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 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.

The separator of a nonaqueous electrolyte secondary battery is characterized by having a composite nanofiber fiber which is a nanosize fiber that contains two or more kinds of aqueous resins whose melting points are different.

The separator of a nonaqueous electrolyte secondary battery is characterized by having a composite nanofiber fiber which is a nanosize fiber that contains two or more kinds of aqueous resins whose melting points are different.

A non-woven fabric, non-woven fabric producing method and an acoustic absorbent of desirable properties are provided. The non-woven fabric is a non-woven fabric including a plurality of ultrafine fibers configured from a thermoplastic resin, and comprises: a base portion configured by entangling of some of the plurality of ultrafine fibers; and a fiber bundle configured by entangling and bundling of other ultrafine fibers in the plurality of ultrafine fibers, and that is entangled with the base portion. The fiber bundle has a lower void fraction than a void fraction of the base portion.

A natural fiber felt is provided, which is a film formed by processes of binding a natural fiber net with a binder, extruding, drying and shaping the natural fiber net. A surface of the film is coated with a waterproof layer. The foam binder is formed by combining modified starch serving as a binder and urea serving as a foaming agent with water. A water-repellent agent fruit wax emulsion is employed to form the waterproof layer. The natural fiber net is carded by a carding machine at one time, and the foam binder is sprayed onto the natural fiber net to bind the natural fiber net so as to form the film. The product has characteristics of ultra-thinness and high strength with good performances on heat preservation, moisturizing ability, waterproof and air permeability.

A natural fiber felt is provided, which is a film formed by processes of binding a natural fiber net with a binder, extruding, drying and shaping the natural fiber net. A surface of the film is coated with a waterproof layer. The foam binder is formed by combining modified starch serving as a binder and urea serving as a foaming agent with water. A water-repellent agent fruit wax emulsion is employed to form the waterproof layer. The natural fiber net is carded by a carding machine at one time, and the foam binder is sprayed onto the natural fiber net to bind the natural fiber net so as to form the film. The product has characteristics of ultra-thinness and high strength with good performances on heat preservation, moisturizing ability, waterproof and air permeability.

A partially separated fiber bundle includes a separated fiber section and an unseparated fiber section, being configured to give a ratio A.sub.max/A.sub.min of 1.1 or larger and 3 or smaller, when the number of fiber bundles contained in the width direction of the partially separated fiber bundle (fiber separating number: N.sub.n) measured at a freely selected point P.sub.n (where, n represents an integer of 1 to 100, and freely selected points P.sub.n and P.sub.n+1, excluding n=100, being 50 cm or more away from each other), is divided by a full width of W.sub.n of the partially separated fiber bundle, to calculate the fiber separating number per unit width A.sub.n, and assuming its maximum value as A.sub.max and its minimum value as A.sub.min.

Provided are: a high-melting-point resin fiber having heat resistance and solvent resistance, offering excellent workability/formability, and having a diameter of 4 μm or less; and a nonwoven fabric including the high-melting-point resin fiber. Also provided is a method for efficiently producing a high-melting-point resin fiber having a diameter of 4 μm or less, via laser melt electrospinning. The high-melting-point resin fiber according to the present invention includes a resin having a melting point of 250° C. or higher and has a diameter of 4 μm or less. In the high-melting-point resin fiber, the resin having a melting point of 250° C. or higher is preferably a PEEK. The fiber preferably has a degree of crystallinity of 30% or less.

Provided are: a high-melting-point resin fiber having heat resistance and solvent resistance, offering excellent workability/formability, and having a diameter of 4 μm or less; and a nonwoven fabric including the high-melting-point resin fiber. Also provided is a method for efficiently producing a high-melting-point resin fiber having a diameter of 4 μm or less, via laser melt electrospinning. The high-melting-point resin fiber according to the present invention includes a resin having a melting point of 250° C. or higher and has a diameter of 4 μm or less. In the high-melting-point resin fiber, the resin having a melting point of 250° C. or higher is preferably a PEEK. The fiber preferably has a degree of crystallinity of 30% or less.