Copolymerization catalyst and process for polymerizing impact resistant ethylene-propylene polymers
AssigneeShell Oil Company
InventorsIsrael G. Burstain, Brian L. Goodall
Life of this patent
Estimating the term…
Abstract
A process for the preparation of ethylene-propylene impact copolymers at improved catalyst productivity rates involving the formation of a propylene prepolymer by polymerization of propylene in liquid phase in the presence of a catalyst system containing titanium halide supported on magnesium halide and aluminum alkyl complexed with an electron donor. Ethylene and propylene are block polymerized onto the prepolymer in a vapor phase reaction zone in the presence of a second catalyst system comprising a solution of a C.sub.5 -C.sub.9 polyalpha-monoolefin/catalyst/diluent.
Claims13
In the process for preparing impact resistant ethylene-propylene polymers having high impact properties combined with high stiffness, which process comprises:
- (a) preparing a propylene prepolymer by polymerizing propylene in a first liquid phase reaction zone in the presence of a first catalyst system comprising:
- (i) a highly active solid catalyst component comprising titanium tetrachloride, magnesium chloride, and an electron donor,
- (ii) as cocatalyst a compound AlR.sub.3 where R represents an alkyl group of from 2 to 8 carbon atoms, and
- (iii) a selectivity control agent which may be partly or totally complexed with the co-catalyst;
- (b) separating the propylene prepolymer from volatile constituents;
- and
- (c) introducing said separated propylene prepolymer, ethylene monomer and propylene monomer into at least one vapor phase reaction zone;
- the improvement wherein a second catalyst system is introduced into said vapor phase reaction zone, said second catalyst system comprising the solution prepared by:
- (i) polymerizing a C.sub.5 -C.sub.9 alpha-monoolefin in a second liquid phase reaction zone in the presence of a second catalyst system selected from the group consisting of:
- (i) a MgCl.sub.2 supported-type catalyst system comprising a highly active solid catalyst component comprising titanium tetrachloride, magnesium chloride, and an electron donor, and as cocatalyst a compound AlR.sup.1.sub.3 where R.sup.1 represents an alkyl group of from 2 to 8 carbon atoms;
- and
- (ii) a Ziegler/Natta-type catalyst system comprising an active TiCl.sub.3 catalyst component and an organo-aluminum compound of the formula AlR.sup.2.sub.n X.sub.3-n where R.sup.2 is an alkyl group of 2 to 12 carbon atoms, X is hydrogen or halogen and n has a value of from 0.1 to 3;
- and a diluent, wherein said diluent is selected such that the resulting polymer is soluble therein and wherein the amount of C.sub.5 -C.sub.9 alpha-monoolefin polymerized therein is about 0.05 to about 100 grams per gram of second catalyst system;
- and
- (ii) recovering the resultant catalyst-diluent-polymer mass.
Dependencies are inferred from the claim text.