Polyurethane elastic fiber and its manufacturing method

Abstract

The present invention provides a material recycled polyurethane elastic fiber and a method for producing the same, which uses, as raw materials, recovered fabrics containing polyurethane fibers and final products. The material recycled polyurethane elastic fiber is made of recovered fabrics containing polyurethane fibers, and the components separated by solvent extraction separation of the fabric are used, as at least a part of the raw materials.

Description

[Technical field]

[0001] The present invention relates to a polyurethane elastic fiber, and more particularly to a polyurethane elastic fiber using recycled polyurethane elastic fiber as at least a part of the raw material, and a method for producing the same. [Background technology]

[0002] In recent years, there has been a demand for contributions to the Sustainable Development Goals (SDGs), and recycling resource utilization is a top priority issue for all industrial products. For example, for polyurethane elastic fibers, there is a known technology for recovering and recycling fiber waste generated during the manufacturing process and necessary fibers from used products. As shown in Patent Documents 1 and 2, the technology for dissolving and recycling fiber waste has been known for a long time. In addition, as shown in Patent Documents 3 and 4, a technology for producing cascade-type recycled yarn in which polyurethane material is broken down as a raw material and then dissolved using a solvent has been discovered in recent years.

[0003] However, in the horizontal recycling of polyurethane elastic fiber to polyurethane elastic fiber, there are problems specific to polyurethane elastic fiber. For example, although there was a concept of recovering polyurethane from a wound polyurethane elastic fiber in the process, there was no concept of recovering polyurethane from fabrics containing polyurethane elastic fiber. This is because the content of polyurethane elastic fiber in fabrics is small, and the concept of recovery was not reached. In addition, the conventional thinking has been that pulverization is essential to effectively recover polyurethane (Patent Document 3). Furthermore, the method of Patent Document 3 sometimes reduced the recovery rate and properties of polyurethane elastic fiber from recovered fabrics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 56-122836 [Patent Document 2] Special Publication No. 57-42657 [Patent Document 3] Publication number CN101096781 [Patent Document 4] Special Publication No. 2002-538314 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a polyurethane elastic fiber containing polyurethane by material recycling. More specifically, the object of the present invention is to provide a material recycled polyurethane elastic fiber and a manufacturing method thereof that enable efficient fiber-to-fiber recycling in which recovered fabrics and final products containing polyurethane fibers are used as raw materials and reused for the same material and application as horizontal recycling. [Means for solving the problem]

[0006] When polyurethane is recovered from a recovered fabric containing polyurethane elastic fiber itself as a raw material, it is necessary to separate the polyurethane from other fibers such as nylon and polyester. In addition, if chemical recycling or material recycling is performed on the remaining recovered fabric after polyurethane recovery, it is desirable that the polyurethane in the recovered fabric is recovered at the highest possible recovery rate and that no polyurethane remains in the remaining recovered fabric. In response to these, the present inventors have found that by using a solvent extraction separation method, polyurethane can be easily separated from fibers other than polyurethane and polyurethane can be obtained at a high recovery rate. They have also found that by blending polyurethane recovered with high accuracy with a virgin polymer, it is possible to obtain polyurethane elastic fiber containing recycled polyurethane, which also enables horizontal recycling of polyurethane elastic fiber.

[0007] That is, the present invention has the following configuration. (1) Material recycled polyurethane elastic fiber, in which recovered fabrics containing polyurethane fibers are used as at least a part of the raw material. (2) The polyurethane elastic fiber according to (1), wherein a component separated by solvent extraction separation of the fabric is used as at least a part of the raw material. (3) The polyurethane elastic fiber according to (2), wherein the fabric is used at least as a part of the raw material without being pulverized. (4) The polyurethane elastic fiber according to (2) or (3), wherein the components separated by the solvent extraction separation are separated via centrifugation. (5) The polyurethane elastic fiber according to (4), wherein the centrifugation is carried out using a dry cleaning machine. (6) The polyurethane elastic fiber according to any one of (2) to (5), wherein the bath ratio (solvent mass:fabric mass) in the solvent extraction separation is in the range of 3:1 to 50:1. (7) The polyurethane elastic fiber according to any one of (2) to (6), wherein the temperature of the solvent extraction separation is in the range of the freezing point of the solvent +10°C to the boiling point of the solvent -10°C. (8) The polyurethane elastic fiber according to any one of (2) to (7), wherein the solvent used in the solvent extraction separation has a flash point of 30° C. or higher or has no flash point and is nonflammable. (9) The polyurethane elastic fiber according to any one of (2) to (8), wherein the solvent for the solvent extraction separation is any one of dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, and diethylformamide. (10) The polyurethane elastic fiber according to any one of (2) to (9), wherein a surfactant is used in the solvent extraction separation. (11) The polyurethane elastic fiber according to any one of (2) to (10), wherein an amine is used in the solvent extraction separation. (12) A polyurethane elastic fiber according to any one of (2) to (11), wherein the polyurethane contained in the fabric has a number average molecular weight based on gel permeation chromatography (GPC) of 20,000 or more and 120,000 or less, and the detection intensity curve in the region of the molecular weight based on GPC of 30,000 or less has no peak or shoulder. (13) AνC=O 1730 based on the infrared spectrum (IR) of the polyurethane fiber contained in the fabric -1 / AνC=O 1710 -1 The polyurethane elastic fiber according to any one of (2) to (12), wherein the value is 1.05 or more and 1.50 or less. (14) The polyurethane elastic fiber according to any one of (2) to (13), wherein the fabric is used for clothing products that are washed frequently. (15) The polyurethane elastic fiber according to (14), wherein the fabric is used for underwear. (16) A method for producing material recycled polyurethane elastic fibers, comprising recovering a fabric containing polyurethane fibers and using the recovered fabric as at least a part of a raw material. (17) The method for producing a polyurethane elastic fiber according to (16), further comprising subjecting the recovered fabric to solvent extraction separation, and using the components separated by the solvent extraction separation as at least a part of the raw material. (18) The method for producing a polyurethane elastic fiber according to (17), wherein the recovered fabric is used at least as a part of the raw material without being pulverized. (19) The method for producing a polyurethane elastic fiber according to (17) or (18), wherein the components separated by the solvent extraction separation are separated via centrifugation. (20) The method for producing a polyurethane elastic fiber according to (19), wherein the centrifugation is carried out using a dry cleaning machine. (21) The method for producing a polyurethane elastic fiber according to any one of (17) to (20), wherein the solvent extraction separation is carried out in a bath ratio (solvent mass:fabric mass) in the range of 3:1 to 50:1. (22) The method for producing a polyurethane elastic fiber according to any one of (17) to (21), wherein the solvent extraction separation is carried out within a temperature range of from the freezing point of the solvent +10°C to the boiling point of the solvent -10°C. (23) The method for producing a polyurethane elastic fiber according to any one of (17) to (22), wherein a solvent having a flash point of 30° C. or higher, or having no flash point and being nonflammable, is used in the solvent extraction and separation. (24) The method for producing a polyurethane elastic fiber according to any one of (17) to (23), wherein any one of dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, and diethylformamide is used as a solvent for the solvent extraction separation. (25) The method for producing a polyurethane elastic fiber according to any one of (17) to (24), wherein a surfactant is used in the solvent extraction separation. (26) The method for producing a polyurethane elastic fiber according to any one of (17) to (25), wherein an amine is used for the solvent extraction separation. Effect of the Invention

