CYCLIC ORGANOSILICON COMPOUNDS AS ELECTRON DONORS IN ZEIGLER ?NATTA CATALYST SYSTEMS FOR PRODUCING PROPYLENE POLYMER HAVING HIGH MELT-FLOWABILITY

Abstract

Cyclic organosilicon compounds having a structure represented by the general formula

##STR00001##

and a method for using thereof as a component of catalysts for producing propylene polymer having a very high melt-flowability are disclosed. The cyclic organosilicon compounds are employed as external electron donors in Ziegler-Natta catalyst systems to dramatically improve the hydrogen response, and therefore the catalyst systems can be used to prepare polymer having high melt-flowability and high isotacticity at high yield.

Claims

1. A catalyst system for the polymerization or co-polymerization of alpha-olefin comprising a solid Ziegler-Natta type catalyst component, a co-catalyst component, and an electron donor component comprising at least one cyclic organosilicon compound represented by the formula: ##STR00005## wherein R.sup.1 is a hydrocarbon group with 1-20 carbon atoms; wherein R.sup.2 is a bridging group with a backbone chain of 1-9 atoms, wherein the backbone of said bridging group is selected from the group consisting of aliphatic, alicyclic, and aromatic radicals; wherein R.sup.3 is a hydrocarbon group with 1-6 carbon atoms; wherein m is 0 or 1; and wherein R.sup.4 is an aliphatic, alicycylic, or aromatic group.

2. The catalyst system according to claim 1, wherein R.sup.2 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents extending off the backbone chain.

3. The catalyst system according to claim 1, wherein the backbone chain length of the bridging group R.sup.2 is from 2 to 4 atoms.

4. The catalyst system according to claim 1, wherein R.sup.3 is a methyl or ethyl group.

5. The catalyst system according to claim 1, wherein R.sup.4 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents.

6. The catalyst system according to claim 1, wherein two or more of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are linked to form one or more saturated or unsaturated ring structures.

7. The catalyst system according to claim 1, wherein at least one of carbon atoms or hydrogen atoms of R.sup.1, R.sup.2, R.sup.3, and R.sup.4, including any substituents thereof, is replaced by a hetero-atom selected from the group consisting of N, O, S, Si, B, P, and halogen atoms.

8. The catalyst system according to claim 1, wherein the at least one cyclic organosilicon compound is selected from the list: ##STR00006##

9. A method for producing olefin homo-polymer or copolymer, comprising: a. providing a composition comprising at least one compound of the formula: ##STR00007## wherein R.sup.1 is a hydrocarbon group with 1-20 carbon atoms; wherein R.sup.2 is a bridging group with a backbone chain of 1-9 atoms, wherein the backbone of said bridging group is selected from the group consisting of aliphatic, alicyclic, and aromatic radicals; wherein R.sup.3 is a hydrocarbon group with 1-6 carbon atoms; wherein m is 0 or 1; and wherein R.sup.4 is an aliphatic, alicycylic, or aromatic group; and b. reacting monomer in the presence of the composition to produce the olefin homo-polymer or copolymer.

10. The method according to claim 9, wherein two or more of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are linked to form one or more saturated or unsaturated ring structures.

11. The method according to claim 9, wherein R.sup.2 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents extending off the backbone chain.

12. The method according to claim 9, wherein R.sup.4 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents.

13. The method according to claim 9, wherein said R.sup.3 is a methyl or ethyl group.

14. The method according to claim 9, wherein at least one of carbon atoms or hydrogen atoms of R.sup.1, R.sup.2, R.sup.3, and R.sup.4, including any substituents thereof, is replaced by a hetero-atom selected from the group consisting of N, O, S, Si, B, P, and halogen atoms.

15. A composition comprising at least one compound of the formula: ##STR00008## wherein R.sup.1 is a hydrocarbon group with 1-20 carbon atoms; wherein R.sup.2 is a bridging group with a backbone chain of 1-9 atoms, wherein the backbone of said bridging group is selected from the group consisting of aliphatic, alicyclic, and aromatic radicals; wherein R.sup.3 is a hydrocarbon group with 1-6 carbon atoms; wherein m is 0 or 1; and wherein R.sup.4 is an aliphatic, alicycylic, or aromatic group.

16. The composition according to claim 15, wherein two or more of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are linked to form one or more saturated or unsaturated ring structures.

17. The composition according to claim 15, wherein R.sup.2 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents extending off the backbone chain.

