Melt-spun thermoplastic polyurethane fibers

Abstract

The present invention relates to melt-spun thermoplastic polyurethane fibers comprising a copolymer diol derived from caprolactone and a polyether polyol, and fabrics made therefrom, both of which can be dyed under disperse dyeing conditions.

Description

[Background technology]

[0001] The apparel market is increasingly interested in fabrics that can stretch yet maintain their shape and fit. Thermoplastic polyurethane (TPU) fibers show great potential for providing stretch and fit properties, but they have several drawbacks. Many polyurethane fibers are made by a dry-spinning process, which involves dissolving reactive components in a solvent. While such fibers generally have good heat resistance, the dry-spinning process is expensive, time-consuming, and involves the use of volatile solvents, which raises environmental concerns. While melt-spinning fibers has manufacturing advantages, not all TPUs are suitable for forming fibers under melt-spinning conditions. In addition, prior art TPUs that can be melt-spun into fibers lack the heat resistance that allows them to withstand certain dyeing conditions. This makes it difficult to combine melt-spun TPU fibers with other common synthetic or natural fibers because TPU fibers can lose their stretch and recovery properties after exposure to dyeing conditions.

[0002] Therefore, it would be desirable to have melt-spun TPU fibers that have good stretch and recovery properties, but that can be dyed under disperse dyeing conditions (e.g., temperatures of about 130° C. to 135° C.). It would also be desirable to have fabrics made from TPU fibers alone or in combination with other fiber materials to provide fabrics that can be dyed and have desirable properties.

[0003] Additionally, recycling of scrap or post-consumer textiles is an area of ​​growing interest. It would be desirable to have a method for recycling textile materials to make other articles. Summary of the Invention [Means for solving the problem]

[0004] In one embodiment, the invention is a melt-spun fiber, the fiber comprising a thermoplastic polyurethane composition and an isocyanate-functional crosslinker. The thermoplastic polyurethane composition used in the fiber comprises the reaction product of (i) a polyol component comprising or consisting of a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol), (ii) a hydroxyl-terminated chain extender component, and (iii) a first diisocyanate component.

[0005] In another embodiment, the present invention comprises a process for preparing a thermoplastic polyurethane having the following steps: (a) preparing a reactive thermoplastic polyurethane composition that is the reaction product of (a) a polyol component comprising a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol), (b) a chain extender component comprising 1,4-bis(β-hydroxyethoxy)benzene, and (c) a diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer into the extruder; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer to at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; and (8) winding the melt-spun fibers onto a bobbin.

[0006] In yet another embodiment, the present invention provides a fabric comprising: a first fiber component comprising hard yarns, e.g., polyester fibers, having an ultimate elongation of 10% to 75% as measured according to ASTM D2256; and a second fiber component comprising melt-spun thermoplastic polyurethane filaments having an ultimate elongation of at least 300% as measured according to ASTM D2731; the first fiber component and the second fiber component are knitted together to form a fabric; and the fabric is dyed using disperse dyeing conditions.

[0007] In another embodiment, the present invention provides a method for recycling the fabrics made herein to make other articles.

[0008] These various embodiments are described in more detail below. DETAILED DESCRIPTION OF THE INVENTION

[0009] Features and embodiments of the present invention are described below by way of the following non-limiting examples.

[0010] The disclosed technology includes melt-spun fibers comprising a thermoplastic polyurethane ("TPU") composition and an isocyanate-functional crosslinker. The TPU composition useful for making the melt-spun fibers of the present invention is the reaction product of a polyol component, a hydroxyl-terminated chain extender component, and a diisocyanate component. The isocyanate-functional crosslinker is the reaction product of a polyol and an excess of isocyanate. Each of these components is described in more detail below.

[0011] As used herein, weight average molecular weight (Mw) is determined by gel permeation chromatography using polystyrene standards, and number average molecular weight (Mn) is determined by end group analysis.

[0012] Thermoplastic polyurethane composition The TPU compositions useful for making the melt-spun fibers of the present invention include a polyol component, which may also be described as a hydroxyl-terminated intermediate. In the present invention, the polyol component comprises or consists of a copolymer diol derived from caprolactone monomers and a hydroxyl-functional polyether intermediate.

[0013] Caprolactone monomers useful for making the copolymer polyols used in the present invention include ε-caprolactone and 2-oxepanone. In one embodiment, caprolactone monomer is reacted with a polyether diol to form the copolymer diol. In another embodiment, ε-caprolactone can be reacted with another difunctional initiator (e.g., diethylene glycol, 1,4-butanediol, neopentyl glycol, or any other glycol and / or diol known to those skilled in the art).

[0014] In one embodiment in which ε-caprolactone is reacted with a polyether polyol intermediate, suitable hydroxyl-functional polyether intermediates include polyether polyols derived from diols or polyols having a total of 2 to 15 carbon atoms, and in some embodiments, alkyl diols or glycols reacted with ethers containing alkylene oxides having 2 to 6 carbon atoms, typically ethylene oxide or propylene oxide, or mixtures thereof. For example, hydroxyl-functional polyethers can be produced by first reacting propylene glycol with propylene oxide, followed by reaction with ethylene oxide. Primary hydroxyl groups resulting from ethylene oxide are more reactive than secondary hydroxyl groups and therefore may be preferred. Useful commercially available polyether polyols include poly(ethylene glycol), which contains ethylene oxide reacted with ethylene glycol; poly(propylene glycol), which contains propylene oxide reacted with propylene glycol; and poly(tetramethylene ether glycol), which contains water reacted with tetrahydrofuran (also described as polymerized tetrahydrofuran and commonly referred to as PTMEG). In some embodiments, the hydroxyl-functional polyether intermediate used in the present invention comprises or consists of PTMEG.

