Process to visbreak propylene-based polymers with C—C initiators
The invention provides a process to prepare a second propylene-based polymer from a first propylene-based polymer, each propylene-based polymer having a melt flow rate (MFR; 2.16 kg/230° C.) with the MFR of the second propylene-based polymer greater than the MFR of the first propylene-based polymer, the process comprising the step of contacting under visbreaking conditions the first propylene-based polymer with at least one carbon-carbon (C—C) free-radical initiator of Structure (I): (Structure (I)) wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each, independently, a hydrocarbyl group or a substituted hydrocarbyl group, and wherein, optionally, two or more R groups (R 1 , R 2 , R 3 , R 4 , R 5 and R 6 ) form a ring structure.
1. A process to prepare a second propylene-based polymer from a first propylene-based polymer, each propylene-based polymer having a melt flow rate (MFR; 2.16kg/230° C.) with the MFR of the second propylene-based polymer greater than the MFR of the first propylene-based polymer, the process comprising the step of contacting under visbreaking conditions in the absence of oxygen and in the absence of oxygen-containing compounds the first propylene-based polymer with at least one carbon-carbon (C-C) free-radical initiator of Structure I:
wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each, independently, a C 1 -C 12 hydrocarbyl group.
2. The process of claim 1 , wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each, independently, a C 1 -C 8 hydrocarbyl group.
3. The process of claim 1 comprising contacting the first propylene-based polymer with from 0.05 wt % to 0.5 wt % C-C free-radical initiator, based on the weight of the first propylene-based polymer.
4. The process of claim 1 , wherein the C-C free-radical initiator has a decomposition temperature of greater than 130° C. based on DSC measurements.
5. The process of claim 1 , comprising contacting the first propylene-based polymer with at least two different C-C free-radical initiators.
6. The process of claim 1 , wherein R 1 and R 4 are each a phenyl group.
7. The process of claim 1 , wherein the at least one C-C free radical initiator is 3,4-diethyl-3,4-diphenyl hexane.
8. The process of claim 1 , wherein the MFR of the second propylene-based polymer is at least 130% of the MFR of the first propylene based polymer.
9. The process of claim 1 , wherein the visbreaking conditions further include contacting the first propylene-based polymer with the C-C free radical initiator under an inert atmosphere.
10. The process of claim 1 , wherein the first propylene-based polymer has a density from 0.83 g/cc to 0.90 g/cc.
11. The process of claim 10 , wherein the first propylene-based polymer has a molecular weight distribution from 3 to 5.
12. The process of claim 1 , wherein the visbreaking conditions further include activating the C-C free radical initiator by radiation.
13. The process of claim 1 wherein the visbreaking conditions further include contacting the first propylene-based polymer with the C-C free radical initiator at a temperature from 200° C. to 350° C.
14. The process of claim 1 , wherein the at least one C-C free radical initiator is selected from the group consisting of 2,3-dimethyl-2,3-diphenyl butane, 3,4-diethyl-3,4-diphenyl hexane, 3,4-diisobutyl-3,4-diphenyl hexane, 3,4-dibenzyl-3,4-ditolyl hexane, 2,7-dimethyl-4,5-diethyl-4,5-diphenyl octane, 3,4-diethyl-3,4-di(dimethylphenyl) hexane, 3,4-dibenzyl-3,4-diphenyl hexane, poly-1,4-diisopropyl benzene, and combinations thereof.