18. The composition according to claim 15, wherein R.sup.4 comprises one or more C1-C20 linear or branched, saturated or unsaturated substituents.

19. The composition according to claim 15, wherein said R.sup.3 is a methyl or ethyl group.

20. The composition according to claim 15, wherein at least one of carbon atoms or hydrogen atoms of R.sup.1, R.sup.2, R.sup.3, and R.sup.4, including any substituents thereof, is replaced by a hetero-atom selected from the group consisting of N, O, S, Si, B, P, and halogen atoms.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a plot showing the relationship between the amount of hydrogen used and the melt flow rate, in order to compare the hydrogen reactivity according to the species of the external donors, based on the results from examples 10-14 and comparative examples 1-5 in the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0013] The present invention relates to novel cyclic organosilicon compounds, a method for the preparation thereof and use thereof as a component of catalysts for olefins polymerization. In olefins polymerization or copolymerization, in particular, in propylene polymerization or copolymerization, it has been discovered that Ziegler-Natta catalyst systems comprising the cyclic organosilicon compounds of the present invention as the external electron donor component exhibit dramatically-improved hydrogen response, and therefore can be used to prepare polymer having high melt-flowability and high isotacticity at high yield.

[0014] In accordance with various embodiments of the present invention, a series of organosilicon compounds, which are useful as electron donors in polymerization catalyst systems for the production of polyolefins, particularly polypropylene, are disclosed. The organosilicon compounds of the present invention may be used alone as single constituent in an electron donor component of the catalyst system or may be used in combination with one or more other compounds as an electron donor component of the catalyst system. If more than one compound is used as the electron donor component, one or more of the constituents may be organosilicon compounds of the present invention.

[0015] The organosilicon compounds of the present invention that may be used as electron donors in polymerization catalyst systems have a structure represented by the General Formula:

##STR00003##

wherein R.sup.1 is a hydrocarbon group with 1-20 carbon atoms.

[0016] R.sup.2 is a bridging group with a backbone chain of 1-9 atoms. “Backbone chain” in this context refers to the atoms that are in the direct linkage between N and O atoms. For example, if —CH.sub.2—CH.sub.2— is the bridging group, the backbone chain has two atoms, referring to the carbon atoms that provide the direct linkage between N and O atoms. Similarly, if the bridging group has the iso-structure, —CH(CH.sub.3)—CH.sub.2—, the associated backbone chain also has two atoms.

[0017] The backbone of the bridging group is selected from the group consisting of aliphatic, alicyclic, and aromatic radicals. Preferably, the backbone of the bridging group is selected from the group consisting of aliphatic radicals, with or without unsaturation. The bridging group may have one or more C.sub.1-C.sub.20 substituents (or side chains) extending off the backbone chain. The substituents may be branched or linear and may be saturated or unsaturated. Similarly, the substituents may comprise aliphatic, alicyclic, and aromatic radicals.

[0018] R.sup.3 is a hydrocarbon group with 1-6 carbon atoms. In preferred embodiments of the present invention, R.sup.3 is a methyl or ethyl group.

[0019] R.sup.4 is an aliphatic, alicycylic, or aromatic group, which may have one or more C.sub.1-C.sub.20 linear or branched, saturated or unsaturated substituents. The subscript m can be 0 or 1.

[0020] One or more of carbon atoms and/or hydrogen atoms of R.sup.1, R.sup.2, R.sup.3, and R.sup.4, including any substituents thereof, may be replaced by a hetero-atom selected from the group consisting of N, O, S, Si, B, P, and halogen atoms.

[0021] In various embodiments of the present invention, two or more of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may be linked to form one or more saturated or unsaturated ring structures.

[0022] Examples of suitable cyclic organosilicon compounds of the General Formula include, but not limited to:

##STR00004##

[0023] The present invention further relates to a process for olefin polymerization or copolymerization, wherein a cyclic organosilicon compound according to the invention is used as the external electron donor component in Zeigler-Natta catalyst systems. In a preferable embodiment, said process is homopolymerization or copolymerization of alpha olefins such as propylene. Processes for the polymerization of alpha olefins such as propylene and application mode and amount of external electron donor compounds therein are well known in the art.

[0024] To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the invention.

