A provided stretched porous polytetrafluoroethylene membrane has a node-fibril structure including a plurality of nodes and a fibril connecting the plurality of nodes. A ratio of an average length of the plurality of nodes in a thickness direction of the stretched porous polytetrafluoroethylene membrane to a thickness of the stretched porous polytetrafluoroethylene membrane is 10% or more. The above stretched porous polytetrafluoroethylene membrane is less likely to suffer breakage. In the above stretched porous polytetrafluoroethylene membrane, assuming that there is a cuboid region having an upper surface and a lower surface respectively positioned at one membrane surface and the other membrane surface of the stretched porous polytetrafluoroethylene membrane, the number of the nodes included in the region may be 4 or less per micrometer thickness, the upper surface and the lower surface each having dimensions of 280 μm×280 μm.

A method to manufacture a ceramic foam filter includes: sintering a filter body to a temperature greater than a molten metal to be filtered through the body; creating multiple tortuous path channels extending through the filter body individually having a repeated and controlled passage geometry creating a continuously changing diameter and area of a flow path through the multiple tortuous path channels causing localized increases and decreases in molten metal flow rate through the multiple tortuous path channels; and applying a mixture of at least one ceramic powder and at least one binder using additive manufacturing to shape the filter body including the multiple tortuous path channels.

In an exhaust gas purification filter, a partition wall has communicating pores. Each communicating pore has a surface opening on the gas-inflow-side surface and a plurality of portions, each portion having a diameter being reduced and then increased from the surface opening, one of the portions, whose diameter is the smallest, being defined as an inlet neck portion. As viewed in cross section in a thickness direction of the partition wall, the surface opening of each communication pore has a diameter defined as a surface opening diameter, the inlet neck portion of each communication pore has a diameter defined as an inlet neck diameter. The inlet neck diameter is smaller than the surface opening diameter, and an average value of the inlet neck diameters is 15 μm or less. A surface opening ratio of the communicating pores in plan view of the gas-inflow-side partition wall surface is 40% or more.

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.

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.

The disclosure relates to a filtration media comprising a fibrous web impregnated with a resin composition comprising lignin. The fibrous web comprises the lignin in an amount of from 0.1 to 30 wt % by weight of the fibrous web, and the lignin has a density of less than 1.2 g/cm.sup.3 or a weight average molecular weight of less than 20,000 g/mol. The disclosure further relates to a method of manufacturing the filtration media.

Provided is a fiber structure which can have both a high filtering efficiency and a small pressure loss. The fiber structure comprises ultrafine fibers having a number average single fiber diameter of 4.5 μm or smaller and non-ultrafine fibers having a number average single fiber diameter of 5.5 μm or larger, wherein the ultrafine fibers and the non-ultrafine fibers are unitedly intermingled, and the fiber structure includes projections on at least one surface thereof. For example, in the fiber structure, the ultrafine fibers may be heat-resistant ultrafine fibers, and the non-ultrafine fibers may be heat-resistant non-ultrafine fibers.

A blood processing filter includes a flexible container having an inlet and an outlet for blood, a filter medium disposed between the inlet and the outlet, and a flow passage-securing member disposed between the filter medium and the outlet. The filter medium includes a filter layer X1 including a filter component unit A1, and a filter layer Y including a filter component unit B. The filter layer X1 is disposed between the filter layer Y and the flow passage-securing member, a ventilation resistance per thickness of the filter component unit A1 is 5.0 Pa.Math.s/m.sup.2 or more and less than 9.0 Pa.Math.s/m.sup.2, a ventilation resistance per thickness of the filter component unit B is 9.0 Pa.Math.s/m.sup.2 or more, a ventilation resistance of the filter layer X1 is 4.0 kPa.Math.s/m or more and 20.0 kPa.Math.s/m or less, and a ventilation resistance of the filter medium is 55.0 kPa.Math.s/m or more and less than 75.0 kPa.Math.s/m.

The filter medium for a filter of the present invention has a laminate structure in which a long-fiber non-woven fabric and a wet non-woven fabric are stacked, wherein the wet non-woven fabric comprises vinylon, polyester, and polyvinyl alcohol, is disposed on a most upstream side of air flow, has a surface located on the most upstream side of air flow, the surface having a surface roughness (SMD) not larger than 2.7 μm, and has a surface stacked on the long-fiber non-woven fabric, the surface having (a) a surface roughness (SMD) not smaller than 3.0 μm or (b) a rough texture (MMD) not lower than 0.02.

A melt-blown nonwoven fabric includes polybutylene terephthalate, in which an intrinsic viscosity of the melt-blown nonwoven fabric is 0.45 dl/g or more and 0.60 dl/g or less.