Process for the Preparation of Polyolefin Fibers

Abstract

The present invention relates to a process for the preparation of polyolefin fibers having mean fiber diameters of less than 5000 nm, comprising the steps of: a) preparing a polyolefin solution in a solvent, b) placing said polyolefin solution in a fiber producing device comprising a body configured to receive said polyolefin solution, said body comprising one or more openings, and c) rotating the fiber producing device, wherein rotation of the fiber producing device causes the polyolefin solution to be passed through said one or more openings to produce polyolefin fibers having mean fiber diameters of less than 5000 nm, wherein said polyolefin is selected from the group comprising polyethylene polymers and copolymers having a weight average molecular weight M w of at least 40 000 daltons, and polypropylene polymers and copolymers, having a weight average molecular weight Mw of at least 120 000 daltons; wherein said fiber producing device is rotated at a speed of at least 10 000 revolutions per minutes (RPM). The invention also relates to said polyolefin fibers, and to articles comprising said fibers.

1 .- 14 . (canceled) 
     
     
         15 . A process for the preparation of polyolefin fibers having mean fiber diameters of less than 5000 nm, comprising the steps of:
 a) preparing a polyolefin solution in a solvent,   b) placing the polyolefin solution in a fiber producing device comprising a body configured to receive the polyolefin solution, the body comprising one or more openings, and   c) rotating the fiber producing device, wherein rotation of the fiber producing device causes the polyolefin solution to be passed through the one or more openings to produce polyolefin fibers having mean fiber diameters of less than 5000 nm,
 wherein the polyolefin comprises polyethylene polymers or copolymers having a weight average molecular weight Mw of at least 40,000 daltons, or polypropylene polymers or copolymers, having a weight average molecular weight Mw of at least 120,000 daltons, 
 wherein the fiber producing device is rotated at a speed of at least 10,000 revolutions per minutes (RPM). 
   
     
     
         16 . The process according to  claim 15 , wherein the polyolefin is selected from the group comprising polyethylene polymers and copolymers, and polypropylene polymers and copolymers, having a weight average molecular weight Mw of at least 120,000 daltons. 
     
     
         17 . The process according to  claim 15 , wherein the polyolefin fibers produced have mean fiber diameters of less than 2000 nm. 
     
     
         18 . The process according to  claim 15 , wherein the polyolefin solution comprises at least 1% and at most 50% by weight of the polyolefin based on the total weight of the polyolefin solution, preferably at least 5% and at most 20% by weight. 
     
     
         19 . The process according to  claim 15 , wherein the solvent is selected from the group comprising C6-C16 alcohols, fully saturated white mineral oil, vegetable oils, C4-C20 carboxylic acid, aliphatic and alicyclic hydrocarbons, petroleum fractions, mineral oil, kerosene, aromatic hydrocarbons and hydrogenated derivatives thereof, halogenated hydrocarbons, cycloalkanes, cycloalkenes, and terpenes. 
     
     
         20 . The process according to  claim 15 , wherein the one or more openings have at least one diameter of at least 2 mm, preferably at least 1 mm, preferably of at least 0.5 mm, preferably of at least 0.1 mm. 
     
     
         21 . The process according to  claim 15 , wherein the polyolefin is polyethylene. 
     
     
         22 . The process according to  claim 15 , wherein the polyolefin is UHMWPE. 
     
     
         23 . Polyolefin fibers having mean fiber diameters of less than 5000 nm obtained by the process according to  claim 15 . 
     
     
         24 . The polyolefin fibers according to  claim 23 , having mean fiber diameters of less than 5000 nm, wherein the polyolefin is selected from the group comprising polyethylene polymers and copolymers having a weight average molecular weight Mw of at least 40,000 daltons, and polypropylene polymers and copolymers, having a weight average molecular weight Mw of at least 120,000 daltons. 
     
     
         25 . The polyolefin fibers according to  claim 23 , in the form of a nonwoven web. 
     
     
         26 . The polyolefin fibers according to  claim 23 , wherein the polyolefin is polyethylene. 
     
     
         27 . The polyolefin fibers according to  claim 23 , wherein the polyolefin is UHMWPE. 
     
     
         28 . An article comprising the polyolefin fibers made according to  claim 23 .