EXAMPLES

[0025] The catalyst components and properties of polymers in the examples were measured according to the following methods: [0026] 1. Organosilicon compounds were characterized by .sup.1H-NMR and GC-MS. [0027] 2. Isotacticity of polymer was measured by heptane extraction method (heptane boiling extraction for 6 hours). Isotacticity is represented as heptane insoluable (HI), which is the ratio of the residual polymer weight after extraction to the initial polymer weight. [0028] 3. Melt flow rate (MFR) of polymer was measured according to ASTM D-1238, determined at 230° C., under the load of 2.16 kg. [0029] 4. Molecular weight distribution (MWD) of polymer was measured as Mw/Mn (weight average molecular weight / number average molecular weight) by gel permeation chromatography (GPC).

[0030] Unless otherwise indicated, all reactions were conducted under an inert atmosphere.

Organosilicon Compound Preparation

Example 1

Preparation of 3-tert-butyl-2,2-diethoxy-[1,3,2]oxazasilolidine

[0031] This example illustrates an organosilicon compound in accordance with the present invention and a method of preparing the same.

[0032] To a 500 mL flask was charged a solution of 2-(tert-butylamino)ethanol (100 mmol) in 100 ml of anhydrous THF. n-Butyllithium (2.5 M solution in hexanes, 200 mmol) was added dropwise to keep the solution below the boiling temperature. After addition of n-butyllithium, the reaction mixture was stirred for 30 minutes without external heating or cooling. Then a solution of tetraethyl orthosilicate Si(OEt).sub.4 (100 mmol) in anhydrous hexane (20 mL) was added over 10 minutes at room temperature. The resulting reaction mixture was heated to 60° C. and stirred at that temperature for 6 hours. Precipitates were slowly formed during the reaction process. GC analysis indicated that no starting materials were left. The solid byproduct was removed by centrifugation and the clear solution concentrated under reduced pressure. The crude product was further purified through vacuum distillation to afford the title product as a colorless oil. [0033] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.1 (m, 2H), 3.8 (m, 4H), 3.1 (m, 1H), 2.7 (t, 1H), 1.2 (m, 15H).

Example 2

Preparation of 3-tert-butyl-2,2-diethoxy-5-methyl-[1,3,2]oxazasilolidine

[0034] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0035] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-(tert-butylamino)-1-methyl-ethanol (100 mmol). [0036] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.2 (m, 1H), 3.8 (m, 4H), 3.1 (m, 1H), 2.7 (t, 1H), 1.2 (m, 18H).

Example 3

Preparation of 3-tert-butyl-2,2-diethoxy-5-ethyl-[1,3,2]oxazasilolidine

[0037] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0038] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-(tert-butylamino)-1-ethyl-ethanol (100 mmol). [0039] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.0 (m, 1H), 3.8 (m, 4H), 3.1 (m, 1H), 2.8 (t, 1H), 1.6 (m, 1H), 1.2 (m, 15H), 0.9 (t, 3H).

Example 4

Preparation of hexahydro-1,1-diethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline

[0040] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0041] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol). [0042] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.0 (m, 1H), 3.8 (m, 4H), 3.2 (m, 1H), 3.0 (m, 1H), 2.6 (t, 1H), 1.8 (m, 2H), 1.6 (m, 3H), 1.2 (m, 9H).

Example 5

Preparation of hexahydro-1,1-dimethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline

[0043] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0044] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol) and tetraethyl orthosilicate (100 mmol) by tetramethyl orthosilicate (100 mmol). [0045] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.0 (m, 2H), 3.5 (s, 6H), 3.2 (m, 1H), 3.0 (m, 1H), 2.6 (t, 1H), 1.8 (m, 2H), 1.6 (m, 3H), 1.2 (m, 3H).

Example 6

Preparation of hexahydro-1-ethoxy-1-(2-methylpropyl)-1H,3H-pyridol[1,2-c][1,3,2]oxazasiline

[0046] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0047] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol) and tetraethyl orthosilicate (100 mmol) by isobutyltriethoxysilane (100 mmol). [0048] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.0 (m, 2H), 3.6 (m, 2H), 3.2 (t, 1H), 2.9 (m, 1H), 2.6 (m, 1H), 2.0-0.8 (m, 18H), 0.6 (d, 2H).

Example 7

Preparation of hexahydro-1-ethoxy-1-propyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline

[0049] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0050] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol) and tetraethyl orthosilicate (100 mmol) by propyltriethoxysilane (100 mmol). [0051] GC purity: >99.0%; 1H-NMR (CDCl3, 400 MHz) δ (ppm): 3.9 (m, 4H), 3.2 (t, 1H), 2.9 (m, 1H), 2.6 (m, 1H), 2.0-0.9 (m, 16H), 0.6 (m, 2H).

