Melt-spun thermoplastic polyurethane fibers

Abstract

Melt spun thermoplastic polyurethane fibers are provided that provide elastic properties and exhibit chemical resistance.

Description

[Background technology]

[0001] Thermoplastic polyurethane ("thermoplastic polyurethane, TPU") fibers show great potential for providing stretch and fit properties in various applications, but have some drawbacks. Many polyurethane fibers are made by a dry spinning process that involves dissolving reactive components in a solvent. Although such fibers generally have good heat resistance, the dry spinning process is expensive, time consuming, and involves the use of volatile solvents that raise environmental concerns. Although melt spinning of 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 do not exhibit sufficient chemical resistance for certain applications, such as those used in electronics, automotive, and apparel applications. Therefore, it is desirable to have melt spun TPU fibers that have excellent elastomeric properties, but also exhibit chemical resistance. Summary of the Invention

[0002] In one embodiment, the invention is a melt spun fiber, the fiber comprising a reactive thermoplastic polyurethane composition and an isocyanate-functional prepolymer crosslinker. The reactive thermoplastic polyurethane composition used in the fiber comprises the reaction product of (i) a polyol component comprising or consisting of a first polycarbonate polyol, (ii) a hydroxyl-terminated chain extender component, and (iii) a first diisocyanate component. The isocyanate-functional prepolymer crosslinker comprises the reaction product of a second polycarbonate polyol or polycaprolactone polyol and a second diisocyanate component.

[0003] In another embodiment, the present invention provides a process for preparing a thermoplastic polyurethane having the steps of: (a) preparing a reactive thermoplastic polyurethane composition that is the reaction product of: (a) a polyol component, the polyol component comprising or consisting 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) melting an isocyanate-functional prepolymer that is a second polycarbonate polyol. (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; (8) optionally applying a finishing oil; and (9) winding the melt spun fibers onto bobbins.

[0004] In yet another embodiment, the present invention provides a fiber comprising melt spun thermoplastic polyurethane filaments that retain at least 80% tenacity as measured according to ASTM D2653 after exposure to a chemical, such as oleic acid as measured according to ASTM D543-20. In another embodiment, the invention provides a fabric comprising melt spun thermoplastic polyurethane filaments capable of retaining at least 80% of its original tensile properties measured according to ASTM D2653 after exposure to oleic acid, the fibers having a fiber modulus measured according to ASTM D2731 of less than 0.9 grams-force at 50% elongation during the fifth load cycle, less than 2.1 grams-force at 100% elongation during the fifth load cycle, less than 4.3 grams-force at 200% elongation during the fifth load cycle, less than 2.8 grams-force at 200% elongation during the fifth unload cycle, less than 1.2 grams-force at 100% elongation during the fifth unload cycle, and less than 0.4 grams-force at 50% elongation during the fifth unload cycle, and an ultimate elongation of 300% measured according to ASTM D2731.

