An air filter medium having a large thickness and a low filling factor, a filter pack, an air filter unit, and methods for producing the air filter medium, the filter pack, and the air filter unit are provided. The air filter medium includes a fluororesin porous film having a portion with a filling factor of 3.5% or less, and the portion with a filling factor of 3.5% or less has a thickness of 45 μm or more.

A method for controlling fiber cross-alignment in a nanofiber membrane, comprising: providing a multiple segment collector in an electrospinning device including a first and second segment electrically isolated from an intermediate segment positioned between the first and second segment, collectively presenting a cylindrical structure, rotating the cylindrical structure around a longitudinal axis proximate to an electrically charged fiber emitter; electrically grounding or charging edge conductors circumferentially resident on the first and second segment, maintaining intermediate collector electrically neutral; dispensing electrospun fiber toward the collector, the fiber attaching to edge conductors and spanning the separation space between edge conductors; attracting electrospun fiber attached to the edge conductors to the surface of the cylindrical structure, forming a first fiber layer; increasing or decreasing rotation speed of the cylindrical structure to alter the angular cross-alignment relationship between aligned nanofibers in adjacent layers, the rotation speed being altered to achieve a target relational angle.

A tetrafluoroethylene polymer is provided in an air filter medium having a pressure loss that can be reduced and made uniform at a plurality of positions. The tetrafluoroethylene polymer may also be provided in an air filter medium, a filter pack, or an air filter unit. The tetrafluoroethylene polymer has drawability and non-melt processability. The tetrafluoroethylene polymer has a ratio S.sub.2/S.sub.1 of 0.60 or more, where S.sub.2 represents an endotherm mJ/mg in a range of T.sub.0° C. or higher and 350° C. or lower, T.sub.0° C. is a temperature 2.5° C. lower than a temperature T.sub.p° C. (340≤T.sub.p≤345) at which a minimum point is given on a heat-of-fusion curve obtained by measuring an unbaked polymer for measurement having no history of heating to a temperature of 300° C. or higher using a differential scanning calorimeter at a temperature-increasing rate of 2° C./min, and S.sub.1 represents an endotherm mJ/mg in a range of 320° C. or higher and T.sub.0° C. or lower.

It is an object of the present invention to provide a nonwoven fabric having mechanical strength which is hardly cut and broken by an external force, and a separator for electrochemical devices using the nonwoven fabric.

The inventive nonwoven fabric has a sum of tensile strengths by zero-span per basis weight in the machine direction and the cross-machine direction of 6.5N/50 mm or more. Thus, the strength of the constituent fibers of this nonwoven fabric against an external force is high, and this nonwoven fabric has mechanical strength which is hardly cut and broken by an external force.

The separator for electrochemical devices of the present invention is composed of this nonwoven fabric.

To provide a filament for obtaining a palatable beverage extracting filter having excellent formability, which is less expensive, and having excellent extractability.

A core-sheath type composite multifilament for a palatable beverage extracting filter, including a core component and a sheath component, the core component being a homopolyester having a melting point of 220° C. or more, the sheath component being a copolyester containing terephthalic acid and a diol as major components and having a melting point at least 40° C. lower than that of the core component, and a number of filaments is 2 to 5.

Filter media comprising adsorptive particles are generally described. In some embodiments, the adsorptive particles are present in a relatively large amount, in a layer discrete from one or more other layers and/or fiber webs also present in the filter media, and/or in a layer that comprises a relatively low amount of fibers. In some embodiments, the filter media further comprises a non-woven fiber web comprising fibers with relatively small diameters.

The subject matter disclosed herein relates generally to microdenier fabrics comprising fibrillated bicomponent fibers. The bicomponent fibers can be fibrillated mechanically by hydroentangling, where the hydroentangling energy is sufficient for fibrillating as well as entangling or bonding the fibers. The bicomponent fibers can have an island-in-the-sea configuration. The micro-denier fabrics can be woven, knitted, or nonwoven. A nonwoven fabric made from the bicomponent fibers can be formed by either spunbonding or through the use of bicomponent staple fibers formed into a web by any one of several means and bonded similarly to those used for the spunbonded filament webs.

This depth filter comprises a substrate layer, a filtration layer, and a skin layer in this order. The substrate layer and the skin layer are layers obtained by winding and thermally fusing a nonwoven cloth configured from fibers having an average fiber diameter of 150 μm or more. The filtration layer is a layer obtained by winding a layered body two or more times, the layered body containing at least a net and a nonwoven cloth included only in the filtration layer. The average fiber diameter of the nonwoven cloth constituting the substrate layer and the average fiber diameter of the nonwoven cloth constituting the skin layer are larger than the average fiber diameter of the nonwoven cloth included only in the filtration layer.

A filter medium of the present disclosure has a laminate structure composed of a first polytetrafluoroethylene (PTFE) porous membrane, a first air-permeable supporting member, a second PTFE porous membrane, and a second air-permeable supporting member laminated in this order. The first PTFE porous membrane constitutes an exposed surface of the filter medium. A ratio of a transmittance of the first PTFE porous membrane to a transmittance of the second PTFE porous membrane is 100 or more. The filter medium of the present disclosure is a filter medium which includes the PTFE porous membranes, from which dust deposited on a surface over a period of use can be easily removed, and which has excellent reusability demonstrated by reduction of a filtration performance decrease caused by removal of dust.

Filter media comprising non-woven fiber webs having one or more advantageous physical properties are generally described. In some embodiments, a filter media and/or non-woven fiber web described herein comprises a combination of fibers that results in enhanced physical properties. For example, the non-woven fiber web may comprise a combination of fiber types that is advantageous, such as a combination comprising fibrillated fibers, glass fibers, and/or binder fibers. In some cases, the filter media and/or non-woven fiber web comprising the combination of fibers may be formed into undulations (e.g., by a creping and/or microcreping process) to further enhance the physical properties of the filter media and/or non-woven fiber.