| 摘要 |
A head for the coextrusion of a plurality of N thermoplastic materials, N representing a positive integer, consisting of N+1 thermally insulated plates which are substantially modular and fit together and are aligned by respective projections and recesses on each plate, each plate having a conduit to feed a thermoplastic material, one half of a collector-distributor cavity on one face for collecting and distributing the material, and one half of a channel on the same face which extends radially from the collector-distributor to a narrow annular space created by the separation between a central male inner body and the concentric inner surface of each plate. The intermediate plates between the end plates each also have on their second face a second half of a collector-distributor cavity and a second half of a channel which, by respective coupling with opposite halves of a collector-distributor cavity and opposite halves of a channel on the opposite face of an adjacent plate form a complete collector-distributor cavity and a complete channel which extend annularly over the entire plate, the radial position and width of the collector-distributor cavity and the channel being circumferentially eccentric with respect to the center of the head. The collector-distributor cavity is pear-shaped to impart a uniform velocity to the molten thermoplastic material and to avoid the formation of a flow junction which creates a weakness in the thin-film extruded product.
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