Abstract: The present invention relates to a method for the production of polypropylene fibers resulting in improved shrinkage percentages and to polypropylene fibers themselves having improved shrinkage percentages. The method includes providing a polypropylene polymer with a melt flow index of no more than about 25 grams per 10 minutes. This polymer should include isotactic polypropylene produced by the polymerization of propylene in the presence of an isospecific metallocene catalyst. The polymer is then heated to a molten state and extruded to form a fiber preform. The preform is spun and subsequently drawn at a take-away speed and a drawing speed providing a draw ratio of no more than about 3, and more preferably no more than about 2.5, to produce a continuous polypropylene fiber.

Abstract: The present invention relates to a method for the production of polypropylene fibers resulting in improved shrinkage percentages and to polypropylene fibers themselves having improved shrinkage percentages. The method includes providing a polypropylene polymer with a melt flow index of no more than about 25 grams per 10 minutes. This polymer should include isotactic polypropylene produced by the polymerization of propylene in the presence of an isospecific metallocene catalyst. The polymer is then heated to a molten state and extruded to form a fiber preform. The preform is spun and subsequently drawn at a take-away speed and a drawing speed providing a draw ratio of no more than about 3, and more preferably no more than about 2.5, to produce a continuous polypropylene fiber.

Abstract: The present invention relates to a method for the production of polypropylene fibers resulting in improved shrinkage percentages and to polypropylene fibers themselves having improved shrinkage percentages. The method includes providing a polypropylene polymer with a melt flow index of no more than about 25 grams per 10 minutes. This polymer should include isotactic polypropylene produced by the polymerization of propylene in the presence of an isospecific metallocene catalyst. The polymer is then heated to a molten state and extruded to form a fiber preform. The preform is spun and subsequently drawn at a take-away speed and a drawing speed providing a draw ratio of no more than about 3, and more preferably no more than about 2.5, to produce a continuous polypropylene fiber.

Abstract: A polymer blend, fibers manufactured from the blend and method of producing the fibers is disclosed. The polymer blend includes from 92 wt % to 98.5 wt % of a base polypropylene having a melt flow rate of less than 20 g/10 min, and a maximum draw ratio D, a Crimp Stability of CS, when drawn into filaments at 1000 m/sec, and from 8 wt % to 1.5 wt % of an amorphous polystyrene having a melt flow rate of less than 15 g/10 min. The polymer blend is drawable at greater than 800 m/sec to produce filaments having a maximum draw ratio of D2, the ratio of D2: D1, being greater than 1.15:1 and a Crimp Stability of CS2, the ratio of CS2: CS1 being greater than 1.45. Preferably, the base polypropylene has a melt flow rate of between 8 and 15 g/10 min. In one embodiment, the amorphous polystyrene is characterized by a melt flow between 2 and 15 g/10 min.

Abstract: Process for the production of polypropylene fibers from polypropylene polymers produced by the polymerization of polypropylene in the presence of a metallocene catalyst characterized by a bridged racemic bis(indenyl) ligand substituted at the proximal position. The polypropylene contains 0.5 to 2% 2,1 insertions and has an isotacticity of at least 95% meso diads and is heated to a molten state and extruded to form a fiber preform. The preform is subjected to spinning at a spinning speed of at least 500 meters per minutes and subsequent drawing at a speed of at least 1,500 meters per minute to provide a draw ratio of at least 3 to produce a continuous polypropylene fiber. The draw speed and/or the draw ratio can be varied to produce fibers of different mechanical properties. Different polypropylene polymers produced by different metallocene catalysts can be used. Such fibers can be characterized by having an elongation at break of at least 100% and a specific toughness of at least 0.5 grams per denier.

Abstract: A process for the production and treatment of a stereoregular polypropylene, such as isotactic polypropylene in which a polymerization reactor is operated under conditions to react propylene supplied to the reactor to produce a stereoregular propylene polymer fluff. A product stream containing the fluff and unreacted propylene is withdrawn from the reactor and at least a portion of the unreacted propylene is separated from the product stream. The propylene polymer fluff is heated to a temperature sufficient to melt the propylene polymer, and a lactone is incorporated into the propylene polymer. The lactone is a 5,7 dialkyl-3-(2,3 dialkyl phenyl)-3H-benzofuran-2-one, in which the 5,7 and 2,3 substituents are of relatively low molecular weights. The phenyl alkyl substituents, each contain 1 or 2 carbon atoms, and the 5,7 alkyl substituents each contain from 2 to 5 carbon atoms.

Abstract: Process for the production of polypropylene fibers from polypropylene polymers produced by the polymerization of polypropylene in the presence of a metallocene catalyst characterized by a bridged racemic bis(indenyl) ligand substituted at the proximal position. The polypropylene contains 0.5 to 2% 2,1 insertions and has an isotacticity of at least 95% meso diads and is heated to a molten state and extruded to form a fiber preform. The preform is subjected to spinning at a spinning speed of at least 500 meters per minutes and subsequent drawing at a speed of at least 1,500 meters per minute to provide a draw ratio of at least 3 to produce a continuous polypropylene fiber. The draw speed and/or the draw ratio can be varied to produce fibers of different mechanical properties. Different polypropylene polymers produced by different metallocene catalysts can be used. Such fibers can be characterized by having an elongation at break of at least 100% and a specific toughness of at least 0.5 grams per denier.