The last few "K" exhibitions have featured few new materials or technologies. This year's fair (Düsseldorf, October 5-12) promises to at least have a new topic of dicussion. Along with the omnipresent subject of selling prices, the possibilities offered by metallocene catalysts are sure to give visitors and exhibitors something different to talk about. Although not an entirely new idea, the commercialisation process for metallocenes has just begun to get off the ground. The backers of these flexible catalysts believe metallocenes will revolutionise plastics production, as they allow existing polymers – led by PP – to be significantly modified and tailored to specific applications. A number of international polymer manufacturers will be spotlighting metallocenes in Düsseldorf.

Metallocene catalysts have been around since the early 1950s, their development based on previous catalyst research carried out by the German chemist Karl Ziegler (1895-1973) and his Italian colleague Giulio Natta (1903-1979). The duo was awarded the Nobel prize for chemistry in 1963. Ziegler's work became the key to PE, while Natta provided the foundation for PP catalyst technology on an industrial scale. This simplified the production process, while making it cheaper and easier to monitor. Today, nearly 30m t of PE and PP are produced using the Ziegler/Natta catalysts. If metallocenes live up to current expectations, their use in future could put the Ziegler/ Natta figures in the shade. While traditional catalysts are difficult to analyse, these bear no secrets. They offer chemists a transparent, easy to use tool for experimentation, which has virtually unfathomable possibilities.

The current enthusiasm for metallocenes goes back to trials with polypropylene in the late 1970s and early 1980s. Researchers at universities and large chemical companies discovered tremendous advantages in producing PP by this route. With these catalysts, chemists can vary every single molecular characteristic of the polymer independently; for example, viscosity can be improved, while retaining heat stability. At the same time, monitoring the behaviour of the thermoplastic material during processing is facilitated. This, in turn, considerably brightens the future for such a polymeric "ace" as PP.

Besides helping "middle aged" polymers to new vigour and attractiveness, metallocenes are expected to play a role in the development of new products. The new polymer "family" known under the abbreviation COC (cycloolefin copolymers) virtually owes its existence to metallocenes. Japanese and German chemical companies have joined forces to develop these high performance plastics for future markets. The Japanese already produce COCs for their home market, and US companies have announced plans for investment in production facilities.

Cycloolefin copolymers are thermoplastics transparent as glass, but not nearly as fragile. Depending on type and molecular structure, they are highly resistant to heat, as well as chemicals and ultraviolet rays. This opens a variety of lucrative possibilities for use, in optical data carriers, for example, and in other optical applications such as lenses and medical technology. Because of their limited moisture absorption, COCs are also thinkable as packaging materials. Blended with other polymers, they can be used by the automotive, electrical and electronics industries. In this connection: the new polyolefin plastomers (POPs) "Affinity" and the polyolefin elastomers (POEs) "Engage", produced by Dow Europe SA (HQ: Bachtobelstr. 3, CH-8810 Horgen) are based on the "Insite" process, the group's patented constrained geometry (metallocene catalyst) technology. – A collection of data sheets (in English) on "Affinity": PIE-No. 37757 – "Engage": PIE-No. 37758.

Metallocene technology also will be a central theme for the Hoechst group (HQ: D-65926 Frankfurt) at "K '95". The drop-in technology (using metallocenes in existing processes) will be exhibited on a large scale model. Integrated monitors will display applications for the catalysts, as well as for PP produced with metallocenes, small quantitites of which now are being marketed by Hoechst under the name Hostacen". At a press conference in advance of the fair, the Frankfurt group's polyolefins research group head, Prof. Ludwig Böhm, shed some light on Hoechst's activities in the field. Based on research begun in 1985, he said Hoechst "has a strong patent position." In addition to high performance metallocenes, the group has found "structures which can be used to polymerise cyclic olefins and synthesise ethylene and propylene waxes." Hoechst expects "good profits" for metallocenes in future, he emphasised.

The COC polymer developed by Hoechst in cooperation with Mitsui Sekka of Japan is to be marketed under the name "Topas" (for thermoplastic olefin polymer of amorphous structure). The partners are currently modifying a 3,000 t/y plant to make the polymer, and. if trials are successful, a plant "ten imes that size" is being considered, according to Hoechst. Among application possiblities, Hoechst also sees a future for its COCs as a replacement for polycarbonate in CDs. At the Frankfurt press conference, plastics division head Claudio Sonder said he could envisage metallocene technology accounting for 15% of PP production within five years.

READER SERVICE: Comprehensive press conference material (in English) "Hoechst as a partner in the polymer field", including speech by Prof. Böhm: PIE-No. 38184.