[0005] The following embodiments of the present subject matter are contemplated. 1. A melt spun fiber comprising: (a) a reactive thermoplastic polyurethane composition comprising the reaction product of: (i) a polyol component, the polyol component comprising a first polycarbonate polyol; (ii) a hydroxyl-terminated chain extender component; and (iii) a first diisocyanate component; (b) an isocyanate-functional prepolymer crosslinker comprising the reaction product of a second polycarbonate polyol and a second diisocyanate component; or (c) an isocyanate-functional prepolymer crosslinker comprising the reaction product of a polycaprolactone polyol and a second diisocyanate component. 2. The melt spun fiber of embodiment 1, wherein the polyol component comprises at least 60% of the first polycarbonate polyol. 3. The melt spun fiber of embodiment 1 or 2, wherein the first polycarbonate polyol contains the repeat unit -ROC(=O)-O-, where R contains from 4 to 6 carbon atoms. 4. The melt spun fiber of any of embodiments 1-3, wherein the first polycarbonate polyol has a number average molecular weight of about 1000-3000 Daltons as determined by end group analysis. 5. The melt spun fiber of any of the preceding 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 according to any one of embodiments 1 to 5, wherein the polyol component consists of a first polycarbonate polyol. 7. The melt spun fiber of any one of embodiments 1-6, wherein the chain extender component comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene or 1,3 propanediol. 8. The melt spun fiber of any one of embodiments 1-7, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate. 9. The melt spun fiber of embodiment 8, wherein the first diisocyanate comprises or consists of 4,4'-diphenylmethane diisocyanate. 10. The melt spun fiber of any one of embodiments 1-7, wherein the first diisocyanate component comprises or consists of an aliphatic diisocyanate. 11. The melt spun fiber of embodiment 10, wherein the first diisocyanate component comprises or consists of HDI. 12. The melt spun fiber of any one of the preceding embodiments, wherein the second diisocyanate component comprises or consists of an aromatic diisocyanate. 13. The melt spun fiber of embodiment 12, wherein the second diisocyanate comprises or consists of 4,4'-diphenylmethane diisocyanate. 14. The melt spun fiber of any one of the preceding embodiments, wherein the second diisocyanate component comprises or consists of an aliphatic diisocyanate. 15. The melt spun fiber of embodiment 14, wherein the second diisocyanate component comprises or consists of HDI. 16. The melt spun fiber of any one of the preceding embodiments, wherein the second polycarbonate polyol is selected from HDO-carbonate, BDO-carbonate, 3-MPD-carbonate, or a mixture thereof. 17. The melt spun fiber of any one of the preceding embodiments, wherein the polycaprolactone polyol comprises ε-caprolactone and can be reacted with a difunctional initiator. 18. The melt-spun fiber of embodiment 17, wherein the difunctional initiator is selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol), or a mixture thereof. 19. The melt spun fiber of any of the preceding 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 preceding embodiments, wherein the combined weight of the hydroxyl terminated chain extender component and the first diisocyanate component constitutes the hard segments of the thermoplastic polyurethane composition, and the thermoplastic polyurethane composition has a hard segment content of 15% to 45% or 20% to 35% by weight. 21. The melt spun fiber of any of the preceding embodiments, wherein the isocyanate-functional prepolymer crosslinker comprises the reaction product of 65% to 80% or 70% to 80% by weight of a second polycarbonate polyol and 20% to 35% or 20% to 30% by weight of a second diisocyanate component. 22. The melt spun fiber of any one of the preceding embodiments, comprising 85%-90% TPU and 10%-15% prepolymer. 23. The melt-spun fiber of any one of embodiments 1-22, wherein the melt-spun thermoplastic polyurethane fiber has a weight average molecular weight of 100,000 Daltons to 300,000 Daltons as measured by gas permeation chromatography. 24. The melt spun fiber of any of the preceding embodiments, wherein the thermoplastic polyurethane fiber is capable of retaining at least 80% of its original tensile properties, as measured according to ASTM D2653, after exposure to oleic acid, as measured by ASTM D543-20. 25. A fabric comprising the melt spun fiber of any one of embodiments 1 to 24. 26. A process for preparing a thermoplastic polyurethane, comprising the steps of: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of (a) a polyol component, the polyol component comprising a 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; (4) adding an isocyanate-functional prepolymer into the extruder, the isocyanate-functional prepolymer comprising a reaction product of a second polycarbonate polyol or a polycaprolactone polyol 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 to at least one spinneret to produce melt spun fibers; (7) cooling the melt spun fibers; (8) optionally applying a finishing oil; and (9) winding the melt spun fibers onto bobbins. 27. The process of embodiment 26, wherein the polyol component comprises at least 60% of the first polycarbonate polyol. 28. The process of embodiment 26 or 27, wherein the first polycarbonate polyol contains the repeat unit -ROC(=O)-O-, where R contains from 4 to 6 carbon atoms. 29. The process of any one of embodiments 26-28, wherein the first polycarbonate polyol has a number average molecular weight of about 1000 to 3000 Daltons as determined by end group analysis. 30. The process of any one of embodiments 26-29, wherein the first polycarbonate polyol is selected from 2-MPD carbonate, BDO carbonate, DEG carbonate, HDO carbonate, or a mixture thereof. 31. The method of any one of embodiments 26-30, wherein the polyol component consists of a first polycarbonate polyol. 32. The process of any one of embodiments 26-31, wherein the chain extender component comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene or 1,3 propanediol. 33. The process of any one of embodiments 26-32, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate. 34. The process of embodiment 33, wherein the first diisocyanate comprises or consists of 4,4'-diphenylmethane diisocyanate. 35. The process of any one of embodiments 26-32, wherein the first diisocyanate component comprises or consists of an aliphatic diisocyanate. 36. The process of embodiment 35, wherein the first diisocyanate component comprises or consists of HDI. 37. The process of any one of embodiments 26-36, wherein the second diisocyanate component comprises or consists of an aromatic diisocyanate. 38. The process of embodiment 37, wherein the second diisocyanate comprises or consists of 4,4'-diphenylmethane diisocyanate. 39. The process of any one of embodiments 26-36, wherein the second diisocyanate component comprises or consists of an aliphatic diisocyanate. 40. The process of embodiment 39, wherein the second diisocyanate component comprises or consists of HDI. 41. The process of any one of embodiments 26-40, wherein the second polycarbonate polyol is selected from HDO-carbonate, BDO-carbonate, 3-MPD-carbonate, or a mixture thereof. 42. The process of any one of embodiments 26 to 40, wherein the polycaprolactone polyol comprises ε-caprolactone and can be reacted with a difunctional initiator. 43. The process of embodiment 42, wherein the difunctional initiator is selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol), or a mixture thereof. 44. The process of any of embodiments 26-43, 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 of embodiments 26-44, wherein the combined weight of the hydroxyl-terminated chain extender component and the first diisocyanate component constitutes the hard segments of the thermoplastic polyurethane composition, and the thermoplastic polyurethane composition has a hard segment content of 15% to 30% by weight or 20% to 25% by weight. 46. ​​The process of any of embodiments 26-45, wherein the isocyanate-functional prepolymer crosslinker comprises the reaction product of 65% to 80% or 70% to 80% by weight of a second polycarbonate polyol and 20% to 35% or 20% to 30% by weight of a second diisocyanate component. 47. The process of any one of embodiments 26-46, wherein the melt spun fiber comprises 85%-90% TPU and 10%-15% prepolymer. 48. The process of any one of embodiments 26-47, wherein the melt-spun thermoplastic polyurethane fibers have a weight average molecular weight of 100,000 Daltons to 300,000 Daltons as measured by gas permeation chromatography.

