Porous membrane wipes and methods of manufacture and use

Abstract

A microporous membrane wipe and a method of using such microporous membrane wipe are disclosed. The microporous membrane wipe may be uniaxially or biaxially oriented microporous membrane. The uniaxially or biaxially oriented microporous membrane may be made from one or more block and/or impact copolymers of polyethylene and/or polypropylene. A method of using such a microporous membrane wipe for skin oil blotting is also disclosed. Further disclosed is a method of using such a microporous membrane wipe for cleaning a surface for the removal of fingerprints, smudges and the like, where such surfaces may include, for example, eyeglasses, electronics, cell phones, displays, optical devices, camera lenses, microscope lenses and other precision optics, and/or the like.

1 - 24  (canceled) 
     
     
         25 . A microporous membrane wipe. 
     
     
         26 . The microporous membrane wipe of  claim 25  comprising:
 at least one layer of porous polymer film made by a dry-stretch process including the steps of: 
 extruding a polymer into at least a single layer nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching optionally including a simultaneous controlled machine direction relax, and having substantially round shaped pores, a porosity of about 40% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 0.5 to 5.0 and an Aquapore size of at least about 0.06 microns. 
 
     
     
         27 . The microporous membrane wipe of  claim 26 , wherein the machine direction stretching of said biaxially stretching includes the step of transverse direction stretching with simultaneous machine direction stretching, and wherein said biaxially stretching optionally includes the step of transverse direction relax. 
     
     
         28 . The microporous membrane wipe of  claim 26 , wherein said biaxially stretching of said nonporous precursor further includes an additional step of machine direction stretching. 
     
     
         29 . The microporous membrane wipe of  claim 26 , wherein said dry-stretch process further includes the step of:
 machine direction stretching to form a porous intermediate prior to said biaxial stretching.   
     
     
         30 . The microporous membrane wipe of  claim 26 , wherein said biaxially stretching of said nonporous precursor includes the machine direction stretching, an additional transverse direction stretching with simultaneous machine direction stretching, and an optional transverse direction relax. 
     
     
         31 . The microporous membrane wipe of  claim 26 , wherein said dry-stretch process includes the steps of:
 machine direction stretching followed by said biaxial stretching including said transverse direction stretching with simultaneous controlled machine direction relax, a second transverse direction stretching with simultaneous machine direction stretching, followed by optional transverse direction relax.   
     
     
         32 . The microporous membrane wipe of  claim 26  wherein said dry-stretch process includes the step of transverse direction stretching without machine direction stretch or relax (machine direction stays at 100%). 
     
     
         33 . The microporous membrane wipe of  claim 26 , with said porous polymer film further having a thickness of at least about 8 microns, a transverse direction tensile strength of at least about 225 kgf/cm 2 . 
     
     
         34 . The microporous membrane wipe of  claim 26 , with said porous polymer film further having a transverse direction shrinkage of:
 less than about 6.0% at 90° C.;   less than about 15.0% at 120° C.   
     
     
         35 . The microporous membrane wipe of  claim 26 , with said porous polymer film further having a thickness in a range of about 8 microns to 80 microns. 
     
     
         36 . The microporous membrane wipe of  claim 26 , wherein said nonporous precursor is one of a blown film and a slot die film. 
     
     
         37 . The microporous membrane wipe of  claim 26 , wherein said nonporous precursor is a single layer or multilayer precursor formed by at least one of single layer extrusion and multilayer extrusion, or a multilayer precursor formed by at least one of coextrusion and lamination. 
     
     
         38 . The microporous membrane wipe of  claim 26 , wherein said porous polymer film comprises one of polypropylene, polyethylene, blends thereof, impact copolymers, and combinations thereof. 
     
     
         39 . The microporous membrane wipe of  claim 26 , wherein said precursor is one of a single layer precursor and a multilayer precursor, said membrane further includes at least one nonwoven, woven, or knit layer bonded to at least one side of said porous polymer film, said membrane has substantially round shaped pores, a porosity of about 40% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 0.5 to 5.0 and an Aquapore size of at least about 0.07 microns, and a hydro-head pressure greater than about 140 psi, said polymer being selected from the group consisting of polyolefins, fluorocarbons, polyamides, polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyphenyl sulfide, polyvinyl alcohols, impact copolymers, co-polymers thereof, blends thereof, and combinations thereof, said porous polymer film further having a porosity of about 65% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 1.0 to 5.0, a JIS Gurley of less than about 60, and an Aquapore size of at least about 0.08 microns, said biaxially stretching step of said dry-stretch process includes the simultaneous biaxial stretching of a plurality of separate, superimposed, layers or plies of nonporous precursor, wherein none of the plies are bonded together during the stretching process, and/or said biaxially stretching step of said dry-stretch process includes the simultaneous biaxial stretching of a plurality of bonded, superimposed, layers or plies of nonporous precursor, wherein all of the plies are bonded together during the stretching process. 
     
     
         40 . A method of making a microporous membrane wipe, of making a microporous membrane wipe for skin oil blotting, of making a microporous membrane wipe for the removal of fingerprint, smudges and the like from surfaces like eyeglasses and electronics, like phone screens and other displays, of making a microporous membrane wipe as shown and described herein, and/or of making a layer of a microporous membrane wipe comprising the steps of:
 extruding a polymer into a nonporous precursor, and   biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction including a simultaneous controlled machine direction relax.   
     
     
         41 . The method according to  claim 40  wherein the polymer excludes any oils for subsequent removal to form pores or any pore-forming materials to facilitate pore formation, the polymer being a semi-crystalline polymer, the polymer being selected from the group consisting of polyolefins, fluorocarbons, polyam ides, polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyvinyl alcohols, co-polymers thereof, and combinations thereof, further comprising the step of:
 annealing the non-porous precursor after extruding and before biaxially stretching, wherein annealing being conducted at a temperature in the range of Tm-80° C. to Tm-10° C., wherein biaxially stretching comprising the steps of: 
 machine direction stretching, and
 thereafter transverse direction stretching including a simultaneous machine direction relax, wherein machine direction stretching being conducted either hot or cold or both, wherein cold machine direction stretching being conducted at a temperature <Tm-50° C. and/or hot machine direction stretching being conducted at a temperature <Tm-10° C., and/or wherein the total machine direction stretch being in the range of 50-500%, the total transverse direction stretch being in the range of 100-1200%, the machine direction relax from the transverse direction stretch being in the range of 5-80%, or combinations thereof.