A method of making polyurethane or polyurethane urea strands containing siloxane in the polyurethane or polyurethane urea backbone including the steps of: (a) reacting a macroglycol with a diisocyanate to form a prepolymer; (b) reacting the prepolymer with a diamine to form a spinning solution; (c) spinning the spinning solution to form polyurethane or polyurethane urea strands, wherein: i. a diol-polydimethylsiloxane is reacted with the macroglycol and the diisocyanate in step (a); ii. a diamine-polydimethylsiloxane is reacted with the prepolymer prior to the reaction of the prepolymer with the diamine in step (b); or iii. a diamine-polydimethylsiloxane is reacted at the same time as the prepolymer and diamine in step (b), and wherein the polyurethane or polyurethane urea strands comprise less than or equal to 6% of siloxane by weight based on the weight of the polyurethane or polyurethane urea strands and elastic fibers made thereby. An elastic fiber including two or more polyurethane or polyurethane urea strands including siloxane in the polyurethane or polyurethane urea backbone that are bundled together, wherein the siloxane is present in an amount of greater than or equal to 0.01% and less than or equal to 4.0% by weight based on the weight of the fiber. In some aspects, the siloxane is free of urethane radicals.

A method of making polyurethane or polyurethane urea strands containing siloxane in the polyurethane or polyurethane urea backbone including the steps of: (a) reacting a macroglycol with a diisocyanate to form a prepolymer; (b) reacting the prepolymer with a diamine to form a spinning solution; (c) spinning the spinning solution to form polyurethane or polyurethane urea strands, wherein: i. a diol-polydimethylsiloxane is reacted with the macroglycol and the diisocyanate in step (a); ii. a diamine-polydimethylsiloxane is reacted with the prepolymer prior to the reaction of the prepolymer with the diamine in step (b); or iii. a diamine-polydimethylsiloxane is reacted at the same time as the prepolymer and diamine in step (b), and wherein the polyurethane or polyurethane urea strands comprise less than or equal to 6% of siloxane by weight based on the weight of the polyurethane or polyurethane urea strands and elastic fibers made thereby. An elastic fiber including two or more polyurethane or polyurethane urea strands including siloxane in the polyurethane or polyurethane urea backbone that are bundled together, wherein the siloxane is present in an amount of greater than or equal to 0.01% and less than or equal to 4.0% by weight based on the weight of the fiber. In some aspects, the siloxane is free of urethane radicals.

The present invention is directed to a reactive dye-dyeable polyurethane-urea elastic yarn including a reaction product of at least two polyols, a diisocyanate compound, a diamine chain extender, an amine chain terminator, and a diethylenetriamine compound, wherein one of the polyols is polyethylene glycol, which is included in an amount of 20 to 30.0 mol % based on the total amount of the polyols, a polyurethane-urea polymer includes 10 meq/kg to 45 meq/kg of primary amine ends, and the capping ratio (CR) of the diisocyanate to the polyols is 1.8 to 2.0.

An object of the present invention is to provide a polyurethane urea elastic fiber whose physical properties do not change much over time and which retains its initial mechanical properties, and a method for obtaining this fiber by modifying the molecular chain and ends of the polyurethane urea polymer. Another object of the present invention is to provide a polyurethane urea elastic fiber whose use can improve inventory management and fiber processing condition management, and which can be used to obtain a fabric with stable physical properties and qualities, and to provide a method for producing this fiber. The present invention is 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 on at least one end; and polyurethane urea polymer B using a polymer diol, a diisocyanate, an organic amine, and an organic carboxylic acid as starting materials, and containing an amide bond, wherein the polyurethane urea elastic fiber contains primary or secondary amino end groups in the range of 0.1 meq or more and 20 meq or less per kilogram of polyurethane urea elastic fiber.

An object of the present invention is to provide a polyurethane urea elastic fiber whose physical properties do not change much over time and which retains its initial mechanical properties, and a method for obtaining this fiber by modifying the molecular chain and ends of the polyurethane urea polymer. Another object of the present invention is to provide a polyurethane urea elastic fiber whose use can improve inventory management and fiber processing condition management, and which can be used to obtain a fabric with stable physical properties and qualities, and to provide a method for producing this fiber. The present invention is 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 on at least one end; and polyurethane urea polymer B using a polymer diol, a diisocyanate, an organic amine, and an organic carboxylic acid as starting materials, and containing an amide bond, wherein the polyurethane urea elastic fiber contains primary or secondary amino end groups in the range of 0.1 meq or more and 20 meq or less per kilogram of polyurethane urea elastic fiber.