increased bulk density would help the PP producers to produce the granules at higher output rate and thereby reduce the capital cost of the extrusion line. In fact, the maximum output per plant could go up from the existing 250-300KT to 350KT.

Similarly, process developments have helped Polyolefin producers to produce at an economic rate. In addition, these developments have helped in manufacture of copolymers with much higher impact-rigidity balance, not possible a few decades ago. The advent of gas phase from the late 70s and the latest development of multizone circulation to enhance homogenity of the polymer particles are some examples of innovation in process developments.

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