[0006] These various embodiments are described in more detail below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Features and embodiments of the present invention are illustrated below by the following non-limiting examples.

[0008] The disclosed technology includes melt spun fibers comprising a reactive thermoplastic polyurethane ("TPU") composition and an isocyanate-functional crosslinker. The reactive 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 an isocyanate. Each of these components is described in more detail below.

[0009] 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.

[0010] Thermoplastic polyurethane composition The reactive 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 polycarbonate polyol.

[0011] Suitable hydroxyl-terminated polycarbonates include those prepared by reacting a glycol with a carbonate. U.S. Patent No. 4,131,731 is incorporated herein by reference for its disclosure of hydroxyl-terminated polycarbonates and their preparation. Such polycarbonates are linear and essentially have terminal hydroxyl groups to the exclusion of other end groups. The essential reactants are a glycol and a carbonate. Suitable glycols are selected from cycloaliphatic and aliphatic diols containing 4 to 40 and or even 4 to 12 carbon atoms, and from polyoxyalkylene glycols containing 2 to 20 alkoxy groups per molecule, each alkoxy group containing 2 to 4 carbon atoms. Suitable diols include aliphatic diols containing 4 to 12 carbon atoms, such as 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,10-decanediol, hydrogenated dilinoleyl glycol, hydrogenated dioleyl glycol, 3-methyl-1,5-pentanediol, and alicyclic diols, such as 1,3-cyclohexanediol, 1,4-dimethylolcyclohexane, 1,4-cyclohexanediol-, 1,3-dimethylolcyclohexane-, 1,4-endomethylene-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 properties desired in the final product. Hydroxyl-terminated polycarbonate intermediates are generally known in the art and literature. Suitable carbonates are selected from alkylene carbonates composed of 5- to 7-membered rings. Suitable carbonates for use herein include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 2,3-pentylene carbonate, and 2,4-pentylene carbonate.Also suitable herein are dialkyl carbonates, alicyclic carbonates, and diaryl carbonates. Dialkyl carbonates can contain 2-5 carbon atoms in each alkyl group, specific examples of which are diethyl carbonate and dipropyl carbonate. Alicyclic carbonates, particularly bicyclic aliphatic carbonates, can contain 4-7 carbon atoms in each ring structure, and there can be one or two such structures. When one group is alicyclic, the other can be either alkyl or aryl. On the other hand, when one group is aryl, the other can be alkyl or alicyclic. Examples of suitable diaryl carbonates that can contain 6-20 carbon atoms in each aryl group are diphenyl carbonate, ditolyl carbonate, and dinaphthyl carbonate.

