Melt-spun thermoplastic polyurethane fiber, fabric comprising the same, and process for preparing the same

Abstract

A melt-spun thermoplastic polyurethane fiber is provided. This melt-spun thermoplastic polyurethane fiber provides elastic properties and exhibits chemical resistance.

Description

Technical Field

[0001] none. Prior Technology

[0002] Thermoplastic polyurethane (“TPU”) fibers show great potential for providing tensile and adaptable properties in a variety of applications, but they also have some drawbacks. Many polyurethane fibers are produced by dry spinning processes, which involve dissolving reactive components in a solvent. These fibers generally have good heat resistance, but dry spinning processes are expensive, time-consuming, and involve the use of volatile solvents, causing environmental problems. Melt spinning of fibers offers manufacturing advantages, but not all TPUs can be formed into fibers under melt spinning conditions. Furthermore, prior art TPUs that can be melt-spun into fibers have not shown sufficient chemical resistance for certain applications, such as those used in electronics, automotive, and apparel applications. Therefore, there is a need for a melt-spun TPU fiber that possesses superior elastic properties while also exhibiting chemical resistance. Summary of the Invention

[0003] In one embodiment, the present invention relates to a melt-spun fiber, wherein the fiber comprises a reactive thermoplastic polyurethane composition and an isocyanate-functionalized prepolymer crosslinking agent. The reactive thermoplastic polyurethane composition used in the fiber comprises the following reaction products: (i) a polyol component comprising or composed of a first polycarbonate polyol; (ii) a hydroxyl-terminated chain extender component; and (iii) a first diisocyanate component. The isocyanate-functionalized prepolymer crosslinking agent comprises the reaction product of a second polycarbonate polyol or polycaprolactone polyol and a second diisocyanate component.

[0004] In another embodiment, the present invention includes a method for preparing thermoplastic polyurethane, comprising the following steps: (a) preparing a reactive thermoplastic polyurethane composition, which is a reaction product of: (a) a polyol component, wherein the polyol component comprises or is composed of a first polycarbonate polyol; (b) a chain extender component; and (c) a diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; and (4) adding an isocyanate functional prepolymer to the extruder. (5) The reactive thermoplastic polyurethane composition and the isocyanate functional prepolymer are mixed in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) The crosslinked thermoplastic polyurethane polymer is fed into at least one spinning nozzle to produce melt-spun fibers; (7) The melt-spun fibers are cooled; (8) An oiling agent is optionally applied; and (9) The melt-spun fibers are wound onto a bobbin.

[0005] In yet another embodiment, the present invention provides a fiber comprising a melt-spun thermoplastic polyurethane filament that retains at least 80% of its toughness as measured by ASTM D2653 after exposure to chemicals such as oleic acid as measured by ASTM D543-20. In another embodiment, the present invention provides a fabric comprising melt-spun thermoplastic polyurethane filaments that, upon exposure to oleic acid, retain at least 80% of their original tensile properties as measured according to ASTM D2653, and wherein the fiber modulus as measured according to ASTM D2731 is less than 0.9 gf at 50% elongation during the fifth load cycle, less than 2.1 gf at 100% elongation during the fifth load cycle, less than 4.3 gf at 200% elongation during the fifth load cycle, less than 2.8 gf at 200% elongation during the fifth unload cycle, less than 1.2 gf at 100% elongation during the fifth unload cycle, and less than 0.4 gf at 50% elongation during the fifth unload cycle, and an ultimate elongation of 300% as measured according to ASTM D2731.