[0008] According to the present invention, a high recovery rate of polyurethane can be achieved by using a recycled fabric containing polyurethane fiber as a raw material, particularly by performing solvent extraction separation. Furthermore, even if the polyurethane elastic fiber contains a large amount of recycled polyurethane, it is possible to provide a polyurethane elastic fiber that has sufficient functionality as a polyurethane elastic fiber. [Brief description of the drawings]

[0009] [Figure 1] 1 is a graph showing an example of measurement by GPC in Example 10. [Diagram 2] 13 is a graph showing an example of IR measurement in Example 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below with reference to the embodiments. First, the polyurethane used as the main component in the polyurethane elastic fiber of the present invention will be described. Here, the main component is a component contained in the polyurethane elastic fiber in an amount of more than 50% by mass.

[0011] The polyurethane used in the present invention may be any polyurethane having a structure starting from a polymer diol and a diisocyanate, and is not particularly limited. The synthesis method is also not particularly limited. That is, for example, it may be a polyurethane urea consisting of a polymer diol, a diisocyanate, and a low molecular weight diamine as a chain extender, or it may be a polyurethane urethane consisting of a polymer diol, a diisocyanate, and a low molecular weight diol as a chain extender. It may also be a polyurethane urea using a compound having a hydroxyl group and an amino group in the molecule as a chain extender. It is also preferable to use a polyfunctional glycol or isocyanate having three or more functionalities within a range that does not interfere with the effects of the present invention. Furthermore, the processing method is not particularly limited. That is, the polyurethane may be recycled through remolding and re-spinning.

[0012] The polymer diol is preferably a polyether-based diol, a polyester-based diol, a polycarbonate diol, etc. In particular, it is preferable to use a polyether-based diol from the viewpoint of imparting flexibility and elongation to the yarn.

[0013] As the polyether diol, for example, polyethylene oxide, polyethylene glycol, a derivative of polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol (hereinafter sometimes abbreviated as PTMG), modified PTMG which is a copolymer of tetrahydrofuran (hereinafter sometimes abbreviated as THF) and 3-methyltetrahydrofuran, modified PTMG which is a copolymer of THF and 2-methyltetrahydrofuran, modified PTMG which is a copolymer of THF and 2,3-dimethylTHF, polyols having side chains on both sides as disclosed in Japanese Patent No. 2615131, random copolymers in which THF and ethylene oxide and / or propylene oxide are irregularly arranged, etc. may be preferably used. These polyether diols may be used alone or in a mixture or copolymer of two or more kinds.

[0014] From the viewpoint of obtaining abrasion resistance and light resistance as a polyurethane elastic fiber, polyester diols such as butylene adipate, polycaprolactone diol, and polyester polyols having side chains disclosed in JP-A-61-26612 and polycarbonate diols disclosed in JP-B-2-289516 are preferably used.

[0015] Moreover, such polymer diols may be used alone, or two or more kinds may be mixed or copolymerized for use.

[0016] From the viewpoint of obtaining elongation, strength, heat resistance, etc. when made into a thread, the molecular weight of the polymer diol is preferably a number average molecular weight of 1,000 or more and 8,000 or less, and more preferably 1,500 or more and 6,000 or less. By using a polyol with a molecular weight in this range, an elastic thread excellent in elongation, strength, elastic recovery force, and heat resistance can be easily obtained.

[0017] Next, as diisocyanates, aromatic diisocyanates such as diphenylmethane diisocyanate (hereinafter sometimes abbreviated as MDI), tolylene diisocyanate, 1,4-diisocyanate benzene, xylylene diisocyanate, and 2,6-naphthalene diisocyanate are particularly suitable for synthesizing polyurethanes with high heat resistance and strength. Furthermore, as alicyclic diisocyanates, for example, methylene bis(cyclohexyl isocyanate), isophorone diisocyanate, methylcyclohexane 2,4-diisocyanate, methylcyclohexane 2,6-diisocyanate, cyclohexane 1,4-diisocyanate, hexahydroxylylene diisocyanate, hexahydrotolylene diisocyanate, and octahydro 1,5-naphthalene diisocyanate are preferred. Alicyclic diisocyanates can be used effectively, particularly when suppressing yellowing of polyurethane elastic yarn. These diisocyanates may be used alone or in combination of two or more.

[0018] The chain extender used in synthesizing polyurethane is preferably at least one of low molecular weight diamines and low molecular weight diols, although those having both a hydroxyl group and an amino group in one molecule, such as ethanolamine, may also be used.

[0019] Examples of preferred low molecular weight diamines include ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, hexamethylenediamine, p-phenylenediamine, p-xylylenediamine, m-xylylenediamine, p,p'-methylenedianiline, 1,3-cyclohexyldiamine, hexahydrometaphenylenediamine, 2-methylpentamethylenediamine, and bis(4-aminophenyl)phosphine oxide. It is preferable to use one or more of these. Ethylenediamine is particularly preferred. By using ethylenediamine, it is possible to easily obtain threads that are excellent in elongation, elastic recovery, and heat resistance. A triamine compound capable of forming a crosslinked structure, such as diethylenetriamine, may be added to these chain extenders to an extent that the effect is not lost.

