Rogers Tool Works, Inc.

Trw Limited

John R Wolfe, Jr

A die assembly for plastic pelletizing apparatus of the type including a cooling bath into which the plastic is extruded. The die assembly includes a heated main body having first and second oppositely disposed exterior faces connected by a plurality of relatively small extrusion passageways. A layer of thermal insulation material overlies the second face, and a cover member having an outer surface adapted to be exposed to the cooling bath is positioned over the thermal insulation material and joined to the main body. Wear resistant insert members formed from a material having a higher coefficient of thermal conductivity than the material from which the cover member is made extend from the outer surface of the cover member through the layer of insulation into the main body. Extrusion outlet orifices are formed through the insert members and define continuations of the extrusion passageways of the main body. The relationship between the inserts, the cover, the insulation, and the main body produces an increased heat flow from the main body to the outer die face in confined areas about the orifices. This heat flow advantageously reduces the possibility of freeze-off and plugging of the orifices due to premature solidification of the extruded plastic.

Internally insulated extrusion die

An extrusion die of the type particularly suited for use in underwater pelletizing of polymeric materials. The die includes a die body having a forward end face with a plurality of extrusion ports passing therethrough terminating at the forward end face. A layer of insulating material is interposed between the forward end face at the area of the extrusion ports and a subplate which is constructed from the same material as the die body. The subplate is fixedly secured to the die body so as to form a substantially integral relationship therewith. A hardened facing construction is fixedly secured to the outer end face of the subplate. Both the facing and subplate allow communication therethrough with the extrusion ports. The insulating material retards or reduces heat transfer from the heated die body to the cooled facing during an extruding operation. A die body heating fluid flow passage in heat transfer relationship with the extrusion ports may include insulating material on a portion of the side walls thereof. Also, insulating material may be included on the die body forward end face radially adjacent the hardened facing.

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Rogers, AR, United States of America

John R Wolfe, Jr