[0015] In one embodiment, the polyol component comprises or consists of a copolymer diol that is the reaction product of caprolactone monomers and poly(tetramethylene ether glycol). In another embodiment, the polyol component comprises or consists of the reaction product of about 50% by weight of ε-caprolactone monomers and about 50% by weight of poly(tetramethylene ether glycol).

[0016] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises from about 50% to about 80% by weight, such as from about 60% to about 75% by weight, or even from about 65% to about 70% by weight, of a polyol component.

[0017] Chain extender component The TPU compositions described herein are made using a chain extender component. Suitable chain extenders include diols, diamines, and combinations thereof.

[0018] Suitable chain extenders include relatively small polyhydroxy compounds, such as lower aliphatic or short chain glycols having 2 to 20, or 2 to 12, or 2 to 10 carbon atoms. Suitable examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol (BDO), 1,6-hexanediol (HDO), 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol (CHDM), 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane (HEPP), 1,4-bis(β-hydroxyethoxy)benzene (HQEE), hexamethylenediol, heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butanediamine, hexamethylenediamine, and hydroxyethyl resorcinol (HER), and mixtures thereof. In one embodiment, the chain extender comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene (HQEE).

[0019] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises from about 5% to about 25% by weight, such as from about 5% to about 15% by weight, or even from about 8% to 10% of the chain extender component.

[0020] Isocyanate component The TPU of the present invention is made using an isocyanate component. The isocyanate component may include one or more polyisocyanates, or more specifically, one or more diisocyanates. Suitable polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, or combinations thereof. In some embodiments, the polyisocyanate component includes one or more aromatic diisocyanates. In some embodiments, the polyisocyanate component is essentially free of, or completely free of, aliphatic diisocyanates. In other embodiments, the polyisocyanate component includes one or more aliphatic diisocyanates. In some embodiments, the polyisocyanate component is essentially free of, or completely free of, aromatic diisocyanates. In some embodiments, a mixture of aliphatic and aromatic diisocyanates may be useful.

[0021] Examples of useful polyisocyanates include aromatic diisocyanates such as 4,4'-methylenebis(phenylisocyanate) (MDI), 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), m-xylene diisocyanate (XDI), phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, and toluene diisocyanate (TDI), as well as 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (C1H2O3), and 1,6-hexamethylene diisocyanate (HDI). Examples of suitable diisocyanates include aliphatic diisocyanates such as decane-1,10-diisocyanate, lysine diisocyanate (LDI), 1,4-butane diisocyanate (BDI), isophorone diisocyanate (PDI), and dicyclohexylmethane-4,4'-diisocyanate (HI2MDI). Isomers of these diisocyanates may also be useful. Mixtures of two or more polyisocyanates may also be used. In some embodiments, the isocyanate component comprises or consists of an aromatic diisocyanate. In some embodiments, the isocyanate component comprises or consists of MDI.

[0022] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises from about 15% to about 30% by weight, such as from about 15% to about 25% by weight, or even from about 18% to about 20% by weight, of the isocyanate component.

[0023] Optionally, one or more polymerization catalysts may be present during the polymerization reaction of the TPU. Generally, any conventional catalyst can be used to react the diisocyanate with the polyol intermediate or the chain extender. In particular, examples of suitable catalysts that promote the reaction between the NCO group of the diisocyanate and the hydroxyl group of the polyol and the chain extender are conventional tertiary amines known from the prior art (e.g., triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, etc.), and also, in particular, organometallic compounds (e.g., titanium esters, iron compounds (e.g., iron acetylacetonate), tin compounds (e.g., tin diacetate, tin octanoate, tin dilaurate), bismuth compounds (e.g., bismuth trineodecanoate), or dialkyltin salts of aliphatic carboxylic acids (e.g., dibutyltin diacetate, dibutyltin dilaurate), etc.). A typical amount of catalyst used is 0.001 to 0.1 parts by weight per 100 parts by weight of the polyol component. In some embodiments, the reaction to form the TPU of the present invention is substantially free or completely free of catalyst.

[0024] The TPU compositions used in the present invention can be made via a "one-shot" process, in which all components are added simultaneously or substantially simultaneously to a heated extruder and reacted to form the TPU. The equivalent ratio of diisocyanate to the total equivalents of hydroxyl-terminated intermediate and chain extender is generally from about 0.95 to about 1.10, e.g., from about 0.97 to about 1.03, or even from about 0.98 to about 1.0. In one embodiment, the equivalent ratio may be less than 1.0 so that the TPU has terminal hydroxyl groups to enhance reaction with crosslinkers during the fiber spinning process. The weight average molecular weight (MW) of the TPU is generally from about 25,000 to about 300,000, e.g., from about 50,000 to about 200,000, or further e.g., from about 75,000 to about 150,000.

[0025] In another embodiment, TPUs can be prepared using a prepolymer process. In the prepolymer process, a hydroxyl-terminated intermediate is generally reacted with an equivalent excess of one or more diisocyanates to form a prepolymer solution having free or unreacted isocyanates therein. Subsequently, a chain extender, as described herein, is added, generally in an equivalent amount equal to the isocyanate end groups and any free or unreacted diisocyanate compounds. Thus, the total equivalent ratio of total diisocyanates to the total equivalents of hydroxyl-terminated intermediates and chain extenders is about 0.95 to about 1.10, e.g., about 0.97 to about 1.03, or even about 0.98 to about 1.0. In one embodiment, the equivalent ratio can be less than 1.0 so that the TPU has terminal hydroxyl groups to enhance reaction with a crosslinker during the fiber spinning process. Typically, the prepolymer process can be carried out in any conventional device, such as an extruder.

