Process for preparation of propylene copolymer

1. A process for the preparation of a propylene copolymer in a multistage polymerisation process in the presence of a single site catalyst, said process comprising:

(I) in a slurry polymerisation step, polymerising propylene and optionally at least one C2-10 alpha olefin comonomer in the presence of a single site catalyst; and subsequently

(II) in a gas polymerisation step polymerising propylene and optionally at least one C2-10 alpha olefin comonomer, in the presence of the catalyst and polymer from step (I);

(III) in a second gas polymerisation step, polymerising propylene and at least one C2-10 alpha olefin comonomer in the presence of the catalyst and polymer from step (II);

wherein said catalyst comprises

(i) a metallocene complex of a group (IV) metal, said metallocene comprising at least two cyclopentadienyl type ligands;

(ii) a boron based cocatalyst; and

(iii) an aluminoxane cocatalyst;

said catalyst being in solid form, and being free from an external carrier.

2. A process for the preparation of a propylene copolymer in a multistage polymerisation process in the presence of a single site catalyst,said process comprising:

(Ia) prepolymerising a single site catalyst in the presence of propylene;

(Ib) in a slurry polymerisation step, polymerising propylene and optionally at least one C2-10 alpha olefin comonomer with the prepolymerised catalyst of step (Ia); and subsequently

(II) in a gas polymerisation step polymerising propylene and optionally at least one C2-10 alpha olefin comonomer in the presence of catalyst and polymer from step (Ib);

(III) in a second gas polymerisation step, polymerising propylene and at least one C2-10 alpha olefin comonomer in the presence of the catalyst and polymer from step (II);

wherein said catalyst comprises

(i) a metallocene complex of a group (IV) metal, said metallocene comprising at least two cyclopentadienyl type ligands;

(ii) a boron based cocatalyst; and

(iii) an aluminoxane cocatalyst;

said catalyst being in solid form, and being free from an external carrier.

3. A process as claimed in claim 1 wherein the gas phase to slurry phase split is at least 50:50 wt %.

4. A process as claimed in claim 1 wherein the boron based cocatalyst is a borate cocatalyst.

5. A process as claimed in claim 1 wherein the solid catalyst is obtainable by a process in which

(a) a liquid/liquid emulsion system is formed, said liquid/liquid emulsion system comprising a solution of the catalyst components (i) to (iii) dispersed in a solvent so as to form dispersed droplets; and

(b) solid particles are formed by solidifying said dispersed droplets.

6. A process as claimed in claim 5 wherein the solid catalyst is obtained using a catalyst prepolymerisation step (c) wherein the solid catalyst from step (b) is prepolymerised with at least one alpha-olefin monomer and optionally one or more C 3 -C 10 alpha-olefin comonomers.

7. A process as claimed in claim 6 wherein catalyst prepolymerisation is effected sing propylene.

8. A process as claimed in claim 1 wherein step (I) is a slurry bulk step.

9. A process as claimed in claim 1 wherein the ratio of boron to the transition metal ion of the metallocene in the catalyst is be in the range 1:10 to 10:1 (mol/mol).

10. A process as claimed in claim 1 wherein the ratio of Al in the aluminoxane to the transition metal ion of the metallocene is in the range 1:1 to 1200:1 mol/mol.

11. A process as claimed in claim 1 wherein the polymerisation temperature in step (I) is above 70° C.

12. A process as claimed in claim 1 wherein the complex is of formula (II):

wherein

M is zirconium or hafnium;

each X is a sigma ligand;

L is a divalent bridge selected from —R′ 2 C—, —R′ 2 C—CR′ 2 —, —R′ 2 Si—, —R′ 2 Si—SiR′ 2 —, —R′ 2 Ge—, wherein each R′ is independently a hydrogen atom, C 1 -C 20 -hydrocarbyl, tri(C 1 -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl;

R 2 and R 2′ are each independently a C 1 -C 20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16;

R 5 and R 5′ are each independently hydrogen, or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 and optionally substituted by one or more halo atoms;

R 6 and R 6′ are each independently hydrogen or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; or

R 5 and R 6 taken together can form a 5 or 6 membered saturated or unsaturated carbon ring fused to the 6-membered ring of the indenyl group; or

R 5′ and R 6′ taken together can form a 5 or 6 membered saturated or unsaturated carbon ring fused to the 6-membered ring of the indenyl group;

R 7 and R 7′ are each independently hydrogen or C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;

Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;

Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;

each R 1 is a C 1-20 hydrocarbyl group or two R 1 groups on adjacent carbon atoms taken together can form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R 4 ; and

each R 4 is a C 1-20 hydrocarbyl group.

