Process for producing propylene copolymers with low VOC content

1. A process comprising:

polymerizing propylene and at least one olefin comonomer selected from C 2 and C 4 -C 8 with a Ziegler Natta catalyst system and hydrogen in a single gas-phase reactor, to form a propylene polymer,

the polymerization being conducted in a temperature range of from 78 to 90° C. with a H 2 /C 3 molar ratio of 0.005 to 0.25,

the Ziegler Natta catalyst system comprising:

a solid catalyst component comprising a transition metal compound, a Group 2 metal compound and at least one internal electron donor comprising a substituted phenylene aromatic diester;

an activity limiting agent;

an organo-aluminum compound; and

an external electron donor composition comprising at least one silane, wherein if the olefin comonomer is ethylene it is present in the propylene polymer in an amount from 0.5-7.0 wt % based on the total weight of the propylene polymer, and if the olefin comonomer is C 4 -C 8 , it is present in an amount from 1.0-15.0 mol % based on the total amount of the propylene polymer.

2. The process of claim 1 wherein the propylene polymer has a melt flow rate of 0.2 to 400 g/10 min as determined according to ASTM D1238.

3. The process of claim 1 wherein the melt flow rate is 30.0 to 150 g/10 min as determined according to ASTM D1238.

4. The process of claim 1 wherein the polymerization temperature is from 78 to 82° C.

5. The process of claim 1 wherein the internal electron donor is a single internal electron donor selected from substituted phenylene aromatic diesters.

6. The process of claim 5 wherein the substituted phenylene aromatic diesters are selected from 1,2-phenylene aromatic diesters with the structure:

wherein:

R 1 -R 4 are individually selected from the group consisting of a hydrogen, substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom and combinations thereof;

at least one of R 1 -R 4 is selected from a substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom, and combinations thereof; or any consecutive R groups in R 1 -R 4 may be linked to form cyclic structure; and

each of R 5 -R 14 is selected from the group consisting of a hydrogen, substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom and combinations thereof; or any consecutive R groups in R 5 -R 14 may be linked to form cyclic structure.

7. The process of claim 6 wherein each of the R 5 -R 14 is hydrogen.

8. The process of claim 6 wherein at least one of R 5 -R 14 is selected from the group consisting of a substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom, and combinations thereof.

9. The process of claim 6 wherein at least one of R 1 -R 4 , at least one of R 5 -R 9 , and at least one of R 10 -R 14 is an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms.

10. The process of claim 6 wherein each of R 1 , R 3 and R 4 is hydrogen and R 2 is an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms.

11. The process of claim 10 wherein each of R 5 -R 14 is selected from the group consisting of hydrogen, a substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a halogen, and combinations thereof.

12. The process of claim 6 wherein each of R 2 , R 3 and R 4 is hydrogen and R 1 is an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms.

13. The process of claim 12 wherein at least one of R 5 -R 14 is selected from the group consisting of hydrogen, a substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a halogen, and combinations thereof.

14. The process of claim 6 wherein R 1 is a methyl group and each of R 5 -R 14 is hydrogen.

15. The process of claim 6 wherein the cyclic structure is a C 5 or a C 6 membered ring.

16. The process of claim 5 wherein the substituted 1,2-phenylene aromatic diester is selected from the group consisting of 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate; 3,5-diisopropyl-1,2-phenylene dibenzoate; 3,6-dimethyl-1,2-phenylene dibenzoate; 4-t-butyl-1,2-phenylene dibenzoate; 4-methyl,2-phenylene dibenzoate; 1,2-naphthalene dibenzoate; 2,3-naphthalene dibenzoate; 3-methyl-t-tert-butyl-1,2-phenylene di (4-methylbenzoate); 3-methyl-5-tert-butyl-1,2-phenylene di (2,4,6-trimethylbenzoate); 3-methyl-5-tert-butyl-1,2-phenylene di (4-fluoro benzoate); and 3-methyl-5-tert-butyl-1,2-phenylene di(4-chlorobenzoate).

17. The process of claim 1 wherein the propylene polymer has a total VOC content as measured by PV-3341 of less than 200 ppm.

18. The process of claim 17 wherein the total VOC content is less than 100 ppm.

19. The process of claim 1 wherein the propylene polymer has a C 9 VOC content, as measured by Modified ASTM D4526 of less than 100 ppm.

20. The process of claim 19 wherein the C 9 VOC content is less than 65 ppm.

21. The process of claim 1 wherein the propylene polymer is a propylene random copolymer with ethylene.

22. The process of claim 1 wherein the propylene polymer is a propylene random copolymer with C 4 -C 8 .

23. A process comprising:

polymerizing propylene and at least one olefin comonomer selected from C 2 and C 4 -C 8 with a Ziegler Natta catalyst system and hydrogen in a single gas-phase reactor, to form a propylene polymer,

the polymerization being conducted in a temperature range of from 78 to 90° C. with a H 2 /C 3 molar ratio of 0.005 to 0.25,

the Ziegler Natta catalyst system comprising:

a solid catalyst component comprising a transition metal compound, a Group 2 metal compound, and at least one internal electron donor selected from succinates, diethers, phthalates or benzoates;

an activity limiting agent;

an organo-aluminum compound; and

an external electron donor composition comprising at least one silane, wherein if the olefin comonomer is ethylene it is present in the propylene polymer in an amount from 1.0-7.0 wt % based on the total weight of the propylene polymer, and if the olefin comonomer is C 4 -C 8 , it is present in an amount from 1.0-15.0 mol % based on the total amount of the propylene polymer.

24. A process comprising:

polymerizing propylene and at least one olefin comonomer selected from C2 and C4-C8 with a Ziegler Natta catalyst system and hydrogen in a single gas-phase reactor, to form a propylene polymer,

the polymerization being conducted in a temperature range of from 78 to 90° C. with a H 2 /C 3 molar ratio of 0.005 to 0.25,

the Ziegler Natta catalyst system comprising:

a solid catalyst component comprising a transition metal compound, a Group 2 metal compound and at least one internal electron donor comprising a compound of structure:

an activity limiting agent;

an organo-aluminum compound; and

an external electron donor composition comprising at least one silane, wherein if the olefin comonomer is ethylene it is present in the propylene polymer in an amount from 0.5-7.0 wt % based on the total weight of the propylene polymer, and if the olefin comonomer is C 4 -C 8 , it is present in an amount from 1.0-15.0 mol % based on the total amount of the propylene polymer;

wherein:

the propylene polymer has a melt flow rate of 0.2 to 400 g/10 min as determined according to ASTM D1238;

R 1 -R 4 are individually selected from the group consisting of a hydrogen, substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom and combinations thereof; and at least one of R 1 -R 4 is selected from a substituted hydrocarbyl group having 1 to 20 carbon atoms, an unsubstituted hydrocarbyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a heteroatom, and combinations thereof; or any consecutive R groups in R 1 -R 4 may be linked to form a cyclic structure;

each of R 5 -R 14 is hydrogen; and

the propylene polymer has a total VOC content as measured by PV-3341 of less than 100 ppm.