Polymer or polymer composite membrane having through-thickness micropores, and method for preparing same

Abstract

A polymer or polymer composite membrane having through-thickness micropores and a method of preparing the same are provided. More particularly, a polymer or polymer composite membrane having a pore structure such that micropores are aligned in a mesh structure in the thickness direction of the polymer or polymer composite membrane due to unidirectional freezing in the thickness direction of a solvent. The membrane has through-thickness micropores, and thus has improved permeability in the thickness direction and superior uniformity in size of the micropores and wall thickness between the micropores. For these reasons, the membrane can be used for a porous membrane substrate, microfiltration membrane, etc.

1 . A method of preparing a polymer or polymer composite membrane having through-thickness pores, comprising:
 unidirectionally freezing a polymer solution; and   freeze-drying the resulting frozen materials by the freezing.   
     
     
         2 . The method of  claim 1 , wherein the polymer includes at least one selected from the group consisting of a fluorine-based polymer having a C—F bond and a hydrophobic polymer. 
     
     
         3 . The method of  claim 2 , wherein the fluorine-based polymer includes at least one selected from the group consisting of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), ethylenetetrafluoroethylene (ETFE), perfluoroalkoxyalkane (PFA), vinylfluoride (VF), chlorotrifluoroethylene (CTFE), fluorinated ethylene propylene (FEP), hexafluoropropylene (HFP), and perfluoro(propyl vinylether). 
     
     
         4 . The method of  claim 3 , wherein the hydrophobic polymer includes at least one selected from the group consisting of polyethylene-, polypropylene-, polysulfone-, polyketone-, polyethersulfone-, cellulose-, cellulose acetate-, cellulose triacetate-, regenerative cellulose-, acryl resin-, nylon-, polyamide-, epoxy-, and polyimide-based polymers and copolymers thereof. 
     
     
         5 . The method of  claim 1 , wherein the polymer solution is prepared by dissolving or dispersing polymers in water, a mixture of water and alcohol or an organic solvent. 
     
     
         6 . The method of  claim 5 , wherein the organic solvent includes at least one selected from the group consisting of acetone, acetonitrile, acetaldehyde, acetic acid, acetophenone, acetylchloride, acrylonitrile, aniline, benzylalcohol, 1-butanol, n-butylacetate, cyclohexanol, cyclohexanone, 1,2-dibromoethane, diethylketone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, 1,4-dioxane, ethanol, ethyl acetate, ethyl formate, formic acid, glycerol, hexamethyl phosphoamide, methyl acetate, methyl ethyl ketone, methyl isobutyl ketone, N-methyl-2-pyrolidone, nitrobenzene, nitromethane, 1-propanol, propylene-1,2-carbonate, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate, ethylenediamine, and N-methylmorpholine N-oxide (NMMO). 
     
     
         7 . The method of  claim 5 , wherein the polymer is included at 0.01 to 70 parts by weight with respect to 100 parts by weight of the solvent. 
     
     
         8 . The method of  claim 1 , wherein the polymer solution further includes an inorganic material or an insoluble organic material. 
     
     
         9 . The method of  claim 8 , wherein the inorganic material includes at least one selected from the group consisting of titanium oxide, silica, fumed silica, silicon carbide, silicon nitride, spinel, silicon oxycarbide, glass powder, glass fiber, carbon fiber, graphene, nanotubes, gold microparticles, silver microparticles, alumina, magnesia, silicon nitride, zirconia, zirconium carbide, sialon, nasicon, silceram, mullite, aluminum, copper, nickel, steel, titanium, titanium carbide, and titanium diborate. 
     
     
         10 . The method of  claim 8 , wherein the insoluble organic material includes at least one selected from the group consisting of reinforced particles and a fiber. 
     
     
         11 . The method of  claim 10 , wherein the reinforced particle includes at least one selected from the group consisting of vinylon, polyvinylidene chloride, polyvinyl chloride, polyester, acryl, polyacryl, aramid and nylon. 
     
     
         12 . The method of  claim 10 , wherein the fiber includes at least one selected from the group consisting of a spectra fiber and an aramid fiber. 
     
     
         13 . The method of  claim 8 , wherein the insoluble organic material is included at 0.01 to 60 parts by weight with respect to 100 parts by weight of the polymer solution. 
     
     
         14 . The method of  claim 1 , wherein the polymer solution is frozen at a freezing rate of 5 to 500 μm/s using liquid nitrogen from one side in one direction. 
     
     
         15 . The method of  claim 14 , wherein an unfrozen part is insulated by an insulator. 
     
     
         16 . The method of  claim 1 , wherein the resulting frozen materials by the freezing are dried in a freeze drier for 1 hour to 3 days. 
     
     
         17 . The method of  claim 1 , further comprising reinforcing the membrane by at least one selected from the group consisting of solvent annealing, thermal annealing, stretching and pressing. 
     
     
         18 . A polymer or polymer composite membrane having micropores aligned in a mesh structure in a width direction, the micropores passing through the membrane unidirectional in a thickness direction. 
     
     
         19 . The membrane of  claim 18 , wherein the pores have a diameter of 0.1 to 1000 μm, and a distance between the pores is 0.001 to 50 μm. 
     
     
         20 . A product comprising one of a porous membrane substrate, a microfiltration membrane, a waterproof and breathable membrane, and a membrane for controlling diffusion in an energy device, all of which include the polymer or polymer composite membrane of  claim 18 . 
     
     
         21 . A method of controlling a pore size of a polymer or polymer composite membrane having through-thickness pores, comprising:
 controlling a unidirectional freezing rate of a polymer solution.   
     
     
         22 . The method of  claim 21 , wherein the freezing rate is 5 to 500 μm/s.