[0012] In one embodiment, the polyol component in the TPU composition comprises or consists of a polycarbonate polyol containing repeat units of -ROC(=O)-O-, where R contains from 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.

[0013] In some embodiments, the polyol component of the TPU composition may contain one or more copolyols, such as polyester, polyether, polysiloxane polyols, 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% of polycarbonate polyol.

[0014] In one embodiment, the polyol component may comprise a polyester polyol. The polyester polyols useful in the present invention may be produced by (1) an esterification reaction of one or more glycols with one or more dicarboxylic acids or anhydrides, or (2) a transesterification reaction, i.e., the reaction of one or more glycols with esters of dicarboxylic acids. To obtain linear chains with a predominance of terminal hydroxyl groups, a mole ratio of glycol to acid of greater than 1 mole is generally preferred. Suitable polyester intermediates also include various lactones, such as polycaprolactone, which is typically made from ε-caprolactone and a difunctional initiator, e.g., diethylene glycol. The dicarboxylic acids of the desired polyester may be aliphatic, cycloaliphatic, aromatic, or combinations thereof. In some embodiments, the dicarboxylic acids that may be used alone or in mixtures generally have a total of 4 to 15 carbon atoms and include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, and the like. Anhydrides of the above dicarboxylic acids, such as phthalic anhydride, tetrahydrophthalic anhydride, etc., may also be used. The glycols reacted to form the desired polyester intermediate may be aliphatic, aromatic, or combinations thereof, including any of the glycols described in the chain extender section above, 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-cyclohexanedimethanol, decamethylene glycol, dodecamethylene glycol, and mixtures thereof.

[0015] The polyester polyol component may also include one or more polycaprolactone polyester polyols. The polycaprolactone polyester polyols useful in the technology described herein include polyester diols derived from caprolactone monomers. The polycaprolactone polyester polyols are terminated with primary hydroxyl groups. Suitable polycaprolactone polyester polyols can be made from ε-caprolactone and a difunctional initiator, such as diethylene glycol, 1,4-butanediol, or any of the other glycols and / or diols listed herein. In some embodiments, the polycaprolactone polyester polyol is a linear polyester diol derived from caprolactone monomers.

[0016] Useful examples include CAPA™ 2202A, a linear polyester diol having a number average molecular weight (Mn) of 2,000, and CAPA™ 2302A, a linear polyester diol having a Mn of 3,000, both of which are commercially available from Perstorp Polyols Inc. These materials may also be described as polymers of 2-oxepanone and 1,4-butanediol.

[0017] The polycaprolactone polyester polyols can be prepared from 2-oxepanone and a diol, which 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 polycaprolactone polyester polyol has a number average molecular weight of 500 to 10,000, or 500 to 5,000, or 1,000, or even 2,000 to 4,000, or even 3,000.

[0018] In one embodiment, the polyol component may include a polyether polyol. Suitable polyether polyol intermediates include polyether polyols derived from alkyl diols or glycols reacted with ethers including diols or polyols having a total of 2 to 15 carbon atoms, and in some embodiments, 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 are therefore preferred. Useful commercially available polyether polyols include poly(ethylene glycol) comprising ethylene oxide reacted with ethylene glycol, poly(propylene glycol) comprising propylene oxide reacted with propylene glycol, and poly(tetramethylene ether glycol) comprising water reacted with tetrahydrofuran (sometimes described as polymerized tetrahydrofuran, commonly referred to as polymerized tetrahydrofuran, PTMEG). In some embodiments, the polyether intermediate comprises PTMEG. Suitable polyether polyols also include polyamide adducts of alkylene oxides, such as ethylenediamine adducts including the reaction product of ethylenediamine and propylene oxide, diethylenetriamine adducts including the reaction product of diethylenetriamine and propylene oxide, and similar polyamide-type polyether polyols. Copolyethers can also be utilized in the described compositions. Exemplary copolyethers include the reaction products of THF and ethylene oxide or THF and propylene oxide. These are available from BASF as block copolymers PolyTHF® B and random copolymers PolyTHF® R.The various polyether intermediates generally have a number average molecular weight (Mn) as determined by assay of the terminal functional groups that is an average molecular weight greater than about 700, such as from about 700 to about 10,000, from about 1,000 to about 5,000, or from about 1,000 to about 2,500. In some embodiments, the polyether intermediate comprises a blend of two or more different molecular weight polyethers, such as a blend of PTMEG with Mn 2000 and Mn 1000.