[0026] Optional additive components may be present during the polymerization reaction and / or incorporated into the TPU elastomers described above to improve processing and other properties. These additives include antioxidants, organic phosphites, phosphines and phosphonites, hindered amines, organic amines, organic sulfur compounds, lactone and hydroxylamine compounds, biocides, fungicides, antimicrobial agents, compatibilizers, electrically dissipative or antistatic additives, fillers and reinforcing agents (e.g., titanium dioxide, alumina, clay, and carbon black), flame retardants (e.g., phosphates, halogenated materials, and metal salts of alkylbenzene sulfonates), impact modifiers (e.g., methacrylate-butadiene-styrene (MBS) and methyl methacrylate butyl acrylate (MMBS)). butyl acrylate, MBA)), mold release agents (e.g., waxes, fats and oils, pigments and colorants, plasticizers, polymers), rheology modifiers (e.g., monoamines, polyamide waxes, silicones, and polysiloxanes), slip additives (e.g., paraffin waxes, hydrocarbon polyolefins, and / or fluorinated polyolefins), and UV stabilizers (which may be of the hindered amine light stabilizer (HALS) and / or UV light absorber (UVA) type). Other additives may be used to improve the performance of the TPU composition or blend product. All of the above additives may be used in effective amounts customary for these materials.

[0027] These additional additives can be incorporated into the ingredients for preparing the TPU resin, into the reaction mixture for preparing the TPU resin, or after the TPU resin has been made. In an alternative process, all materials can be mixed with the TPU resin and then melted, or they can be incorporated directly into the melt of the TPU resin.

[0028] Isocyanate-functional crosslinkers The TPU composition is combined with an isocyanate-functional crosslinker. The crosslinker is a reaction product of a hydroxyl-terminated polyol selected from polyethers, polyesters, polycaprolactones, polycarbonates, and mixtures thereof with an excess of a diisocyanate. In one embodiment, the hydroxyl-terminated polyol used in the crosslinker is a polyether polyol. For example, the hydroxyl-terminated polyether can comprise or consist of poly(tetramethylene ether glycol). In another embodiment, the hydroxyl-terminated polyol used in the crosslinker is a polyester. For example, the hydroxyl-terminated polyester can comprise or consist of neopentyl glycol adipate. In one embodiment, the polyisocyanate component is an aromatic diisocyanate, such as MDI. In another embodiment, the polyisocyanate component is an aliphatic diisocyanate, such as H12MDI. The crosslinker has an isocyanate functionality greater than 1.0, such as from about 1.5 to 2.5, and further such as from about 1.8 to 2.2. Isocyanate-functional crosslinkers can be prepared using the prepolymer process described herein, in which a hydroxyl-terminated intermediate is reacted with an equivalent excess of one or more diisocyanates to form a prepolymer solution having free or unreacted isocyanate.

[0029] The weight percent of the crosslinker used with the TPU polymer is about 5.0% to about 20% by weight, for example, about 8.0% to about 15% by weight, where the percentage of crosslinker used is based on the total weight of the TPU and crosslinker.

[0030] Thermoplastic polyurethane fiber Melt-spun TPU fibers are made by melting a TPU composition in an extruder and adding a crosslinking agent to the molten TPU. The TPU melt with crosslinking agent is fed into a spinneret. The melt exits the spinneret to form a fiber, which is cooled and wound onto a bobbin. The method includes the following steps: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of (a) a polyol component comprising, or consisting of, a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol), (b) a chain extender component comprising, or consisting of, 1,4-bis(β-hydroxyethoxy)benzene, and (c) a diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer into the extruder; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer to at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; and (8) winding the melt-spun fibers onto a bobbin core. The steps of this process are described in more detail below.

[0031] The melt spinning process begins by feeding preformed TPU polymer into an extruder. The TPU is melted in the extruder, and the crosslinking agent is added either downstream near the point where the TPU melt exits the extruder, or continuously after the TPU melt has left the extruder. If the crosslinking agent is added after the melt has left the extruder, it must be mixed with the TPU melt using a static or dynamic mixer to ensure proper mixing of the crosslinking agent into the TPU polymer melt. After exiting the extruder and mixer, the molten TPU polymer containing the crosslinking agent flows into a manifold. The manifold splits the melt stream into different streams, each of which feeds multiple spinnerets. Typically, there is a melt pump for each different stream flowing from the manifold, and each melt pump feeds several spinnerets. The spinneret has small holes through which the melt is extruded and exits the spinneret in the form of fibers. The size of the spinneret holes depends on the desired fiber size (denier). The fibers are stretched or drawn as they exit the spinneret and cooled before being wound onto the bobbin. The fibers are drawn by winding the bobbin at a speed faster than the fiber exiting the spinneret. For melt-spun TPU fibers, the bobbin is typically wound at a speed greater than the fiber exiting the spinneret, for example, in some embodiments, 4 to 8 times the fiber exiting the spinneret, although slower or faster winding may be used depending on the specific equipment. Typical bobbin winding speeds can vary from 100 to 3,000 meters per minute, with 300 to 1,200 meters per minute being more typical for TPU melt-spun fibers. A finishing oil, such as silicone oil, is typically added to the surface of the fiber after cooling and immediately before winding onto the bobbin.

[0032] An important aspect of the melt spinning process is the mixing of the TPU polymer melt with the crosslinking agent. Proper, uniform mixing is important for achieving uniform fiber properties and long run times without fiber breakage. The mixing of the TPU melt with the crosslinking agent should be in a plug flow, i.e., first-in, first-out, manner. Proper mixing can be achieved using a dynamic mixer or a static mixer. For example, a dynamic mixer with a feed screw and mixing pins can be used. U.S. Patent No. 6,709,147 describes such a mixer, which has rotatable mixing pins.

