Method for producing processed fibers

Abstract

Provided is a method for producing processed fibers having functionality such as photothermal performance.　The method for producing processed fibers includes a step 1 for applying a melanin precursor solution to fibers, and a step 2 for performing an oxidation promotion treatment of the melanin precursor following step 1.

Description

Manufacturing methods for processed fibers

[0001] This invention relates to a method for producing processed fibers.

[0002] In the apparel industry, the market size for clothing with various functions such as antibacterial properties, deodorizing properties, quick-drying properties, heat retention, shape retention, UV protection, antistatic (static) properties, and conductivity is expanding. In particular, due to consumers' increasing awareness of hygiene and a preference for cleanliness, there is a high demand for antibacterial processed products and deodorizing processed products that eliminate unpleasant odors such as sweat odor, cigarette odor, and age-related odor. Furthermore, for clothing worn in winter, there is a preference for products with thermal properties and antistatic properties that reduce dust adhesion and clinging due to static electricity, thereby enhancing comfort. For example, thermal functional fiber products include fibers that generate heat by absorbing moisture from sweat, as well as synthetic fibers with ceramic particles that have photothermal properties that convert light into heat kneaded into the core. In addition, there have been reports of the production of wool fabric with photothermal properties by adsorbing vanadium ions with photothermal properties onto wool (Patent Document 1).

[0003] On the other hand, melanin is a yellow to black pigment formed in animals and plants, and is known to have functions such as UV absorption, radical scavenging, and antioxidant properties. Because melanin is a highly safe substance derived from living organisms, it is widely used in cosmetics, foods, plastic products, etc., as a UV absorber, antioxidant, and pigment.

[0004] In living organisms, melanin is biosynthesized when tyrosine, a substrate compound, is oxidized by the catalytic action of tyrosinase, a melanin-producing enzyme, to produce dihydroxyindole compounds (5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, etc.) via dopa and dopaquinone, and these dihydroxyindole compounds then polymerize. When using melanin as a dye, it is difficult to penetrate and dye the object to be dyed by using melanin itself, which is a high molecular weight compound. Therefore, low molecular weight compounds such as melanin precursors, dihydroxyindole compounds, are used as dyes to allow melanin to form inside the object to be dyed. For example, a method for dyeing cotton fibers and human gray hair using a dye solution containing 5,6-dihydroxyindole (Patent Document 2), and a method for dyeing fibers with an aqueous solution containing tyrosinase and tyrosine (Patent Document 3) have been reported. According to Patent Documents 2 and 3, cotton fibers dyed black to dark brown can be obtained, but the function of the melanin produced within the fibers is completely unknown.

[0005] (Patent Document 1) Japanese Unexamined Patent Publication No. 2021-42480 (Patent Document 2) Japanese Unexamined Patent Publication No. 2011-46658 (Patent Document 3) Japanese Unexamined Patent Publication No. Hei 9-87977

[0006] The present invention provides a method for producing processed fibers, comprising step 1 of applying a melanin precursor solution to fibers, and step 2 of performing an oxidation-promoting treatment on the melanin precursor after step 1. Detailed description of the invention

[0007] In functional clothing, there is a demand for materials made from natural fibers, particularly for consumers with sensitive skin. However, when imparting functionalities such as photothermal heat generation to natural fibers, one method is to coat them with functional particles using a binder. This method is impractical in terms of fiber durability and changes in texture. The inventors have discovered that by using a melanin precursor and generating melanin within the fibers of natural fibers under specific conditions, it is possible to impart functionalities such as photothermal heat generation to fibers.

[0008] The present invention relates to a method for producing processed fibers having functional properties such as photothermal heat generation.

[0009] The present inventors have discovered that by applying a melanin precursor solution to fibers and then performing a treatment to promote the oxidative polymerization of the melanin precursor, processed fibers with excellent functionality, such as photothermal performance, can be obtained.

[0010] According to the present invention, processed fibers with excellent functionality, such as light-induced heat generation performance, can be obtained.

[0011] The present invention provides a method for producing processed fibers comprising step 1 of applying a melanin precursor solution to fibers, and step 2 of performing an oxidation-promoting treatment on the melanin precursor after step 1. While applying a melanin precursor solution to fibers and generating melanin can impart functional properties such as photothermal performance to the fibers, the present invention, by performing the oxidation-promoting treatment on the melanin precursor in step 2 after step 1, yields processed fibers with even better functional properties such as photothermal performance than when the melanin precursor is subjected to air oxidation polymerization. The reason is not entirely clear because the structure of melanin cannot be identified, but it is presumed that in the method of the present invention, the oxidation-promoting treatment of the melanin precursor forms an oxidized polymer different from that formed in the case of simple air oxidation.

