The present disclosure provides a high-efficiency degassing polyolefin hollow fiber membrane and a preparation therefor and use thereof. The membrane comprises a main body, wherein one side of the main body is an inner surface facing an inner cavity, the other side of the main body is an outer surface, a non-directional tortuous pathway is formed in the main body, the outer surface is a dense surface, and the area ratio of air pores in the inner surface is 10%-30%; the average thickness of the hollow fiber membrane is 45-65 m and the ratio of the average outer diameter to the average inner diameter of the hollow fiber membrane is 1.45-1.55; the TOC dissolving-out amount of the hollow fiber membrane itself is less than or equal to 0.5 g/L; and the deoxidation efficiency of the hollow fiber membrane is greater than 80%.

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 microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler, providing a processing plasticizer, adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.

Microporous sheet product and methods of making and using the same. In one embodiment, the microporous sheet product is made by a process that includes melt-extruding a sheet material using an extrusion mixture that includes (i) a cyclic olefin copolymer, (ii) an electrolyte swellable thermoplastic, and (iii) a compatibilizing agent that promotes mixing of the cyclic olefin copolymer and the electrolyte swellable thermoplastic, the compatibilizing agent having a boiling point in the range of 135-300 C. As an example, the cyclic olefin copolymer may be an ethylene-norbornene copolymer, the electrolyte swellable thermoplastic may be polyethylene oxide, and the compatibilizing agent may be mineral spirits. After extrusion, the sheet material may be cooled, and the compatibilizing agent may be removed, forming an ionically-conductive microporous sheet product. The microporous sheet product has high-temperature stability and gels when exposed to a liquid electrolyte, enabling high ionic conductivity when used as a battery separator.

Provided is a porous polytetrafluoroethylene (PTFE) membrane that satisfies the following expressions: 0.2F4.0; 0.2R1.0; and R0.1F+0.5, for the Frazier number F [cm.sup.3/sec/cm.sup.2] and the water entry pressure R [MPa]. This porous PTFE membrane may be a single-layer membrane. This porous PTFE membrane has the properties suitable for use as a waterproof air-permeable membrane, and achieves a good balance between high water resistance and high air permeability.

A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler, providing a processing plasticizer, adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.

A porous polytetrafluoroethylene film comprising a fluororesin containing polytetrafluoroethylene as a main component, wherein an envelope surface area of resin fibers included per film having an area of 1 m.sup.2 and a thickness of 25 m is 4,000 m.sup.2 or more, and a melting point peak is 333 C. or lower.

A method of producing a microporous plastic film is disclosed. The method achieves various characteristics such as strength while having an excellent appearance grade by using a wet stretching method. The method includes kneading a diluent and a polymer with an extruder to produce a kneaded polymer, discharging the kneaded polymer into a sheet, and stretching the sheet in a conveying direction of the sheet with a plurality of rollers. The diluent is applied to at least one of the rollers and the sheet while stretching the sheet.

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.

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.