Catalyst composition for polyolefin polymers
A Ziegler-Natta catalyst composition is disclosed. The catalyst composition is formed from a procatalyst containing a magnesium moiety and a titanium moiety. At least one internal electron donor is incorporated into the procatalyst. During a titanation procedure in conjunction with the internal electron donor, a titanium extractant is used to remove or deactivate low activity or atactic titanium active sites.
1 . A process for producing a Ziegler-Natta procatalyst composition comprising: subjecting a procatalyst comprising magnesium to at least a first titanation step and a second titanation step; incorporating an internal electron donor into the procatalyst during the first titanation step; and contacting the procatalyst with a titanium extractant during the second titanation step or after the titanation steps, the titanium extractant removing titanium on the procatalyst, wherein the internal electron donor comprises an aryl diester, and wherein the titanium extractant comprises a monoester, a ketone, a carbonate, or mixtures thereof.
2 . The process of claim 1 , wherein the titanium extractant comprises a monoester.
3 . The process of claim 1 , wherein the titanium extractant comprises an alkyl benzoate.
4 . The process of claim 1 , wherein the aryl diester comprises a naphthyl dibenzoate having the following formula:
wherein:
each R 5 and R 6 is independently hydrogen, halogen, alkyl having 1 to about 8 carbon atoms, phenyl, arylalkyl having 7 to about 18 carbon atoms, or alkylaryl having 7 to about 18 carbon atoms.
5 . The process of claim 1 , wherein the procatalyst is contacted with the titanium extractant during the first titanation step.
6 . The process of claim 1 , wherein the procatalyst is contacted with the titanium extractant during the second titanation step.
7 . The process of claim 1 , wherein during the first titanium step, the procatalyst is contacted with the internal electron donor in the absence of the titanium extractant and wherein during the second titanation step, the procatalyst is contacted with the titanium extractant in the absence of the internal electron donor.
8 . The process of claim 1 , wherein during the first titanation step, the procatalyst is contacted with the internal electron donor and the titanium extractant and wherein during the second titanation step, the procatalyst is contacted with the titanium extractant, or both the internal electron donor and the titanium extractant.
9 . The process of claim 1 , wherein the procatalyst comprises a spray crystallized magnesium halide compound.
10 . The process of claim 9 , wherein the spray crystallized magnesium halide compound comprises ethanol and magnesium chloride in a weight ratio of from about 1.5:1 to about 3.1:1.
11 . The process of claim 1 , wherein the aryl diester is represented as:
wherein:
R 1 and R 4 are each hydrogen or a hydrocarbyl group having from 1 to 20 carbon atoms; and
at least one of R 2 and R 3 is hydrogen; and
at least one of R 2 and R 3 comprises a substituted or unsubstituted hydrocarbyl group having from 1 to 20 carbon atoms;
E 1 and E 2 are the same or different and selected from the group consisting of an alkyl having 1 to 20 carbon atoms, a substituted alkyl having 1 to 20 carbon atoms, an aryl having 6 to 20 carbon atoms, a substituted aryl having 6 to 20 carbon atoms, or an inert functional group having 1 to 20 carbon atoms and optionally containing heteroatoms;
X 1 and X 2 are each O, S, an alkyl group or NR 5 and wherein R 5 is a hydrocarbyl group having 1 to 20 carbon atoms or is hydrogen.
12 . The process of claim 11 , wherein at least one of R 2 and R 3 comprises a hydrocarbyl group having a branched or linear structure or comprising a cycloalkyl group having from 5 to 15 carbon atoms.
13 . The process of claim 1 , wherein the procatalyst comprises a magnesium moiety having the following formula:
Mg(OR) n X 2−n L m
wherein:
R comprises an alkyl or aryl group containing a halogen atom;
n is 0 to 2;
L comprises coordinated ligand groups of ethers and/or alcohols;
m is from 0 to 10; and
a titanium moiety represented by the following formula:
Ti(OR′) g X 4−g
wherein each R′ is independently a C 1 -C 4 alkyl group; X is bromine, chlorine or iodine; and g is 0, 1, 2 or 3.
14 . A catalyst composition comprising:
the procatalyst composition produced by the process of claim 13 ;
a cocatalyst; and
optionally, a selectivity control agent.
15 . The catalyst composition of claim 14 , wherein the cocatalyst comprises triethylaluminum.
16 . The catalyst composition of claim 14 , wherein the selectivity control agent is present and comprises an alkoxysilane.
17 . The catalyst composition of claim 14 , wherein the selectivity control agent comprises dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane, methylcyclohexyldiethoxysilane, ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, di-n-propyldimethoxysilane, diisobutyldimethoxysilane, diisobutyldiethoxysilane, isobutylisopropyldimethoxysilane, di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, diethylaminotriethoxysilane, cyclopentylpyrrolidinodimethoxysilane, bis(pyrrolidino)dimethoxysilane, bis(perhydroisoquinolino)dimethoxysilane, dimethyldimethoxysilane or mixtures thereof.
18 . The catalyst composition of claim 14 , wherein the catalyst composition further comprises an activity limiting agent.
19 . A process for producing a polyolefin polymer comprising: polymerizing a propylene monomer and optionally one or more comonomers in the presence of a catalyst composition as defined in claim 14 .
20 . A process as defined in claim 19 , wherein the process produces a polypropylene polymer having a xylene solubles content of from about 0.5% to about 6% by weight.