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1. WO1996039450 - PROCESS FOR TRANSITIONING BETWEEN INCOMPATIBLE POLYMERIZATION CATALYSTS

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[ EN ]

CLAIMS
We Claim:

1. A process for transitioning from a polymerization reaction catalyzed by a first catalyst to one catalyzed by a second catalyst comprising a metallocene catalyst, wherein said first and second catalysts are incompatible, said process comprising the steps of:
a) discontinuing the introduction of the first catalyst into a reactor;
b) introducing into and dispersing throughout the reactor a
deactivating agent in an amount greater than about 1 molar
equivalent, based on the total gram atom metal of the first catalyst in the reactor;
c) purging the reactor; and
d) introducing the second catalyst into the reactor in the absence of
any scavenger.

2. A process for converting a continuous olefin polymerization reaction catalyzed by a first catalyst that is Ziegler-Natta-type catalyst comprising a transition metal halide and an organometallic compound of Groups 1, 2 or 3, to a continuous olefin polymerization reaction catalyzed by a second catalyst that is a metallocene-type catalyst comprising a metallocene component and an activator, said process for converting comprising the steps of:
a) discontinuing the introduction of the first catalyst into a reactor;
b) introducing into and dispersing throughout the reactor a
deactivating agent in an amount greater than about 1 molar
equivalent based on the total gram atom metal of the first catalyst in the reactor;
c) purging the reactor of any remaining deactivating agent; and
d) introducing the second catalyst into the reactor in the absence of
any scavenger.

3. The process of claim 1 wherein the first catalyst comprises a traditional Ziegler-Natta catalyst.

4. The process of any preceding claim wherein the amount of deactivating agent is greater than about 2 molar equivalent, based on the total gram atom metal of the first catalyst in the reactor.

5. The process of any preceding claim wherein said polymerization reaction is a gas phase process.

6. The process of any preceding claim wherein the scavenger is an
organometallic compound represented by the formula Al R(3-a) Xa where R is branched or straight chain alkyl, cycloalkyl or a hydride radical having from 1 to 30 carbon atoms, x is a halogen and a is 0, 1 or 2.

7. The process of any preceding claim wherein the deactivating agent is carbon dioxide.

8. The process of any preceding claim wherein the molar ratio of the deactivating agent to the total metal of the first catalyst and any activator and any scavenger in the reactor is in the range of from greater than 1 to about 1000.

9. The process of any preceding claim wherein the polymerization is conducted in a fluidized bed reactor.

10. The process of any of claims 6-9 wherein the deactivating agent is reactive towards the organometallic compound to form at least one compound having a carboxylic acid functionality.

11. The process of any preceding claim wherein the first catalyst in the presence of the second catalyst under the same reactive conditions reduces the activity of the second catalyst by greater than 50%.