US 9,809,664 B2
Bimodal propylene polymers and sequential polymerization
Luo Lubin, Houston, TX (US); Matthew W. Holtcamp, Huffman, TX (US); and Gregory S. Day, College Station, TX (US)
Assigned to ExxonMobil Chemical Patents Inc., Baytown, TX (US)
Filed by ExxonMobil Chemical Patents Inc., Baytown, TX (US)
Filed on Apr. 29, 2016, as Appl. No. 15/142,268.
Claims priority of provisional application 62/171,630, filed on Jun. 5, 2015.
Prior Publication US 2016/0355655 A1, Dec. 8, 2016
Int. Cl. C08F 4/02 (2006.01); C08F 210/06 (2006.01); C08F 4/6592 (2006.01); C08F 110/06 (2006.01); C08F 4/659 (2006.01)
CPC C08F 110/06 (2013.01) [C08F 4/02 (2013.01); C08F 4/65916 (2013.01); C08F 210/06 (2013.01); C08F 4/65912 (2013.01)] 26 Claims
 
1. A process to polymerize propylene comprising:
(a) contacting monomer comprising propylene under polymerization conditions with a catalyst system comprising a single site catalyst precursor compound, an activator, and a support comprising an average particle size of more than 30 μm, a surface area of 400 m2/g or more, a pore volume of from 0.5 to 2 mL/g, and a mean pore diameter of from 1 to 20 nm (10 to 200 Å);
(b) polymerizing the propylene in (a) for a time period, A1 to form a first mode of propylene polymer comprising at least 50 mol % propylene;
(c) adding hydrogen or other chain transfer agent and optional comonomer to the polymerization after time period A1;
(d) then polymerizing the propylene in (a) in the presence of at least 1 mmol of the hydrogen or other chain transfer agent per mol of propylene for a time period, A2, wherein a concentration of the hydrogen or other chain transfer agent during time period A2 is greater than the concentration of the hydrogen or other chain transfer agent in time period A1 to form a second mode of the propylene polymer having a lower Mw with respect to the first mode; and
(e) forming a matrix of the propylene polymer, the matrix having a porosity, after time period A2, of 15% or more, as determined by mercury intrusion porosimetry.