Physical blend of polyethylenes
This invention discloses a process for the preparation of polyethylene resins having a multimodal molecular weight distribution that comprises the steps of: (i) providing a first high molecular weight metallocene-produced linear low density poly-ethylene (mLLDPE) resin having a density of from 0.920 to 0.940 g/cm 3 and a HLMI of from 0.05 to 2 g/10 min; (ii) providing a second high density polyethylene (HDPE) prepared either with a Ziegler-Natta or with a chromium based catalyst, said polyethylene having a density ranging from 0.950 to 0.970 g/cm 3 and a HLMI of from 5 to 100 g/10 min; (iii) physically blending together the first and second polyethylenes to form a polyethylene resin having a semi-high molecular weight, a broad or multimodal molecular weight distribution, a density ranging from 0.948 to 0.958 g/cm 3 and a HLMI of from 2 to 20 g/10 min.
1 - 13 . (canceled)
14 . A process involving the preparation of polyethylene resins having a broad or multimodal molecular weight distribution that comprises the steps of:
a. providing a first high molecular weight metallocene-produced linear low density polyethylene (mLLDPE) resin having a density of from 0.92 to 0.94 g/cm 3 and a HLMI of from 0.01 to 2 g/10 min;
b. providing a second high density polyethylene (HDPE) prepared either with a Ziegler-Natta catalyst or with a chromium-based catalyst, said polyethylene having a density ranging from 0.95 to 0.97 g/cm 3 and an HLMI of from 5 to 100 g/10 min; and
c. physically blending together the first and second polyethylenes to form a polyethylene resin having a semi-high molecular weight, a broad or multimodal molecular weight distribution, a density ranging from 0.948 to 0.958 g/cm 3 and an HLMI of less than 20 g/10 min.
15 . The process of claim 14 wherein said first polyethylene has a monomodal molecular weight distribution.
16 . The process of claim 15 wherein said second polyethylene has a bimodal molecular weight distribution.
17 . The method of claim 15 wherein said second polyethylene has a broad monomodal molecular weight distribution.
18 . The process of claim 14 wherein said second polyethylene is produced using a chromium oxide-based catalyst.
19 . The process of claim 14 wherein said first metallocene-produced linear low density polyethylene has a density of not more than 0.935 g/ml.
20 . The process of claim 19 wherein said first metallocene produced linear low density polyethylene has a density of not more than 0.93 g/ml.
21 . The process of claim 19 wherein said first metallocene produced linear low density polyethylene has a density of less than 0.925 g/ml.
22 . The process of claim 14 wherein the polyethylene blend has an HLMI of from 2 to 12 g/10 min.
23 . The process of claim 14 wherein the final polyethylene resin is a physical blend comprising at least 5 wt. % of the first metallocene-produced linear low density polyethylene.
24 . The process of claim 23 wherein the final polyethylene resin is a physical blend comprising from 15 to 50 wt. % of the first metallocene-produced linear low density polyethylene and from 85 to 50 wt. % of the second high density polyethylene.
25 . The process of claim 14 wherein said first high molecular weight polyethylene has a molecular weight distribution within the range of 2-4.5.
26 . The process of claim 14 wherein said first high molecular weight polyethylene has a molecular weight distribution of about 3.
27 . The process of claim 14 wherein said blended polyethylene resin has an impact resistance which is greater than 200 kJ/m 2 .
28 . The process of claim 14 further comprising blow molding the physically blended polyethylene resin of paragraph (c) to form an enclosure capable of containing a fluid and having an impact resistance at 23° C. greater than 200 kJ/m 2 .
29 . The process of claim 14 further comprising blow molding the physically blended polyethylene resin of paragraph (c) to form an enclosure capable of containing a fluid and having an impact resistance at −30° C. greater than 200 kJ/m 2 .
30 . A process involving the preparation of polyethylene resins having a bimodal molecular weight distribution that comprises the steps of:
a. providing a first polyethylene by contacting an ethylene monomer and a co-monomer comprising an alpha olefin having from 3 to 10 carbon atoms with a first catalyst system in a first reactor under first polymerization conditions to produce a first polyethylene having a first molecular weight, an HLMI of not more than 1.5 g/10 min. and a first density of not more than 0.94 g/ml and the first catalyst system comprising (i) a metallocene catalyst comprising a bis tetrahydroindenyl catalyst component; and (ii) an activating agent capable of activating the catalyst component;
b. providing a second polyethylene having a second higher density within the range of 0.95 to 0.97 g/cm 3 and a second larger HLMI within the range of 5 to 100 g/10 min., said polyethylene having a monomodal molecular weight distribution and being prepared with a Ziegler-Natta catalyst or a chromium-based catalyst; and
c. physically blending together the first and second polyethylenes to form a polyethylene resin having a bimodal molecular weight distribution, an HLMI of from 10 to 20 g/10 min. and a density of from 0.948 to 0.958 g/ml.
31 . The process of claim 30 wherein the metallocene catalyst used to prepare the first linear low density polyethylene is ethylene bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride.
32 . The process of claim 30 wherein said alpha olefin is hexene.
33 . The process of claim 30 wherein said first polyethylene has a density of no more than 0.93 g/ml.