[0019] In one embodiment, the polyol component may include a polysiloxane polyol. Suitable polysiloxane polyols include α-ω-hydroxyl or amine or carboxylic acid or thiol or epoxy terminated polysiloxanes. Examples include poly(dimethylsiloxanes) terminated with hydroxyl or amine or carboxylic acid or thiol or epoxy groups. In some embodiments, the polysiloxane polyol is a hydroxyl terminated polysiloxane. In some embodiments, the polysiloxane polyol has a number average molecular weight in the range of 300 to 5,000 or 400 to 3,000.

[0020] Polysiloxane polyols can be obtained by introducing alcoholic hydroxy groups into the polysiloxane skeleton by a dehydrogenation reaction between a polysiloxane hydride and an aliphatic polyhydric alcohol or a polyoxyalkylene alcohol.

[0021] In some embodiments, the polysiloxane may be represented by one or more compounds having the following formula:

[0022] [ka] (wherein each R1 and R2 is independently an alkyl group of 1 to 4 carbon atoms, a benzyl group, or a phenyl group; and each E is OH or NHR 3 (In the formula, R 3is hydrogen, an alkyl group of 1 to 6 carbon atoms, or a cycloalkyl group of 5 to 8 carbon atoms, a and b are each independently an integer of 2 to 8, and c is an integer of 3 to 50. In the amino-containing polysiloxane, 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, R 1 and R 2 are both methyl groups.

[0023] Suitable examples include α,ω-hydroxypropyl-terminated poly(dimethylsiloxane) and α,ω-aminopropyl-terminated poly(dimethylsiloxane), both of which are commercially available materials. Further examples include copolymers of poly(dimethylsiloxane) materials with poly(alkylene oxides).

[0024] The polyol component, if present, may include poly(ethylene glycol), poly(tetramethylene ether glycol), poly(trimethylene oxide), ethylene oxide-capped poly(propylene glycol), poly(butylene adipate), poly(ethylene adipate), poly(hexamethylene adipate), poly(tetramethylene-co-hexamethylene adipate), poly(3-methyl-1,5-pentamethylene adipate), polycaprolactone diol, poly(hexamethylene carbonate) glycol, poly(pentamethylene carbonate) glycol, poly(trimethylene carbonate) glycol, dimeric fatty acid based polyester polyols, vegetable oil based polyols, or any combination thereof.

[0025] Examples of dimer fatty acids that can be used to prepare suitable polyester polyols include Priplast™ polyester glycols / polyols available from Croda, and Radia® polyester glycols available from Oleon.

[0026] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises from about 70% to about 85% by weight, for example, from about 80% to about 85% by weight, of the polyol component.

[0027] Chain extender component The TPU compositions described herein are made using a chain extender component. Suitable chain extenders include diols, diamines, and combinations thereof.

[0028] 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 ((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), hi another embodiment, the chain extender comprises or consists of 1,3-propanediol.

[0029] 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 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 or completely free of aromatic diisocyanates. In some embodiments, a mixture of aliphatic and aromatic diisocyanates may be useful.

[0030] 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 aromatic diisocyanates such as 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CDI), and the like. 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 (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 an aromatic diisocyanate. In some embodiments, the isocyanate component comprises or consists of MDI.

[0031] The combined weight percentage of the diisocyanate and chain extender components in the TPU composition is referred to as the “hard segment content.” In one embodiment of the present invention, the TPU compositions useful in the present invention contain from 15% to 50%, or even from 20% to 35% by weight of hard segments.

[0032] Optionally, one or more polymerization catalysts may be present during the polymerization reaction of the TPU. In general, any conventional catalyst can be utilized to react the diisocyanate with the polyol intermediate or the chain extender. Examples of suitable catalysts that promote the reaction between the NCO group of the diisocyanate and the hydroxyl groups 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 particularly 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.

[0033] The reactive TPU composition used in the present invention may be made via a "one shot" process, where all ingredients are added together at the same time or substantially the same time 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, such as 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, such that the TPU has terminal hydroxyl groups to enhance reaction with the crosslinker during the fiber spinning process. The weight average molecular weight (MW) of the TPU is generally from about 25,000 to about 300,000, such as from about 50,000 to about 200,000, or even from about 75,000 to about 150,000.

