Process for producing fiber of ultra high molecular weight polyethylene

Abstract

A process for producing fiber of ultra high molecular weight polyethylene, with a flat cross-section and high cohesiveness, is disclosed. The process includes: distributing the powder of UHMWPE into a solvent evenly; preparing an uniform emulsion mixture by properly untangling with high shear; at the same time adding polar polymer comprising polar groups, for example a carboxyl group, a carbonyl group, an ether group, or an ester group and so on; evenly distributing the polar polymer together with the polyethylene powder in the solvent to form an uniform emulsion mixture; forming a gel filament from the emulsion mixture by gel spinning method, then extracting, drying, and stretching so as to obtain the UHMWPE fiber, with a flat cross section, high strength and cohesiveness. By properly untangling, the swelling and dissolving of the ultra high molecular weight polyethylene can be accelerated, while the polar polymer being evenly distributed therein can significantly improve the adhesive property of the fiber. The operations in the production method are easy, and furthermore, time, labor and cost can be saved. The section of the fiber is of a flat rectangle shape and the wall is thin and even, so the path for the solvent in the fiber diffusing out of the gel filament can be significantly shorten, and thus the efficiency of extraction and the uniformity of the fiber can be improved.

1 - 26 . (canceled) 
   
   
       27 . A method for preparing UHMWPE fiber, comprising:
 mixing UHMWPE powder having a relative average molecular weight of 1 million to 6 million with polar polymer in a solvent to form an emulsion mixture;   feeding the mixture into an extruder wherein the mixture swells and dissolves to form a solution;   extruding the solution through a spinnerette to spin into a gel filament; and   subjecting the filament to cooling, extraction, drying and stretching to provide the UHMWPE fiber.   
   
   
       28 . The method of  claim 27 , wherein the UHMWPE powder, the polar polymer and the solvent are fed into an untwisting equipment to untwist to form an emulsion mixture. 
   
   
       29 . The method of  claim 27 , wherein the concentration of the emulsion mixture is 4%-60%. 
   
   
       30 . The method of  claim 27 , wherein the polar polymer comprises an ester group, a carbonyl group or an ether group. 
   
   
       31 . The method of  claim 27 , wherein the polar polymer is selected from ethylene/vinyl acetate co-polymer, polyacrylates, polyethylene pyrrolidone/vinyl acetate co-polymer, polyoxyethylene polymer and mixtures thereof. 
   
   
       32 . The method of  claim 27 , wherein the amount of the polar polymer relative to the UHMWPE powder is 1-10% by weight. 
   
   
       33 . The method of  claim 27 , wherein the amount of the polar polymer relative to the UHMWPE powder is 2-8% by weight. 
   
   
       34 . The method of  claim 28 , wherein silicone oil or its derivative is added during said untwisting and/or cooling process, in which the silicone oil or its derivative comprises 0.05-5% by weight of the UHMWPE fiber. 
   
   
       35 . The method of  claim 34 , wherein at least one additional agent is added during the untwisting process, in which the additional agent is an antioxidant, a stabilizer, a coloring agent, a fire retardant or mixtures thereof. 
   
   
       36 . The method of  claim 28 , wherein the untwisting equipment provides a cutting speed of at least 1000 S −1 . 
   
   
       37 . The method of  claim 28 , wherein the untwisting equipment provides a cutting speed of 1000 to 5000 S −1 . 
   
   
       38 . The method of  claim 28 , wherein the untwisting equipment provides a cutting speed of 2000 to 4000 S −1 . 
   
   
       39 . The method of  claim 28 , wherein the untwisting equipment is selected from high-speed dispersion machine, mixer, colloid mill, homogenizer, venturi, and combinations thereof. 
   
   
       40 . The method of  claim 27 , wherein the UHMWPE has a relative average molecular weight of 4 million to 6 million. 
   
   
       41 . The method of  claim 27 , wherein the UHMWPE has a relative average molecular weight of 2 million to 5 million. 
   
   
       42 . The method of  claim 27 , wherein the solvent used to form an emulsion mixture is in liquid form at room temperature, and is selected from alkane or its derivative, cycloalkane or its derivative, aromatic hydrocarbon or its derivative, and mixtures thereof. 
   
   
       43 . The method of  claim 27 , wherein the nominal concentration of the UHMWPE powder in the solvent is 1-50wt %. 
   
   
       44 . The method of  claim 27 , wherein the extruder is selected from a single screw extruder, a double-screw extruder, a three-screw extruder, and a four-screw extruder, and wherein the operating temperature for the extruder is 80-250° C. 
   
   
       45 . The method of  claim 44 , wherein the double-screw extruder can rotate in same direction or reverse direction, and wherein the Length/Diameter ratio of the screw rod is 1:30-65. 
   
   
       46 . The method of  claim 45 , wherein the residence time for the emulsion mixture in the double-screw extruder is 10-60 minutes, material temperature inside the extruder is 50-280° C., and the temperature of the extruded gel filament is 140-280° C. 
   
   
       47 . The method of  claim 46 , wherein the residence time for the emulsion mixture in the double-screw extruder is 20-40 minutes, and the temperature of the extruded gel filament is 200-260° C. 
   
   
       48 . The method of  claim 27 , wherein the spinnerette comprises apertures having a rectangle shape with a Length/Width ratio of 4:20. 
   
   
       49 . The method of  claim 27 , wherein the spinnerette comprises apertures having a shape of rectangle with a Length/Width ratio of 5:15. 
   
   
       50 . The method of  claim 27 , wherein the emulsion mixture can be fed into the extruder directly or via a storage vessel equipped with an agitator. 
   
   
       51 . The method of  claim 27 , wherein the stretching is conducted at a temperature of 80-130° C. and at a draw ratio of at least 20/1. 
   
   
       52 . The method of  claim 51 , wherein the draw ratio from 30/1 to 60/1. 
   
   
       53 . UHMWPE fiber prepared according to the method of  claim 27 .