Rotomolding process with reduced cycle times

Details Rotomolding process with reduced cycle times Rotomolding process with reduced cycle times

2007-04-10

2007-04-10

Johnson, Christina (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

C264S319000

Reexamination Certificate

active

10886928

ABSTRACT:
The cycle time for a rotomolding process is improved through the use of a molding material comprising a blend of at least two polyethylenes having narrow molecular weight distributions and homogeneous comonomer distributions. Alternatively, the molding temperature may be reduced to conserve energy and reduce energy costs. The polyethylene blend also has a narrow molecular weight distribution of less than 3 and a density of from 0.930 to 0.950 g/cc. Rotomolded parts prepared from the blend composition have excellent impact resistance and are also resistant to warpage. A preferred process employs a blend composition which contains a blend component having a higher molecular weight and a lower density than another blend component—this blend may be used to prepare rotomolded parts with warpage resistance and improved environmental stress crack resistance (ESCR). A highly preferred process uses a blend composition which further contains a minor amount (from 0.5 to 10 weight %) of a third ethylene blend component which has a higher molecular weight and density—this highly preferred composition may be used to prepare rotomolded parts having warpage resistance, very good ESCR and comparatively high modulus (or stiffness).

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