Bimodal polyethylene resins and pipes produced therefrom
Disclosed herein are ethylene-based polymers generally characterized by a density of at least 0.94 g/cm 3 , a high load melt index from 4 to 20 g/10 min, a zero-shear viscosity at 190° C. from 20,000 to 400,000 kPa-sec, and a relaxation time at 190° C. from 225 to 3000 sec. These ethylene polymers can be produced by peroxide-treating a broad molecular weight distribution Ziegler-catalyzed resin, and can be used in large diameter, thick wall pipes and other end-use applications.
1. An ethylene polymer having:
a density of at least about 0.94 g/cm 3 ;
a HLMI (I 21 ) in a range from about 4 to about 20 g/10 min;
a ratio of Mw/Mn in a range from about 13 to about 38;
a zero-shear viscosity (go) at 190° C. in a range from about 20,000 to about 400,000 kPa-sec; and
a relaxation time (τ η ) at 190° C. in a range from about 225 to about 3000 sec.
2. An article of manufacture comprising the polymer of claim 1 .
3. The polymer of claim 1 , wherein:
the density is in a range from about 0.94 to about 0.96 g/cm 3 ;
the HLMI (I 21 ) is in a range from about 4 to about 18 g/10 min;
the zero-shear viscosity (η 0 ) at 190° C. is in a range from about 30,000 to about 300,000 kPa-sec; and
the relaxation time (τ η ) at 190° C. is in a range from about 250 to about 2500 sec.
4. A pipe comprising the polymer of claim 3 .
5. The polymer of claim 3 , wherein the ethylene polymer has:
a CY-a parameter at 190° C. in a range from about 0.06 to about 0.25;
a number of long chain branches (LCB) in a range from about 5 to about 50 LCB per million total carbon atoms;
a viscosity at 0.01 sec −1 at 190° C. in a range from about 300 to about 800 kPa-sec; and
a viscosity at 0.001 sec −1 at 190° C. in a range from about 800 to about 3000 kPa-sec.
6. The polymer of claim 5 , wherein:
the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, an ethylene homopolymer, or a combination thereof; and
the ethylene polymer further comprises an additive selected from an antioxidant, an acid scavenger, an antiblock additive, a slip additive, a colorant, a filler, a processing aid, a UV inhibitor, or any combination thereof.
7. The polymer of claim 6 , wherein:
the CY-a parameter at 190° C. is in a range from about 0.1 to about 0.18;
the number of long chain branches (LCB) is in a range from about 7 to about 20 LCB per million total carbon atoms;
the viscosity at 0.01 sec −1 at 190° C. is in a range from about 450 to about 750 kPa-sec; and
the viscosity at 0.001 sec −1 at 190° C. is in a range from about 1200 to about 2100 kPa-sec.
8. The polymer of claim 7 , wherein the ratio of Mw/Mn is in a range from about 18 to about 35.
9. The polymer of claim 3 , wherein the ratio of Mw/Mn is in a range from about 16 to about 37.
10. A pipe comprising:
an ethylene polymer characterized by a density of at least about 0.94 g/cm 3 , a HLMI (I 21 ) in a range from about 4 to about 20 g/10 min, a ratio of Mw/Mn in a range from about 13 to about 38, a zero-shear viscosity (η 0 ) at 190° C. in a range from about 20,000 to about 400,000 kPa-sec, and a relaxation time (τ η ) at 190° C. in a range from about 225 to about 3000 sec; and
an additive selected from an antioxidant, an acid scavenger, an antiblock additive, a slip additive, a colorant, a filler, a processing aid, a UV inhibitor, or any combination thereof.
11. The pipe of claim 10 , wherein the pipe comprises a colorant, and the colorant comprises carbon black.
12. The pipe of claim 10 , wherein the pipe comprises:
from about 1000 ppm to about 4500 ppm of a phenolic antioxidant; and
from about 250 ppm to about 4000 ppm of a phosphite antioxidant.
13. The pipe of claim 12 , wherein:
the pipe has a thickness in a range from about 0.5 to about 5 inches;
the pipe has an outer diameter in a range from about 12 to about 100 inches; and
the pipe comprises from about 250 ppm to about 800 ppm of an acid scavenger, and from about 300 ppm to about 600 ppm of a processing aid.
14. The pipe of claim 13 , wherein the ratio of Mw/Mn is in a range from about 16 to about 37.
15. The pipe of claim 10 , wherein the pipe is characterized by:
a failure time of at least 1200 hr under chlorinated water conditions at 90° C. and 450 psi;
a failure time of at least 3400 hr under chlorinated water conditions at 90° C. and 450 psi; or
a failure time of at least 7400 hr under chlorinated water conditions at 90° C. and 450 psi; or
any combination thereof.
16. The pipe of claim 10 , wherein the pipe is produced by a process that comprises melt processing the ethylene polymer and the additive through a pipe die to form the pipe, wherein the ethylene polymer comprises an ethylene/α-olefin copolymer.
17. An ethylene polymer having:
a density of at least about 0.94 g/cm 3 ;
a HLMI (I 21 ) in a range from about 4 to about 20 g/10 min;
a Mn in a range from about 10,200 to about 16,100 g/mol;
a zero-shear viscosity (η 0 ) at 190° C. in a range from about 20,000 to about 400,000 kPa-sec; and
a relaxation time (τ η ) at 190° C. in a range from about 225 to about 3000 sec.
18. The polymer of claim 17 , wherein:
the density is in a range from about 0.94 to about 0.96 g/cm 3 ;
the HLMI (I 21 ) is in a range from about 4 to about 18 g/10 min;
the zero-shear viscosity (η 0 ) at 190° C. is in a range from about 30,000 to about 300,000 kPa-sec; and
the relaxation time (τ η ) at 190° C. is in a range from about 250 to about 2500 sec.
19. The polymer of claim 18 , wherein the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, an ethylene homopolymer, or a combination thereof, and is further characterized by:
a CY-a parameter at 190° C. in a range from about 0.1 to about 0.18;
a number of long chain branches (LCB) in a range from about 7 to about 20 LCB per million total carbon atoms;
a viscosity at 0.01 sec −1 at 190° C. in a range from about 450 to about 750 kPa-sec; and
a viscosity at 0.001 sec −1 at 190° C. in a range from about 1200 to about 2100 kPa-sec.
20. A pipe comprising the polymer of claim 19 , a colorant, a phenolic antioxidant, and a phosphite antioxidant; wherein:
the pipe has a thickness in a range from about 0.5 to about 5 inches; and
the pipe has an outer diameter in a range from about 12 to about 100 inches.