[0006] The following examples cover this topic: 1. A melt-spun fiber comprising: (a) a reactive thermoplastic polyurethane composition comprising a reaction product of: (i) a polyol component comprising a first polycarbonate polyol; (ii) a hydroxyl-terminated chain extender component; and (iii) a first diisocyanate component; and (b) an isocyanate-functionalized prepolymer crosslinking agent comprising a reaction product of a second polycarbonate polyol and a second diisocyanate component, or (c) an isocyanate-functionalized prepolymer crosslinking agent comprising a reaction product of a polycaprolactone polyol and a second diisocyanate component. 2. The melt-spun fiber as in Example 1, wherein the polyol component comprises at least 60% of the first polycarbonate polyol. 3. The melt-spun fiber as in Example 1 or 2, wherein the first polycarbonate polyol contains a repeating unit -ROC(=O)-O-, wherein R contains 4 to 6 carbon atoms. 4. The melt-spun fiber of any of the foregoing embodiments, wherein the first polycarbonate polyol has a number-average molecular weight of about 1,000 to 3,000 Daltons, as measured by end-group analysis. 5. The melt-spun fiber of any of the foregoing embodiments, wherein the first polycarbonate polyol is selected from 2-MPD carbonate, BDO carbonate, DEG carbonate, HDO carbonate, or a mixture thereof. 6. The melt-spun fiber as described in any of the foregoing embodiments, wherein the polyol component is composed of the first polycarbonate polyol. 7. The melt-spun fiber of any of the foregoing embodiments, wherein the chain extender component comprises or is composed of 1,4-bis(β-hydroxyethoxy)benzene or 1,3-propylene glycol. 8. The melt-spun fiber of any of the foregoing embodiments, wherein the first diisocyanate component comprises or is composed of an aromatic diisocyanate. 9. The melt-spun fiber of Example 8, wherein the first diisocyanate comprises or is composed of 4,4'-diphenylmethane diisocyanate. 10. The melt-spun fiber of any one of Examples 1 to 7, wherein the first diisocyanate component comprises or is composed of an aliphatic diisocyanate. 11. The melt-spun fiber of Example 10, wherein the first diisocyanate component comprises or is composed of HDI. 12. The melt-spun fiber of any of the foregoing embodiments, wherein the second diisocyanate component comprises or is composed of an aromatic diisocyanate. 13. The melt-spun fiber of Example 12, wherein the second diisocyanate comprises or is composed of 4,4'-diphenylmethane diisocyanate. 14. The melt-spun fiber of any one of Examples 1 to 11, wherein the second diisocyanate component comprises or is composed of an aliphatic diisocyanate. 15. The melt-spun fiber of Example 14, wherein the second diisocyanate component comprises or is composed of HDI. 16. The melt-spun fiber of any of the foregoing embodiments, wherein the second polycarbonate polyol is selected from HDO-carbonate, BDO-carbonate, 3-MPD-carbonate, or mixtures thereof. 17. The melt-spun fibers of Examples 1 to 15, wherein the polycaprolactone polyol comprises ε-caprolactone that can react with a bifunctional initiator. 18. The melt-spun fiber of Example 17, wherein the bifunctional initiator is selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol) or mixtures thereof. 19. The melt-spun fiber of any of the foregoing embodiments, wherein the reactive thermoplastic polyurethane composition contains 70% to 85% by weight, or 75% to 85% by weight, or 80% to 85% by weight of the first polycarbonate polyol component. 20. The melt-spun fiber of any of the foregoing embodiments, wherein the combined weight of the hydroxyl-terminated chain extender component and the first diisocyanate component constitutes the hard segment of the thermoplastic polyurethane composition, and wherein the thermoplastic polyurethane composition has a hard segment content of 15% to 45% by weight or 20% to 35% by weight. 21. The melt-spun fiber of any of the foregoing embodiments, wherein the isocyanate functional prepolymer crosslinking agent comprises 65% to 80% or 70% to 80% by weight of the reaction product of the second polycarbonate polyol and 20% to 35% or 20% to 30% by weight of the second diisocyanate component. 22. The melt-spun fiber of any of the foregoing embodiments comprises 85% to 90% TPU and 10% to 15% of the prepolymer. 23. The melt-spun fiber of any of the foregoing embodiments, wherein the melt-spun thermoplastic polyurethane fiber has a weight-average molecular weight of 100,000 to 300,000 Daltons as measured by gas permeation chromatography. 24. The melt-spun fiber of any of the foregoing embodiments, wherein the thermoplastic polyurethane fiber, after exposure to oleic acid as measured according to ASTM D543-20, is able to retain at least 80% of its original tensile properties as measured according to ASTM D2653. 25. A fabric comprising melt-spun fibers as described in any of the foregoing embodiments. 26. A process for preparing thermoplastic polyurethane fibers, comprising the steps of: (1) preparing a reactive thermoplastic polyurethane composition, which is a reaction product of: (a) a polyol component, wherein the polyol component comprises a first polycarbonate polyol; (b) a chain extender component; and (c) a first diisocyanate; (2) Dry the reactive thermoplastic polyurethane composition; (3) Melt the reactive thermoplastic polyurethane composition in an extruder; (4) Add an isocyanate functional prepolymer to the extruder, wherein the isocyanate functional prepolymer comprises a reaction product of a second polycarbonate polyol or polycaprolactone polyol and a second diisocyanate component; (5) Mix the reactive thermoplastic polyurethane composition and the isocyanate functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) Feed the crosslinked thermoplastic polyurethane polymer into at least one spinning nozzle to produce melt-spun fibers; (7) Cool the melt-spun fibers; (8) Optionally, apply an oiling agent; and (9) Wind the melt-spun fibers onto a bobbin. 27. The process of Example 26, wherein the polyol component comprises at least 60% of the first polycarbonate polyol. 28. The process of Example 26 or 27, wherein the first polycarbonate polyol contains a repeating unit -ROC(=O)-O-, wherein R contains 4 to 6 carbon atoms. 29. The process of any one of Examples 26 to 28, wherein the first polycarbonate polyol has a number average molecular weight of about 1,000 to 3,000 Daltons, as measured by end-group analysis. 30. The process of any one of Examples 26 to 29, wherein the first polycarbonate polyol is selected from 2-MPD carbonate, BDO carbonate, DEG carbonate, HDO carbonate, or mixtures thereof. 31. The process of any one of Examples 26 to 30, wherein the polyol component is composed of the first polycarbonate polyol. 32. The process of any one of Examples 26 to 31, wherein the chain extender component comprises or is composed of 1,4-bis(β-hydroxyethoxy)benzene or 1,3-propanediol. 33. The process of any one of Examples 26 to 32, wherein the first diisocyanate component comprises or is composed of an aromatic diisocyanate. 34. The process of Example 33, wherein the first diisocyanate comprises or is composed of 4,4'-diphenylmethane diisocyanate. 35. The process of any one of Examples 26 to 32, wherein the first diisocyanate component comprises or is composed of an aliphatic diisocyanate. 36. The process of Example 35, wherein the first diisocyanate component comprises or is composed of HDI. 37. The process of any one of Examples 26 to 36, wherein the second diisocyanate component comprises or is composed of an aromatic diisocyanate. 38. The process of Example 37, wherein the second diisocyanate comprises or is composed of 4,4'-diphenylmethane diisocyanate. 39. The process of any one of Examples 26 to 36, wherein the second diisocyanate component comprises or is composed of an aliphatic diisocyanate. 40. The process of Example 39, wherein the second diisocyanate component comprises or is composed of HDI. 41. The process of any one of Examples 26 to 40, wherein the second polycarbonate polyol is selected from HDO-carbonate, BDO-carbonate, 3-MPD-carbonate, or mixtures thereof. 42. The process of any one of Examples 26 to 40, wherein the polycaprolactone polyol comprises ε-caprolactone that can react with a bifunctional initiator. 43. The process of Example 42, wherein the bifunctional initiator is selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol) or a mixture thereof. 44. The process of any one of Examples 26 to 43, wherein the reactive thermoplastic polyurethane composition contains 70% to 85% by weight, or 75% to 85% by weight, or 80% to 85% by weight of the first polycarbonate polyol component. 45. The process of any one of Examples 26 to 44, wherein the combined weight of the hydroxyl-terminated chain extender component and the first diisocyanate component constitutes the hard segment of the thermoplastic polyurethane composition, and wherein the thermoplastic polyurethane composition has a hard segment content of 15% to 30% or 20% to 25% by weight. 46. ​​The process of any one of Examples 26 to 45, wherein the isocyanate functional prepolymer crosslinking agent comprises 65% to 80% or 70% to 80% by weight of the reaction product of the second polycarbonate polyol and 20% to 35% or 20% to 30% by weight of the second diisocyanate component. 47. The process of any one of Examples 26 to 46, wherein the melt-spun fiber comprises 85% to 90% TPU and 10% to 15% of the prepolymer. 48. The process of any one of Examples 26 to 47, wherein the melt-spun thermoplastic polyurethane fiber has a weight-average molecular weight of 100,000 to 300,000 Daltons as measured by gas permeation chromatography.

[0007] These various embodiments are described in more detail below. Simple Explanation of the Diagram

[0008] none. Implementation

[0009] The features and embodiments of the present invention will now be described by way of the following non-limiting description.

[0010] The disclosed technology includes melt-spun fibers comprising a reactive thermoplastic polyurethane ("TPU") composition and an isocyanate-functionalized crosslinking agent. The reactive TPU composition used to manufacture the melt-spun fibers of this invention is a reaction product of a polyol component, a hydroxyl-terminated chain extender component, and a diisocyanate component. The isocyanate-functionalized crosslinking agent is a reaction product of a polyol and excess isocyanate. Each of these components is described in more detail below.

