Composite spinneret plate unit

Claim 1

AN IMPROVED COMPOSITE SPINNERET PLATE UNIT FOR SPINNING FILAMENTS OF POLYMERIC MATERIAL AND HAVING AN EXTREMELY PROLONGED USEFUL LIFE PERIOD AT OPERATING PRESSURES FROM BETWEEN 250 P.S.I. AND 2,000 P.S.I. AND AT TEMPERATURES ABOVE 600*C., SAID UNIT COMPRISING A STAINLESS STEEL PLATE PROVIDED WITH A LIQUID POLYMER CONTACTING SURFACE AND ANOTHER SURFACE SUBSTANTIALLY PARALLEL THERETO, SAID OTHER SURFACE CHARACTERIZED BY A ROUGHENED ETCHED CONDITION, A UNIFORM LAYER OF A WEAR-RESISTANT, NON-WETTABLE, ALUMINUM OXIDE MATERIAL HAVING A FIRST SURFACE EXTENDING EVENLY ALONG AND IN CONTACT WITH SAID OTHER ROUGHENED SURFACE OF SAID PLATE SECURELY BONDED THERETO OVER THE ENTIRE AREA OF CONTACT, SAID LAYER PROVIDED WITH A SECOND SURFACE SPACED FROM SAID FIRST SURFACE OF SAID LAYER TO DEFINE A TRUE PLANAR HIGHLY POLISHED SPINNERET FACE, THE STRUCTURE OF SAID PLATE AND SAID LAYER BONDED THERETO PROVIDED WITH A PLURALITY OF PASSAGEWAYS EXTENDING THERETHROUGH, EACH SAID PASSAGEWAYS HAVING ONE END PORTION INTERSECTING THE LIQUID POLYMER CONTACTING FACE OF SAID PLATE AND THE OTHER END PORTION HAVING AN ACCURATELY CONTROLLED INTERIOR SURFACE INTERSECTING SAID SPINNERET FACE SUBSTANTIALLY PERPENDICULAR THERETO TO FORM AN EXTRUSION ORIFICE, EACH ORIFICE PRECISELY DEFINED BY A FIRST EDGE LYING IN THE SPINNERET POLISHED PLANAR FACE AND SECOND EDGE LYING IN THE ACCURATELY CONTROLLED INTERIOR SURFACE OF SAID OTHER END PORTION OF THE PASSAGEWAY LYING IN THE SAID CERAMIC LAYER, SAID CERAMIC LAYER AND SAID ACCURATELY CONTROLLED SURFACES THEREOF FORMING THE EDGES OF SAID ORIFICES, COOPERATING TO MAINTAIN PROPER JET ACTION DURING SPINNING WHILE PREVENTING WETTING OF THE ORIFICES STRUCTURE, STICKING, OR DRIPPING OF THE POLYMERIC MATERIAL AND MINIMIZING EROSION.