| 摘要 |
Filaments are produced by extruding a homogeneous solution of a linear crystallizable high polymer of propylene through a nozzle, volatilizing the solvent from the filaments thus formed and stretching them at an elevated temperature. The polypropylene may be prepared by the low-pressure polymerization of propylene in the presence of catalysts prepared from organo-metallic compounds and compounds of metals of Group IVA, VA and VIA of the Periodic Table and preferably has an intrinsic viscosity of 0,5-5, as measured in solution in tetrahydronaphthalene at 135 DEG C. Solutions containing 15-80% by weight of polypropylene are preferably used, suitable solvents being hydrocarbons, e.g. the various fractions of petroleum, petroleum jelly, paraffin, toluene, xylene, tetrahydronaphthalene, decahydronaphthalene, mixtures of diphenyl and diphenyl ether, halogenated hydrocarbons, e.g. tetrachloroethane, chlorobenzene, orthodichlorobenzene, alpha-chloro-naphthalene and ethylene dibromide, ketanes, e.g. methyl-ethyl-ketane, cyclopentanone and cyclohexanone, cetyl alcohol, cyclohexanol, butyl acetate, isoamyl acetate, ethylene glycol, triethylene glycol, butylene glycol, nitrobenzene, benzonitrile and thiophene. The polypropylene is preferably dissolved in the solvent at 100 DEG to 170 DEG C. and extruded in that temperature range. Stabilizers, e.g. diphenyl ethyl phosphite, dibutyl-tin dilaurate and dibutyltin dibutyl mercaptide may be added in an amount of 0,05 to 0,5% based on the weight of the solution. The solvent may be removed from the filaments by evaporation in a stream of hot gas, e.g. air or nitrogen, and the filaments are preferably stretched at 80-150 DEG C. with a stretch ratio of 1 : 3 to 1 : 12. |
