Rotational moulding
AssigneeRotec Chemicals Limited
InventorRonald Ian Kliene
Life of this patent
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Abstract
A method of producing a plastics article having solid skin and a foam core by a rotational moulding process, comprises charging a mold with a skin-forming component and substantially simultaneously with a foam core-forming component of bulk density greater than 0.5 g/cc, providing a first heating stage in which the mold is heated to a first temperature and is rotated for a first predetermined time to form a substantially impervious skin within the mold, and providing a second heating stage in which the mold is heated to a higher second temperature and is rotated for a second predetermined time to cause foaming of said foam core-forming component, thereby forming a foam core within said substantially impervious skin.
Claims19
A method of producing a plastics article having solid skin and a foam core by a rotational moulding process, the method comprising:
- charging a mould with a skin-forming component including a first plastics material in the form of a comparatively fine powder and substantially simultaneously with a foam core-forming component including a second plastics material and a blowing agent in the form of comparatively large pellets,
- providing a first heating stage in which the mould is heated in an oven to a first controlled temperature that is equal to the melting temperature of the first plastics material plus 0-10° C., said first controlled temperature being sufficient to melt the first plastics material without causing foaming of the second plastics material and the mould is rotated for a first predetermined time to form within the mould a skin,
- providing a second heating stage in which the oven temperature is increased so that the mould is heated to a higher second controlled temperature that is sufficient to cause foaming of the second plastics material and is rotated for a second predetermined time to cause foaming of said foam core-forming component, thereby forming a foam core within said skin.
Dependencies are inferred from the claim text.