The present invention relates to a filter medium suitable for air filtration as well as related assemblies and methods.

Disclosed is a porous support including fine porous structures formed between nanofibers, wherein the fine porous structures have a porosity of 50% to 90%, a pore size of 0.01 μm to 10 μm and an air permeability of 0.01 to 7 sec/100 cc.Math.air, and the porous support has a thickness of 5 μm to 50 μm, a method of manufacturing the same and a reinforced membrane including the same.

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 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.

A filter media comprises a first fiber layer and a second fiber layer positioned downstream of the first fiber layer. The first fiber layer has a first geometric mean fiber diameter of less than 1 pm such that the geometric standard deviation of fiber diameter is greater than 2. The second fiber layer has a second geometric mean fiber diameter of less than 1 pm such that the geometric standard deviation of fiber diameter is less than 2.

There are provided an air filter medium, a filter pack, and an air filter unit in which the decrease in collection efficiency can be suppressed. The air filter medium includes a fluororesin. The PAO permeability ratio (final permeability/initial permeability) is less than 3.0. The initial permeability is a permeability of polyalphaolefin particles when air containing the polyalphaolefin particles having a number median diameter of 0.25 μm is passed through the air filter medium at a flow velocity of 5.3 cm/s. The final permeability is a permeability of polyalphaolefin particles when air containing the polyalphaolefin particles having a number median diameter of 0.25 μm is continuously passed through the air filter medium at a flow velocity of 5.3 cm/s and the pressure loss is increased by 250 Pa.

A method for manufacturing a filtration media with improved filtration, strength, tear resistance and air permeability in the form of a relatively thin and lightweight wet-laid fibrous web that has a wet Mullen ratio of 20% to 90% to ensure that the media is flexible enough to be formed into a fluted structure, and strong enough to retain the fluted structure when would into a roll and to permit further processing.

Fine fiber products including fiber webs, as well as related assemblies, systems and methods, are described. In some embodiments, fiber webs described herein may include fine fibers and relatively low amounts of degraded polymer formed during a fiber extrusion process. The fiber webs may be used for filter media applications.

The filter medium of the present disclosure includes a base layer having air permeability, and the base layer has a modified surface by fibrils of polytetrafluoroethylene. The modified surface of the base layer may be exposed. A modification amount of the fibrils in the modified surface is, for example, less than 0.5 g/m.sup.2. The base layer may include a fiber material, and an example of the base layer including a fiber material is a non-woven fabric. In the filter medium of the present disclosure, permeation of water into the inside of the medium can be inhibited.

A filter media and methods are provided. The media is stretchable and exhibits a high degree of elongation which thereby extends its surface area during pleating. By extending surface area of media during pleating, the initial differential pressure is lowered as the area of media is stretched while keeping the same efficiency range with a compressed thickness of media on the affected area.