[0011] As used herein, the weight-average molecular weight (Mw) was measured by gel permeation chromatography using polystyrene standards, and the number-average molecular weight (Mn) was measured by end-group analysis. Thermoplastic polyurethane composition

[0012] The reactive TPU composition that can be used to manufacture the melt-spun fibers of this invention includes a polyol component, which can also be described as a hydroxyl-terminated intermediate. In this invention, the polyol component comprises or is composed of polycarbonate polyols.

[0013] Suitable hydroxyl-terminated polycarbonates include those prepared by reacting a glycol with a carbonate. U.S. Patent No. 4,131,731 is hereby incorporated by reference, disclosing hydroxyl-terminated polycarbonates and their preparation. Such polycarbonates are linear and have terminal hydroxyl groups, substantially excluding other terminal groups. The basic reactants are a glycol and a carbonate. Suitable glycols are selected from cycloaliphatic and aliphatic glycols containing 4 to 40 and or even 4 to 12 carbon atoms, and polyoxyethylene glycols containing 2 to 20 alkoxy groups per molecule, wherein each alkoxy group contains 2 to 4 carbon atoms. Suitable diols include aliphatic diols containing 4 to 12 carbon atoms, such as 1,4-butanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,10-decanediol, hydrogenated dilinolediol, hydrogenated dilinolediol, and 3-methyl-1,5-pentanediol; and cycloaliphatic diols, such as 1,3-cyclohexanediol, 1,4-dihydroxymethylcyclohexane, 1,4-cyclohexanediol-, 1,3-dihydroxymethylcyclohexane-, 1,4-methylene-2-hydroxy-5-hydroxymethylcyclohexane, and polyalkylene glycols. The diol used in the reaction can be a single diol or a mixture of diols, depending on the desired properties of the finished product. Hydroxyl-terminated polycarbonate intermediates are generally those known in this art and in the literature. Suitable carbonate systems are selected from alkyl carbonate diesters composed of 5 to 7 member rings. Carbonates suitable for use herein include ethylene carbonate, propylene carbonate, butyl carbonate, 1,2-propylene carbonate, 1,2-butanediol carbonate, 2,3-butanediol carbonate, 1,2-ethylene carbonate, 1,3-pentanediol carbonate, 1,4-pentanediol carbonate, 2,3-pentanediol carbonate, and 2,4-pentanediol carbonate. Furthermore, suitable systems herein are dialkyl carbonates, cyclic aliphatic carbonates, and diaryl carbonates. Dialkyl carbonates may contain 2 to 5 carbon atoms in each alkyl group, with diethyl carbonate and dipropyl carbonate being specific examples. Cyclic aliphatic carbonates, especially bicyclic aliphatic carbonates, may contain 4 to 7 carbon atoms in each cyclic structure, and one or two such structures may be present. When one group is cyclic aliphatic, the other may be alkyl or aryl. On the other hand, if one group is aryl, the other can be alkyl or cycloaliphatic. Suitable examples of diaryl carbonates, each containing 6 to 20 carbon atoms, are diphenyl carbonate, dimethyl carbonate, and dinaphthalene carbonate.

[0014] In one embodiment, the polyol component of the TPU composition comprises or is composed of a polycarbonate polyol containing a -ROC(=O)-O- repeating unit, wherein R contains 4 to 6 carbon atoms. In some embodiments, the polycarbonate polyol component may be selected from 2-methylpentanediol (MPD) carbonate, butanediol (BDO) carbonate, diethylene glycol (DEG) carbonate, hexanediol (HDO) carbonate, or mixtures thereof. In one embodiment, the polyol component comprises a mixture of polycarbonate polyols.

[0015] In some embodiments, the polyol component in the TPU composition may contain one or more copolyols, such as polyester, polyether, polysiloxane polyol, or combinations thereof. However, in one embodiment, the polyol component contains at least 60% by weight of polycarbonate polyol. In some embodiments, the polyol component contains at least 70%, at least 80%, at least 90%, or even 100% polycarbonate polyol.

[0016] In one embodiment, the polyol component may include a polyester polyol. Polyester polyols usable in this invention may be prepared by (1) esterification of one or more diols with one or more dicarboxylic acids or anhydrides, or (2) transesterification, i.e., reaction of one or more diols with dicarboxylic acid esters. Generally, a mole ratio of more than one mole of diol to acid is preferred to obtain a linear chain with a large number of terminal hydroxyl groups. Suitable polyester intermediates also include various lactones, such as polycaprolactone, typically prepared from ε-caprolactone and a bifunctional initiator, such as diethylene glycol. The desired polyester dicarboxylic acid may be aliphatic, cycloaliphatic, aromatic, or a combination thereof. In some embodiments, dicarboxylic acids, which may be used alone or in mixtures, generally have 4 to 15 carbon atoms and include: succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, and the like. Anhydrides of the aforementioned dicarboxylic acids, such as phthalic anhydride, tetrahydrophthalic anhydride, or similar compounds, may also be used. The diol used to form the desired polyester intermediate may be aliphatic, aromatic, or a combination thereof, including any of the diols described in the chain extender section above, and having a total of 2 to 20 or 2 to 12 carbon atoms. Suitable examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanediol, decanediol, dodecanediol, and mixtures thereof.

[0017] The polyester polyol component may also include one or more polycaprolactone polyester polyols. Polycaprolactone polyester polyols usable in the techniques described herein include polyester diols derived from autolactone monomers. Polycaprolactone polyester polyols are terminally capped with primary hydroxyl groups. Suitable polycaprolactone polyester polyols may be prepared from ε-caprolactone and a bifunctional initiator, such as diethylene glycol, 1,4-butanediol, or any other glycols and / or diols listed herein. In some embodiments, the polycaprolactone polyester polyol is a linear polyester diol derived from an autolactone monomer.

[0018] Useful examples include CAPA™ 2202A, a linear polyester diol with a number average molecular weight (Mn) of 2,000, and CAPA™ 2302A, a linear polyester diol with a Mn of 3,000, both of which are available from Perstorp Polyols Inc. These materials can also be described as polymers of 2-oxetaneheptanone and 1,4-butanediol.

[0019] Polycaprolactone polyester polyols can be prepared from 2-oxetaneheptanone and a diol, wherein the diol can be 1,4-butanediol, diethylene glycol, monoethylene glycol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, or any combination thereof. In some embodiments, the diol used to prepare the polycaprolactone polyester polyol is linear. In some embodiments, the polycaprolactone polyester polyol is prepared from 1,4-butanediol. In some embodiments, the number average molecular weight of the polycaprolactone polyester polyol is 500 to 10,000, or 500 to 5,000, or 1,000 or even 2,000 to 4,000 or even 3,000.