[0033] The TPU reacts with the crosslinker during the fiber spinning process to provide a weight average molecular weight (MW) of the TPU in fiber form of about 200,000 to about 800,000, preferably about 250,000 to about 500,000, and more preferably about 300,000 to about 450,000. The reaction rate between the TPU and the crosslinker during the fiber spinning process at the point where the TPU exits the spinneret should be greater than 20%, preferably about 30% to about 60%, and more preferably about 40% to about 50%. Typical prior art TPU melt-spinning reactions between the TPU polymer and the crosslinker are less than 20%, usually about 10-15%. The reaction rate is determined by the disappearance of NCO groups. The higher reaction rate of the present invention improves melt strength and therefore allows for higher spinning temperatures, which improves the spinnability of the TPU. The fiber is typically aged on the bobbin in an oven until the molecular weight levels off.

[0034] The spinning temperature (temperature of the polymer melt in the spinneret) must be higher than the melting point of the polymer, preferably about 10°C to about 20°C higher than the melting point of the polymer. The higher the spinning temperature that can be used, the better the spinning. However, if the spinning temperature is too high, the polymer may decompose. Therefore, a temperature about 10°C to about 20°C higher than the melting point of the TPU polymer is optimal to achieve a balance of good spinning without polymer decomposition. If the spinning temperature is too low, the polymer may solidify in the spinneret, causing fiber breakage. The spinning temperature for fibers produced by the present invention is above 190°C, preferably about 190°C to about 220°C, or even about 190°C to about 200°C.

[0035] A key aspect of producing melt-spun TPU fibers is the amount of time the process can run continuously without stopping. The need to stop the process is usually the result of fiber breakage. Fiber breakage occurs when the pressure at the spinneret increases to an unacceptable level. Fiber breakage typically occurs when the pressure reaches approximately 140-200 kg of force per square centimeter. Pressure buildup can occur for several reasons, including improper mixing. This leads to the formation of products due to crosslinker self-reaction, which can cause partial blockage of the small exit holes in the spinneret for the fiber. This invention allows for much longer run times before a detrimental pressure buildup occurs, resulting in fiber breakage.

[0036] Melt-spun TPU fibers can be made in a variety of deniers. The term "denier" is defined as the mass in grams of 9000 meters of fiber, filament, or yarn. It describes the linear density, which is the mass per unit length of the fiber, filament, or yarn, and is measured according to ASTM D1577, Option B. Typical melt-spun TPU fibers are made in denier sizes below 240, more typically 10 to 240, with 20 and 40 denier being common sizes.

[0037] Prior art melt-spun TPU fibers are not typically used in combination with polyester fibers due to the high temperatures required to dye polyester. Disperse dyes are typically used for dyeing due to the lack of polarity and extremely high crystallinity of polyester polymers and fibers. Such fibers are typically dyed at 120°C to 135°C, e.g., about 130°C, for 60 minutes at 1 to 1.5 kg / cm. 2 The fabric is dyed at a pressure of 1000 kJ / min. This pressure dyeing "opens" the polyester polymer, allowing the dye molecules to penetrate. Once dyeing is complete and the fabric is removed from the pressurized dyeing vessel (called a dyeing machine), the polyester polymer system "closes" again, "trapping" the disperse dye molecules inside. None of the prior art melt-spun TPU fibers can withstand this type of temperature for 60 minutes without losing physical properties such as tenacity and strain rate as measured according to ASTM D2731. In addition, prior art melt-spun TPU fibers also tend to fuse to adjacent fibers when exposed to the aforementioned high temperatures and pressures, which is detrimental to the fabric's elongation properties.

[0038] The high heat resistance of the melt-spun TPU fibers of the present invention allows them to withstand the dyeing operations of polyester fibers while retaining sufficient physical properties to maintain elasticity.

[0039] Another property of the high heat resistant melt-spun TPU fibers of the present invention is their ability to absorb disperse dyes. The process for disperse dyeing involves exposure to a temperature of about 130°C for about 60 minutes (dyeing conditions for polyester fibers). Many TPU fibers fail to exhibit dye pickup, color fastness (after washing), and bleach resistance after exposure to these temperatures.

[0040] Melt-spun fibers made according to the present invention have unique physical properties not exhibited by prior art TPU fibers. First, the fibers exhibit unique elastic properties. For example, fibers made according to the present invention exhibit hysteresis after the fifth load-unload cycle of less than 20% at 100% elongation, less than 18% at 150% elongation, and less than 18% at 200% elongation. The term "hysteresis" is defined as the residual physical effect after an external stimulus is removed, and in fibers, it is observed as a change in dimension after stretching and recovery. It is expressed as a percentage hysteresis at the corresponding elongation (or strain). Hysteresis is measured according to ASTM D2731. Calculation of hysteresis can be performed using the following information and formula: Elastic modulus at 100% elongation during the load cycle = m1 Elastic modulus at 100% elongation during unloading cycle = m2 % Hysteresis at 100% elongation = (m1 - m2) / m1 x 100. Hysteresis can be calculated similarly at 150% and 200% elongation.

[0041] The melt-spun TPU fibers produced according to the present invention also have an ultimate elongation of at least 300%, e.g., 300% to 650%, as measured by ASTM D2731. Typically, elastic materials are characterized by extensibility and elasticity; when an external force is released, these materials almost completely return to their original dimensions. For an ideal elastic material, there is only one curve on a stress-strain plot that tracks the loading and unloading cycles. However, due to the loss of energy (in the form of heat) in most materials, most materials exhibit different curves for loading and unloading, also known as "hysteresis." A lower % hysteresis value indicates excellent elasticity. The use of elastic fibers with very low % hysteresis can be used to achieve fabrics with less deformation in clothing.

