Polyolefin production
Use of a metallocene compound of general formula Ind 2 R″MQ 2 as a component of a catalyst system in producing polyethylene, wherein each Ind is the same or different and is indenyl or substituted indenyl; R″ is a bridge which comprises a C 1 to C 4 alkylene radical, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine, which bridge is substituted or unsubstituted, M is a Group IV metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3. The metallocene may be supported. The ethylene may be polymerized in a reaction medium that is substantially free of any external comonomer, with comonomer being formed in situ. The produced polyethylene may have long chain branching. The produced polyethylene may be atactic.
1. A branched polyethylene copolymer formed by a process comprising:
supplying ethylene monomer;
supplying hexene monomer;
forming butene in situ and copolymerizing the ethylene monomer, the hexene monomer and the butene monomer formed in situ in a reaction medium which comprises a solution or slurry with a catalyst system comprising:
a metallocene compound of general formula Ind 2 R″MQ 2 having a mole ratio of meso to racemic forms of the metallocene of at least 1:3, wherein
each Ind is the same or different and is indenyl or substituted indenyl,
R″ is a bridge that is substituted or unsubstituted and comprises a C 1 to C 4 alkylene radical, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine,
M is a Group IV metal or vanadium,
each Q is a hydrocarbyl having 1 to 20 carbon atoms or a halogen,
said catalyst being further comprised of an inert support; and
using a cocatalyst which activates the metallocene compound;
wherein the shear ratio of the copolymer is between 35 and 60.
2. The copolymer of claim 1 , wherein the cyclopentadienyl ring of at least one of the indenyls is unsubstituted.
3. The copolymer of claim 1 , wherein the R″ is an ethylene bridge.
4. The copolymer of claim 1 , wherein both indenyls are unsubstituted.
5. The copolymer of claim 1 , wherein M is Zr.
6. The copolymer of claim 1 , wherein the Q is a halogen.
7. The copolymer of claim 1 , wherein the cocatalyst comprises an aluminum-containing cocatalyst or a boron-containing cocatalyst.
8. The copolymer of claim 7 , wherein the cocatalyst is an aluminum-containing cocatalyst comprising an alumoxane, an alkyl aluminum or a Lewis acid.
9. The copolymer of claim 1 , wherein the butene monomer is formed in situ by dimerization of the ethylene.
10. The copolymer of claim 1 , wherein the copolymer has ethyl branching arising from butene incorporation into the backbone of the copolymer.
11. The copolymer of claim 10 , wherein the copolymer has butane branching.
12. The copolymer of claim 1 , wherein there is no diffusion barrier between the butene monomer formed in situ and the growing copolymer.