Process for producing propylene polymer compositions

1. A process for the preparation of propylene polymer compositions (P) by polymerizing propylene with a C4 to C8 α-olefin comonomer and ethylene in a sequential polymerization process comprising at least two reactors connected in series, wherein said process comprises the steps of:

(A) polymerizing in a first reactor (R-1) propylene, optionally a C4 to C8 α-olefin comonomer and optionally ethylene, and obtaining a propylene polymer fraction (A),

(B) transferring said propylene polymer fraction (A), optionally with unreacted propylene monomers and optionally with the unreacted ethylene and C4 to C8 α-olefin comonomers from the first reactor into a second reactor (R-2),

(C) feeding to said second reactor (R-2) additional propylene, optionally additional C4 to C8 α-olefin comonomer and optionally additional ethylene,

(D) polymerizing propylene, optionally C4 to C8 α-olefin comonomer and optionally ethylene in said second reactor (R-2), in the presence of said propylene polymer fraction (A), and

obtaining the propylene polymer composition (P) comprising the propylene polymer fraction (A) and a propylene polymer fraction (B) produced in said second reactor (R-2),

wherein the C4 to C8 α-olefin and the ethylene comonomers are fed at least to one of the reactors (R-1) and (R-2), and wherein the propylene composition (P) is a terpolymer that comprises C4 to C8 α-olefin comonomer in an amount of at least 4.5 wt-%, and

wherein,

the polymerization takes place in the presence of a solid catalyst component (SC),

i) having a surface area measured according to ASTM D 3663 of less than 20 m 2 /g,

ii) that is free of any external carrier material, and

iii) comprising:

(a) a transition metal compound selected from one of the groups 4 to 6 of the periodic table (IUPAC),

(b) a compound of a metal selected from one of the groups 1 to 3 of the periodic table (IUPAC), and

(c) a non-phthalic internal electron donor (ID), and

wherein said solid catalyst component (SC) does not contain any phthalic compounds.

2. The process according to claim 1 , wherein the non-phthalic internal electron donor (ID) is selected from (di)esters of non-phthalic (di)carboxylic acids, 1,3-diethers, and derivatives thereof.

3. The process according to claim 1 wherein the transition metal compound is a compound of the group 4 metal and the compound of a group 1 to 3 metal is compound of group 2 metal.

4. The process according to claim 1 , wherein the catalyst comprises a cocatalyst of an organoaluminium compound and an external donor selected from silanes of the general formula:

R a p R b q Si(OR c ) (4-p-q)

wherein R a , R b and R c are chosen independently from one another and can be the same or different and denote a linear alkyl or cycloalkyl group, and wherein p and q are numbers ranging from 0 to 3 with their sum p+q being equal to or less than 3.

5. The process according to claim 1 , wherein the first reactor (R-1) is a slurry reactor and the second reactor (R-2) is a gas phase reactor.

6. The process according to claim 1 , wherein in the first reactor (R-1) the polymerization temperature is in the range of 60° C. to 85° C., and in the second reactor (R-2) the polymerization temperature is in the range of 65° C. to 85° C.

7. The process according to claim 1 , wherein the propylene polymer composition (P) is a terpolymer having a C4 to C8 α-olefin comonomer content in the range of 4.5 wt % to 14 wt %, and ethylene content in the range of 0.5 to 3.0 wt-%.

8. The process according to claim 1 , wherein the propylene terpolymer composition has a combined content of ethylene and C4 to C8 α-olefin comonomer in the range of 5.0 to 17 wt %.

9. The process according to claim 1 , wherein the C4 to C8 α-olefin comonomer is 1-butene or 1-hexene.

10. The process according to claim 1 , wherein the catalyst is prepared by a method comprising:

a) providing a solution of:

a 1 ) at least a Group 2 metal alkoxy compound (Ax), the Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound and an alcohol (A) comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium; or

a 2 ) at least a Group 2 metal alkoxy compound (Ax′), the Group 2 metal alkoxy compound (Ax′) being the reaction product of a Group 2 metal compound and an alcohol mixture of the alcohol (A) and a monohydric alcohol (B) of formula ROH, where R is an alkyl of 2 to 16 C-atoms, optionally in an organic liquid reaction medium; or

a 3 ) a mixture of the Group 2 metal alkoxy compound (Ax) and a Group 2 metal alkoxy compound (Bx) that is the reaction product of a Group 2 metal compound and the monohydric alcohol (B), optionally in an organic liquid reaction medium; or

a 4 ) Group 2 metal alkoxy compound of formula M(OR 1 ) n (OR 2 ) m X 2-n-m or mixture of Group 2 alkoxides M(OR 1 ) n′ X 2-n′ and M(OR 2 ) m′ X 2-m′ where M is Group 2 metal, X is halogen, R 1 and R 2 are different alkyl groups of C 2 to C 16 carbon atoms, and 0<n<2, 0<m<2 and n+m<2, provided that both n and m are not simultaneously zero, 0<n′<2 and 0<m′<2; and

b) adding said solution from step a) to at least one compound of a transition metal of Group 4 to 6 and

c) obtaining the solid catalyst component particles,

and adding a non-phthalic internal electron donor (ID) at any step prior to step c).

11. The process according to claim 1 , wherein the propylene polymer composition (P) has a melting temperature in the range of 120° C. to 145° C.

12. The process according to claim 1 , wherein the propylene composition (P) has a MFR 2 in the range of 1 to 50 g/10 min.