Method and apparatus for high speed extrusion of thermoplastic materials
AssigneeW. R. Grace & Co.
InventorsMichael D. Esakov, David C. Hudgens, Jr., Frederick D. Stringer
Life of this patent
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Abstract
In the process of extruding tubular thermoplastic film or tape, the production rate can be improved by using a smooth support plug to stabilize and shape the extrudate after it has been cooled and at least partially solidified. A principal function of the support plug is to assist in supporting the long slender column of partially solidified extrudate which is above the plug. The result is a significant increase in the output of the extrusion process.
Claims17
In the process of extruding thermoplastic materials in tubular form without expanding the tubular extrudate radially to a diameter greater than that of the extruder die the improvement which comprises:
- (a) disposing support means within said extruded tube, said support means being of larger diameter than said tube at the point of its contact therewith and having a passageway therethrough to equalize air pressure above and below said support means;
- and,
- (b) cooling and solidifying the inner wall of said tube prior to contact between said wall and said support means whereby the contact of said support means and tube wall causes the unsolidified extrudate upstream from said support means to be stable at high extrusion rates.
A method for the high speed production of tubular thermoplastic extrudate comprising the steps of:
- (a) providing a circular extrusion die,
- (b) providing an air mandrel having a porous outer surface through which air can be delivered, said mandrel being of smaller diameter than tubular melt extruded from said circular die, and said mandrel being supported below said extrusion die by air delivery means;
- (c) providing a support plug of diameter greater than the diameter of the tubular melt at the point of the plug's contact with the melt but less than the diameter of the extrusion die, said plug being located below said air mandrel and having an air pressure equalization passageway therethrough to equalize pressure above and below said support plug;
- (d) extruding a tubular thermoplastic extrudate downwardly from said extrusion die;
- (e) passing said tubular extrudate around but not in contact with said mandrel;
- (f) delivering air to said porous mandrel so that the emission of air from the mandrel's surface prevents contact between the extrudate and mandrel, said air cooling and solidifying the inner wall of said extrudate;
- and,
- (g) passing said extrudate over and around and in contact with said support plug, the contact between said plug and extrude causing the unsolidified extrudate upstream from said extrudate to be stable at high production rates.
Apparatus for the high speed production of tubular thermoplastic extrudate comprising:
- (a) a circular extrusion die;
- (b) means for delivering molten thermoplastic material to said die;
- (c) interior cooling means located below said die for solidifying the interior wall of said extrudate while not in direct contact therewith, said interior cooling means having a diameter smaller than the tubular extrudate;
- and,
- (d) support means located below said interior cooling means and having an air pressure equalization passageway therethrough, said support means having a diameter greater than that of the tubular extrudate at the point of contact therewith but less than the diameter of the extrusion die and being in contact with the inner periphery of said tubular extrudate thereby causing the unsolidified extrudate upstream of said support means to be stable under high speed operation.
Apparatus for high speed production of tubular thermoplastic extrudate comprising:
- (a) an extruder for producing a thermoplastic melt;
- (b) a circular extrusion die fed by said extruder for extruding a tubular extrudate downwardly;
- (c) a porous air mandrel having a diameter smaller than the diameter of said extrudate;
- (d) mandrel air supply means coaxially mounted to said circular extrusion die and extending downwardly therefrom to support said mandrel;
- and,
- (e) support plug means mounted coaxilly below said mandrel, said support plug having an air pressure equalization passageway therethrough and a diameter larger than said extrudate but less than the diameter of the extrusion die whereby contact between said plug and extrudate stabilizes the extrudate upstream from said plug.
Dependencies are inferred from the claim text.