Start-up polymerization process

Details Start-up polymerization process Start-up polymerization process

2000-06-15

2001-07-24

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S061000, C526S116000, C526S901000, C526S905000, C526S125800

Reexamination Certificate

active

06265502

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a process for starting up a reaction for the polymerization of an olefin in the gas phase in a fluidized bed in the presence of a catalyst of Ziegler-Natta type.
It has been observed that when the polymerization of an olefin is carried out in the gas phase in a fluidized bed, the formation of agglomerates and/or of polymer of an undesirable quality can often take place at the time of start-up of the polymerization. This appears in particular after having begun to introduce the catalyst into the fluidized bed and up to the time when a certain amount of polymer is produced, in particular up to the time when a stable level of full hourly production of polymer is achieved, that is to say the maximum level of hourly production desired.
It has also been observed that, during the start-up period, the instability of the polymerization conditions in a fluidized bed often leads to uncontrolled reactions and the formation of agglomerates.
A novel process for starting up a reaction for the polymerization of an olefin in the gas phase carried out in a fluidized-bed reactor has now been found which makes it possible to solve the problems mentioned previously. More particularly, the process of the invention makes it possible to initiate a polymerization reaction with a very limited, indeed zero, formation of agglomerates.
SUMMARY OF THE INVENTION
According to the present invention there is provided a process for starting up a gas phase olefin polymerisation reaction carried out using a Ziegler-Natta type catalyst based on a transition metal in a fluidized-bed reactor, through which passes a reaction gas mixture comprising the olefin, an inert gas, hydrogen and optionally at least one comonomer and which operates under conditions of temperature and pressure which make it possible to start up the polymerization reaction, characterized in that the partial pressure of the olefin and the rate of introduction of catalyst into the reactor are increased whilst maintaining the ratios of the partial pressures of the olefin to the hydrogen and to the optional comonomer or comonomers substantially constant.


REFERENCES:
patent: 5077358 (1991-12-01), Durand et al.
patent: 0 130 607 (1985-01-01), None
patent: WO 96/39450 (1996-12-01), None

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