Process for producing large symmetrical polymer particles

Claim 2

A process for producing large symmetrical polyolefin particles comprising: (a) prepolymerizing a precipitated active complex of an organoaluminum compound and a metallocene catalyst by contacting said complex with an olefin monomer at a temperature significantly below the polymerization temperature of said olefin monomer, wherein said metallocene catalyst is described by the formula; R˝(C₅R′ m )₂ Me Q p (C₅R′ m ) is a cyclopentadienyl or substituted cyclopentadienyl; R′ is hydrogen or hydrocarbyl radical(s) having 1-20 carbon atoms, and each R′ can be the same or different; R˝ is an alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl compound, a germanium hydrocarbyl compound, an alkyl phosphine, or an alkyl amine, and R˝ acts to bridge the two (C₅R′ m ) rings; Q is a hydrocarbon radical having 1-20 carbon atoms or a halogen; Me is a group 4b, 5b, or 6b metal of the Periodic Table of Elements; M is an integer from 0-4; and P is an integer from 0-3; and (b) polymerizing said olefin monomer under polymerization conditions thereby producing large symmetrical polyolefin particles.

Claim 3

The process according to claim 1 wherein said precipitated active complex is prepared by precontacting said organoaluminum compound with said metallocene catalyst thereby forming an active complex, followed by precipitating said active complex with a hydrocarbon that is a nonsolvent for said active complex.

Claim 4

The process according to claim 1 wherein said olefin monomer is selected from alpha olefins having 3 to 5 carbon atoms.

Claim 5

The process according to claim 3 wherein said olefin monomer is propylene, step (a) is commenced below about 40°C and step (b) is conducted at a temperature below about 85°C.

Claim 6

The process according to claim 2 wherein said metallocene catalyst is selected from the group consisting of syndiospecific and isospecific metallocenes.

Claim 7

The process according to claim 1 wherein said metallocene catalyst is selected from the group consisting of zirconocene, hafnocene and titanocene catalysts.

Claim 8

The process according to claim 6 wherein said metallocene catalyst is a zirconocene catalyst.

Claim 9

The process according to claim 1 wherein said organoaluminum compound is a methylalumoxane.

Claim 10

The large symmetrical polyolefin particles prepared according to the process of claim 1.

Claim 11

A process for producing large symmetrical polyolefin particles having a relatively narrow particle size distribution comprising: (a) precontacting an oranoaluminum compound with a metallocene catalyst thereby forming an active complex, wherein said metallocene catalyst is described by the formula: R˝(C₅R′ m )₂ Me Q p (C₅R′ m ) is a cyclopentadienyl or substituted cyclopentadienyl; R′ is hydrogen or hydrocarbyl radical(s) having 1-20 carbon atoms, and each R′ can be the same or different; R˝ is an alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl compound, a germanium hydrocarbyl compound, an alkyl phosphine, or an alkyl amine, and R˝ acts to bridge the two (C₅R′ m ) rings; Q is a hydrocarbon radical having 1-20 carbon atoms or a halogen; Me is a group 4b, 5b, or 6b metal of the Periodic Table of Elements; M is an integer from 0-4; and P is an integer from 0-3; (b) precipitating the complex of (a) with a hydrocarbon that is a nonsolvent for said complex wherein said hydrocarbon is selected from the group consisting of alycyclic and aliphatic hydrocarbons; (c) prepolymerizing the precipitated complex of (b) by contacting said complex with an olefin monomer having 3 to 12 carbon atoms at a temperature significantly below the polymerization temperature of said olefin monomer; and (d) polymerizing said olefin monomer under polymerization conditions thereby producing large symmetrical polyolefin particles.

Claim 12

A process for producing large symmetrical polyolefin particles having a relatively narrow particle size distribution comprising: (a) precontacting an oranoaluminum compound with a metallocene catalyst thereby forming an active complex, wherein said metallocene catalyst is described by the formula: R˝(C₅R′ m )₂ Me Q p (C₅R′ m ) is a cyclopentadienyl or substituted cyclopentadienyl; R′ is hydrogen or hydrocarbyl radical(s) having 1-20 carbon atoms, and each R′ can be the same or different; R˝ is an alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl compound, a germanium hydrocarbyl compound, an alkyl phosphine, or an alkyl amine, and R˝ acts to bridge the two (C₅R′ m ) rings; Q is a hydrocarbon radical having 1-20 carbon atoms or a halogen; Me is a group 4b, 5b, or 6b metal of the Periodic Table of Elements; M is an integer from 0-4; and P is an integer from 0-3; (b) precipitating the complex of (a) with a hydrocarbon that is a nonsolvent for said complex wherein said hydrocarbon is selected from the group consisting of alycyclic and aliphatic hydrocarbons; (c) prepolymerizing the precipitated complex of (b) by contacting said complex with an olefin monomer having 3 to 12 carbon atoms at a temperature significantly below the polymerization temperature of said olefin monomer; and (d) polymerizing said olefin monomer under polymerization conditions thereby producing large symmetrical polyolefin particles.

Claim 13

The process according to claim 10 wherein said temperature significantly below the polymerization temperature of said step (c) is held for a time between 1 and 6 minutes followed by heating said complex and said olefin monomer to the polymerization temperature of said olefin monomer at a rate of at least 5°C per minute.

Claim 14

The process according to claim 10 wherein said hydrocarbon of step (b) and said olefin monomer of step (c) are identical, and said step (b) is conducted at a temperature significantly below the polymerization of said olefin monomer.

Claim 15

The process according to claim 12 wherein said olefin monomer is propylene, step (c) is commenced below about 40°C and step (d) is conducted at a temperature below about 80°C.

Claim 16

The process according to claim 13 wherein said metallocene catalyst is selected from the group consisting of syndiospecific and isospecific metallocenes.

Claim 17

The process according to claim 10 wherein said metallocene catalyst is selected from the group consisting of zirconocene, hafnocene and titanocene catalysts.

Claim 18

The process according to claim 15 wherein said metallocene catalyst is a zirconocene catalyst.

Claim 19

The process according to claim 15 wherein said organoaluminum compound is a methylalumoxane.

Claim 20

A composition comprising large symmetrical polyolefin particles containing metallocene having a bulk density greater than about 0.3 g/ml with the majority of the particles being larger than 400 microns.

Claim 21

A composition comprising large symmetrical polyolefin particles containing metallocene having a bulk density greater than about 0.3 g/ml with the majority of the particles being larger than 400 microns.

Claim 22

The composition according to claim 18 wherein said polyolefin particles are polypropylene particles.

Claim 23

The composition according to claim 19 wherein said polypropylene particles are selected from the group consisting of isotactic and syndiotactic polypropylene particles.

Claim 24

The composition according to claim 18 wherein said particles have a particle size distribution within the range of about 300 to 800 microns.