[0020] Representative examples of low molecular weight diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, bishydroxyethoxybenzene, bishydroxyethylene terephthalate, and 1-methyl-1,2-ethanediol. It is preferable to use one or more of these. Ethylene glycol, 1,3-propanediol, and 1,4-butanediol are particularly preferable. When these are used, the heat resistance of the diol-extended polyurethane is increased, and a stronger thread can be obtained.

[0021] In the present invention, the molecular weight of the polyurethane is preferably in the range of 30,000 to 150,000 in terms of number average molecular weight, from the viewpoint of obtaining polyurethane elastic fibers having high durability and strength. The molecular weight is measured by GPC and converted into polystyrene.

[0022] It is also preferable to use one or more kinds of terminal blocking agents in combination for the polyurethane. Examples of the terminal blocking agent include monoamines such as dimethylamine, diisopropylamine, ethylmethylamine, diethylamine, methylpropylamine, isopropylmethylamine, diisopropylamine, butylmethylamine, isobutylmethylamine, isopentylmethylamine, dibutylamine, and diamylamine, monools such as ethanol, propanol, butanol, isopropanol, allyl alcohol, and cyclopentanol, and monoisocyanates such as phenylisocyanate.

[0023] In the material recycled polyurethane elastic fiber according to the present invention, the polyurethane elastic fiber made of polyurethane having the above basic structure is constituted as a polyurethane elastic fiber using recycled polyurethane elastic fiber as at least a part of the raw material, and in the present invention, in particular, it is constituted as a polyurethane elastic fiber using recovered fabric containing polyurethane fiber as at least a part of the raw material. Here, the material recycled polyurethane elastic fiber includes those recovered from the form of fabric, those recovered from general consumer products such as underwear, and those recovered from repeated recycling. There is no particular limitation on the recovery method, and recycled polyurethane elastic fiber recovered by any method is included.

[0024] In the present invention, material recycling refers to reusing the polyurethane of recovered polyurethane elastic fibers as a raw material for new polyurethane elastic fibers without reducing the molecular weight or converting the polyurethane into monomers.

[0025] In the polyurethane elastic fiber of the present invention, the polyurethane fiber-containing recovered fabric is used as at least a part of the raw material, and the first characteristic of the specific form of the polyurethane elastic fiber is that it is recovered by solvent extraction separation. The solvent extraction separation of the present invention refers to a method of selectively recovering the polyurethane elastic fiber without crushing the recovered fabric by selectively using a solvent that can dissolve the polyurethane elastic fiber present in the recovered fabric and the like and does not dissolve other fibers such as the recovered fabric.

[0026] From the standpoint of safety and affinity with polyurethane, the solvent used in this solvent extraction separation may be any solvent that has a flash point of 30°C or higher or has no flash point and is non-flammable. However, from the standpoint of solubility with polyurethane elastic fibers in particular, it is preferable to use any of the following: dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, or diethylformamide.

[0027] In the present invention, "without crushing the fabric" means that, for example, in the case of an apparel product, the apparel product itself is subjected to solvent extraction without being cut. 2 Less than 0.5m, more preferably 0.5m 2 In addition, when it comes to underwear and other apparel products, products that are usually S, M, L sizes should not be cut, as cutting can cause problems such as filtering fiber waste, which can affect the physical properties of the polyurethane elastic fiber, mainly resulting in a decrease in breaking strength and elongation.

[0028] The fabric in the present invention mainly refers to a mixed fabric with any fiber, regardless of the content of polyurethane. However, it may be a fabric composed only of polyurethane elastic fibers. Examples of fibers other than polyurethane in the mixed fabric include, for example, representative synthetic fibers such as polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, polytetramethylene glycol terephthalate, or polyester fibers obtained from polyester resins mainly composed of these structural units and copolymerized with other copolymerization components, and polyethylene terephthalate fibers are preferred, that is, fibers whose main polymer is polyethylene terephthalate or copolymerized polyethylene terephthalate. For example, fibers made of polyethylene terephthalate, polybutylene terephthalate, or ethylene terephthalate units as the main repeating components (specifically, 90 mol% or more of the repeating units), butylene terephthalate units as the main repeating components (specifically, 90 mol% or more of the repeating units), etc. can be preferably used. Among them, fibers made of polyesters containing 90 mol% or more of ethylene terephthalate units as repeating components are preferred, and fibers made of polyesters containing 95 mol% or more of ethylene terephthalate units as repeating components are more preferred. Fibers made of polyesters containing 100 mol% of ethylene terephthalate units as repeating components (i.e., polyethylene terephthalate) are even more preferred. These polyethylene terephthalate-based fibers have good texture and luster, and are easy to care for, such as wrinkle resistance, and are suitable as fiber materials for constituting elastic fabrics. In addition, polyethylene terephthalate-based fibers are suitable when used in combination with polyurethane urea-based elastic yarns, which are preferably used in the present invention, and can be used to make good stretch fabrics. Representative examples of semi-synthetic and natural fibers include cellulose fibers. Examples of the cellulose fibers include natural cellulose fibers such as cotton and hemp, regenerated cellulose fibers such as rayon, semi-synthetic cellulose fibers, and so-called non-designated fibers (lyocell, cupra).

[0029] Furthermore, the number of types of fibers to be mixed is preferably as small as possible, preferably 6 or less, more preferably 3, and most preferably 2. For example, a fabric made of a mixture of two types of fibers, polyurethane elastic fiber and polyester fiber.

[0030] In carrying out the above-mentioned solvent extraction separation, in order to recover polyurethane elastic fibers in a higher yield, the liquor ratio (solvent mass:fabric mass) is preferably in the range of 3:1 to 50:1. More preferably, it is in the range of 5:1 to 20:1. In addition, from the viewpoint of recovering polyurethane elastic fibers in a higher yield, the temperature during the solvent extraction separation is preferably in the range of the solvent's freezing point +10°C to the solvent's boiling point -10°C. Specifically, from the viewpoint of operability and suppressing the outflow of low molecular weight compounds such as dyes in the fabric, the solvent temperature is preferably in the range of 20°C to 50°C. More preferably, it is 30 to 40°C.