[0020] In one embodiment, the polyol component may include a polyether polyol. Suitable polyether polyol intermediates include polyether polyols derived from diols or polyols having a total of 2 to 15 carbon atoms. In some embodiments, alkyl diols or diols are reacted with ethers containing alkyl oxides having 2 to 6 carbon atoms, typically ethylene oxide or propylene oxide, or mixtures thereof. For example, hydroxyl-functionalized polyethers can be prepared by first reacting propylene glycol with propylene oxide, followed by a subsequent reaction with ethylene oxide. Primary hydroxyl groups derived from ethylene oxide are more reactive than secondary hydroxyl groups and are therefore preferred. Available commercial polyether polyols include poly(ethylene glycol) containing ethylene oxide reacted with ethylene glycol, poly(propylene glycol) containing propylene oxide reacted with propylene glycol, and poly(tetramethylene ether glycol) containing water reacted with tetrahydrofuran, which may also be described as polymerized tetrahydrofuran, commonly referred to as PTMEG. In some embodiments, the polyether intermediate includes PTMEG. Suitable polyether polyols also include polyamide adducts of alkyl epoxides, and may include, for example, ethylenediamine adducts comprising the reaction product of ethylenediamine and propylene oxide, diethylenetriamine adducts comprising the reaction product of diethylenetriamine and propylene oxide, and similar polyamide-type polyether polyols. Coethers may also be used in the compositions described. Typical coethers include the reaction product of THF and ethylene oxide or THF and propylene oxide. These are available from BASF, such as PolyTHF® B, a block copolymer, and PolyTHF® R, a random copolymer. Various polyether intermediates typically have a number average molecular weight (Mn) determined by terminal functional group analysis, with an average molecular weight greater than about 700, such as about 700 to about 10,000, about 1,000 to about 5,000, or about 1,000 to about 2,500. In some embodiments, the polyether intermediate includes a blend of two or more polyethers of different molecular weights, such as a blend of 2,000 Mn and 1,000 Mn PTMEG.

[0021] In one embodiment, the polyol component may include a polysiloxane polyol. Suitable polysiloxane polyols include polysiloxanes terminated with α-ω-hydroxyl, amine, carboxylic acid, thiol, or epoxy groups. Examples include poly(dimethylsiloxane) terminated with hydroxyl, amine, carboxylic acid, thiol, or epoxy groups. In some embodiments, the polysiloxane polyol is a hydroxyl-terminated polysiloxane. In some embodiments, the number-average molecular weight of the polysiloxane polyol is in the range of 300 to 5,000, or 400 to 3,000.

[0022] Polysiloxane polyols can be obtained by dehydrogenation reaction between polysiloxane hydrides and aliphatic polyols or polyoxyenols, thereby introducing alcohol hydroxyl groups onto the polysiloxane backbone.

[0023] In some embodiments, the polysiloxane may be represented by one or more compounds having the following formula:

[0024] Wherein: each of R1 and R2 is independently an alkyl, benzyl, or phenyl group with 1 to 4 carbon atoms; each of E is OH or NHR 3, wherein R 3 is hydrogen, an alkyl group with 1 to 6 carbon atoms, or a cycloalkyl group with 5 to 8 carbon atoms; a and b are each independently an integer from 2 to 8; c is an integer from 3 to 50. In amino-containing polysiloxanes, at least one of the E groups is NHR 3. In hydroxyl-containing polysiloxanes, at least one of the E groups is OH. In some embodiments, R1 and R2 are both methyl groups.

[0025] Suitable examples include α,ω-hydroxypropyl-terminated poly(dimethylsiloxane) and α,ω-aminopropyl-terminated poly(dimethylsiloxane), both of which are commercially available materials. Other examples include copolymers of poly(dimethylsiloxane) materials and poly(epoxide).

[0026] When present, the polyol component may include poly(ethylene glycol), poly(tetramethylene ether glycol), poly(propylene oxide), ethylene oxide-terminated poly(propylene glycol), poly(butylene adipate), poly(ethylene adipate), poly(hexamethylene adipate), poly(butylene adipate-co-hexamethylene adipate), poly(3-methyl-1,5-pentanediol adipate), polycaprolactone diol, poly(hexamethylene carbonate) diol, poly(pentanediol carbonate) diol, poly(propylene carbonate) diol, polyester polyols based on dimer fatty acids, vegetable oil-based polyols, or any combination thereof.

[0027] Examples of dimer fatty acids that can be used to prepare suitable polyester polyols include Priplast™ polyester diols / polyols available from Croda and Radia® polyester diols available from Oleon.

[0028] In one embodiment of the invention, the reaction mixture forming the TPU composition used herein comprises about 70% to about 85% by weight of a polyol component, for example about 80% to about 85% by weight. Chain extender components

[0029] The TPU compositions described in this article are made using chain extender components. Suitable chain extenders include glycols, diamines, and combinations thereof.

[0030] Suitable chain extenders include relatively small polyhydroxy compounds, such as low-carbon aliphatic or short-chain diols having 2 to 20, 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, neopentanediol, 1,4-cyclohexanediol (CHDM), 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane (HEPP), 1,4-bis(β-hydroxyethoxy)benzene (HQEE), hexamethylenediol, heptaethylenediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butylenediamine, hexamethylenediamine, and hydroxyethyl resorcinol (HER), and their analogues, as well as mixtures thereof. In one embodiment, the chain extender comprises or is composed of 1,4-bis(β-hydroxyethoxy)benzene (HQEE). In another embodiment, the chain extender comprises or is composed of 1,3-propanediol. Isocyanate components

[0031] The TPU of this invention is made using an isocyanate component. The isocyanate component may comprise 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 comprises one or more aromatic diisocyanates. In some embodiments, the polyisocyanate component is substantially free of or even completely free of aliphatic diisocyanates. In other embodiments, the polyisocyanate component comprises one or more aliphatic diisocyanates. In some embodiments, the polyisocyanate component is substantially free of or even completely free of aromatic diisocyanates. In some embodiments, a mixture of aliphatic and aromatic diisocyanates may be useful.

