| 摘要 |
963,195. Spinnerets. HERCULES POWDER CO. May 16, 1963, No. 19507/63. Heading B5B. A spinneret has a plurality of orifices, each orifice being composed of a cylindrical egress section B having a length to diameter ratio of at least 3 and a conical entry section A having a taper of from 5 to 35 degrees from the axis of the orifice. Fig. 3 illustrates an alternative orifice shape. Preferably, the egress section of each orifice has a diameter of from 0.008 to 0.025 inch and a length of 3-20 times the diameter. Stereoregular polypropylene containing preferably less than 5% of amorphous polymer may be dissolved in a suitable solvent to give a solution of about 25-45% concentration and dry spun through such a spinneret at e.g. 120-170‹ C. into a drying column through which a hot gas e.g. nitrogen, carbon dioxide, or steam is passed in order to evaporate the solvent. Specified solvents include paraffinic hydrocarbons, especially those boiling above about 170‹ C., e.g. toluene and xylene, chlorobenzene, tetrahydronaphthalene and decahydronaphthalene. Specification 851,611 is referred to.
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