[0034] In another embodiment, the TPU may be prepared using a prepolymer process. In the prepolymer process, a hydroxyl-terminated intermediate is reacted with a generally equivalent excess of one or more diisocyanates to form a prepolymer solution having free or unreacted isocyanates therein. A chain extender as described herein is then added in an amount generally 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, such as about 0.97 to about 1.03, or even 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 the crosslinking agent during the fiber spinning process. Typically, the prepolymer process can be carried out in any conventional device, such as an extruder.

[0035] 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, lactones and hydroxylamine compounds, biocides, fungicides, antimicrobial agents, compatibilizers, electrically dissipative or antistatic additives, fillers and reinforcing agents (e.g., titanium dioxide, alumina, clays 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 (MMA). butylacrylate, MBA)), 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 the conventional effective amounts of these materials.

[0036] These additional additives can be incorporated into the ingredients for the preparation of the TPU resin, into the reaction mixture for the preparation of 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.

[0037] Isocyanate-functional prepolymer crosslinker The reactive TPU composition described above is combined with an isocyanate-functional prepolymer crosslinker to make the melt-spun fibers of the present invention. The prepolymer crosslinker is the reaction product of a hydroxyl-terminated polyol that includes or consists of a second polycarbonate polyol or polycaprolactone polyol with an excess of a diisocyanate. The polycarbonate polyol or polycaprolactone polyol useful for forming the isocyanate-functional prepolymer crosslinker can be selected from those described herein for the TPU composition. For example, the polycarbonate polyol ε-caprolactone can be reacted with a difunctional initiator (e.g., diethylene glycol, 1,4-butanediol, neopentyl glycol, PTMEG, or any other glycol and / or diol known in the art). The diisocyanates useful for preparing the isocyanate-functional prepolymer crosslinker can also be selected from those described herein for the TPU composition. The prepolymer crosslinker has an isocyanate functionality of greater than 1.0, such as from about 1.5 to 2.5, further such as from about 1.8 to 2.2. Isocyanate-functional prepolymer 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.

[0038] Thermoplastic Polyurethane Fiber The thermoplastic polyurethane fibers of the present invention comprise from about 80% to about 95%, or even from about 85% to 90%, by weight of a reactive TPU as described herein, and from about 5% to about 20%, or even from about 10% to about 15%, by weight of an isocyanate-functional prepolymer crosslinker. The percentage of crosslinker used is a weight percent based on the total weight of the TPU and crosslinker.

[0039] 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 fibers, which are cooled and wound onto bobbins. The process includes the following steps: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of (a) a polyol component, the polyol component comprising or consisting 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 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, (8) optionally applying a finishing oil, and (9) winding the melt-spun fibers onto a bobbin core. The steps of this process are described in more detail below.

[0040] The melt spinning process begins with feeding preformed reactive TPU polymer into an extruder. The reactive TPU is melted in the extruder and the crosslinker is added downstream near the point where the TPU melt exits the extruder or continuously after the TPU melt has exited the extruder. If the crosslinker is added after the melt has exited the extruder, it needs to be mixed with the TPU melt using a static or dynamic mixer to ensure proper mixing of the crosslinker into the TPU polymer melt. After exiting the extruder and mixer, the molten TPU polymer with crosslinker flows into a manifold. The manifold splits the melt stream into different streams, each of which feeds into multiple spinnerets. Typically, there is a melt pump for each different stream flowing from the manifold, and each melt pump feeds into 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 holes in the spinneret depends on the desired size (denier) of the fiber. The fiber is stretched or drawn as it exits the spinneret and cooled before being wound onto the bobbin. The fiber is stretched by winding the bobbin at a speed greater than the speed of the fiber exiting the spinneret. For melt spun TPU fibers, the bobbin is typically wound at a speed greater than the speed of the fiber exiting the spinneret, for example, in some embodiments, 4 to 8 times the speed of the fiber exiting the spinneret, but may be wound slower or faster depending on the specific equipment. Typical bobbin winding speeds can vary from 100 to 3000 meters / minute, but more typical speeds are 300 to 1200 meters / minute for TPU melt spun fibers. A finishing oil, such as silicone oil, is usually added to the surface of the fiber after cooling and just before winding onto the bobbin.

[0041] An important aspect of the melt spinning process is the mixing of the TPU polymer melt with the crosslinker. Proper uniform mixing is important to achieve uniform fiber properties and achieve long run times without experiencing fiber breakage. The mixing of the TPU melt with the crosslinker should be in a manner that achieves plug flow, i.e., first in, first out. Proper mixing can be achieved using dynamic or static mixers. 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, with rotatable mixing pins.

