Catalyst composition for ethylene polymerization

1. A process for polymerizing an olefin monomer comprising:

(i) contacting, in a reactor, the olefin monomer, the olefin monomer consisting of ethylene, with a catalyst composition comprising one or more Group 3-10 transition metal containing Ziegler-Natta procatalyst compounds; and one or more alkylaluminum cocatalysts;

(ii) providing to the reactor one or more polymerization control agents, wherein at least one such polymerization control agent is an alkyl or aryl ester of an aliphatic or aromatic (poly)carboxylic acid optionally containing one or more substituents comprising a Group 13, 14, 15, or 16 heteroatom and the polymerization control agents is or are provided at a polymerization to co-catalyst ratio from 1:1 to 1:100 such that the polymerization control agent stops the polymerization reaction at a temperature greater than 100° C.;

(iii) gas phase polymerizing at a reactor temperature of greater than 80° C. to form a polymer; and

(iv) extracting the polymer from the reactor.

2. A process according to claim 1 wherein the Ziegler-Natta procatalyst is selected from the group consisting of: TiCl 4 , TiCl 3 , Ti(OC 2 H 5 ) 3 Cl, Ti(OC 2 H 5 ) 2 Cl 2 , Ti(OC 2 H 5 ) 3 Cl, Ti(OC 3 H 7 )Cl 3 , Ti(OC 3 H 7 ) 2 Cl 2 , Ti(OC 4 H 9 )Cl 3 , Ti(OC 4 H 9 ) 2 Cl 2 , TiCl 3 .1/3AlCl 3 , Ti(OC 12 H 25 )Cl 3 , MgTi(OC 2 H 5 ) 5 Cl 1 , MgTi(OC 2 H 5 ) 4 Cl 2 , MgTi(OC 2 H 5 ) 3 Cl 3 , MgTi(OC 2 H 5 ) 2 Cl 4 , MgTi(OC 2 H 5 ) Cl 5 , MgCl 2 .TiCl 4 , and mixtures thereof.

3. A process according to claim 1 wherein the Ziegler-Natta procatalyst compound is TiCl 4 or TiCl 3 supported on MgCl 2 .

4. A process according to claim 1 wherein the cocatalyst is a trialkylaluminum compound.

5. A process according to claim 4 wherein the cocatalyst is triisobutylaluminum or triethylaluminum.

6. A process according to claim 1 which is a continuous, gas phase polymerization process.

7. A process according to claim 1 which is conducted in more than one reactor operating in series.

8. A process of claim 7 wherein the catalyst composition is added to only the first reactor of the series.

9. A process of claim 8 in which two reactors are used.

10. A process according to claim 6 which is conducted in more than one reactor operating in series.

11. A process of claim 10 wherein the catalyst composition is added to only the first reactor of the series.

12. A process of claim 11 in which two reactors are used.

13. A process according to any one of claims 1 - 12 wherein the polymerization control agent is a single compound selected from the group consisting of alkyl or aryl esters of aliphatic or aromatic (poly)carboxylic acids containing one or more substituents comprising a Group 13, 14, 15, or 16 heteroatom having up to 50 atoms not counting hydrogen.

14. A process according to claim 13 wherein the polymerization control agent is selected from the group consisting of C 1-10 alkyl monoether derivatives of C 1-10 alkyl esters of benzoic acid, C 1-10 alkyl monoether derivatives of C 1-10 dialkyl esters of phthalic acid, and C 1-10 alkyl monoether derivatives of C 1-10 dialkyl esters of terephthalic acid.

15. A process according to claim 13 wherein the polymerization control agent is ethyl p-ethoxybenzoate.

16. A process of claim 1 , wherein the operating temperature of the reactor is greater than 85° C.

17. A process of claim 1 , wherein the temperature where the polymerization control agent stops the polymerization reaction is greater than 110° C.

18. A process of claim 1 , wherein the polymerization control agent is separately added to the reactor.