A method for producing a porous polyimide film comprises: forming a first un-burned composite film wherein the first film is formed on a substrate using a first varnish that contains (A1) a polyamide acid or a polyimide and (B1) fine particles at a volume ratio (A1):(B1) of from 19:81 to 45:65; forming a second un-burned composite film wherein the second film is formed on the first film using a second varnish that contains (A2) a polyamide acid or a polyimide and (B2) fine particles at a volume ratio (A2):(B2) of from 20:80 to 50:50 and has a lower fine particle content ratio than the first varnish; burning wherein an un-burned composite film composed of the first film and the second film is burned, thereby obtaining a polyimide-fine particle composite film; and a fine particle removal step wherein the fine particles are removed from the polyimide-fine particle composite film.

The present invention is directed to methods of treating a hydrocarbon-containing waste stream to form a hydrocarbon-containing retentate and an aqueous permeate which is substantially free of hydrocarbon. The method includes passing the hydrocarbon-containing waste stream through a microporous membrane to yield the hydrocarbon-containing retentate and the aqueous permeate. The membrane comprises a substantially hydrophobic, polymeric matrix and substantially hydrophilic, finely divided, particulate filler distributed throughout the matrix. The polymeric matrix has pores with a volume average diameter less than 1.0 micron, and at least 50 percent of the pores have a mean diameter of less than 0.35 micron.

Disclosed are a copolymer, porous membranes made from the copolymer, and a method of treating fluids using the porous membranes to remove metal ions, for example, from fluids originating in the microelectronics industry, wherein the copolymer includes polymerized monomeric units I and II, wherein monomeric unit I is of the formula A-XCH.sub.2B, wherein A is Rf(CH.sub.2)n, Rf is a perfluoro alkyl group of the formula CF.sub.3(CF.sub.2).sub.x, wherein x is 3-12, n is 1-6, X is O or S, and B is vinylphenyl, the monomeric unit II is haloalkyl styrene, and optionally wherein the halo group of haloalkyl is replaced with an optional substituent, for example, ethylenediamine tetra acetic acid, iminodiacetic acid, or iminodisuccinic acid.

There is provided a production method for a resist composition purified product, which includes a step (i) of filtering a resist composition with a filter having a porous structure in which adjacent spherical cells are connected to each other. The filter includes a porous membrane containing at least one resin selected from the group consisting of polyimide and polyamide imide. The resist composition contains a base material component (A) that exhibits changed solubility in a developing solution under action of acid, an onium salt, and an organic solvent component (S), where the content of the organic solvent component (S) is 97% by mass or more.

The present invention relates to a membrane (M) comprising a sulfonated poly(arylene ether sulfone) polymer (sP) and a non-sulfonated poly(arylene sulfone) polymer (P), to a method for the preparation of the membrane (M) and to the use of the membrane as nanofiltration membrane. Further, the present invention relates to a monolithic film (F) comprising a sulfonated poly(arylene ether sulfone) polymer (sP) and a non-sulfonated poly(arylene sulfone) polymer (P), wherein the monolithic film has a contact angle of 63 to 77.

A polyolefin multilayer microporous membrane is disclosed. The polyolefin multilayer microporous membrane has at least three layers, the membrane comprising a first microporous layer composed of a polyethylene resin containing an ultrahigh molecular weight polyethylene (surface layers) and a second microporous layer composed of a polyolefin rein containing a high-density polyethylene and polypropylene (intermediate layer), wherein (I) the pin puncture strength is at least 25 g/m, (II) the coefficient of static friction with respect to a metal foil is at least 0.40, and (III) the meltdown temperature is at least 180 C.

A method for producing a porous polyimide film comprises: forming a first un-burned composite film wherein the first film is formed on a substrate using a first varnish that contains (A1) a polyamide acid or a polyimide and (B1) fine particles at a volume ratio (A1):(B1) of from 19:81 to 45:65; forming a second un-burned composite film wherein the second film is formed on the first film using a second varnish that contains (A2) a polyamide acid or a polyimide and (B2) fine particles at a volume ratio (A2):(B2) of from 20:80 to 50:50 and has a lower fine particle content ratio than the first varnish; burning wherein an un-burned composite film composed of the first film and the second film is burned, thereby obtaining a polyimide-fine particle composite film; and a fine particle removal step wherein the fine particles are removed from the polyimide-fine particle composite film.

A method of manufacturing a porous fluorine-containing polymer membrane is provided, which includes mixing a fluorine-containing polymer, a pore creating agent, and a solvent to form a mixture; forming a membrane of the mixture, and removing the pore creating agent and the solvent in the membrane to form the porous fluorine-containing polymer film. The pore creating agent has a chemical formula of

##STR00001##

wherein R.sup.1 is a C.sub.1-8 alkyl group, a C.sub.2-8 alkenyl group, a C.sub.2-8 alkynyl group, or a C.sub.6-12 aromatic group, and A.sup. is hydrogen sulfite ion, dihydrogen phosphate ion, nitrate ion, halogen ion, or a combination thereof. The solvent has a chemical formula of

##STR00002##

A fluid permeable anodic oxide film includes a plurality of regularly-disposed pores formed by anodizing metal and a plurality of permeation holes having an inner width larger than an inner width of the pores and extending through the fluid permeable anodic oxide film. Also provided is a fluid permeable body which makes use of the fluid permeable anodic oxide film.

An embodiment of the invention provides a substrate for a liquid filter, the substrate including at least one A layer which is a microporous membrane-like layer containing a polyolefin, and at least one B layer which is a microporous membrane-like layer containing a polyolefin and a filler, the substrate having a bubble point of from 0.40 Mpa to 0.80 Mpa and a water permeation efficiency of from 1.0 mL/min.Math.cm.sup.2 to 4.0 mL/min.Math.cm.sup.2.