13. A process as claimed in claim 1 wherein the complex is of formula (VII) or (VII′):

wherein each X is a sigma ligand;

R′ is independently a C 1-6 alkyl or C 3-10 cycloalkyl;

R 1 is independently C 3-8 alkyl;

R 6 is hydrogen or a C 3-8 alkyl group;

R 6′ is a C 3-8 alkyl group or C 6-10 aryl group;

R 3′ is a C 1-6 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups; and

n is independently 0, 1 or 2.

14. A process as claimed in claim 1 wherein gas phase step (III) produces at least 30 wt % of the formed polymer.

15. A process as claimed in claim 1 wherein the propylene copolymer is a heterophasic propylene copolymer.

16. A process as claimed in claim 1 wherein said catalyst is in solid particulate form.

17. A process as claimed in claim 13 wherein in said metallocene, each X is independently a hydrogen atom, a halogen atom, C 1-6 -alkoxy group, C 1-6 -alkyl, phenyl or benzyl group.

18. A process as claimed in claim 3 wherein the gas phase to slurry phase split is at least 60:40wt %.

19. A process as claimed in claim 2 wherein the solid catalyst is obtainable by a process in which

(a) a liquid/liquid emulsion system is formed, said liquid/liquid emulsion system comprising a solution of the catalyst components (i) to (iii) dispersed in a solvent so as to form dispersed droplets; and

(b) solid particles are formed by solidifying said dispersed droplets.

20. A process as claimed in claim 19 wherein the solid catalyst is obtained using a catalyst prepolymerisation step (c) wherein the solid catalyst from step (b) is prepolymerised with at least one alpha-olefin monomer and optionally one or more C 3 -C 10 alpha-olefin comonomers.

21. A process as claimed in claim 20 wherein catalyst prepolymerisation is effected using propylene.

22. A process as claimed in claim 2 wherein the complex is of formula (II):

wherein

M is zirconium or hafnium;

each X is a sigma ligand;

L is a divalent bridge selected from —R′ 2 C—, —R′ 2 C—CR′ 2 —, —R′ 2 Si—, —R′ 2 Si —SiR′ 2 —, —R′ 2 Ge—, wherein each R′ is independently a hydrogen atom, C 1 -C 20 -hydrocarbyl, tri(C i -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl;

R 2 and R 2′ are each independently a C 1 -C 20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16;

R 5 and R 5′ are each independently hydrogen, or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 and optionally substituted by one or more halo atoms;

R 6 and R 6′ are each independently hydrogen or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; or

R 5 and R 6 taken together can form a 5 or 6 membered saturated or unsaturated carbon ring fused to the 6-membered ring of the indenyl group; or

R 5 ′ and R 6′ taken together can form a 5 or 6 membered saturated or unsaturated carbon ring fused to the 6-membered ring of the indenyl group;

R 7 and R 7′ are each independently hydrogen or C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;

Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;

Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;

each R 1 is a C 1-20 hydrocarbyl group or two R 1 groups on adjacent carbon atoms taken together can form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R 4 ; and

each R 4 is a C 1-20 hydrocarbyl group.

23. A process as claimed in claim 2 wherein the complex is of formula (VII) or (VII'):

wherein each X is a sigma ligand;

R′ is independently a C 1-6 alkyl or C 3-10 cycloalkyl;

R 1 is independently C 3-8 alkyl;

R 6 is hydrogen or a C 3-8 alkyl group;

R 6′ is a C 3-8 alkyl group or C 6-10 aryl group;

R 3′ is a C 1-6 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups; and

n is independently 0, 1 or 2.

24. A process as claimed in claim 2 , wherein the propylene copolymer is a heterophasic propylene copolymer.

25. A process as claimed in claim 2 , wherein said catalyst is in solid particulate form.