Example 8

Preparation of hexahydro-1-ethoxy-1-ethyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline

[0052] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0053] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol) and tetraethyl orthosilicate (100 mmol) by ethyltriethoxysilane (100 mmol). [0054] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 4.0 (m, 2H), 3.6 (m, 2H), 3.2 (t, 1H), 2.9 (m, 1H), 2.6 (m, 1H), 2.0-0.9 (m, 14H), 0.6 (m, 2H).

Example 9

Preparation of hexahydro-1-ethoxy-1-methyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline

[0055] This example illustrates another organosilicon compound in accordance with the present invention and a method of preparing the same.

[0056] The procedure and ingredients of Example 1 were followed except that 2-(tert-butylamino)ethanol (100 mmol) was replaced by 2-piperidineethanol (100 mmol) and tetraethyl orthosilicate (100 mmol) by methyltriethoxysilane (100 mmol). [0057] GC purity: >99.0%; .sup.1H-NMR (CDCl.sub.3, 400 MHz) δ (ppm): 3.9 (m, 4H), 3.2 (m, 1H), 2.9 (m, 1H), 2.6 (m, 1H), 2.0-0.9 (m, 11H), 0.2 (s, 3H).

Propylene Polymerization

[0058] Examples 10-22 illustrate alpha olefin polymers in accordance with certain teachings of the present invention, and a method of preparing the same.

Example 10

[0059] A bench scale 2-liter reactor was used. The reactor was first preheated to 100° C. with a nitrogen purge to remove residual moisture and oxygen. The reactor was thereafter cooled to 50° C.

[0060] Under nitrogen, 1 liter of dry heptane was introduced into the reactor. When the reactor temperature was about 50° C., 2.5 mmol of triethyl aluminum, 1.2 mmol of hexahydro-1,1-dimethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, and then 30 mg Toho 53-009 catalyst (available from Toho Catalyst Ltd.) were added to the reactor. The pressure of the reactor was raised to 28.5 psig by introducing nitrogen. Then, 200 ml of hydrogen was flashed into the reactor with propylene.

[0061] The reactor temperature was then raised to 70° C. Propylene was introduced to the reactor continually to keep the total reactor pressure at 90 psig. The polymerization was allowed to proceed for 1 hour. After completion of the polymerization reaction, the reactor was vented and cooled to 50° C.

[0062] Then the reactor was opened and 500 mL of methanol added. The resulting mixture was stirred for 5 minutes followed by filtration to obtain the propylene homopolymer. The obtained polymer was dried at 80° C. under vacuum for 6 hours.

[0063] The polymerization activity per hour was estimated with the weight of the obtained polymer, and hexane insoluble (HI), melt flow rate (MFR) and molecular weight distribution (Mw/Mn) were measured. The results are represented in Table 1 below.

Examples 11-14

[0064] A propylene polymer was prepared in the same manner as in Example 10 above, except that the amount of hydrogen was changed to 400 ml, 600 ml, 800 ml and 1000 ml, respectively. The results are represented in Table 1.

Examples 15-22

[0065] A propylene polymer was prepared in the same manner as in Example 10 above, except that the following external electron donors: [0066] 1.2 mmol of hexahydro-1,1-diethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, [0067] 1.2 mmol of hexahydro-1-ethoxy-1-(2-methylpropyl)-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, [0068] 1.2 mmol of hexahydro-1-ethoxy-1-propyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, [0069] 1.2 mmol of hexahydro-1-ethoxy-1-ethyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, [0070] 1.2 mmol of hexahydro-1-ethoxy-1-methyl-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline, [0071] 1.2 mmol of 3-tert-butyl-2,2-diethoxy-[1,3,2]oxazasilolidine, [0072] 1.2 mmol of 3-tert-butyl-2,2-diethoxy-5-methyl-[1,3,2]oxazasilolidine, [0073] 1.2 mmol of 3-tert-butyl-2,2-diethoxy-5-ethyl-[1,3,2]oxazasilolidine,
were used respectively, instead of 1.2 mmol of hexahydro-1,1-dimethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline in example 10. The results are represented in Table 1.

Comparative Example 1

[0074] A propylene polymer was prepared in the same manner as in Example 10 above, except that 1.2 mmol of cyclohexylmethyldimethoxysilane (CHMDMS) was used as an external electron donor, instead of 1.2 mmol of hexahydro-1,1-dimethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline in example 10. The results are represented in Table 1.

