Stabilization of mixed catalyst polyethylene
AssigneeNOVA Chemicals (International) S.A.
InventorsDerek Wasylenko, Tony Tikuisis, Owen Lightbody, Fraser Waldie
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Abstract
The present disclosure relates to systems including a ternary stabilization package that contains a first phosphite, a second phosphite and a primary antioxidant is used in combination with a polyethylene that is polymerized with a mixed catalyst system that contains two different types of catalysts. In some embodiments the stabilized polyethylene exhibits improved color performance.
Claims19
A process for stabilizing a thermoplastic polyethylene product during melt processing conditions wherein said thermoplastic polyolefin product is prepared with at least two catalyst systems and contains catalyst residues comprising
- a) titanium;
- b) aluminum from at least one aluminoxane;
- and
- c) magnesium from magnesium chloride;
- said process comprising the step of incorporating into said thermoplastic polyolefin a stabilizer package comprising:
- (i) a first phosphite defined by the formula (I);
- wherein R1, R2, R4 and R5 are each independently chosen from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and R3 is chosen from a hydrogen atom or an alkyl group having 1 to 8 carbon atoms;
- X is chosen from a single bond, a sulfur atom or a —CHR6 group (R6 is chosen from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms);
- A is chosen from an alkylene group having 1 to 8 carbon atoms or a *—COR7 group (R7 is chosen from a single bond or an alkylene group having 1 to 8 carbon atoms, and * denotes a bonding hand on the side of oxygen);
- and one of Y and Z is chosen from a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other one of Y and Z is chosen from a hydrogen atom or an alkyl group having 1 to 8 carbon atoms);
- (ii) a second phosphite that is different from said first phosphite;
- and
- (iii) a hindered phenolic antioxidant;
- subjecting said thermoplastic polyethylene product to sufficient temperature to cause it to melt.
A process for preparing a thermoplastic polyethylene product comprising:
- 1) polymerizing polyethylene, optionally with one or more C3-10 alpha olefins, under solution polymerization conditions in the presence of a first single site catalyst system comprising an organotitanium catalyst and an aluminoxane cocatalyst to form a first polyethylene solution;
- 2) polymerizing polyethylene, optionally with one or more C3-10 alpha olefins, under solution polymerization conditions in the presence of a second catalyst system comprising a titanium catalyst;
- an organoaluminum cocatalyst and magnesium chloride to form a second polyethylene solution;
- 3) combining said first polyethylene solution and said second polyethylene solution to form a combined polyethylene solution;
- 4) recovering said thermoplastic polyethylene product from said combined polyethylene solution;
- and
- 5) adding to said thermoplastic polyethylene product a stabilizer system comprising:
- (i) a first phosphite defined by the formula (I);
- wherein R1, R2, R4 and R5 each is independently chosen from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and R3 is chosen from a hydrogen atom or an alkyl group having 1 to 8 carbon atoms;
- X is chosen from a single bond, a sulfur atom or a —CHR6 group (R6 is chosen from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms);
- A is chosen from an alkylene group having 1 to 8 carbon atoms or a *—COR7 group (R7 is chosen from a single bond or an alkylene group having 1 to 8 carbon atoms, and * denotes a bonding hand on the side of oxygen);
- and one of Y and Z is chosen from a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other one of Y and Z is chosen from a hydrogen atom or an alkyl group having 1 to 8 carbon atoms);
- (ii) a second phosphite that is different from said first phosphite;
- and
- (iii) a hindered phenolic antioxidant.
Dependencies are inferred from the claim text.