Filter media, such as electret-containing filtration media for filtering gas streams (e.g., air), are described herein. In some embodiments, the filter media may be designed to have desirable properties such as stable filtration efficiency over the lifetime of the filter media, increased normalized gamma, relatively low pressure drop (i.e. resistance), and/or relatively low basis weight. In certain embodiments, the filter media may be a composite of two or more types of fiber layers where each layer may be designed to enhance its function without substantially negatively impacting the performance of another layer of the media. For example, one layer of the media may be designed to have a relatively low basis weight and/or a relatively high air permeability, and another layer of the media may be designed to have stable filtration efficiency and/or a relatively high efficiency throughout the filter media's lifetime. The filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment), though the media may also be used in other applications.

A BAK removal device is constructed as a plug of microparticles of a hydrophilic polymeric gel that displays a hydraulic permeability greater than 0.01 Da. The polymer hydrophilic polymeric gel comprises poly(2-hydroxyethyl methacrylate) (pHEMA). The particles are 2 to 100 m and the plug has a surface area of 30 mm.sup.2 to 2 mm.sup.2 and a length of 2 mm to 25 mm and wherein the microparticles of a hydrophilic polymeric gel has a pore radius of 3 to 60 m.

A nanofiber nonwoven product is disclosed which comprises a polyamide with a relative viscosity from 2 to 330, spun into nanofibers with an average diameter of less than 1000 nanometers (1 micron). In general, the inventive products are prepared by: (a) providing a polyamide composition, wherein the polyamide has a relative viscosity from 2 to 330; (b) melt spinning the polyamide composition into a plurality of nanofibers having an average fiber diameter of less than 1 micron, followed by (c) forming the nanofibers into the product.

A filter bag is disclosed that comprises a porous membrane having a strength in the transverse direction to improve durability. There is a filter assembly for filtering particulates from a gas stream comprising a support substructure and a filter bag at least partially surrounding the support substructure. The filter bag comprises a porous membrane having a upstream surface exposed to the gas stream. The porous membrane is lightweight and has a structure to collect the particulates on the upstream surface. In particular, the porous membrane has a bubble point of 0.06 MPa or more and has a strength in a transverse direction that is 100N/m or more. Other filter bags disclosed comprise a laminate comprising a porous membrane having a bubble point of 0.06 MPa or more and a second layer that acts as a sacrificial material.

A filter bag is disclosed that comprises a porous membrane having a strength in the transverse direction to improve durability. There is a filter assembly for filtering particulates from a gas stream comprising a support substructure and a filter bag at least partially surrounding the support substructure. The filter bag comprises a porous membrane having a upstream surface exposed to the gas stream. The porous membrane is lightweight and has a structure to collect the particulates on the upstream surface. In particular, the porous membrane has a bubble point of 0.06 MPa or more and has a strength in a transverse direction that is 100 N/m or more. Other filter bags disclosed comprise a laminate comprising a porous membrane having a bubble point of 0.06 MPa or more and a second layer that acts as a sacrificial material.

Air filtration media including synthetic and cellulose fiber layers are provided. More particularly, the air filtration media have high initial efficiency with improved durability, fire retardance, anti-microbial activity, and moisture resistance. The air filtration media can be used in air filters for a variety of applications.

A filter comprising a nanofiber nonwoven product is disclosed which comprises a polyamide with a relative viscosity from 2 to 330, spun into nanofibers with an average diameter of less than 1000 nanometers (1 micron). In general, the inventive products are prepared by: (a) providing a polyamide composition, wherein the polyamide has a relative viscosity from 2 to 330; (b) melt spinning the polyamide composition into a plurality of nanofibers having an average fiber diameter of less than 1 micron, followed by (c) forming the nanofibers into the product.

A coalescence separator for separating liquid droplets from a gas flow has a gas inlet and a gas outlet. A multi-layer structure of a plurality of individual layers of a coalescence filter medium is arranged between the gas inlet and the gas outlet, wherein the coalescence filter medium is provided with a glass fiber paper with glass fibers. The individual layers of the coalescence filter medium each have an individual layer thickness of more than 0.8 mm and maximally 5 mm, a grammage of greater than 80 g/m.sup.2 and less than 500 g/m.sup.2, and an air permeability of 350 l/m.sup.2s to 1,800 l/m.sup.2s. The multi-layer structure has between 2 and 80 of the individual layers.

Provided is a melt-blown nonwoven fabric including a propylenic polymer that shows at least one peak top at a position of a molecular weight of 20,000 or higher and at least one peak top at a position of a molecular weight of less than 20,000 in a discharge curve obtained by gel permeation chromatography, and has an intrinsic viscosity [] of from 0.50 (dl/g) to 0.75 (dl/g).

A filter medium is provided with a first layer as a support layer and a second layer as a filtration layer arranged downstream of the first layer. The first layer and the second layer both are provided with at least one active agent that is at least antibacterial. The active agent can be applied as a coating or as an impregnation. Examples of active agents are pyrithione, a metal salt of pyrithione, a pyrithione derivative, a metal salt of a pyrithione derivative, and a quaternary ammonium salt. A filter element is provided with such a filter medium in the form of a filter media pack. The filter medium and filter element can be used in a water injection system for internal combustion engines.