METHOD OF POLYMERIZING PROPYLENE COMPRISING OLEFIN PRE-POLYMERIZATION STEP

Abstract

The present invention relates to a method of polymerizing olefin containing the step of pre-polymerization. More precisely, according to the method of the present invention, the reaction speed and temperature are regulated for pre-polymerization of a catalyst and then the pre-polymerized catalyst is added for the polymerization of propylene. Propylene having an improved molecular weight distribution, hydrogen reactivity and tacticity is produced.

Description

Claims

1. A method of polymerizing propylene comprising the following steps: pre-polymerizing a Ziegler-Natta catalyst with olefin in the presence of an external electron donor; andpolymerizing the pre-polymerized Ziegler-Natta catalyst with propylene.

2. The method of polymerizing propylene according to claim 1, wherein the reaction temperature for the pre-polymerization is −10˜50° C.

3. The method of polymerizing propylene according to claim 1, wherein the reaction temperature for the pre-polymerization is 0˜40° C.

4. The method of polymerizing propylene according to claim 1, wherein the reaction time of the pre-polymerization is 0.1˜10 hours.

5. The method of polymerizing propylene according to claim 1, wherein the reaction time of the pre-polymerization is 0.5˜5 hours.

6. The method of polymerizing propylene according to claim 1, wherein the Ziegler-Natta catalyst contains a transition metal compound comprising elements of family 4, family 5 or family 6 of the periodic table; and an organic metal compound comprising elements of family 12 or family 13 of the periodic table.

7. The method of polymerizing propylene according to claim 6, wherein the molar ratio of the organic metal compound to the transition metal compound is 5˜50:95˜50.

8. The method of polymerizing propylene according to claim 6 wherein the transition metal compound is a solid titanium catalyst containing magnesium, titanium, a halogen element and an internal electron donor.

9. The method of polymerizing propylene according to claim 6, wherein the organic metal compound is an organic aluminum compound.

10. The method of polymerizing propylene according to claim 6, wherein the organic metal compound is selected from a group consisting of a trialkyl aluminum, a dialkyl aluminum halide, an alkyl aluminum dihalide, an aluminum dialkyl hydride, an alkyl aluminum sesquihalide, and a mixture thereof.

11. The method of polymerizing propylene according to claim 6, wherein the organic metal compound is selected from a group consisting of Al(C2H5)3, Al(C2H5)2H, Al(C3H7)3, Al(C3H7)2H, Al(i-C4H9)2H, Al(C8H17)3, Al(C12H25)3, Al(C2H5)(C12H25)2, Al(i-C4H9)(C12H25)2, Al(i-C4H9)3, (C2H5)2AlCl, (i-C4H9)2AlCl, and (C2H5)3Al2Cl3.

12. The method of polymerizing propylene according to claim 6, wherein the organic metal compound is selected from a group consisting of a mixture of Al(C2H5)3 and Al(i-C4H9)3; a mixture of Al(C2H5)3 and Al(C8H17)3; a mixture of Al(C4H9)2H and Al(C8H17)3; a mixture of Al(i-C4H9)3 and Al(C8H17)3; a mixture of Al(C2H5)3 and Al(C12H25)3; a mixture of Al(i-C4H9)3 and Al(C12H25)3; a mixture of Al(C2H5)3 and Al(C16H33)3; and a mixture of Al(C3H7)3 and Al(C18H37)2(i-C4H9).

13. The method of polymerizing propylene according to claim 6, wherein the molar ratio of the external electron donor to the transition metal compound is 1˜50.

14. The method of polymerizing propylene according to claim 1, wherein the external electron donor is an organic silane compound containing one or more oxygen atoms and one or more functional groups selected from a group consisting of a substituted or unsubstituted C1˜C20 alkyl group, a substituted or unsubstituted C6˜C30 aryl group, a substituted or unsubstituted C5˜C30 cycloalkyl group, and a substituted or unsubstituted C1˜C20 alkoxy group.

15. The method of polymerizing propylene according to claim 1, wherein the external electron donor is selected from a group consisting of aromatic organic silane compounds of diphenylmethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane and phenylmethyldimethoxysilane; aliphatic organic silane compounds of trimethylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane and dicyclohexyldimethoxysilane; and a mixture thereof.

16. The method of polymerizing propylene according to claim 1, wherein the olefin is added to the pre-polymerization process at 0.02˜10 g olefin/g Ziegler-Natta catalyst/hour.

17. The method of polymerizing propylene according to claim 1, wherein the olefin is added to the pre-polymerization process at 0.02˜6 g olefin/g Ziegler-Natta catalyst/hour.

18. The method of polymerizing propylene according to claim 1, wherein the molecular weight distribution (Mw/Mn) of the produced polymer is 5.0±0.5.

19. The method of polymerizing propylene according to claim 1, wherein the tacticity of the produced polymer is 99±1%.

20. The method of polymerizing propylene according to claim 1, wherein the melt flow rate (230° C., 2.16 kg) of the produced polymer is 4±2 g/10 minutes.