The use of polyethylene compositions, such as linear low density polyethylenes and/or high density polyethylenes, in fabrication of rotational molded articles is generally known. Any conventional method, such as gas phase process, slurry process, solution process or high pressure process, may be employed to produce such polyethylene compositions.
In general, in the rotational molding process, polymeric materials are placed into a heated mold. The heated mold causes the polymeric materials to melt and form a puddle at the bottom of the mold cavity. The mold is then slowly rotated, usually around two perpendicular axes, causing the melted polymeric materials to flow into to the mold and stick to its walls. In order to maintain even thickness throughout the part, the mold continues to rotate during the cooling phase.
Various polymerization techniques using different catalyst systems have been employed to produce such polyethylene compositions suitable for rotational molding applications. However, the currently available polyethylene compositions fail to provide a stiffness/toughness balance that is required for rotational moldings applications.
Despite the research efforts in developing polyethylene compositions suitable for rotational molding, there is still a need for a polyethylene composition having a narrow molecular weight distribution, narrow composition distribution, and improved impact resistance while maintaining stiffness and processability properties. Additionally, there is a need for a method of producing such polyethylene compositions having a narrow molecular weight distribution, narrow composition distribution, and improved impact resistance while maintaining stiffness and processability properties.
USPTO Backgrounds
USPTO Backgrounds