Process for producing large symmetrical polymer particles

Claim 2

A process for producing symmetrical polypropylene particles comprising : (a) prepolymerizing a precipitated active complex of an organoaluminum compound and a metallocene catalyst by contacting said complex with propylene at a temperature from 25 ° C to 40 ° C (b) further prepolymerizing the complex by heating to the polymerization temperature as rapidly as possible, and (c) polymerizing the propylene at a polymerization temperature higher than 50 ° C and lower than 85 ° C thereby producing symmetrical polypropylene particles between 300 and 800 microns with 90% of the particles being larger than 100 microns, wherein said metallocene catalyst is described by the formula; (C 5 R'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 group, a germanium hydrocarbyl group, 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.

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 2 wherein said metallocene catalyst is selected from the group consisting of syndiospecific and isospecific metallocenes.

Claim 5

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

Claim 6

The process according to claim 4 wherein said metallocene catalyst is a zirconocene catalyst.

Claim 7

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

Claim 8

The process according to Claim 1 wherein the prepolymerization temperature of step (a) is held for a time between 0 and 10 minutes.

Claim 9

The process according to Claim 1 wherein the prepolymerization temperature is 30 ° C and the polymerization temperature is 70 ° C.

Claim 10

The process according to Claim 1 wherein the complex is further prepolymerized by heating to the polymerization temperature at a rate of at least 5 ° C per minute.

Claim 11

The process according to Claim 1 wherein the complex is further prepolymerized by heating to the polymerization temperature at a rate of at least 10 ° C per minute.

Claim 12

A process according to claim 1 wherein the symmetrical polypropylene particles have a relatively narrow particle size distribution, said process comprising : (a) precontacting an organoaluminum compound with a metallocene catalyst thereby forming an active complex, wherein said metallocene catalyst is described by the formula : (C 5 R'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 group, a germanium hydrocarbyl group, an alkyl phosphine, or an alkyl amine, and R" acts to bridge the two (C 5 R'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 propylene at a temperature from 25 ° C to 40 ° C; and (d) polymerizing the propylene at a polymerization temperature higher than 50 ° C and lower than 85 ° C thereby producing symmetrical propylene particles between 300 and 800 microns with 90% of the particles being larger than 100 microns.

Claim 13

The process according to Claim 11 wherein the hydrocarbon is propylene and the precipitation is carried out at a temperature below the polymerization temperature.

Claim 14

The process according to Claim 11 wherein the temperature of said step (c) is held for a time between 1 and 6 minutes.

Claim 15

The process according to Claim 13 wherein the temperature of said step (c) is held for 5 minutes.

Claim 16

The process according to Claim 11 wherein said metallocene catalyst is selected from the group consisting of syndiospecific and isospecific metallocenes.

Claim 17

The process according to Claim 11 wherein said metallocene catalyst is selected from the group consisting of zirconocene, hafnocene and titanocene catalysts.

Claim 18

The process according to Claim 16 wherein said metallocene catalyst is a zirconocene catalyst.

Claim 19

The process according to Claim 16 wherein said organoaluminum compound is a methylalumoxane.