Disclosed is a composite filter media. The composite filter media is formed from multiple layers of media material including a nanofiber media layer, where the layers are laminated, bound, or otherwise composited to each other. The composite filter media can comprise at least one nanofiber layer comprising polymeric media material having a geometric mean fiber diameter of about 100 nm to 1 m, and fibers configured in a gradient such that ratio of the geometric mean diameter of fibers at the upstream face of the nanofiber layer to the geometric mean diameter of fibers at the downstream face of the nanofiber layer is about 1.1 to 2.8, preferably about 1.2 to 2.4.

Filter elements for gaseous fluid (e.g., air) filtration for wafer processing systems. The filter elements have a pleat ratio of no greater than 7, where the pleat ratio is the number of pleats per mean diameter of the filter. By having a pleat ratio no greater than 7, and in some implementations also greater than 5, the filter is optimized for wafer processing systems and methods. This pleat ratio optimizes the spacing between pleats, thus balancing filtration media area against effective area, such as what might be lost due to contaminant bridging.

A honeycomb structure body, which includes a honeycomb body and a skin layer, the honeycomb body including axially extending channels defined by a porous wall, wherein a radial path of a radial section of the honeycomb body from a central axis to the skin layer consists of a porous wall inner section and a porous wall outer section in sequence, an average wall thickness of inner porous walls provided in the porous wall inner section is smaller than an average wall thickness of outer porous walls provided in the porous wall outer section, and a length of the porous wall inner section in the radial path accounts for 71%-95%. The specific structure of the honeycomb structure body not only increases the strength of the honeycomb structure body, but also ensures good thermal shock resistance and small back pressure.

An object of the present invention is to provide a method for producing a propionic acid derivative with high productivity. The object can be achieved by a method for producing a compound represented by formula (1): ##STR00001##
wherein R.sup.1 is a halogen atom or the like, R.sup.2 and R.sup.3 are each independently a hydrogen atom, a halogen atom, or an organic group, X is an oxygen atom or a sulfur atom, R.sup.4 and R.sup.5 are each independently a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having one or more substituents, R.sup.6 is a hydrocarbon group optionally having one or more substituents; the method comprising step A of reacting a compound represented by formula (2): ##STR00002##
with a compound represented by formula (3):
M(R.sup.1).sub.n, wherein M is a cation, n is an integer corresponding to the valence of M, and a compound represented by formula (4):
R.sup.6XH; and
step B of separating, by filtration, the compound represented by formula (5): MF.sub.n from the mixture obtained by the above reaction.

The present application is direction to a system and method for preparing filter media from macro and nanofibers by ventilating a nanofiber media, combining the nanofiber media with macro fibers to form a hybrid media, inserting the hybrid media between a stitching plate and a stripper plate and alternatively inserting and withdrawing needles to combine the macro fibers with the nanofiber media and create a fiber web along at least one surface of the nanofiber media.

A particulate filter for use in an exhaust aftertreatment system includes a ceramic substrate and a plurality of ceramic nanofibers associated with pores of the ceramic substrate. The plurality of ceramic nanofibers may be positioned on pores of the ceramic substrate, within pore channels of the ceramic substrate, or both on pores of the ceramic substrate and within pore channels of the ceramic substrate.

A filter having a plurality of filter pores penetrating one surface and another surface of the filter, wherein the filter pore has a first opening on the one surface and a second opening on the another surface, a ratio (L1/W1) of a major axis diameter L1 to a minor axis diameter W1 of the first opening is 1.00 or more and 1.20 or less, the minor axis diameter W1 is 7.0 ?m or more and 9.0 ?m or less, a ratio (L2/W2) of a major axis diameter L2 to a minor axis diameter W2 of the second opening is 1.00 or more and 1.20 or less, and a ratio (W2/W1) of the minor axis diameter W2 to the minor axis diameter W1 and a ratio (L2/L1) of the major axis diameter L2 to the major axis diameter L1 are both 1.20 or more and 1.50 or less.

Provided are a filter medium for an air filter capable of having extended life even when composed of embossable material. The filter medium (1) has a tensile elongation of 10% or greater, and includes a main collection layer (30) having a filing rate of 5% to 15%, a thickness of 0.35 mm to 0.70 mm, and a peak in a fiber diameter distribution at less than 1.0 m and a peak at 1.0 m or greater. An average fiber diameter of small fiber diameters of less than 1.0 m is from 0.1 m to less than 0.8 m, and an average fiber diameter of large fiber diameters of 1.0 m or greater is from 1.2 m to less than 3.0 m. A volume ratio of the fibers having the small fiber diameter to the fibers having the large fiber diameter is from 30:70 to 80:20.

A particulate filter for use in an exhaust aftertreatment system includes a ceramic substrate and a plurality of ceramic nanofibers associated with pores of the ceramic substrate. The plurality of ceramic nanofibers may be positioned on pores of the ceramic substrate, within pore channels of the ceramic substrate, or both on pores of the ceramic substrate and within pore channels of the ceramic substrate.

Filter elements for gaseous fluid (e.g., air) filtration for wafer processing systems. The filter elements have a pleat ratio of no greater than 7, where the pleat ratio is the number of pleats per mean diameter of the filter. By having a pleat ratio no greater than 7, and in some implementations also greater than 5, the filter is optimized for wafer processing systems and methods. This pleat ratio optimizes the spacing between pleats, thus balancing filtration media area against effective area, such as what might be lost due to contaminant bridging.