Borealis Holding A/s

Berggren Oy Ab

Neste Oy

Hannu Salminen

Tarja Soderberg

Jari Tervonen

Antero Ahvenainen

Timo Leinonen

Pirjo Jääskeläinen

Eero I Iiskola

Mika Harkonen

Jukka Tulisalo

Paivi L Pitkanen

Ann Britt Bjaland

Olefins or mixtures of olefins, particularly propene or mixtures of propene advantageously with ethene, can be polymerized using a Ziegler-Natta catalyst system containing, besides a transition-metal-based procatalyst and cocatalyst which is an organometallic compound, a compound particularly suited for controlling the stereospecificity of the produced polymer. Such a compound called an external donor may also have other effects. By using an acetal derivative of an aldehyde that has two ether groups for this purpose, advantageously selected from the group of dialkoxyphenylalkanes, e.g., dimethoxyphenylpropane, a good stereospecificity of the product is attained combined with the high hydrogen sensitivity of the catalyst system, whereby the use of hydrogen as the chain transfer agent offers an easy control method of the molecular weight of the product by means of adjusting the amount of hydrogen available in the polymerization reaction. The acetal derivative is a compound according to formula (III): ##STR1## wherein R is C.sub.1-4 alkyl group, R.sup.1 and R.sup.2 are the same or different and each is a hydrocarbon group or a group which can together form a ring, R.sup.3 is hydrogen or a hydrocarbon group. If with the acetal derivative donor is used a clearly less hydrogen sensitive donor, e.g., alkoxysilanes, much broader MWD's of the product are achieved.

Stereospecific catalyst system for polymerization of olefins

The polymerization of certain alpha-olefins in a gas phase involves the problem of agglomeration of the product into particles disadvantageous from the viewpoint of its handling. In the present invention this problem has been solved by means of a new type of process for the homo- or copolymerization of alpha-olefins. In the process the catalyst system is pretreated by contacting and reacting a transition-metal compound which is solid or on a solid carrier with an organoaluminum compound, and possibly an electron donor, in a liquid medium, and by drying the thus formed reaction product to produce a solid catalyst system. The thus pretreated solid and active catalyst system is then fed together with an alpha-olefin in the gaseous state into a gas-phase reactor, and polymerization is carried out by contacting them with each other. By feeding a dry and active catalyst system into the gas-phase reactor, it is possible to avoid the agglomeration of the product which occurs in conventional processes in which an organoaluminum compound and possibly an electron donor are fed in a liquid medium into the reactor.

Process for the gas-phase homo- or copolymerization of alpha-olefin with

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Porvoo, Finland

Tarja Soderberg