[0031] To further improve the recovery rate of polyurethane elastic fiber in the solvent extraction separation, a surfactant may be used as an additive. The surfactant has a high affinity with polyurethane, and is quickly absorbed into the polyurethane, significantly improving the solubility of the polyurethane in the solvent. In addition to significantly improving the solubility, the surfactant can reduce the effect of metal soaps that accumulate during recycling. When the surfactant content in the yarn is in the range of 0.003% by mass or more and 0.5% by mass or less, the polyurethane elastic fiber has practically preferable properties, particularly a preferable wound yarn shape and breaking strength and elongation.

[0032] More specifically, the surfactant used may be a nonionic surfactant, an anionic surfactant, or a cationic surfactant. Examples of the nonionic surfactant used in the present invention include polyoxyethylene alkyl ether, alkyl monoglyceryl ether, polyoxyethylene alkylamine, fatty acid sorbitan ester, and fatty acid diethanolamide. Of these, the hydrophilic part (Hydrophil) of the surfactant is preferably an ether type, and is preferably at least one of ethylene oxide polymer, propylene oxide polymer, and copolymer of ethylene oxide and propylene oxide. By containing at least one of terminal modified derivatives of ethylene oxide polymer, terminal modified derivatives of propylene oxide polymer, and terminal modified derivatives of copolymer of ethylene oxide and propylene oxide as a nonionic surfactant, it is possible to improve the spinnability while, for example, improving the antibacterial property. The so-called hydrophobic portion of the surfactant is the aforementioned terminal modified structure, and is preferably an alkyl group, a phenyl group, or a styrenated phenyl group. Specific examples of nonionic surfactants include polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene ethylphenol ether, polyoxyethylene propylphenol ether, polyoxyethylene styrenated phenyl ether, and polyoxyethylene sorbitol tetraoleate. More preferred is polyoxyethylene styrenated phenyl ether, and examples thereof include polyoxyethylene oxypropylene tristyrenated phenyl ether, polyoxyethylene oxypropylene distyrenated phenyl ether, polyoxyethylene oxypropylene monostyrenated phenyl ether, polyoxyethylene oxypropylene-2,4,6-tris(α,α-dimethylbenzyl)phenyl ether, polyoxyethylene oxypropylene-2,4-bis(α,α-dimethylbenzyl)phenyl ether, polyoxyethylene oxypropylene-2-mono(α,α-dimethylbenzyl)phenyl ether, and polyoxyethylene oxypropylene-4-mono(α,α-dimethylbenzyl)phenyl ether.Most preferably, the number of moles of these styrene groups added has a distribution and a mixture of these is used.

[0033] In order to further improve the recovery rate of polyurethane elastic fiber in the solvent extraction separation, an amine may be used as an additive. Examples of the amine to be used include ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, hexamethylenediamine, p-phenylenediamine, p-xylylenediamine, m-xylylenediamine, p,p'-methylenedianiline, 1,3-cyclohexyldiamine, hexahydrometaphenylenediamine, 2-methylpentamethylenediamine, and bis(4-aminophenyl)phosphine oxide. It is preferable to use one or more of these.

[0034] After the above-mentioned solvent extraction separation, it is preferable to use centrifugation to separate the solution of the polyurethane elastic fiber from the recovered fabric. As a specific method of centrifugation, it is preferable to use a dry cleaning machine.

[0035] In the present invention, centrifugation refers to separation using the difference in specific gravity between the solution of polyurethane elastic fiber and the recovered fabric by using centrifugal force. The device used in this case may be any device that generates a slight centrifugal force, such as a washing machine, or a device that generates a strong centrifugal force, such as a centrifuge or ultracentrifuge. The device preferably has a rotation speed in the range of 20 to 5000 rpm, and more preferably a rotation speed in the range of 250 to 750 rpm, such as the deliquor rotation of a dry cleaning machine.

[0036] When the polyurethane elastic fiber of the present invention contains a surfactant, it is preferable that the surfactant content is 0.003% by mass or more and 3.0% by mass or less. The surfactant can reduce the effect of metal soap that accumulates due to recycling, and the surfactant has an appropriate sustained release property and light accumulation during the use of the polyurethane elastic fiber. When the surfactant content is within this range, the polyurethane elastic fiber has practically preferable properties, particularly preferable unwinding property (unwinding tension), wound yarn shape, and breaking strength and elongation, are ensured. The surfactant content is more preferably in the range of 0.03% by mass or more and 2.5% by mass or less, and even more preferably in the range of 0.3% by mass or more and 2.0% by mass or less.

[0037] The surfactant content of the recycled polyurethane elastic fiber recovered and used as a raw material is preferably in the range of 0.003% by mass to 0.5% by mass. When the surfactant content of the recycled polyurethane elastic fiber is within this range, the surfactant content contained in the polyurethane elastic fiber finally produced can be easily controlled to the desired surfactant content described above. The surfactant content of the recycled polyurethane elastic fiber is more preferably in the range of 0.03% by mass to 0.25% by mass, and even more preferably in the range of 0.05% by mass to 0.2% by mass.

[0038] In the present invention, when a cationic surfactant, a quaternary ammonium salt, is used in combination, the antibacterial activity differs depending on the chain length of the alkyl group in the ammonium ion, and one with a strong antibacterial activity is desirable. However, from the viewpoint of suppressing thermal decomposition due to heat exposure during the production of polyurethane elastic yarn, it is preferable to select a chain type such as an alkyl group, such as an alkyl group with a large chain length, i.e., an alkyl group with a large number of carbon atoms. In addition, it is preferable to contain an antibacterial agent from the viewpoint of hygiene, for recycling from old clothes, etc. From this viewpoint, particularly preferred ammonium ions are didecyldimethylammonium ion, oleyltrimethylammonium ion, etc. These are usually supplied by inorganic salts such as chlorides, bromides, and iodides, and organic salts such as sulfonates, carboxylates, and phosphates. Among these, sulfonates and carboxylates are preferred from the viewpoint of stability such as discoloration and heat resistance.

