Extrusion head for expanded plastic tubes
AssigneeSolvay (Societe Anonyme)
InventorsClaude Dehennau, Martine Kaszacs
Life of this patent
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Abstract
The invention relates to an extrusion head for the manufacture of tubes comprising at least one layer of expanded plastic by extruding a stream of molten plastic containing a blowing agent through an annular passage cross section made in the extrusion head and in which the stream of molten plastic containing the blowing agent spreads out circumferentially and welds itself to itself by the recombining of the two stream fronts, the said extrusion head being equipped with a special-purpose thermal regulation device allowing the molten plastic containing the blowing agent to be heated or cooled after the stream fronts have recombined.
Claims10
Extrusion head for the manufacture of tubes comprising at least one layer of expanded plastic by extruding a stream of molten plastic containing a blowing agent through an annular passage cross section made in the extrusion head and in which the stream of molten plastic containing the blowing agent spreads out circumferentially and welds itself to itself by the recombining of the two stream fronts, characterized in that the extrusion head is equipped with a special-purpose thermal regulation device allowing the molten plastic containing the blowing agent to be heated or cooled after the stream fronts have recombined.
Extrusion head according to the preceding claim, comprising at least one duct for the internal circulation of a heat transfer fluid.
Extrusion head according to any one of the preceding claims, in which the special-purpose regulation device ensures a temperature of between Tf+30° C. and Tf within the molten plastic containing the blowing agent, Tf being the melting point of the plastic.
Extrusion head according to any one of the preceding claims, characterized in that the annular passage cross section has a narrowing just before the opening via which the molten plastic containing the blowing agent leaves the extrusion head.
Extrusion head according to any one of the preceding claims, in which all the surfaces of the extrusion head which come into contact with the material that is to be expanded have a coating made of Teflon® resin.
Extrusion head according to any one of the preceding claims, further comprising a passageway for at least one layer of unexpanded plastic on the inside and/or on the outside of the layer of expanded plastic.
Method of manufacturing tubes comprising at least one layer of expanded plastic, using an extrusion head according to any one of the preceding claims.
Dependencies are inferred from the claim text.