[0042] Additionally, the melt spun TPU fibers made according to the present invention may also have an onset of melting of 140°C to 170°C, such as 150°C to 170°C, further such as about 155°C to 166°C, as measured according to ASTM D3418, and an elastic modulus of 3.5E+05 to 12E+05 Pa at 130°C, as measured by DMA (Dynamic Mechanical Analysis). DMA measurements are performed using a parallel plate configuration from -100°C to 250°C at a heating rate of 2°C / min at a strain of 0.1% using a frequency of 1 Hz.

[0043] Fabric The TPU fibers of the present invention can be used alone or can be combined with other fibers, natural or synthetic, by knitting or weaving the fibers to make fabrics that can be used in a variety of articles, and it may be desirable to dye such fabrics in a variety of colors.

[0044] In one embodiment, the melt-spun TPU fibers of the present invention can be woven to make a fabric. In another embodiment, the melt-spun TPU fibers of the present invention can be combined with one or more different TPU fibers to make a fabric. In yet another embodiment, the melt-spun TPU fibers of the present invention can be combined with other fibers, such as cotton, nylon, or polyester, to make a variety of end-use articles, including apparel.

[0045] For example, a fabric according to the present invention can combine the melt-spun TPU fibers of the present invention with yarns that are less elastic than the TPU fibers of the present invention, also referred to herein as "hard yarns." Hard yarns can include, for example, polyester, nylon, cotton, wool, acrylic, polypropylene, or viscose rayon. Hard yarns can also include, for example, other TPU fibers (not of the present invention) that are less elastic than the TPU fibers of the present invention. In one embodiment, the hard yarns have an ultimate elongation of 10% to 200%, e.g., 10% to 75%, or even 10% to 60%, or even 10% to 50%, or even 10% to 30%, while the melt-spun TPU fibers of the present invention have an ultimate elongation of at least 300%, e.g., 300% to 650%. Each of the fiber components can be present in the composition in an amount of 1 to 99% by weight. The weight percent of the melt-spun TPU fibers in the end use application can vary depending on the desired elasticity. For example, woven fabrics have 1-8% by weight of melt-spun TPU fibers, underwear has 2-5% by weight, swimwear and sportswear has 8-30% by weight, foundation has 10-45% by weight, medical hose has 35-60% by weight, and the remaining amount is rigid inelastic fibers. Fabrics made from these two fibrous materials can be constructed by a variety of processes, including, but not limited to, circular knitting, warp knitting, weaving, braiding, nonwovens, or combinations thereof. In one embodiment, fabrics made from the fibers of the present invention have a stretch of greater than 100% as measured according to ASTM D4964. The fibers may be dyed at elevated temperatures of at least 130°C.

[0046] In this application and in the examples below, the following properties are referred to along with methods for measuring such properties. Denier is a measure of linear density and was measured in accordance with ASTM D1577, Option B. · Tenacity of the elastic filaments, which is the tensile strength normalized by denier, was also measured and reported according to ASTM D2731. · The ultimate elongation of the elastic filaments, which is the elongation at break, was also measured and reported according to ASTM D2731. Hysteresis, defined and calculated as previously described herein and reported at each elongation in accordance with ASTM D2731 for elastic filaments. For hard yarns such as polyester, which are inelastic, tenacity and elongation were measured and the ASTM D2256 standard was used. The content of individual components in fabrics was determined according to ASTM D629 Fabric elongation and fabric modulus were measured according to ASTM D4964. Fabric washes were performed using American Association of Textile Chemists and Colorists (AATCC) Test Method 135.

[0047] The present invention will be better understood with reference to the following examples. [Example]

[0048] Table 1 lists the prepared TPU compositions used to make fibers in the present invention. The TPU hard segment is the total amount of isocyanate and chain extender in the TPU composition.

[0049] [Table 1]

[0050] The TPU polymers of Examples A to G were dried in a vacuum batch dryer for 80 o The TPU polymer was pre-dried at 25°C for 12 hours. After drying, the TPU polymer was melted in a 1.25-inch single-screw extruder with an L / D ratio of 24. The extruder had four heating zones that were maintained at 180°C to 225°C throughout the process. Upon exiting the extruder, the TPU polymer melt was mixed with 10% by weight of a prepolymer crosslinker (90% by weight TPU polymer melt / 10% by weight crosslinker). The TPU and crosslinker combinations are summarized in Table 2.

[0051] [Table 2]

[0052] The crosslinker was mixed with the TPU polymer melt in a dynamic mixer and then pumped through a manifold into the spinnerets. Each spinneret had a 0.65 mm orifice size. The polymer stream exiting the spinnerets was cooled with air, a silicone finish oil was applied, and the formed fibers were wound onto bobbins. The fibers on the bobbins were heat-aged at 80°C for 24 hours before testing the physical properties of the fibers. Table 3 summarizes the key properties of the fibers.

[0053] [Table 3]

[0054] The fiber of Example 1 was used to make a single jersey knit fabric on a Vanguard circular knitting machine. A 70D (68 filament) multifilament textured polyester yarn (as the hard yarn) was combined with the examples in Table 3. The knitting tension on the machine was adjusted to knit a balanced ratio throughout the fabric to contain 25% elastomeric yarn and 75% polyester yarn from Table 3 (this was confirmed by mechanical separation by weight of the elastomeric and hard yarns in the fabric snips, per ASTM D629-15). Fiber Example 1 from Table 2 was successfully converted into fabric. Fiber Examples 2-7 were too sticky and consistently broke during the knitting process and could not be converted into fabric.

