Method for producing pen core from filament tows

Claim 1

IN A METHOD FOR PRODUCING PEN CORES FROM A SYNTHETIC FIBER BUNDLE, COMPRISING THE STEPS OF SUBJECTING A TOW OF SYNTHETIC FIBERS TO COMPRESSION-MOLDING UNDER HEAT TO FORM A ROD-SHAPED BODY HAVING A PREDETERMINED CROSS-SECTIONAL SHAPE, IMMERSING SAID COMPRESSION-MOLDED, ROD-SHAPED BODY IN A LIQUID CONTAINING A SYNTHETIC RESIN AND SOLVENT THEREFORE TO IMPREGNATE THE LIQUID INTO THE BODY, SUBJECTING SAID LIQUID IMPREGNATED ROD-SHAPED BODY TO A DIELECTRIC HEATING TREATMENT IN A HIGH FREQUENCY ELECTRIC FIELD OF AN INTENSITY SUFFICIENT TO CAUSE INTERNAL HEATING WITHIN THE ROD-SHAPED BODY TO VOLATILIZE THE SOLVENT IN SAID LIQUID, IN A STATE WHEREIN THE RODSHAPED BODY IS PASSED THROUGH A PIPE OF LOW DIELECTRIC CONSTANT WHICH SHIELDS THE BODY FROM THE EXTERNAL ATMOSPHERE, CUTTING THE THUS TREATED ROD-SHAPED BODY INTO A REQUIRED LENGTH, AND SHAPING AT LEAST ONE END OF THE ROD-SHAPED BODY TO TAPER SAID END INTO A CONFIGURATION REQUIRED FOR A WRITING TIP, THE IMPROVEMENT WHEREIN SAID LIQUID IS PREPARED BY DISSOLVING A SYNTHETIC RESIN IN A SOLVENT CONSISTING ESSENTIALLY OF A PRINCIPAL SOLVENT AND A POLAR SOLVENT HAVING A HIGH DIELECTRIC CONSTANT, A LOWER VOLATILIZATION SPEED THAN THAT OF SAID PRINCIPAL SOLVENT AND A HIGHER BOILING POINT THAN THAT OF SAID PRINCIPAL SOLVENT, SAID POLAR SOLVENT BEING USED AS A HEATING MEDIUM AND FOR GENERATING INTERNAL HEAT DUE TO DIELECTRIC LOSS THEREIN DURING SAID DIELECTRIC HEATING TREATMENT, TO VOLATILIZE THE PRINCIPAL SOLVENT AND TO HEAT THE ROD-SHAPED BODY INTERNALLY, THEREBY GELLING THE SYNTHETIC RESIN.

Claim 9

The method according to calim 1, in which the synthetic fibers are a mixture of nylon and polyester fibers, said method further comprising curing the gelled resin contained in the rod-shaped body, and passing the thus treated rod-shaped body through an orifice which is 0.03 to 0.15 mm smaller than the diameter of the rod-shaped body while heating the rod-shaped body at a temperature higher than the melting point of said synthetic fibers, to form a thin coating film around the periphery of the rod-shaped body.

Claim 10

The method according to calim 1, in which the synthetic fibers are a mixture of nylon and polyester fibers, said method further comprising curing the gelled resin contained in the rod-shaped body, and passing the thus treated rod-shaped body through an orifice which is 0.03 to 0.15 mm smaller than the diameter of the rod-shaped body while heating the rod-shaped body at a temperature higher than the melting point of said synthetic fibers, to form a thin coating film around the periphery of the rod-shaped body.