Comparative examples 2-5

[0075] A propylene polymer was prepared in the same manner as in Example 10 above, except that 1.2 mmol of cyclohexylmethyldimethoxysilane (CHMDMS) was used as an external electron donor, instead of 1.2 mmol of hexahydro-1,1-dimethoxy-1H,3H-pyrido[1,2-c][1,3,2]oxazasiline in example 10, and the amount of hydrogen used was changed to 400 ml, 600 ml, 800 ml and 1000 ml, respectively. The results are represented in Table 1.

TABLE-US-00001 TABLE 1 Hydrogen Activity MFR HI Example External electron donor (ml) (g/gCat-h) (g/10 min) (%) Mw/Mn Ex. 10 hexahydro-1,1-dimethoxy-1H,3H- 200 4074 41.4 97.7 4.2 pyrido[1,2-c][1,3,2]oxazasiline Ex. 11 hexahydro-1,1-dimethoxy-1H,3H- 400 2986 70.5 97.0 4.2 pyrido[1,2-c][1,3,2]oxazasiline Ex. 12 hexahydro-1,1-dimethoxy-1H,3H- 600 2715 130.0 95.3 4.2 pyrido[1,2-c][1,3,2]oxazasiline Ex. 13 hexahydro-1,1-dimethoxy-1H,3H- 800 2642 216.8 95.0 4.2 pyrido[1,2-c][1,3,2]oxazasiline Ex. 14 hexahydro-1,1-dimethoxy-1H,3H- 1000 2595 329.2 94.3 4.2 pyrido[1,2-c][1,3,2]oxazasiline Ex. 15 hexahydro-1,1-diethoxy-1H,3H- 200 2264 33.9 97.4 4.3 pyrido[1,2-c][1,3,2]oxazasiline Ex. 16 hexahydro-1-ethoxy-1-(2- 200 2850 22.8 96.7 5.0 methylpropyl)-1H,3H-pyrido[1,2- c][1,3,2]oxazasiline Ex. 17 hexahydro-1-ethoxy-1-propyl-1H,3H- 200 2532 35.2 96.4 4.9 pyrido[1,2-c][1,3,2]oxazasiline Ex. 18 hexahydro-1-ethoxy-1-ethyl-1H,3H- 200 4116 7.4 97.8 5.0 pyrido[1,2-c][1,3,2]oxazasiline Ex. 19 hexahydro-1-ethoxy-1-methyl-1H,3H- 200 3108 53.8 96.0 4.3 pyrido[1,2-c][1,3,2]oxazasiline Ex. 20 3-tert-butyl-2,2-diethoxy- 200 3450 22.5 95.0 4.4 [1,3,2]oxazasilolidine Ex. 21 3-tert-butyl-2,2-diethoxy-5-methyl- 200 4102 18.2 95.4 4.4 [1,3,2]oxazasilolidine Ex. 22 3-tert-butyl-2,2-diethoxy-5-ethyl- 200 3390 16.5 95.8 4.4 [1,3,2]oxazasilolidine Comp. 1 Cyclohexylmethyldimethoxysilane 200 3086 12.5 98.1 4.2 Comp. 2 Cyclohexylmethyldimethoxysilane 400 2926 25.7 97.6 4.2 Comp. 3 Cyclohexylmethyldimethoxysilane 600 2908 47.3 97.1 4.2 Comp. 4 cyclohexylmethyldimethoxysilane 800 2847 70.1 96.9 4.2 Comp. 5 cyclohexylmethyldimethoxysilane 1000 2754 101.4 96.6 4.2

[0076] As is evident from the above examples and comparative examples, catalyst systems comprising the cyclic organosilicon compounds of the present invention as the external electron donor component exhibit dramatically-improved hydrogen response, and therefore a higher melt-flowability and higher isotacticity at high yield, as compared to catalyst systems utilizing CHMDMS as the electron donor. Although CHMDMS is well known in the art to demonstrate the highest hydrogen response of commonly used commercial electron donors, the catalysts systems of the present invention achieves much higher MFR at the same lower hydrogen loading, or the same MFR as CHMDMS at a much lower hydrogen loading.

[0077] Therefore, the present invention is well adapted to attaint the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings therein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and sprit of the present invention. Whenever a numerical range with a lower limit and an upper limit is disclosed, and number falling within the range is specifically disclosed. Moreover, the indefinite articles “a” or “an”, as use in the claims, are defined herein to mean one or more than one of the element that it introduces.