[0055] The fibers of Example 1 were used to dye knit fabric as follows. Scouring, dyeing, and reduced clear solutions: 1000 ml of scouring solution contained 2 grams Na2CO3, 6 grams NaOH, and the remainder was deionized water. 1000 ml of dye solution contained 2 grams Foron Navy S-2GRL 200 from Archroma US, 6 grams Na2CO3, and the remainder was deionized water. The pH of the dye bath was adjusted to 4.5 using acetic acid. 1000 ml of reduced clear solution contained 6 grams NaOH, and the remainder was deionized water.

[0056] A 10 meter long piece of fabric weighing 1 kg was placed in a Thies miniMaster® dyeing machine, which was programmed for scouring, dyeing, and reduction clearing temperature cycles.

[0057] Scouring was carried out using 1 liter of the above prepared scouring solution at 65°C for 30 minutes, followed by rinsing with warm tap water. The dyeing process was then started at 50°C with the dye vessel filled with 1 liter of dye solution. The bath temperature was then slowly increased to 130°C at a rate of 2°C / min and held at that temperature for 60 minutes. The temperature was then reduced to 80°C, and the dye solution was then drained from the dye vessel, followed by rinsing with two cycles of tap water.

[0058] After rinsing, 1 liter of the reducing clear solution prepared above was introduced into the dyeing vessel at 75-80°C for 30 minutes. The fabric samples were then rinsed with warm tap water until no further dye bleeding occurred. Finally, the fabrics were immersed in a 1% acetic acid neutralizing solution for 30 seconds.

[0059] The wet fabric samples were allowed to air dry overnight. Once dry, the fabric was heat set in a tenter frame, pre-stretching the fabric to 20% more than its original width. The fabric was passed through the tenter frame twice.

[0060] The fabric samples were then washed using American Association of Textile Chemists and Colorists (AATCC) Test Method 135-2018. Following washing, the fabric samples were evaluated for stretch properties after washing according to Table 4 below.

[0061] [Table 4] * Testing was performed in accordance with ASTM D4964 at a constant load of 10 lb-f in both the warp (fabric length) and weft (fabric width) directions.

[0062] Fabrics made using the fibers of the present invention can also be recycled. In one embodiment, fabrics made according to the present invention are recycled to make extruded or molded articles. Thus, the present invention provides a method of making an article, comprising providing a disperse-dyed fabric prepared according to the present invention, chopping the fabric, heat treating the chopped fabric to form granules, and then melting and shearing the granules in an extruder to form the article.

[0063] Each of the documents mentioned above is incorporated herein by reference, including any prior application to which priority is claimed, whether or not specifically listed above. The citation of any document is not an admission that such document qualifies as prior art or constitutes general knowledge of one of ordinary skill in the art in any jurisdiction. Except in the examples, or unless otherwise expressly indicated, all numerical values ​​in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, should be understood to be modified by the word "about." It should be understood that the upper and lower limits of amounts, ranges, and ratios set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.

[0064] As used herein, the transitional term "comprising," which is synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. However, in each occurrence of "comprising" herein, the term is also intended to encompass, as alternative embodiments, the phrases "consisting essentially of" and "consisting of," where "consisting" excludes any unspecified element or step, and "consisting essentially of" permits the inclusion of additional, unrecited elements or steps that do not materially affect the basic and novel characteristics of the composition or method under consideration.