[0042] The TPU reacts with the prepolymer crosslinker during the fiber spinning process to give a weight average molecular weight (MW) of the TPU in fiber form of about 50,000 Daltons to about 400,000 Daltons, preferably about 100,000 Daltons to about 300,000 Daltons. The reaction in the fiber spinning process between the TPU and the prepolymer crosslinker at the point where the TPU leaves the spinneret should be greater than 20%, preferably about 30% to about 60%, more preferably about 40% to about 50%. Typical prior art TPU melt spinning reaction between the TPU polymer and the crosslinker is less than 20%, usually about 10-15% reaction. The reaction is determined by the disappearance of NCO groups. The higher % reaction of the present invention improves the melt strength and therefore allows for higher spinning temperatures, which improves the spinnability of the TPU. The fiber is usually aged in an oven on the bobbin until the molecular weight levels off.

[0043] 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 1080, such as 10 to 240 denier, or even 20, 40, 70, and 140 denier.

[0044] The melt spun fibers made according to the present invention have 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.

[0045] Fabric The TPU fibers of the present invention can be combined with other fibers, natural or synthetic, by knitting or weaving the fibers to create fabrics that can be used in a variety of articles. It may be desirable to dye such fabrics in a variety of colors.

[0046] The melt spun TPU fibers of the present invention can be combined with other fibers, such as different TPU fibers, cotton, nylon, or polyester, to make a variety of end-use articles, including apparel garments.

[0047] For example, a fabric according to the present invention may combine the melt spun TPU fibers of the present invention with different TPU fibers or yarns that are not made from TPU and have less elasticity than the TPU fibers of the present invention, also referred to herein as "hard yarns". The hard yarns may include, for example, different TPU fibers, polyester, nylon, cotton, wool, acrylic, polypropylene, or viscose rayon. In one embodiment, the hard yarns have an ultimate elongation of 10% to 200%, such as 10% to 75%, or even 10% to 50%, or even 10% to 30%, and the melt spun TPU fibers of the present invention have an ultimate elongation of at least 300%, such as 300% to 650%. Each of the fiber components may be included in the composition in an amount of 1 to 99% by weight. The weight percentage of the melt spun TPU fibers in the end use application may vary depending on the elasticity desired. For example, woven fabrics have 1-8% by weight, underwear 2-5% by weight, swimwear and sportswear 8-30% by weight, foundation 10-45% by weight, medical hose 35-60% by weight of melt-spun TPU fibers, and the remaining amount is rigid inelastic fibers. Fabrics made with these two fiber 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 can have a stretch of more than 50% or even more than 100% measured according to ASTM D4964.

[0048] In this application and in the examples which follow, reference is made to the following properties together with methods for measuring such properties. The tensile strength of the prepared films was measured according to ASTM D412. The tensile set of the prepared films was measured according to ASTM D412. Denier is a measure of linear density and is 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 D2653. · The ultimate elongation of the elastic filaments, which is the elongation at break, was also measured and reported according to ASTM D2653. 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 oleic acid chemical resistance of the comparative examples and inventive examples was measured and reported according to ASTM D543-20.

[0049] The invention will be better understood with reference to the following examples.

[0050] Working Example Table 1 lists the prepared TPU compositions used to initially make films in the present invention to evaluate chemical resistance.

[0051] [Table 1]

[0052] Upon exiting the extruder, the TPU candidates from Table 1 were subjected to chemical (oleic acid) exposure per ASTM D543-20 and the examples with the lowest loss in tensile strength were selected for fiber spinning. Table 2 compares the oleic acid resistance of the examples prepared from Table 1.

[0053] [Table 2] 1 Gel = The example labeled "Gel" turned into a complete gel unsuitable for testing any physical properties, suggesting very poor resistance to oleic acid due to plasticization. 2 Not tested

[0054] Examples G, H, L, and R were selected for fiber spinning due to the highest resistance to oleic acid and lowest loss in tensile set from Table 2. Examples G and H were selected for ease of processing during fiber spinning, although Examples M-T also provided chemical resistance.

[0055] For fiber spinning, 10 wt% of the prepolymer crosslinker listed correspondingly in Table 3 was mixed with the TPU polymer melt in a dynamic mixer (90 wt% TPU polymer melt / 10 wt% crosslinker) and then pumped through a manifold to the spinneret. The polymer stream exiting the spinneret was cooled with air, a silicone finish oil was applied, and the formed fiber was wound onto a bobbin. The fiber on the bobbin was heat aged at 80°C for 24 hours before testing the physical properties of the fiber. Table 3 summarizes the TPU and crosslinker combinations used to make the fibers.

