Methods of making stretched filtering membranes and modules

Abstract

A method for stretching a hollow fibre while making a stretched filtering membrane from a precursor involves wrapping the hollow fibre around a structure and modifying the structure such that at least portions of the hollow fibre are forced to elongated. For example, the hollow fibre may be wrapped around around two or more supports and the distance between adjacent supports increased. This produces first portions of the hollow fibre stretched to a first elongation and porous to a first porosity and second portions of the hollow fibre that are not stretched or are stretched to a second elongation less than the first elongation and that remain non-porous or become porous to a second porosity which is less than the first porosity. The membrane may be made into a module with second portions of the membranes located at points where the membranes exit the potting material or at turns in loops of the fibres, if any. In various embodiments, the fibre is potted into modules before or after it is stretched. Some methods of potting involve applying a hot melt adhesive to the second portions. Some embodiments are made entirely of thermoplastic material and can be easily recycled.

1 . A process of potting hollow fiber membranes to produce a header or manifold of a membrane module composing the steps of 
 a) forming a mass of thermoplastic material with a plurality of hollow fiber membranes secured in and passing through the mass of thermoplastic material, ends of the membranes being open;    b) securing the mass of thermoplastic material and membranes into a pan in a manner that creates a sealed plenum in the pan with the open ends of the membranes in fluid communication with the plenum.    
   
   
       2 . The process of  claim 1  wherein the mass of thermoplastic material is secured to the pan with a second quantity of a thermoplastic material.  
   
   
       3 . The process of  claim 2  wherein the pan is made of a thermoplastic material.  
   
   
       4 . The process of  claim 3  wherein the fibers are made of a thermoplastic material.  
   
   
       5 . The process of  claim 1  wherein the step of forming the mass of thermoplastic material further comprises laying lengths of membrane fiber onto a supporting surface such that adjacent lengths of membrane fiber are spaced from each other by at least a minimum spacing, applying a thermoplastic material in liquid state around a portion of the outer surface, the length of membrane fibers and allowing the thermoplastic material to solidify.  
   
   
       6 . The process of  claim 5  further comprising the steps of laying additional lengths of membrane fibers onto the lengths of membrane fiber of  claim 5 , applying additional thermoplastic material in liquid state around the additional lengths of membrane fiber and allowing the additional thermoplastic material to solidify.  
   
   
       7 . The process of  claim 5  wherein the supporting surface is a drum.  
   
   
       8 . The process of  claim 5  wherein the lengths of membranes are cut after the steps of  claim 5  to provide distinct lengths of membrane fiber with open ends.  
   
   
       9 . The process of  claim 5  wherein the lengths of membrane fiber are cut through the solidified thermoplastic material.  
   
   
       10 . The process of  claim 8  wherein the lengths of membrane fiber are cut near the solidified thermoplastic material.