[0039] Specific examples of salts having the above structure are didecyldimethylammonium trifluoride methylsulfonate, di-n-decyldimethylammonium trifluoromethanesulfonate, di-n-decyldimethylammonium pentafluoroethanesulfonate, n-hexadecyltrimethylammonium trifluoromethanesulfonate, and benzyldimethylcocoalkylammonium pentafluoroethanesulfonate.

[0040] From the viewpoint of exerting antibacterial properties and maintaining a balance between discoloration and stretch properties, the quaternary ammonium salt-based antibacterial agent is preferably contained in an amount of 0.1% by mass to 5% by mass based on the total mass of the polyurethane elastic yarn.

[0041] When the polyurethane elastic fiber of the present invention contains an antioxidant, the content is preferably 0.002% by mass or more and 5.0% by mass or less. When the content of the antioxidant is within this range, the properties of the polyurethane elastic fiber are practically preferable, and a particularly preferred antioxidant is a hindered phenol compound, such as a phenol compound generally known as an antioxidant.For example, 3,5-di-t-butyl-4-hydroxy-toluene, n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,3,5-trimethyl-2,4,6'-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, calcium (3,5-di-t-butyl-4-hydroxy-benzyl-monoethyl-phosphate), triethylene glycol-bis[3-( 3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, tocopherol, 2,2'-ethylidenebis(4,6-di-t-butylphenol), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-oxamidebis[ethyl-3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate], 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, ethylene-1,2-bis(3,3-bis[3-t-butyl-4-hydroxyphenyl]butyrate), ethylene-1,2-bis(3-[3-t-butyl-4-hydroxyphenyl]butyrate), 1,1-bis(2-methyl-5-t-butyl-4-hydroxyphenyl)butane, 1,1,3-tris(2-methyl-5-t-butyl-4-hydroxyphenyl)butane, 1,3,5-tris(3',5'-di-t Also suitable are 1,3,5-tris(3'-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3'-t-butyl-4'-hydroxy-5-methylbenzyl)-S-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and furthermore high molecular weight hindered phenol compounds which are known as antioxidants for polyurethane elastic yarns.

[0042] Specific preferred examples of such high molecular weight hindered phenol compounds include addition polymers of divinylbenzene and cresol, addition polymers of dicyclopentadiene and cresol, isobutylene adducts, and polymers of chloromethylstyrene and compounds such as cresol, ethylphenol, and t-butylphenol. Here, divinylbenzene and chloromethylstyrene may be p- or m-. Cresol, ethylphenol, and t-butylphenol may be any of o-, m-, and p-.

[0043] Among them, from the viewpoint of stabilizing the viscosity of the raw material spinning solution of polyurethane yarn, suppressing the volatilization loss during spinning, and obtaining good spinnability, it is preferable to use a compound having a molecular weight of 300 or more. Furthermore, in order to efficiently exhibit a high spinning speed, heat resistance during dyeing, resistance to unsaturated fatty acids, and resistance to heavy metals, it is preferable to use any one of 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], ethylene-1,2-bis(3,3-bis[3-t-butyl-4-hydroxyphenyl]butyrate), and an adduct of divinylbenzene and p-cresol having a repeat number of 6 to 12, or a combination of them. Among them, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione is particularly preferred. In addition, when triazine compounds are selected as compound (a) and compound (c), a particularly high synergistic effect can be obtained in terms of heat resistance during dyeing. Among them, it is particularly preferred that compound (a) is 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and compound (c) is 2,4-di(2',4'-dimethylphenyl)-6-(2"-hydroxy-4"-alkoxyphenyl)-1,3,5-triazine.

[0044] Furthermore, the polyurethane elastic yarn of the present invention preferably contains a singly hindered phenol compound from the viewpoint of suppressing deterioration of properties due to recycling, particularly from the viewpoint of suppressing breaking strength / elongation and discoloration. The singly hindered phenol compound is preferably a compound containing at least two singly hindered hydroxyphenyl groups and having a skeleton selected from bisester and alkylidene. Here, it is more preferable that the alkyl group present at the ring position adjacent to the hydroxyl group in the hydroxyphenyl group is a tertiary butyl group, and it is even more preferable that the equivalent weight of the hydroxyl group is 600 or less.

[0045] Furthermore, the phenol compound in the present invention is preferably a singly hindered phenol compound. For example, a singly hindered phenol compound is preferably ethylene-1,2-bis(3,3-bis[3-t-butyl-4-hydroxyphenyl]butyrate) (chemical formula 1 below) having a structure in which a singly hindered hydroxyphenyl group is covalently bonded to a bisester skeleton.

[0046] [ka]

[0047] By including the above-mentioned single hindered phenol compound, the effect of suppressing the deterioration of properties due to recycling can be enhanced. This type of hindered phenol compound is effective in the case of underwear and the like, which is washed and bleached frequently, because it specifically contributes to suppressing the molecular weight of polyurethane constituting the polyurethane elastic fiber. In order to ensure this effect sufficiently and not to adversely affect the physical properties of the fiber, the single hindered phenol compound is preferably included in the polyurethane elastic yarn at 0.15 to 4 mass %. It is more preferable to include 0.5 to 3.5 mass %, and the breaking strength and elongation, composite durability, yellowing resistance, and light resistance in some cases are ensured. The content of the antioxidant is more preferably in the range of 0.2 mass % to 3.0 mass %. It is even more preferable to include 0.5 mass % to 2.0 mass %.

[0048] The content of the antioxidant in the recycled polyurethane elastic fiber recovered and used as a raw material is preferably in the range of 0.1% by mass to 5.0% by mass. When the content of the antioxidant in the recycled polyurethane elastic fiber is within this range, the content of the antioxidant contained in the polyurethane elastic fiber finally produced can be easily controlled to the above-mentioned desired content of the antioxidant. The content of the antioxidant in the recycled polyurethane elastic fiber is more preferably in the range of 0.2% by mass to 3.0% by mass, and even more preferably in the range of 0.5% by mass to 2.0% by mass.

[0049] The antioxidant contained is more specifically a hindered phenol compound having a molecular weight of 1000 or more, and a hindered phenol compound having a molecular weight of 1,000 or more, which is known as an antioxidant for polyurethane elastic yarn, is preferably used. There is no particular restriction other than the relatively high molecular weight of 1,000 or more, and preferred examples of such high molecular weight hindered phenol compounds include addition polymers of divinylbenzene and cresol, addition polymers of dicyclopentadiene and cresol, isobutylene adducts, and polymers of chloromethylstyrene and compounds such as cresol, ethylphenol, and t-butylphenol. Here, divinylbenzene and chloromethylstyrene may be p- or m-. Cresol, ethylphenol, and t-butylphenol may be any of o-, m-, and p-.