[0065] While certain representative embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention, which in this regard should be limited only by the claims that follow. The present invention provides, for example, the following items. (Item 1) A melt-spun fiber comprising: (a) a thermoplastic polyurethane composition, i. a polyol component comprising a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol); ii. a hydroxyl-terminated chain extender component; and a thermoplastic polyurethane composition comprising the reaction product of a first diisocyanate component with a (b) an isocyanate-functional prepolymer crosslinker. (Item 2) 2. The melt-spun fiber of claim 1, wherein the copolymer diol comprises the reaction product of 50% by weight of a caprolactone monomer polyol and 50% by weight of poly(tetramethylene ether glycol). (Item 3) 3. The melt-spun fiber of claim 1 or 2, wherein the copolymer has a number average of about 2000 Daltons as determined by end group analysis. (Item 4) 4. The melt-spun fiber of any one of items 1 to 3, wherein the chain extender component comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene. (Item 5) 5. The melt-spun fiber of claim 4, wherein the chain extender component further comprises a co-chain extender. (Item 6) 6. The melt spun fiber of item 5, wherein the co-chain extender is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, hexamethylenediol, heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butanediamine, hexamethylenediamine, hydroxyethyl resorcinol, and mixtures thereof. (Item 7) 7. The melt-spun fiber of any one of items 1 to 6, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate. (Item 8) 8. The melt-spun fiber of claim 7, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate. (Item 9) 9. The melt-spun fiber according to any one of items 1 to 8, wherein the thermoplastic polyurethane composition contains 50% by weight to 80% by weight, 60% by weight to 80% by weight, or 70% by weight to 80% by weight of the polyol component. (Item 10) 10. The melt-spun fiber according to any one of items 1 to 9, wherein the thermoplastic polyurethane composition contains 5% to 25% by weight, or 5% to 15% by weight, or 5% to 10% of the chain extender component. (Item 11) 11. The melt-spun fiber according to any one of items 1 to 10, wherein the thermoplastic polyurethane composition contains 15% to 30% by weight, or 15% to 25% by weight, or 15% to 20% by weight of the first diisocyanate. (Item 12) 12. The melt-spun fiber of any one of the preceding claims, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component. (Item 13) 12. The melt-spun fiber of any one of the preceding claims, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of neopentyl glycol adipate and a second diisocyanate component. (Item 14) 14. The melt-spun fiber of claim 12 or 13, wherein the second diisocyanate component comprises an aromatic diisocyanate. (Item 15) 15. The melt-spun fiber of item 14, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate). (Item 16) 14. The melt-spun fiber of claim 12 or 13, wherein the second diisocyanate component comprises an aliphatic diisocyanate. (Item 17) 17. The melt-spun fiber of item 16, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate. (Item 18) 1. A melt-spun thermoplastic polyurethane fiber comprising: (a) a thermoplastic polyurethane composition, i. a polyol component comprising a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol); ii. a hydroxyl-terminated chain extender component comprising or consisting of 1,4-bis(β-hydroxyethoxy)benzene; and a thermoplastic polyurethane composition comprising the reaction product of a first diisocyanate component with a (b) an isocyanate-functional prepolymer, including the reaction product with a crosslinker; A melt-spun thermoplastic polyurethane fiber, wherein the thermoplastic polyurethane fiber has a weight average molecular weight of 300,000 to 450,000 as measured by gas permeation chromatography. (Item 19) 19. The melt-spun thermoplastic polyurethane fiber of item 18, wherein the copolymer diol comprises the reaction product of 50% by weight of a caprolactone monomer polyol and 50% by weight of poly(tetramethylene ether glycol). (Item 20) 20. The melt-spun thermoplastic polyurethane fiber according to item 18 or 19, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate. (Item 21) 21. The melt-spun thermoplastic polyurethane fiber according to item 20, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate. (Item 22) 22. The melt-spun thermoplastic polyurethane fiber according to any one of items 18 to 21, wherein the thermoplastic polyurethane composition contains 50% by weight to 80% by weight, 60% by weight to 80% by weight, or 70% by weight to 80% by weight of the polyol component. (Item 23) 23. The melt-spun thermoplastic polyurethane fiber according to any one of items 18 to 22, wherein the thermoplastic polyurethane composition contains 5% to 25% by weight, or 5% to 15% by weight, or 5% to 10% of the chain extender component. (Item 24) 24. The melt-spun thermoplastic polyurethane fiber according to any one of items 18 to 23, wherein the thermoplastic polyurethane composition contains 15% to 30% by weight, or 15% to 25% by weight, or 15% to 20% by weight of the first diisocyanate. (Item 25) 25. The melt-spun thermoplastic polyurethane fiber of any one of items 18 to 24, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component. (Item 26) 25. The melt-spun thermoplastic polyurethane fiber of any one of items 18 to 24, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of neopentyl glycol adipate and a second diisocyanate component. (Item 27) 27. The melt-spun thermoplastic polyurethane fiber according to item 25 or 26, wherein the second diisocyanate component comprises an aromatic diisocyanate. (Item 28) 28. The melt-spun thermoplastic polyurethane fiber according to item 27, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate). (Item 29) 27. The melt-spun thermoplastic polyurethane fiber according to item 25 or 26, wherein the second diisocyanate component comprises an aliphatic diisocyanate. (Item 30) 30. The melt-spun thermoplastic polyurethane fiber according to item 29, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate. (Item 31) 1. A process for preparing thermoplastic polyurethane fibers, comprising: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of (a) a polyol component comprising a copolymer diol derived from caprolactone monomer and poly(tetramethylene ether glycol), (b) a chain extender component comprising 1,4-bis(β-hydroxyethoxy)benzene, and (c) a first diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer into the extruder; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer into at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; (8) winding the melt-spun fibers onto a bobbin. (Item 32) 32. The process of claim 31, wherein the copolymer diol comprises the reaction product of 50% by weight of a caprolactone monomer polyol and 50% by weight of poly(tetramethylene ether glycol). (Item 33) 33. The process according to item 31 or 32, wherein the thermoplastic polyurethane fibers have a weight average molecular weight of 300,000 to 450,000 as measured by gas permeation chromatography. (Item 34) 34. The process of any one of items 31 to 33, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate. (Item 35) 35. The process of claim 34, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate. (Item 36) 36. The process according to any one of items 31 to 35, wherein the reactive thermoplastic polyurethane composition contains 50% to 80% by weight, or 60% to 80% by weight, or 70% to 80% by weight of the polyol component. (Item 37) 37. The process of any one of items 31 to 36, wherein the reactive thermoplastic polyurethane composition contains 5% to 25% by weight, or 5% to 15% by weight, or 5% to 10% of the chain extender component. (Item 38) 38. The process of any one of items 31 to 37, wherein the reactive thermoplastic polyurethane composition contains 15% to 30% by weight, or 15% to 25% by weight, or 15% to 20% by weight of the first diisocyanate. (Item 39) 39. The process of any one of items 31 to 38, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component. (Item 40) 39. The process of any one of items 31 to 38, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of the reaction product of neopentyl glycol adipate and a second diisocyanate component. (Item 41) 41. The process of claim 39 or 40, wherein the second diisocyanate component comprises an aromatic diisocyanate. (Item 42) Item 42. The process of item 41, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate). (Item 43) 41. The process of claim 39 or 40, wherein the second diisocyanate component comprises an aliphatic diisocyanate. (Item 44) Item 44. The process of item 43, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate.

Claims

1. A melt-spun fiber comprising: (a) a thermoplastic polyurethane composition, i. a polyol component comprising a copolymer diol derived from caprolactone monomers and poly(tetramethylene ether glycol), the copolymer diol comprising the reaction product of 50% by weight of caprolactone monomers and 50% by weight of poly(tetramethylene ether glycol); ii. a hydroxyl-terminated chain extender component; and a thermoplastic polyurethane composition comprising the reaction product of a first diisocyanate component with a (b) an isocyanate-functional prepolymer crosslinker, the isocyanate-functional prepolymer crosslinker comprising, or consisting of, a reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component or a reaction product of neopentyl glycol adipate and a second diisocyanate component.

2. 10. The melt-spun fiber of claim 1, wherein the copolymer has a number average molecular weight of 2000 Daltons as determined by end group analysis.