[0056] [Table 3]

[0057] The data in Tables 4 and 5 illustrate that fiber examples prepared with polycarbonate-based TPU and polycarbonate-based prepolymer crosslinker and polycarbonate-based TPU and polycaprolactone-based prepolymer crosslinker unexpectedly exhibit the best performance after chemical exposure.

[0058] [Table 4]

[0059] [Table 5]

[0060] 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 reference of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled artisan in any jurisdiction. Except in the examples, or unless otherwise expressly indicated, all quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, should be understood as being modified by the word "about". It should be understood that the upper and lower limits of amounts, ranges, and ratios described herein can be independently combined. Similarly, the ranges and amounts for each element of the present invention can be used together with ranges or amounts for any of the other elements.

[0061] 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.

[0062] 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 without departing from the scope of the invention, which in this regard should be limited only by the scope of the claims that follow.

Claims

1. A melt-spun fiber comprising: (a) a reactive thermoplastic polyurethane composition, i. a polyol component, said polyol component comprising a first polycarbonate polyol; ii. a hydroxyl-terminated chain extender component; and a first diisocyanate component; and a reactive thermoplastic polyurethane composition comprising the reaction product of: (b) an isocyanate-functional prepolymer crosslinker comprising the reaction product of a second polycarbonate polyol and a second diisocyanate component; or (c) an isocyanate-functional prepolymer crosslinker comprising the reaction product of a polycaprolactone polyol and a second diisocyanate component.

2. 10. The melt-spun fiber of claim 1, wherein said polyol component comprises at least 60% of said first polycarbonate polyol.

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

4. 10. The melt spun fiber of claim 1, wherein the first polycarbonate polyol has a number average molecular weight of about 1000 to 3000 Daltons as determined by end group analysis, and optionally the first polycarbonate polyol is selected from 2-MPD carbonate, BDO-carbonate, DEG-carbonate, HDO-carbonate, or mixtures thereof.

5. 10. The melt-spun fiber of claim 1, wherein said polyol component consists of said first polycarbonate polyol.

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

7. 10. 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.

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

9. 10. 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.

10. 10. The melt-spun fiber of claim 1, wherein the polycaprolactone polyol comprises ε-caprolactone and can be reacted with a difunctional initiator, optionally the difunctional initiator being selected from diethylene glycol, 1,4-butanediol, neopentyl glycol, poly(tetramethylene ether glycol), or a mixture thereof.

11. 10. The melt-spun fiber of claim 1, wherein said reactive thermoplastic polyurethane composition contains 70% to 85% by weight of said first polycarbonate polyol component.

12. 10. The melt-spun fiber of claim 1, wherein the combined weight of the hydroxyl-terminated chain extender component and the first diisocyanate component constitutes the hard segments of the thermoplastic polyurethane composition, and the thermoplastic polyurethane composition has a hard segment content of 15% to 45% by weight.

13. 10. The melt-spun fiber of claim 1, wherein said isocyanate-functional prepolymer crosslinker comprises the reaction product of 65% to 80% by weight of said second polycarbonate polyol and 20% to 35% by weight of said second diisocyanate component.

14. 10. The melt-spun fiber of claim 1 comprising 85% to 90% of said TPU and 10% to 15% of said prepolymer.

15. 10. The melt-spun fiber of claim 1, wherein the melt-spun thermoplastic polyurethane fiber has a weight average molecular weight of 100,000 to 300,000 daltons as determined by gas permeation chromatography.

16. 10. The melt-spun fiber of claim 1, wherein the thermoplastic polyurethane fiber is capable of retaining at least 80% of its original tensile properties, as measured according to ASTM D2653, after exposure to oleic acid, as measured by ASTM D543-20.

17. A fabric comprising the melt-spun fibers of claim 1.

18. 10. A process for preparing the melt-spun fibers of claim 1, comprising: (1) preparing a reactive thermoplastic polyurethane composition that is the reaction product of: (a) a polyol component, said polyol component comprising a 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; (4) adding an isocyanate-functional prepolymer into the extruder, the isocyanate-functional prepolymer comprising the reaction product of a second polycarbonate polyol or polycaprolactone polyol 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) optionally applying a finishing oil; (9) winding the melt-spun fibers onto a bobbin.