[0050] Among them, from the viewpoint of stabilizing the viscosity of the raw material spinning solution for polyurethane yarn and obtaining good spinnability, a polymer hindered phenol compound derived from cresol is preferable. Furthermore, in order to efficiently exhibit a high spinning speed, heat resistance during dyeing, resistance to unsaturated fatty acids, and resistance to heavy metals, it is preferable to contain a certain amount of the high molecular weight hindered phenol compound. However, from the viewpoint of obtaining better basic physical properties as a polyurethane yarn, it is preferable that the amount is not too much.

[0051] When the polyurethane elastic fiber of the present invention contains a tertiary amine compound, the content is preferably 0.2% by mass or more and 5.0% by mass or less. When the content of the tertiary amine compound is within this range, the properties of the polyurethane elastic fiber that are practically preferable, such as spinnability, dyeability, durability, and yellowing resistance, are improved.

[0052] The tertiary amine compound used in the present invention is not particularly limited as long as it has an amino group in its structure. However, from the viewpoint of the chlorine deterioration resistance and yellowing of the polyurethane elastic yarn, it is particularly preferable to use a compound having only a tertiary amino group in the molecule among the primary to tertiary amino groups.

[0053] If the number average molecular weight of the tertiary amine compound is less than 2,000, the water repellency is deteriorated due to the fact that the compound falls off due to rubbing against guides or knitting needles during knitting of polyurethane elastic yarn, or flows out during processing in a bath such as dyeing. Therefore, the number average molecular weight must be 2,000 or more. In consideration of the solubility in the polyurethane spinning dope, the number average molecular weight is preferably in the range of 2,000 to 10,000. More preferably, the number average molecular weight is in the range of 2,000 to 4,000.

[0054] By including a tertiary amine compound, the recyclability, particularly the yellowing prevention performance, of the polyurethane elastic yarn can be improved. In order to obtain this effect sufficiently and not to adversely affect the physical properties of the fiber, the tertiary amine compound is preferably included in an amount of 0.2% by mass or more and 5.0% by mass or less based on the fiber mass. More preferably, the amount is 0.5% by mass or more and 4.0% by mass or less. The more preferred content of the tertiary amine compound is in the range of 0.5% by mass or more and 3.0% by mass or less. Still more preferably, the content is in the range of 0.5% by mass or more and 2.0% by mass or less.

[0055] More specifically, the tertiary amine compound contained therein may be a linear polymeric compound having a number average molecular weight of 2000 or more obtained by reacting t-butyldiethanolamine with methylene-bis-(4-cyclohexylisocyanate), polyethyleneimine, or a high molecular weight compound having a branched structure containing a primary amino group, a secondary amino group, and a tertiary amino group in the molecular skeleton.

[0056] As a typical example, in the case of recycling in which non-standard fibers for industrial products due to some defect immediately after production, i.e., waste yarn, are blended at a high concentration, if this is repeated, the breaking strength and elongation decrease significantly. In order to avoid such a decrease in properties, it is effective to blend a polyurethane source containing a high molecular weight tertiary amine compound, its decomposition product, a high molecular weight antioxidant, and a low content of its decomposition product, as described above, to reduce the concentration of additives contained. As an index, it is preferable to blend a polyurethane having a number average molecular weight based on gel permeation chromatography (GPC) of 20,000 to 120,000 and no peak or shoulder in the detection intensity curve in the region of the molecular weight based on GPC of 30,000 or less. In consideration of the breaking strength and elongation of polyurethane elastic fiber, the number average molecular weight is preferably in the range of 30,000 to 100,000. More preferably, it is in the range of 40,000 to 80,000. The detection intensity curve is a differential molecular weight distribution curve (the horizontal axis is molecular weight, and the vertical axis is the value obtained by differentiating the concentration fraction by the logarithm of the molecular weight), and the shoulder is the shoulder peak.

[0057] In the present invention, the molecular weight of the polyurethane elastic fiber using the recycled polyurethane elastic fiber as a part of the raw material may be in the range of 10,000 to 50,000 in terms of number average molecular weight when a tertiary amine compound having a number average molecular weight in the range of 2,000 to 10,000 or a preferably used antioxidant having a molecular weight of 1,000 or more is blended. The molecular weight is measured by GPC and converted into polystyrene.

[0058] Furthermore, the absorbance of the carbonyl stretching vibration of the urethane bond based on the infrared spectrum (IR) of the recycled polyurethane elastic fiber, AνC=O 1730cm -1 and AνC=O 1710cm -1 About AνC=O 1730cm -1 AνC=O 1710cm -1 Ratio, i.e., AνC=O 1730 cm -1 / AνC=O 1710 cm -1 It is more preferable to compound a polyurethane having a value of 1.05 or more and 1.50 or less.

[0059] Such a source of recycled polyurethane raw material is more preferable when the application is achieved in clothing products that are washed frequently. In many cases, this can be achieved by using used underwear, i.e., undergarments, collected from the city. The reason for this is that they are repeatedly washed with anionic surfactants, which makes them suitable for use as raw materials for recycled polyurethane elastic fibers. EXAMPLES

[0060] (Examples 1 to 10, Comparative Examples 1 to 8) The production and evaluation of polyurethane elastic fibers obtained by recovering polyurethane from recovered fabrics and adding recycled polyurethane fibers will be described below for Examples 1 to 10 and Comparative Examples 1 to 8 shown in Table 1.

[0061] <Production of dry-spun polyurethane elastic fibers> In Comparative Example 1, a N,N'-dimethylacetamide (hereinafter abbreviated as DMAc) solution (35% by mass) of polyurethane composed of tetramethylene ether glycol having a molecular weight of 2,000, bis-(p-isocyanatephenyl)-methane and ethylenediamine was polymerized to obtain a polymer solution PUU1.

