Granted Patent B2

US 8,202,936 · App. 11/631,588 · Granted Jun 19, 2012

Abstract

Claims (26)

1. A process of producing an ethylene polymer composition in multiple stages, said process comprising polymerizing ethylene, alone, or with a comonomer, to produce an ethylene polymer in a first stage, transferring the polymer produced in the first stage into a second stage, in which a second stage ethylene is polymerized, alone, or with a comonomer, in the presence of the polymer produced in the first stage, and wherein the first stage is a slurry polymerization stage, and the polymerization in the first stage is carried out in the presence of a catalyst system comprising: (a) a solid catalyst precursor comprising a transition metal selected from titanium and vanadium; magnesium, a halide, an electron donor, and a solid particulate material comprising an inorganic oxide, and (b) an organoaluminium compound; and

wherein the median particle diameter of the solid catalyst precursor, based upon the total volume of solid catalyst precursor, D 50 , is from 4 to 9 micrometers.

2. The process of claim 1 , wherein the solid catalyst system, (a), comprises:

(i) a titanium based catalyst precursor having the formula Mg a Ti(OR) b Xc(ED) d , wherein

R is an aliphatic or aromatic hydrocarbon radical having 1 to 14 carbon atoms or COR′, wherein R′ is an aliphatic or aromatic hydrocarbon radical having 1 to 14 carbon atoms; and wherein

each OR group is the same or different;

each X is independently chlorine, bromine, or iodine;

ED is an electron donor;

a is 0.5 to 56;

b is 0, 1 or 2;

c is 2 to 116; and

d is less than or equal to 1.5a+4;

(ii) at least one modifier having the formula BX 3 or AlR( 3-b )X b , wherein each R is alkyl or aryl and is the same or different, and X and b are as defined above for component (a); and

wherein the organoaluminium compound, (b), comprises a hydrocarbyl aluminum compound.

3. The process of claim 1 , wherein the second stage is a slurry polymerization stage.

4. The process of claim 1 , consisting of two or three polymerization stages.

5. The process of claim 1 , consisting of two stages, wherein, in the first stage, from 20-80 weight percent of polymer is produced, and in the second stage, from 80-20 weight percent of polymer is produced, based on the weight of the ethylene polymer composition.

6. The process of claim 4 , wherein, in the first stage, from 40-60 weight percent of polymer is produced, and in the second stage, from 60-40 weight percent of polymer is produced, based on the weight of the ethylene polymer composition.

7. The process of claim 1 , wherein the inorganic oxide is a silica.

8. The process of claim 1 , wherein the electron donor is tetrahydrofuran.

9. The process of claim 1 , wherein the median particle diameter of the solid catalyst precursor composition, D 50 , is from 6 to 9 micrometers.

10. The process of claim 1 , wherein the solid catalyst precursor satisfies the relationship:

2≧( D 90 −D 10 )/ D 50 ,

wherein D 50 is the median particle diameter, D 10 is the diameter for which 10 percent of the total volume of the solid catalyst precursor has a particle diameter of less than D 10 , and D 90 is the particle diameter for which 90 percent of the total volume of the solid catalyst precursor has a particle diameter less than D 90 .

11. The process of claim 1 , wherein the melt flow rate, MI 2 , measured according to ASTM D 1238-04, Condition 190/2.16, of the ethylene polymer leaving the first stage, is from 10 to 1000 g/10 min, and the melt flow rate, MI 5 , measured according to ASTM D 1238-04 Condition 190/5, of the ethylene polymer composition leaving the final reaction stage is from 0.02 to 5 g/10 min.

12. The process of claim 1 , wherein the density of the polymer leaving the first stage is from 0.940 to 0.980 g/cm 3 , and the density of the ethylene polymer composition leaving the final reaction stage is from 0.915 to 0.970 g/cm 3 .

Assignments (9)