Disclosed is a napped artificial leather including: an artificial leather base material that includes a non-woven fabric of polyester fibers having a Young's modulus of 1 to 6 GPa, an average fiber-toughness of 8 to 40 cN.Math.%, and a crystallinity of 35% or less, and an elastic polymer, the artificial leather base material having, on at least one surface thereof, a napped surface on which the polyester fibers are napped. Also disclosed are polyester fibers having a Young's modulus of 1 to 6 GPa, an average fiber-toughness of 8 to 40 cN.Math.%, and a crystallinity of 35% or less, and a non-woven fabric including the polyester fibers.

Coated and expanded, nanofiber structures are provided and methods of use thereof.

A napped artificial leather including a non-woven fabric including ultrafine fibers and a polyurethane, the napped artificial leather including a napped surface formed by napping the ultrafine fibers on a surface thereof, wherein the napped surface has, after a Martindale abrasion test in accordance with JIS L 1096 (6.17.5E method, Martindale method) under a pressing load of 12 kPa and 50000 times of abrasions, a ratio of the polyurethane observed by a surface observation using an electron microscope in a portion that has been subjected to the Martindale abrasion test, of 4.0% or less.

Disclosed is a colored napped artificial leather including: a fiber-entangled body including ultrafine fibers having an average single fiber fineness of 0.5 dtex or less; and an elastic polymer impregnated into the fiber-entangled body, the napped artificial leather having, at least on one side thereof, a napped surface formed by napping the ultrafine fibers, wherein the napped artificial leather further includes particles of a fatty acid amide-based compound that are at least attached to surfaces of the ultrafine fibers and that have an average particle size of 0.1 to 10 μm.

A sheet is produced by (i) producing a sheet by entangling woven or knitted material including a thread composed of a composite fiber such that two kinds or more of polyethylene terephthalate polymers different in intrinsic viscosity are stuck together in a side-by-side type along the fiber length direction and/or of a core-in-sheath type composite fiber such that two kinds or more of polyethylene terephthalate polymers different in intrinsic viscosity form an eccentric core-in-sheath structure, with a fiber capable of converting into ultra fine fibers composed of two kinds or more of polymeric substances different in solubility in solvent, (ii) developing an ultra fine fiber with an average single fiber fineness of 0.001 dtex or more and 0.5 dtex or less by treating the sheet with a solvent to thereafter provide elastomer having polyurethane as a main component by impregnating and solidifying solvent solution of elastomer having polyurethane as a main component into the sheet, or of providing elastomer having polyurethane as a main component by impregnating and solidifying solvent solution of elastomer having polyurethane as a main component into the sheet to thereafter develop an ultra fine fiber with an average single fiber fineness of 0.001 dtex or more and 0.5 dtex or less by treating the sheet with a solvent, and (iii) rubbing and shrinking the woven or knitted material under the condition of 110° C. or more.

An artificial leather is provided having excellent flame retardancy and moderate air permeability and a flexible texture, where the artificial leather feels like natural suede and has an elegant appearance, the artificial leather including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 μm or more and 10 μm or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied: requirement 1: at least the flame retardant surface has a plurality of opening portions; requirement 2: the flame retardant has a tackiness of 0.1 N/cm.sup.2 or more and 2.0 N/cm.sup.2 or less.

Provided is an artificial leather, which exhibits light transmitting properties and maintains its texture and touch while being dark-colored and having a medium or higher density, the artificial leather including a fiber entangled body formed of ultrafine fibers having an average single fiber diameter of 0.1 to μm; and an elastomer, in which the artificial leather has a thickness of 0.4 to 1.2 mm and a weight per unit area of 80 to 450 g/m.sup.2, where one surface of the artificial leather is a design surface colored with a dye and/or a pigment and satisfies the following Formulas (1) to (3):

L*.sub.1≤55 . . .   (1)

L.sub.0>50 . . .   (2)

ΔL* <−5 . . .   (3)

where L*.sub.1, L*.sub.0 and ΔL* are as defined.

A napped artificial leather includes: a fiber-entangled body obtained by entangling ultrafine fibers: and an elastic polymer impregnated into the fiber-entangled body. The napped artificial leather has, on at least one side thereof, a napped surface formed by napping the ultrafine fibers. The ultrafine fibers contain 0.2 to 8 mass% of carbon black and 0.1 to 5 mass% of a chromatic pigment, and a total ratio of the carbon black and the chromatic pigment is 0.3 to 10 mass%. A content ratio of the elastic polymer is 0.1 to 15 mass% in the napped artificial leather. The elastic polymer is uncolored and the ultrafine fibers are undyed.

A method of forming a sheet material. The method comprises advancing an arrangement comprising a body of fibres and a reinforcing structure, wherein the reinforcing structure comprises splittable fibres. The method further comprises subjecting the arrangement to successive hydroentanglement steps, wherein in each such hydroentanglement step the arrangement is exposed to high pressure jets of liquid over a surface of the arrangement. Subjecting the arrangement to successive hydroentanglement steps causes the fibres of the body of fibres to entangle with each other and causes a mechanical bond to form between the fibres of the body of fibres and the reinforcing structure. The mechanical bond is caused by at least:

some of the fibres of the body of fibres being pushed by the high-pressure jets of liquid into gaps in the reinforcing structure;

at least some of the splittable fibres of the reinforcing structure splitting to form split fibres which reduces the space within the gaps such that the reinforcing structure constricts about fibres of the body of fibres which have been pushed in the gaps; and

at least some of the fibres of the body of fibres entangling with at least some of the split fibres and at least some of the splittable fibres of the reinforcing structure.

The present disclosure provides a polyurethane dispersion comprising a polyurethane prepolymer and an ionic surfactant. It further provides a microfiber nonwoven synthetic leather comprising a microfiber nonwoven fabric and the polyurethane dispersion. It further provides a method of preparing the microfiber nonwoven synthetic leather comprising a step of impregnating microfiber nonwoven fabrics into the polyurethane dispersion.