[0032] Examples of useful polyisocyanates include aromatic diisocyanates such as 4,4'-methylenebis(phenyl)isocyanate (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); and aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), decane-1,10-diisocyanate, lysine diisocyanate (LDI), 1,4-butane diisocyanate (BDI), isophorone diisocyanate (PDI), and dicyclohexylmethane-4,4'-diisocyanate (H12MDI). Isomers of these diisocyanates may also be useful. Mixtures of two or more polyisocyanates may be used. In some embodiments, the isocyanate component comprises or consists of aromatic diisocyanates. In some embodiments, the isocyanate component comprises or consists of MDI.

[0033] The combined weight percentage of the diisocyanate component and chain extender component in a TPU composition is referred to as the "hard segment content". In one embodiment of the present invention, the TPU composition used in the present invention contains 15% to 50% by weight or even 20% to 35% by weight of hard segments.

[0034] Optionally, one or more polymerization catalysts may be present during the polymerization reaction of TPU. Generally, any known catalyst can be used to react diisocyanate with polyol intermediates or chain extenders. Examples of suitable catalysts that particularly accelerate the reaction between the NCO group of the diisocyanate and the hydroxyl groups of the polyol and chain extender are known tertiary amines from the prior art, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, and N,N'-dimethylpiperazine. 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane and their analogues, and especially organometallic compounds such as titanates, iron compounds (e.g., acetoacetone iron), tin compounds (e.g., stannous diacetate, stannous octate, stannous dilaurate), bismuth compounds (e.g., bismuth trinedecanoate), or dialkyltin salts of aliphatic carboxylic acids (e.g., dibutyltin diacetate, dibutyltin dilaurate), or their analogues. The catalyst is typically used in an amount of 0.001 to 0.1 parts by weight per 100 parts by weight of the polyol component. In some embodiments, the reaction forming the TPU of the present invention is substantially catalyst-free or completely catalyst-free.

[0035] The reactive TPU composition used in this invention can be produced via a "one-step" process, wherein all components are added simultaneously or substantially simultaneously to a heated extruder and react to form TPU. The equivalence ratio of the total equivalence of the diisocyanate, the hydroxyl-terminated intermediate, and the chain extender is typically from about 0.95 to about 1.10, for example from about 0.97 to about 1.03, or even from about 0.98 to about 1.0. In one embodiment, the equivalence ratio may be less than 1.0, such that the TPU has terminal hydroxyl groups to enhance the reaction with the crosslinking agent during the fiber spinning process. The weight average molecular weight (MW) of the TPU is typically from about 25,000 to about 300,000, for example from about 50,000 to about 200,000, or even further, for example from about 75,000 to about 150,000.

[0036] In another embodiment, TPU can be prepared using a prepolymerization process. In the prepolymerization process, a hydroxyl-terminated intermediate reacts with a generally equivalent excess of one or more diisocyanates to form a prepolymer solution containing free or unreacted isocyanates. Subsequently, as described herein, a chain extender is added in an equivalent amount generally equal to that of the isocyanate end groups and any free or unreacted diisocyanate compounds. Therefore, the total equivalence ratio of total diisocyanates to the total equivalence of the hydroxyl-terminated intermediate and the chain extender is about 0.95 to about 1.10, for example, about 0.97 to about 1.03, or even about 0.98 to about 1.0. In one embodiment, the equivalence ratio may be less than 1.0, such that the TPU has terminal hydroxyl groups to enhance the reaction with the crosslinking agent during the fiber spinning process. Typically, the prepolymerization process can be carried out in any known apparatus, such as an extruder.

[0037] Optional additive components may be present during the polymerization reaction and / or incorporated into the above-mentioned TPU elastomer to improve processing and other properties. Such additives include, but are not limited to, antioxidants, organophosphites, phosphine and phosphonite diesters, hindered amines, organic amines, organosulfur compounds, lactones and hydroxylamine compounds, biocides, fungicides, antimicrobial agents, compatibilizers, dissipative or antistatic additives, fillers and reinforcing agents (such as titanium dioxide, alumina, clay and carbon black), flame retardants (such as phosphates, halogenated materials and metal salts of alkylbenzene sulfonates), impact modifiers (such as butadiene-styrene methacrylate (“MBS”) and methyl methacrylate butyl acrylate (“MBA”)), mold release agents (such as waxes, fats and oils), pigments and colorants, plasticizers, polymers, rheology modifiers (such as monoamines, polyamide waxes, polysiloxanes and polysiloxanes), lubricating additives (such as paraffin waxes, hydrocarbon polyolefins and / or fluorinated polyolefins), and UV stabilizers, which may be hindered amine light stabilizers (HALS) and / or UV light absorbers (UVA). Other additives can be used to enhance the performance of TPU compositions or blends. All additives described above can be used in the conventional effective amounts of these substances.

[0038] These additional additives may be incorporated into the components or reaction mixtures used to prepare the TPU resin, or after the manufacture of the TPU resin. In another process, all materials may be mixed with the TPU resin and then melted, or they may be directly incorporated into the melt of the TPU resin. Isocyanate functional prepolymer crosslinking agent

[0039] The aforementioned reactive TPU composition is combined with an isocyanate-functionalized prepolymer crosslinking agent to manufacture the melt-spun fibers of the present invention. The prepolymer crosslinking agent is a reaction product of a hydroxyl-terminated polyol comprising or composed of a second polycarbonate polyol or a polycaprolactone polyol and an excess of diisocyanate. The polycarbonate polyol or polycaprolactone polyol used to form the isocyanate-functionalized prepolymer crosslinking agent may be selected from those described herein with respect to the TPU composition. For example, the polycaprolactone polyol ε-caprolactone may react with a bifunctional initiator, such as diethylene glycol, 1,4-butanediol, neopentyl glycol, PTMEG, or any other diol and / or diol known in this art. The diisocyanate used to prepare the isocyanate-functionalized prepolymer crosslinking agent may also be selected from those described herein with respect to the TPU composition. The prepolymer crosslinking agent has an isocyanate functionality greater than 1.0, for example, about 1.5 to 2.5, and more further, for example, about 1.8 to 2.2. The isocyanate-functionalized prepolymer crosslinking agent can be prepared using a prepolymer process as described herein, wherein a hydroxyl-terminated intermediate reacts with an equivalence excess of one or more diisocyanates to form a prepolymer solution having free or unreacted isocyanates. thermoplastic polyurethane fibers

[0040] The thermoplastic polyurethane fiber of the present invention comprises about 80% to about 95% by weight, or even about 85% to 90% by weight, of the reactive TPU described herein, and about 5% to about 20% by weight, or even about 10% to about 15% by weight, of an isocyanate-functionalized prepolymer crosslinking agent. The percentage of crosslinking agent used is a weight percentage based on the total weight of the TPU and the crosslinking agent.