[0062] Next, a 1:1 (mass ratio) mixture of polyurethane (DuPont's "Methachlor" (registered trademark) 2462) produced by the reaction of t-butyldiethanolamine with methylene-bis-(4-cyclohexylisocyanate) and a condensation polymer of p-cresol and divinylbenzene (DuPont's "Methachlor" (registered trademark) 2390) was used as an antioxidant. A DMAc solution (35 mass%) of this mixture was prepared and used as additive solution (B).

[0063] The above solution PUU1, additive solution (B), and ethylenediamine (C) were uniformly mixed at 99 mass %, 1.0 mass %, and 0.1 mass %, respectively, to obtain a spinning solution (D).

[0064] The spinning solution thus obtained was dry-spun at a dry nitrogen temperature of 300°C or higher so that the DMAc in the spinning solution and the floating ethylenediamine were 1 / 100 or less of the spinning solution content. At this time, the speed ratio of the godet roller and the winder was set to 1:1.20, and a multifilament polyurethane elastic fiber of 22 dtex / 3fil was spun. A treatment agent (oil agent) described later was applied by a preliminary winding oiling roller, and the fiber was wound using a surface drive winder at a winding speed of 600 m / min on a cylindrical paper tube of 58 mm in length through a traverse guide that gave a winding width of 38 mm. 500 g of wound yarn was obtained as a dry-spun polyurethane elastic fiber. The obtained polyurethane elastic fiber was a fused yarn in which three filaments were fused together.

[0065] In Example 1, knitted fabric (shirt-like underwear sewn from circular knitted fabric that had been repeatedly washed) with a PU (polyurethane) content of 10% was used as a raw material, and DMAc and knitted fabric were added to a dry cleaning machine so that the bath ratio (solvent mass:fabric mass) was 5:1, and the mixture was stirred for 30 minutes at a solvent temperature of 25°C. After that, the mixture was centrifuged in the dry cleaning machine to obtain a polyurethane recovery solution, which was then added to the spinning solution (D) so that the recycled polymer content in the yarn was 20%. This was used as a spinning stock solution and spun in the same manner as in Comparative Example 1.

[0066] In Examples 2 to 9, polyurethane elastic fibers as shown in Table 1 were obtained in the same manner as in Example 1.

[0067] In Example 10, polyurethane elastic fibers were obtained as shown in Table 1 in the same manner as in Example 1. However, the polyurethane elastic fibers were obtained so that the yarn content of a 1:1 (mass ratio) mixture of polyurethane ("Methachlor" (registered trademark) 2462 manufactured by DuPont) produced by the reaction of t-butyldiethanolamine with methylene-bis-(4-cyclohexylisocyanate) and a condensation polymer of p-cresol and divinylbenzene ("Methachlor" (registered trademark) 2390 manufactured by DuPont) as an antioxidant was 6%.

[0068] In Comparative Example 2, a polyurethane injection-molded product having a PU content of 100% was used as a raw material instead of a knitted fabric having a PU content of 10%, and a polyurethane elastic yarn was obtained as shown in Table 1 in the same manner as in Example 1.

[0069] In Comparative Example 3, instead of a knitted fabric with a PU content of 10%, a ground product of this knitted fabric was used to carry out solvent extraction and separation. In addition, a polyurethane recovery liquid was obtained by a squeezing method using a continuous oil extractor, not by centrifugation using a dry cleaning machine. Regarding the other conditions, polyurethane elastic yarn was obtained as shown in Table 1, in the same manner as in Example 1.

[0070] In Comparative Example 4, instead of the knitted fabric having a PU content of 10%, ground material of this knitted fabric was used as the raw material, and polyurethane elastic yarn was obtained as shown in Table 1 in the same manner as in Example 1.

[0071] In Comparative Example 5, a polyurethane recovery liquid was obtained by a squeezing method using a continuous oil extractor instead of the centrifugation using a dry cleaning machine, and a polyurethane elastic yarn was obtained as shown in Table 1 in the same manner as in Example 1.

[0072] In Comparative Examples 6 to 8, polyurethane elastic fibers as shown in Table 1 were obtained.

[0073] In Table 1, the content is a value relative to 100 parts by mass of the polymer solid content in the spinning dope. In Table 1, the recycled polymer is a polymer having a number average molecular weight of 63,000 based on GPC, no peak or shoulder in the detection intensity curve in the region of the molecular weight of 30,000 or less based on GPC, and an AνC=O of 1730 cm based on IR. -1 / AνC=O 1710 cm -1 It has a viscosity coefficient of 1.35 and refers to recycled polyurethane fibers extracted from used circular knitted underwear that has been washed frequently.

[0074] Next, the dry-spun polyurethane elastic fiber obtained above (hereinafter, sample yarn) was subjected to the following evaluations.

[0075] <Elongation at break, strength at break, permanent set rate> The breaking elongation, breaking strength, permanent set rate and stress relaxation rate were measured by subjecting the polyurethane elastic yarn to a tensile test using an Instron 5564 tensile tester, and each property was evaluated according to the following criteria. A sample with a length of 5 cm (L1) was stretched 300% five times at a tensile speed of 50 cm / min. The stress at 300% stretch was defined as (G1). The length of the sample was then held at 300% stretch for 30 seconds. The stress after 30 seconds was defined as (G2). The sample was then restored to its original length, and the length of the sample when the stress became 0 was defined as (L2). This cycle of 300% stretching, holding, and recovery was repeated until the sample broke at the sixth stretch. The stress at break was defined as (G3), and the length of the sample at break was defined as (L3). The above properties are calculated using the following formulas below. Breaking strength (cN) = (G3) 20 or more: ◎, 17~20: 〇, 14~17: △, 14 or less: × Breaking elongation (%) = 100 × ((L3)-(L1)) / (L1) 480 or more: ◎, 460~480: 〇, 430~460: △, 430 or less: × Permanent distortion rate (%)=100×((L2)-(L1)) / (L1) 20 or less: ◎, 20~22: 〇, 22~24: △, 24 or more: ×

