Gas phase catalysts
3 Feb 2005
Basell has introduced a new family of Ziegler catalysts that are designed for use in gas phase polyethylene systems.
Marketed under the grade name Avant Z 230, 'the new catalysts can produce the entire range of narrow molecular weight LLDPE, MDPE and HDPE,' according to Michael Mulrooney, senior vice president of Basell's Technology Business.
Typical applications include film, injection moulding and rotomoulding grades.
'Most gas phase polyethylene catalyst systems use silica supports,' said Mulrooney. 'Silica supports are widely available, but morphological stability in the reactor can be a problem.'
The Avant Z 230 catalyst uses a magnesium chloride support. The combination of new proprietary catalyst chemistry, with a more stable support structure, has resulted in a catalyst with expanded product properties and improved operational stability.
The Z 230 catalyst was developed in Ferrara, Italy and has been demonstrated on commercial Spherilene process plants. 'LLDPE film grades modified with butene and hexene that are produced with these catalysts exhibit good optical properties, high strength, low extractables and a reduced blocking effect,' said Mulrooney.
'Avant Z 230 is a partner to the Avant Z 218 catalyst, which was commercialized in 2004. The Z 218 is designed to produce broad molecular weight HDPE, and both are Ziegler titanium catalysts on magnesium chloride supports, so they are fully compatible,' he added..
When used in gas phase process technologies such as the newest version of Basell's Spherilene process, switching between HDPE and LLDPE can be easily implemented in a normal production schedule.