[0041] Melt-spun TPU fibers are produced by melting a TPU composition in an extruder and adding a crosslinking agent to the molten TPU. The TPU melt containing the crosslinking agent is fed into the spinning nozzle. The melt leaves the spinning nozzle to form fibers, which are then cooled and wound onto a bobbin. The process includes the following steps: (1) preparing a reactive thermoplastic polyurethane composition, which is a reaction product of: (a) a polyol component, wherein the polyol component comprises or is composed of a first polycarbonate polyol; (b) a chain extender component; 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 to 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 spinning nozzle to produce melt-spun fibers; (7) cooling the melt-spun fibers; (8) optionally, applying an oiling agent; and (9) winding the melt-spun fibers onto a bobbin core. The steps of this process are described in more detail below.

[0042] The melt spinning process begins by feeding pre-formed reactive TPU polymer into an extruder. The reactive TPU melts in the extruder, and the crosslinking agent is added continuously downstream either near where the TPU melt exits the extruder or after it has exited. If the crosslinking agent is added after the melt exits the extruder, it needs to be mixed with the TPU melt using a static or dynamic mixer to ensure proper binding within the TPU polymer melt. After exiting the extruder and mixer, the molten TPU polymer with the crosslinking agent flows into a manifold. The manifold divides the melt flow into different streams, each fed to multiple spinning nozzles. Typically, each stream exiting the manifold has a melt pump, which feeds several spinning nozzles. The spinning nozzles have a small orifice through which the melt is forced and exits as fibers. The size of the orifice in the spinning nozzle depends on the desired fiber size (denier). The fibers are elongated or stretched as they leave the spinneret and are cooled before being wound onto the bobbin. The fibers are stretched by winding the bobbin at a higher speed than the speed at which they leave the spinneret. For melt-spun TPU fibers, the bobbin winding rate is typically greater than the speed at which the fibers leave the spinneret; for example, in some embodiments, it is 4 to 8 times the speed at which the fibers leave the spinneret, but depending on the specific equipment, it can be wound slower or faster. Typical bobbin winding speeds can vary from 100 to 3000 meters per minute, but for TPU melt-spun fibers, a more typical speed is 300 to 1200 meters per minute. An oiling agent, such as polysiloxane oil, is typically added to the surface of the fibers after cooling and just before winding into the bobbin.

[0043] A crucial aspect of the melt spinning process is the mixing of the TPU polymer melt and the crosslinking agent. Proper and uniform mixing is essential for achieving uniform fiber properties and long run times without fiber breakage. The mixing of the TPU melt and the crosslinking agent should be a plunger flow method, i.e., first-in, first-out. Both dynamic and static mixers can be used to achieve proper mixing. For example, a dynamic mixer with a feed screw and a mixing pin can be used. U.S. Patent 6,709,147 describes such a mixer and includes a rotatable mixing pin.

[0044] During the fiber spinning process, TPU reacts with a prepolymer crosslinking agent to achieve a weight-average molecular weight (MW) of approximately 50,000 to approximately 400,000 dle tons, preferably approximately 100,000 to approximately 300,000 dle tons, in fibrous form. During fiber spinning, the reaction rate between the TPU and the prepolymer crosslinking agent at the point where the TPU exits the spinning nozzle should be higher than 20%, preferably approximately 30% to approximately 60%, and more preferably approximately 40% to approximately 50%. Typical prior art TPU melt spinning reaction between the TPU polymer and the crosslinking agent is less than 20% and usually around 10-15%. The reaction is determined by the disappearance of NCO groups. The higher percentage of reaction in this invention improves melt strength, thereby allowing for higher spinning temperatures and improving the spinnability of the TPU. The fibers are typically cured in an oven on bobbins until the molecular weight stabilizes.

[0045] Melt-spun TPU fibers can be made in various deniers. The term "denier" is defined as the mass (in grams) of 9000 meters of fiber, filament, or yarn. It describes the linear density of the fiber, filament, or yarn, the mass per unit length, and is measured according to ASTM D1577, Option B. Typical melt-spun TPU fibers are made in denier sizes less than 1080, such as 10 to 240 deniers, or even 20, 40, 70, and 140 deniers.

[0046] The melt-spun fibers manufactured according to the present invention possess unique physical properties not exhibited by prior art TPU fibers. In some embodiments, the fibers of the present invention exhibit unique elastic properties and chemical resistance. fabric

[0047] The TPU fibers of this invention are combined with other natural or synthetic fibers, either knitted or woven, to create fabrics that can be used in a variety of articles. It is desirable to dye such fabrics in a variety of colors.

[0048] The melt-spun TPU fibers of this invention can be combined with other fibers (such as different TPU fibers, cotton, nylon or polyester) to manufacture a variety of end-use articles, including clothing.

[0049] For example, the fabric according to the present invention can combine the melt-spun TPU fibers of the present invention with different TPU fibers or yarns not made of TPU and with lower elasticity than the TPU fibers of the present invention (also referred to herein as "stiff yarns"). Stiff yarns may include, for example, different TPU fibers, polyester, nylon, cotton, wool, acrylic, polypropylene, or viscose rayon. In one embodiment, the stiff yarn has a limiting elongation of 10% to 200%, for example 10% to 75%, or even 10% to 50%, or even 10% to 30%, and the melt-spun TPU fibers of the present invention have a limiting elongation of at least 300%, for example 300% to 650%. Each fiber component may be included in the composition in an amount of 1-99% by weight. The percentage by weight of melt-spun TPU fibers in the end-use application may vary depending on the desired elasticity. For example, woven fabrics contain 1-8 wt.%, underwear contains 2-5 wt.%, swimwear and sportswear contains 8-30 wt.%, basic clothing contains 10-45 wt.%, and medical tubing contains 35-60 wt.% melt-spun TPU fibers, with the remainder being rigid, inelastic fibers. Fabrics made from these two fiber materials can be constructed using various processes, including but not limited to circular knitting, warp knitting, woven fabrics, braided fabrics, non-woven fabrics, or combinations thereof. In one embodiment, fabrics made from the fibers of the present invention can have a tensile strength of more than 50% or even more than 100%, as measured by ASTM D4964.

[0050] In this application and the following examples, the following properties and methods for measuring such properties are mentioned: ● The tensile strength of the prepared membrane was measured according to ASTM D412. ● The tensile permanent deformation of the prepared membrane was measured according to ASTM D412. ● Danel is a measure of linear density and is measured according to ASTM D1577, Option B; ● The toughness of the elastic filament, that is, the tensile strength normalized by denier, is also measured and reported according to ASTM D2653; ● The ultimate elongation at break of the elastic filament, also known as the elongation at break, is measured and reported according to ASTM D2653; ● The hysteresis of elastic filaments is defined and calculated under their respective elongation rates as mentioned above, and according to the ASTM D2731 report; ● For inelastic, stiff yarns like polyester, measure toughness and elongation using ASTM D2256 standard; ● The chemical resistance of oleic acid in comparative and inventive examples is measured and reported according to ASTM D543-20.

