A method for producing a polyurethane elastic fiber according to the present invention contains the steps of: [1] producing a polyurethane urea polymer (A) having a number average molecular weight ranging from 12,000 to 50,000, and represented by general formula (1); [2] preparing a spinning dope by adding the polyurethane urea polymer (A) to a polyurethane urea polymer (B); and [3] spinning a polyurethane elastic fiber using the spinning dope. ##STR00001##
In the formula, R.sup.1 and R.sup.2 are an alkyl group or a hydroxyalkyl group, R.sup.3 is an alkylene group, a polyethyleneoxy group or a polypropyleneoxy group, R.sup.4 is a diisocyanate residue, X is a urethane bond or a urea bond, R.sup.5 and R.sup.6 are a diisocyanate residue, P is a diol residue, Q is a diamine residue, UT is a urethane bond, UA is a urea bond, each of k, l, m and n is 0 or a positive number.

A dye composition and a dyeing method for an elastic fabric are provided. The dyeing method includes: (a) providing an elastic fabric which includes an elastic fiber; and (b) immersing the elastic fabric in a dye composition. The dye composition includes an ion modifier and a dye. The elastic fiber of the elastic fabric has a first ion by contacting the ion modifier, and the first ion has a first charge; the dye has a second ion, and the second ion has a second charge opposite to the first charge. The first ion of the elastic fiber and the second ion of the dye together form an iconic bonding.

A dye composition and a dyeing method for an elastic fabric are provided. The dyeing method includes: (a) providing an elastic fabric which includes an elastic fiber; and (b) immersing the elastic fabric in a dye composition. The dye composition includes an ion modifier and a dye. The elastic fiber of the elastic fabric has a first ion by contacting the ion modifier, and the first ion has a first charge; the dye has a second ion, and the second ion has a second charge opposite to the first charge. The first ion of the elastic fiber and the second ion of the dye together form an iconic bonding.

An elastic fiber is provided that includes polyurethane and/or polyurethaneurea and an additive such as polystyrene, an acrylic polymer, polyvinylpyrrolidone, copolymers thereof, derivatives thereof, and combinations thereof. The elastic fiber is useful in laminate structures, such as disposable hygiene articles as wells as in knit, woven and nonwoven fabric constructions.

An elastic fiber is provided that includes polyurethane and/or polyurethaneurea and an additive such as polystyrene, an acrylic polymer, polyvinylpyrrolidone, copolymers thereof, derivatives thereof, and combinations thereof. The elastic fiber is useful in laminate structures, such as disposable hygiene articles as wells as in knit, woven and nonwoven fabric constructions.

A problem addressed by the present invention is to provide a resin out of which a heat-resistant non-woven fabric having a fine fiber diameter can be made by an electrospinning method. A main object of the present invention is to provide a resin, including a structure(s) represented by at least one selected from the group consisting of the following general formulae (1) to (3), wherein an end of the main-chain of the resin has at least one selected from alkyl groups having 10 or more carbon atoms and fluoroalkyl groups having 4 or more carbon atoms;

##STR00001##

(wherein, in the general formula (1), X independently represents a single bond or NR.sup.3; R.sup.1 and R.sup.2 independently represent a C.sub.4-C.sub.30 bivalent organic group; R.sup.3 represents a hydrogen atom or a C.sub.1-C.sub.10 monovalent organic group; in the general formula (2), R.sup.4 represents a C.sub.4-C.sub.30 bivalent organic group; R.sup.5 represents a C.sub.4-C.sub.30 tetravalent organic group; in the general formula (3), R.sup.6 represents a C.sub.4-C.sub.30 bivalent organic group; R.sup.7 represents a C.sub.4-C.sub.30 trivalent organic group; l, m, and n are each an integer of 0 or greater with the proviso that l+m+n=10 or greater; and wherein the structures represented by the general formulae (1) to (3) do not necessarily need to be consecutively present.)

An object of the present invention is to provide a polyurethane urea elastic fiber with high elasticity and excellent textile property stability over time by modifying the ends of the polyurethane urea polymer molecular chain, and to provide a method for producing such a polyurethane urea elastic fiber. Another object of the present invention is to provide a polyurethane urea elastic fiber that allows for easier inventory control and processing condition management of fibers when it is used, and that can be used to obtain fabrics with stable fabric characteristics and fabric quality, and to provide a method for producing such a polyurethane urea elastic fiber.

[Solution] A polyurethane urea elastic fiber comprising: polyurethane urea polymer A having a molecular chain using a polymer diol, a diisocyanate, and an organic amine as starting materials, and having a primary or secondary amino group at both ends of the molecular chain; and polyurethane urea polymer B having a molecular chain using a polymer diol, a diisocyanate, and an organic amine, and having a sulfonic acid amine salt on at least one end of the molecular chain.

An object of the present invention is to provide a polyurethane urea elastic fiber with high elasticity and excellent textile property stability over time by modifying the ends of the polyurethane urea polymer molecular chain, and to provide a method for producing such a polyurethane urea elastic fiber. Another object of the present invention is to provide a polyurethane urea elastic fiber that allows for easier inventory control and processing condition management of fibers when it is used, and that can be used to obtain fabrics with stable fabric characteristics and fabric quality, and to provide a method for producing such a polyurethane urea elastic fiber.

[Solution] A polyurethane urea elastic fiber comprising: polyurethane urea polymer A having a molecular chain using a polymer diol, a diisocyanate, and an organic amine as starting materials, and having a primary or secondary amino group at both ends of the molecular chain; and polyurethane urea polymer B having a molecular chain using a polymer diol, a diisocyanate, and an organic amine, and having a sulfonic acid amine salt on at least one end of the molecular chain.

A method for producing a polyurethane elastic fiber according to the present invention contains the steps of: [1] producing a polyurethane urea polymer (A) having a number average molecular weight ranging from 12,000 to 50,000, and represented by general formula (1); [2] preparing a spinning dope by adding the polyurethane urea polymer (A) to a polyurethane urea polymer (B); and [3] spinning a polyurethane elastic fiber using the spinning dope.

##STR00001##

In the formula, R.sup.1 and R.sup.2 are an alkyl group or a hydroxyalkyl group, R.sup.3 is an alkylene group, a polyethyleneoxy group or a polypropyleneoxy group, R.sup.4 is a diisocyanate residue, X is a urethane bond or a urea bond, R.sup.5 and R.sup.6 are a diisocyanate residue, P is a diol residue, Q is a diamine residue, UT is a urethane bond, UA is a urea bond, each of k, l, m and n is 0 or a positive number.

A method for producing a polyurethane elastic fiber according to the present invention contains the steps of: [1] producing a polyurethane urea polymer (A) having a number average molecular weight ranging from 12,000 to 50,000, and represented by general formula (1); [2] preparing a spinning dope by adding the polyurethane urea polymer (A) to a polyurethane urea polymer (B); and [3] spinning a polyurethane elastic fiber using the spinning dope.

##STR00001##

In the formula, R.sup.1 and R.sup.2 are an alkyl group or a hydroxyalkyl group, R.sup.3 is an alkylene group, a polyethyleneoxy group or a polypropyleneoxy group, R.sup.4 is a diisocyanate residue, X is a urethane bond or a urea bond, R.sup.5 and R.sup.6 are a diisocyanate residue, P is a diol residue, Q is a diamine residue, UT is a urethane bond, UA is a urea bond, each of k, l, m and n is 0 or a positive number.