3. The melt-spun fiber of claim 1 or 2, wherein the chain extender component comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene.

4. The melt-spun fiber of claim 3 , wherein the chain extender component further comprises a co-chain extender.

5. 5. The melt-spun fiber of claim 4, wherein the co-chain extender is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, hexamethylenediol, heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butanediamine, hexamethylenediamine, hydroxyethylresorcinol, and mixtures thereof.

6. The melt-spun fiber of any one of claims 1 to 5, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate.

7. 7. The melt-spun fiber of claim 6, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate.

8. 8. The melt-spun fiber of any one of claims 1 to 7, wherein the thermoplastic polyurethane composition contains from 50% to 80%, or from 60% to 80%, or from 70% to 80% by weight of the polyol component.

9. 9. The melt-spun fiber of any one of claims 1 to 8, wherein the thermoplastic polyurethane composition contains from 5% to 25% by weight, or from 5% to 15% by weight, or from 5% to 10% of the chain extender component.

10. 10. The melt-spun fiber of any one of claims 1 to 9, wherein the thermoplastic polyurethane composition contains 15% to 30%, or 15% to 25%, or 15% to 20% by weight of the first diisocyanate.

11. The melt-spun fiber of any one of claims 1 to 10, wherein the second diisocyanate component comprises an aromatic diisocyanate.

12. 12. The melt-spun fiber of claim 11, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate).

13. 11. The melt-spun fiber of claim 1 or 10, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

14. 14. The melt-spun fiber of claim 13, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate.

15. 1. A melt-spun thermoplastic polyurethane fiber comprising: (a) a thermoplastic polyurethane composition, i. a polyol component comprising a copolymer diol derived from caprolactone monomers and poly(tetramethylene ether glycol), the copolymer diol comprising the reaction product of 50% by weight of caprolactone monomers and 50% by weight of poly(tetramethylene ether glycol); ii. a hydroxyl-terminated chain extender component comprising or consisting of 1,4-bis(β-hydroxyethoxy)benzene; a thermoplastic polyurethane composition comprising the reaction product of a first diisocyanate component with a (b) an isocyanate-functional prepolymer crosslinker, the crosslinker comprising, or consisting of, the reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component or the reaction product of neopentyl glycol adipate and a second diisocyanate component; A melt-spun thermoplastic polyurethane fiber, wherein the thermoplastic polyurethane fiber has a weight average molecular weight of 300,000 to 450,000 as determined by gas permeation chromatography.

16. 16. The melt-spun thermoplastic polyurethane fiber of claim 15, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate.

17. 17. The melt-spun thermoplastic polyurethane fiber of claim 16, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate.

18. 18. The melt-spun thermoplastic polyurethane fiber of any one of claims 15 to 17, wherein the thermoplastic polyurethane composition contains 50% to 80%, or 60% to 80%, or 70% to 80% by weight of the polyol component.

19. 19. The melt-spun thermoplastic polyurethane fiber of any one of claims 15 to 18, wherein the thermoplastic polyurethane composition contains from 5% to 25% by weight, or from 5% to 15% by weight, or from 5% to 10% of the chain extender component.

20. 20. The melt-spun thermoplastic polyurethane fiber of any one of claims 15 to 19, wherein the thermoplastic polyurethane composition contains 15% to 30%, or 15% to 25%, or 15% to 20% by weight of the first diisocyanate.

21. The melt-spun thermoplastic polyurethane fiber of any one of claims 15 to 20, wherein the second diisocyanate component comprises an aromatic diisocyanate.

22. 22. The melt-spun thermoplastic polyurethane fiber of claim 21, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate).

23. The melt-spun thermoplastic polyurethane fiber of any one of claims 15 to 20, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

24. 24. The melt-spun thermoplastic polyurethane fiber of claim 23, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate.

25. 1. A process for preparing thermoplastic polyurethane fibers, comprising: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of: (a) a polyol component, the polyol component comprising a copolymer diol derived from caprolactone monomers and poly(tetramethylene ether glycol), the copolymer diol comprising the reaction product of 50% by weight of caprolactone monomers and 50% by weight of poly(tetramethylene ether glycol); (b) a chain extender component comprising 1,4-bis(β-hydroxyethoxy)benzene; and (c) a first diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer into the extruder, wherein the isocyanate prepolymer comprises or consists of the reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component or the reaction product of neopentyl glycol adipate and a second diisocyanate component; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer into at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; (8) winding the melt-spun fibers onto a bobbin.

26. 26. The process of claim 25, wherein the thermoplastic polyurethane fibers have a weight average molecular weight of 300,000 to 450,000 as determined by gas permeation chromatography.

27. 27. The process of claim 25 or 26, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate.

28. 28. The process of claim 27, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate.

29. 29. The process of any one of claims 25 to 28, wherein the reactive thermoplastic polyurethane composition contains 50% to 80%, or 60% to 80%, or 70% to 80% by weight of the polyol component.

30. 30. The process of any one of claims 25 to 29, wherein the reactive thermoplastic polyurethane composition contains from 5% to 25% by weight, or from 5% to 15% by weight, or from 5% to 10% of the chain extender component.

31. 30. The process of any one of claims 25 to 29, wherein the reactive thermoplastic polyurethane composition contains 15% to 30%, or 15% to 25%, or 15% to 20% by weight of the first diisocyanate.

32. The process of any one of claims 25 to 31, wherein the second diisocyanate component comprises an aromatic diisocyanate.

33. 33. The process of claim 32, wherein the second diisocyanate component comprises or consists of 4,4'-methylenebis(phenylisocyanate).

34. The process of any one of claims 25 to 31, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

35. 35. The process of claim 34, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4'-diisocyanate.

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