[0051] The invention will be better understood by referring to the following examples. Example

[0052] Table 1 lists the TPU compositions prepared for the initial preparation of films in this invention to evaluate chemical resistance. [Example] [Polyols] [Mn] Chain extender [Diisocyanate] A HDO / BDO adipate 2500 BDO MDI B PTMEG 1000 HQEE MDI C PTMEG / caprolactone 1550 BDO MDI D Polycarbonate (6 carbons) 2000 BDO MDI E PTMEG / Polycarbonate (6-carbon) 1800 / 2000 BDO MDI F Polycarbonate (6 carbons) 2000 HQEE MDI G polycarbonate 2000 HQEE MDI H polycarbonate 2000 HQEE MDI I Polycarbonate (6 carbons) 1000 HQEE MDI J Polycarbonate (6 carbons) 2000 HQEE MDI K Polycarbonate (6-carbon branched) 3000 HQEE MDI L A mixture of polyols Mn=2000, 70% and polyols Mn=3000, 30%. 2000 / 3000 HQEE MDI M A mixture of polyols Mn=2000, 50% and polyols Mn=3000, 50%. 2000 / 3000 HQEE MDI N Polycarbonate (4 carbons) 2000 HQEE MDI O Polycarbonate (4 carbons) 2000 HQEE MDI P Polycarbonate (6 carbons) 2000 PDO MDI Q Polycarbonate (6 carbons) 2000 PDO MDI R Polycarbonate (6 carbons) 2000 PDO MDI

[0053] Upon exiting the extruder, the TPU candidates in Table 1 were chemically (oleic acid) exposed according to ASTM D543-20, and the examples with the lowest decrease in tensile strength were selected for fiber spinning. Table 2 compares the oleic acid resistance of the examples prepared from Table 1. [Table 2] Comparison Chemical resistance change% Permanent deformation due to stretching [Example] stress strain stress strain stress strain % psi % psi % average value average value average value average value A 7058 827 195 116 -97.2 -85.9 0 B Gel 1 C Gel 1 D 8754 359 4524 214 -48.3 -40.5 12.1 E 2 F 5088 474 3490 603 -31.4 27.2 0.4 G 4534 429 4513 621 -0.5 44.8 0.4 H 4502 359 4524 497 0.5 38.2 2.4 I 4504 437 3161 646 -29.8 48.0 2.4 J 4502 359 4524 497 0.5 38.2 2.4 K 3152 530 3249 768 3.1 44.9 1.4 L 4294 398 4646 575 8.2 44.3 0.4 M 3631 477 3945 593 8.7 24.3 0.4 N 4965 367 5685 516 14 41 6.3 O 4452 467 4964 639 11 37 7.4 P 4795 383 5516 704 15 84 0.4 Q 6991 519 4535 889 -35 71 0.4 R 4828 411 3707 919 -23 123 0.4 1 Gel = Instances marked "gel" become completely gelled and are not suitable for testing any physical properties, meaning they have very poor tolerance to oleic acid due to plasticization. 2 Not tested

[0054] Examples G, H, L, and R were selected for fiber spinning due to their highest oleic acid resistance and lowest tensile permanent deformation loss as shown in Table 2. Examples M to T also offer chemical resistance; however, examples G and H were selected for ease of processing during fiber spinning.

[0055] For fiber spinning, 10 wt% of the prepolymer crosslinking agent listed in Table 3 was mixed with the TPU polymer melt in a dynamic mixer (90 wt% TPU polymer melt / 10 wt% crosslinking agent), and then pumped to the spinning nozzle via a manifold pump. The polymer stream ejected from the spinning nozzle was cooled by air, a silicone oil was applied, and the resulting fibers were wound into a bobbin. The fibers on the bobbin were heat-cured at 80°C for 24 hours before testing the physical properties of the fibers. Table 3 summarizes the TPU and crosslinking agent combinations used to manufacture the fibers. [Table 3] [Fiber Examples] [TPU] [Example] [Crosslinking agent type] 1 A PTMEG+MDI prepolymer, with 6.6% isocyanate. 2 B PTMEG+MDI prepolymer, with 6.6% isocyanate. 3 C PTMEG+MDI prepolymer, with 6.6% isocyanate. 4 H none 5 H NPG adipate + MDI prepolymer, can be made with 6.6% isocyanate. 6 H Polycaprolactone MDI prepolymer can be produced using 6.8% isocyanate. 7 H Polycarbonate MDI prepolymer, with 10% isocyanate. 8 H Polycarbonate MDI prepolymer, can be made with 6.6% isocyanate. 9 G none 10 G NPG adipate + MDI prepolymer, can be made with 6.6% isocyanate. 11 G Polycaprolactone MDI prepolymer can be produced using 6.8% isocyanate. 12 G Polycarbonate MDI prepolymer, with 10% isocyanate. 13 G Polycarbonate MDI prepolymer, can be made with 6.6% isocyanate. 14 R none 15 R NPG adipate + MDI prepolymer, can be made with 6.6% isocyanate.

[0056] The data in Tables 4 and 5 illustrate that examples of fibers prepared using polycarbonate-based TPU and polycarbonate-based prepolymer crosslinking agents, as well as polycarbonate-based TPU and polycaprolactone-based prepolymer crosslinking agents, unexpectedly demonstrate optimal performance after chemical exposure. [Table 4] [Fiber Examples] [Comparison] [Values ​​after oleic acid exposure] [change] [%] toughness Elongation at break toughness Elongation at break load elongation Kelp / Danny % Kelp / Danny % 1 1.4 555 0.3 573 -79 3 2 Completely plasticized in oleic acid 3 Completely plasticized in oleic acid 4 1.3 392 1.2 460 -8 17 5 1.1 368 0.9 418 -19 14 6 1.0 424 0.8 586 -twenty three 38 7 1.2 449 0.9 516 -26 15 8 1.0 407 0.7 595 -twenty four 46 9 1.5 290 1.3 446 -14 54 10 1.2 314 0.9 399 -twenty two 27 11 1.0 337 0.8 554 -19 64 12 0.9 267 0.8 405 -7 52 13 0.9 396 0.8 510 -7 29 14 1.2 366 1.1 514 -7 40 15 1.2 378 0.8 488 -35 29 [Table 5] [Fiber Examples] [Permanent Deformation] [-] [Comparison] [(%) [Permanent deformities following chemical exposure] [(%) [No.] [5] [Lag after one cycle] Load Cycle Unloaded loop Load Cycle Unloaded loop Comparison Oleic acid exposure 4 50 83 45 52 33 8 5 40 58 46 68 18 twenty three 6 32 41 37 48 9 11 7 31 39 32 41 8 10 8 27 37 33 44 10 11 9 Sample failure Sample failure 43 56 Sample failure 13 10 41 58 40 58 17 18 11 twenty four 31 29 37 7 8 12 28 42 33 45 14 13 13 25 33 28 35 8 8 14 34 51 37 48 16 11 15 28 42 44 60 14 16

