Reduction of melt fracture in linear polyethylene
AssigneeThe Dow Chemical Company
InventorsLawrence T. Kale, Lionel H. Dagenais, Shih-Yaw Lai, William R. Van Volkenburgh, John O. Bieser
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Abstract
Polymer blends of at least one ethylene interpolymer product and at least one linear polyethylene are disclosed. The blends have a shear rate at the point of onset of melt fracture at least about 2 percent higher than that obtained for the linear polyethylene alone. The polymer blends are particularly useful for forming films and tapes wherein the melt fracture of the polymer blend is substantially reduced or eliminated, thereby improving extrudability and fabricated article appearance.
Claims11
A method of reducing melt fracture in melt processing a linear polyethylene comprising the steps of:
- (A) blending
- (i)a minor amount up to about 15 percent by weight of the final polymer blend of at least one ethylene alpha olefin interpolymer product comprising a higher molecular weight ethylene interpolymer and a lower molecular weight ethylene interpolymer, said interpolymer product having a density of about 0.935 grams/ml or less, a melt index from about 0.1 grams/10 minutes to about 4 grams/10 minutes, a melt flow ratio of at least about 9 and having from about 0.5 percent to about 8 percent by weight of the interpolymer product having a weight average molecular weight of at least about 1,000,000 grams/mole with
- (ii) at least one linear polyethylene having a melt flow ratio less than about 9 to form a polymer blend, and
- (B) extruding the polymer blend to form a fabricated article, wherein the amount of the ethylene interpolymer product is sufficient to increase the shear rate at the onset of melt fracture of the linear polyethylene by at least about 2 percent.
Dependencies are inferred from the claim text.