[0076] <Yellow discoloration> For yellowing, the sample yarn was wound tightly around a 5 x 5 cm sample plate with the minimum load so that the color of the sample plate would not be affected. The front of the sample and the standard white surface (JIS Z 8722 4.3.4) were covered with a homogeneous, flat, transparent glass plate of about 1 mm in thickness. The b value was measured according to JIS L 1013 C method (Hunter's method) and calculated using a Hunter type color difference meter based on the following formula. The measurement was performed five times, and the average value was used. b=7.0(Y-0.847Z) / Y 1 / 2 (X, Y, and Z are calculated according to JIS Z 8701) The yellowing was evaluated based on the degree of yellowing after the exposure treatments (a) and (b). The degree of yellowing (hereinafter abbreviated as Δb) after each exposure treatment was calculated as follows: Δb = b value after exposure treatment - b value before exposure treatment

[0077] Each exposure treatment was carried out as follows. (a) Ultraviolet (UV) exposure treatment Using a carbon arc type weather meter manufactured by Suga Test Instruments Co., Ltd., the samples were exposed to a temperature and humidity of 63°C and 60% RH for 25 hours. (b) Nitrogen oxide (NOx) exposure treatment Using a closed container (Scott Tester) with a rotating sample stand, the samples were exposed to 10 ppm NO2 gas at 40°C and 60% RH for 20 hours.

[0078] The criteria for judgment are as follows: ◎ 〇 △ × Yellowing 3 or less 3~6 6~10 10 or more

[0079] LCA (Life Cycle Assessment) CO2 Emissions (kg-CO2e): The calculations were performed using MiLCAv2 from the Japan Sustainable Management Association. The data used for the calculations was the inventory data IDEA as of 2021.

[0080] LCA waste landfill volume (m 3 ): For the calculation, we used MiLCAv2 from the Japan Sustainable Management Association. The data used for the calculation was the inventory data IDEA as of 2021.

[0081] The molecular weight measurement by GPC was carried out under the following conditions: FIG. Column: Showa Denko SHODEX KF-806M (2 pieces) Solvent: N,N-dimethylacetamide 1mL / min Temperature: 40℃ Detector: Differential refractometer (RI detector)

[0082] The IR spectrum was measured by the KBr pellet method using an FT / IR7300 infrared spectrometer manufactured by JASCO Corporation. This is a graph. FIG. 2 shows an example of the measurement of the IR spectrum in Example 10.

[0083] In Table 1, the overall evaluations of ◯ and △ were deemed to be acceptable, and × was deemed to be unacceptable.

[0084] [Table 1]

Claims

1. A material recycled polyurethane elastic fiber in which recovered fabric containing polyurethane fibers is used as at least a part of the raw material, and components separated by solvent extraction separation of the fabric are used as at least a part of the raw material.

2. The polyurethane elastic fiber according to claim 1 , wherein the fabric is used as at least a part of the raw material without being pulverized.

3. The polyurethane elastic fiber according to claim 1 , wherein the components separated by the solvent extraction separation are separated via centrifugation.

4. The polyurethane elastic fiber according to claim 3 , wherein the centrifugal separation is carried out using a dry cleaning machine.

5. The polyurethane elastic fiber according to claim 1, wherein the bath ratio (solvent mass:fabric mass) for the solvent extraction separation is in the range of 3:1 to 50:

1.

6. 2. The polyurethane elastic fiber according to claim 1, wherein the temperature of the solvent extraction separation is in the range of the freezing point of the solvent +10°C to the boiling point of the solvent -10°C.

7. 2. The polyurethane elastic fiber according to claim 1, wherein the solvent used in the solvent extraction separation has a flash point of 30°C or higher, or has no flash point and is non-flammable.

8. 2. The polyurethane elastic fiber according to claim 1, wherein the solvent used in the solvent extraction separation is any one of dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, and diethylformamide.

9. The polyurethane elastic fiber according to claim 1 , wherein a surfactant is used in the solvent extraction separation.

10. The polyurethane elastic fiber according to claim 1 , wherein an amine is used in the solvent extraction separation.

11. 2. The polyurethane elastic fiber according to claim 1, wherein the polyurethane contained in the fabric has a number average molecular weight of 20,000 or more and 120,000 or less based on gel permeation chromatography (GPC), and the detection intensity curve has no peak or shoulder in the region where the molecular weight based on GPC is 30,000 or less.

12. AνC=O 1730 based on the infrared spectrum (IR) of the polyurethane fiber contained in the fabric -1 / AνC=O 1710 -1 2. The polyurethane elastic fiber according to claim 1, wherein the tensile strength is 1.05 or more and 1.50 or less.

13. The polyurethane elastic fiber according to any one of claims 1 to 12, wherein the fabric is used for clothing products that are washed frequently.

14. The polyurethane elastic fiber according to claim 13, wherein the fabric is used for underwear.

15. A method for producing material recycled polyurethane elastic fibers, comprising recovering a fabric containing polyurethane fibers, using the recovered fabric as at least a part of a raw material, subjecting the recovered fabric to solvent extraction separation, and using the components separated by the solvent extraction separation as at least a part of the raw material.

16. The method for producing polyurethane elastic fibers according to claim 15, wherein the recovered fabric is used as at least a part of the raw material without being pulverized.

17. The method for producing polyurethane elastic fibers according to claim 15, wherein the components separated by the solvent extraction separation are separated by centrifugation.

18. The method for producing polyurethane elastic fibers according to claim 17, wherein the centrifugal separation is carried out using a dry cleaning machine.

19. The method for producing polyurethane elastic fibers according to claim 15, wherein the solvent extraction separation is carried out at a bath ratio (solvent mass:fabric mass) in the range of 3:1 to 50:

1.

20. The method for producing polyurethane elastic fibers according to claim 15, wherein the solvent extraction separation is carried out at a temperature ranging from the freezing point of the solvent +10°C to the boiling point of the solvent -10°C.

21. The method for producing polyurethane elastic fibers according to claim 15, wherein a solvent having a flash point of 30°C or higher, or a solvent having no flash point and being non-flammable, is used for the solvent extraction and separation.

22. 16. The method for producing polyurethane elastic fibers according to claim 15, wherein any one of dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, and diethylformamide is used as a solvent for the solvent extraction separation.

23. The method for producing polyurethane elastic fibers according to claim 15, wherein a surfactant is used in the solvent extraction separation.

24. The method for producing polyurethane elastic fibers according to any one of claims 15 to 23, wherein an amine is used for the solvent extraction separation.

Images