[0057] All documents mentioned above are incorporated herein by reference, including any prior applications claiming priority, whether or not specifically listed above. Reference to any document does not imply endorsement that such document qualifies as prior art or constitutes ordinary knowledge to an ordinary person in any jurisdiction. Unless expressly indicated by example or otherwise, all specified amounts of material, reaction conditions, molecular weights, carbon numbers, and similar quantities in this description shall be understood to be modified by the word "about." It should be understood that the upper and lower limits, ranges, and ratios described herein can be combined independently. Similarly, the ranges and quantities of elements of the invention may be used in conjunction with the ranges or quantities of any other element.

[0058] As used herein, the transitional term "comprising," synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional undescribed elements or method steps. However, in the various descriptions of "comprising" herein, it is intended that the term, as an alternative embodiment, also cover the phrases "consisting essentially of" and "consisting of," wherein "consisting essentially of" excludes any unspecified elements or steps, and "consisting essentially of" allows the inclusion of additional uncited steps that do not substantially affect the essential and novel features of the composition or method under consideration.

[0059] While certain representative embodiments and details have been shown to illustrate the invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention. In this regard, the scope of the invention is limited only by the following claims.

[0060] none

Claims

1. A melt-spun fiber comprising: (a) a reactive thermoplastic polyurethane composition comprising the following reaction products: i. a polyol component comprising a first polycarbonate polyol, wherein the polyol component comprises at least 60% of the first polycarbonate polyol; ii. a hydroxyl-terminated chain extender component; and iii. a first diisocyanate component; and (b) an isocyanate-functionalized prepolymer crosslinking agent comprising the reaction product of a second polycarbonate polyol and a second diisocyanate component, or (c) an isocyanate-functionalized prepolymer crosslinking agent comprising the reaction product of a polycaprolactone polyol and a second diisocyanate component.

2. The melt-spun fiber of claim 1, wherein the first polycarbonate polyol contains a repeating unit -ROC(=O)-O-, wherein R contains 4 to 6 carbon atoms.

3. The melt-spun fiber of claim 1, wherein the number average molecular weight of the first polycarbonate polyol, as measured by end-group analysis, is about 1,000 to 3,000 Daltons, optionally wherein the first polycarbonate polyol is selected from 2-MPD carbonate, BDO carbonate, DEG carbonate, HDO carbonate, or mixtures thereof.

4. The melt-spun fiber of claim 1, wherein the polyol component is composed of the first polycarbonate polyol.

5. The melt-spun fiber of claim 1, wherein the chain extender component comprises or is composed of 1,4-bis(β-hydroxyethoxy)benzene or 1,3-propylene glycol.

6. The melt-spun fiber of claim 1, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate, 4,4'-diphenylmethane diisocyanate, an aliphatic diisocyanate, HDI, or a mixture thereof.

7. The melt-spun fiber of claim 1, wherein the second diisocyanate component comprises or is composed of aromatic diisocyanates, 4,4'-diphenylmethane diisocyanates, aliphatic diisocyanates, HDI, or mixtures thereof.

8. The melt-spun fiber of claim 1, wherein the second polycarbonate polyol is selected from HDO-carbonate, BDO-carbonate, 3-MPD-carbonate, or mixtures thereof.

9. The melt-spun fiber of claim 1, wherein the polycaprolactone polyol comprises ε-caprolactone and is capable of reacting with a bifunctional initiator, optionally wherein the bifunctional initiator is selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol) or mixtures thereof.

10. The melt-spun fiber of any one of claims 1 to 9, wherein the reactive thermoplastic polyurethane composition contains 70% to 85% by weight of the first polycarbonate polyol component.

11. The melt-spun fiber of any one of claims 1 to 9, wherein the combined weight of the hydroxyl-terminated chain extender component and the first diisocyanate component constitutes the hard segment of the thermoplastic polyurethane composition, and wherein the thermoplastic polyurethane composition has a hard segment content of 15% to 45% by weight.

12. The melt-spun fiber of any one of claims 1 to 9, wherein the isocyanate functional prepolymer crosslinking agent comprises 65% to 80% by weight of the reaction product of the second polycarbonate polyol and 20% to 35% by weight of the second diisocyanate component.

13. The melt-spun fiber of any one of claims 1 to 9 comprises 85% to 90% TPU and 10% to 15% of the prepolymer.

14. The melt-spun fiber of any one of claims 1 to 9, wherein the melt-spun thermoplastic polyurethane fiber has a weight-average molecular weight of 100,000 to 300,000 Daltons as measured by gas permeation chromatography.

15. The melt-spun fiber of any one of claims 1 to 9, wherein the thermoplastic polyurethane fiber, after exposure to oleic acid as measured according to ASTM D543-20, is able to retain at least 80% of its original tensile properties as measured according to ASTM D2653.

16. A fabric comprising melt-spun fibers as claimed in any one of claims 1 to 15.

17. A method for preparing melt-spun fibers as claimed in any one of claims 1 to 15, the method comprising the steps of: (1) preparing a reactive thermoplastic polyurethane composition, which is a reaction product of: (a) a polyol component, wherein the polyol component comprises a first polycarbonate polyol, wherein the polyol component comprises at least 60% of the first polycarbonate polyol; (b) a chain extender component; and (c) a first diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; and (4) adding an isocyanate functional prepolymer to the extruder, wherein the isocyanate functional prepolymer comprises a reaction product of a second polycarbonate polyol or polycaprolactone polyol and a second diisocyanate component; (5) The reactive thermoplastic polyurethane composition and the isocyanate functional prepolymer are mixed in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) The crosslinked thermoplastic polyurethane polymer is fed into at least one spinning nozzle to produce melt-spun fibers; (7) The melt-spun fibers are cooled; (8) Optionally, an oiling agent is applied; and (9) The melt-spun fibers are wound onto a bobbin.