[0012] <Step 1> Step 1 is the step of applying the melanin precursor solution to the fibers. In this specification, examples of fibers include natural fibers such as cotton, silk, hemp, wool, paper mulberry, mitsumata, and ganpi; synthetic fibers such as nylon, polyester, and acrylic; cellulose-based regenerated fibers such as rayon; and cellulose fibers such as paper. Among these, natural fibers such as cotton, silk, hemp, wool, paper mulberry, mitsumata, and ganpi are preferred, and cotton, silk, hemp, and wool are more preferred. From the viewpoint of strength as clothing, the fibers are preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. Furthermore, from the viewpoint of ease of penetration of the melanin precursor, the fibers are preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0013] Melanin precursors are compounds that polymerize and are converted into melanin by air oxidation. Examples of melanin precursors in the present invention include tyrosine, dopa, dopaquinone, and dihydroxyindole compounds. One or more melanin precursors can be used. In particular, from the viewpoint of efficiently polymerizing to melanin and exhibiting functionalities such as photothermal performance, one or more selected from tyrosine and dihydroxyindole compounds are preferred, and one or more selected from dihydroxyindole compounds are more preferred. Examples of dihydroxyindole compounds include compounds represented by the following general formula (1) or salts thereof.

[0014]

[0015] (In the formula, the dashed line indicates the presence or absence of a π bond. R 1 R represents a hydroxyl group or an acetoxy group. 2 R represents a hydrogen atom, or -COOR (where R is a hydrogen atom, a methyl group, or an ethyl group). 3 (This represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group.)

[0016] From the viewpoint of ease of penetration into fibers, it is preferable that the dashed line portion in general formula (1) contains a π bond. Also, from the same viewpoint, in general formula (1), R 1 is preferably a hydroxyl group, R 2 R is preferably a hydrogen atom or -COOR (where R is a hydrogen atom, a methyl group, or an ethyl group), more preferably a hydrogen atom or -COOH. 3 Preferably, it is a hydrogen atom.

[0017] Examples of the compound represented by the general formula (1) include 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, methyl 5,6-dihydroxyindole-2-carboxylate, ethyl 5,6-dihydroxyindole-2-carboxylate, N-methyl-5,6-dihydroxyindole, N-methyl-5,6-dihydroxyindole-2-carboxylic acid, N-ethyl-5,6-dihydroxyindole, N-ethyl-5,6-dihydroxyindole-2-carboxylic acid, N-acetyl-5,6-dihydroxyindole, N-acetyl-5,6-dihydroxyindole-2-carboxylic acid, 5-acetoxy-6-hydroxyindole, 5-acetoxy-6-hydroxyindole-2-carboxylic acid, 5,6-dihydroxyindoline, 5,6-dihydroxyindoline-2-carboxylic acid, methyl 5,6-dihydroxyindoline-2-carboxylate, ethyl 5,6-dihydroxyindoline-2-carboxylate, N-methyl-5,6-dihydroxyindoline, N-methyl-5,6-dihydroxyindoline-2-carboxylic acid, N-ethyl-5,6-dihydroxyindoline, N-ethyl-5,6-dihydroxyindoline-2-carboxylic acid, N-acetyl-5,6-dihydroxyindoline, N-acetyl-5,6-dihydroxyindoline-2-carboxylic acid, 5-acetoxy-6-hydroxyindoline, 5-acetoxy-6-hydroxyindoline-2-carboxylic acid, etc. Examples of the salt of the compound represented by the general formula (1) include hydrochloride, hydrobromide, sulfate, phosphate, acetate, propionate, lactate, citrate, etc. of the said compound. Among them, from the viewpoint of availability, hydrobromide is preferable. In the general formula (1), when R 2 is -COOH, examples of the salt of the compound represented by the general formula (1) include its carboxylate (R 2 is -COO - X + (X + is a cation such as an alkali metal ion like Na + , K + , alkaline earth metal ions like Ca + , Mg + , or ammonium ion).

[0018] From the viewpoint of ease of penetration into fibers, the compound represented by general formula (1) or its salt is preferably one or more selected from the group consisting of 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 5,6-dihydroxyindoline, 5,6-dihydroxyindoline-2-carboxylic acid, and salts thereof; more preferably one or more selected from the group consisting of 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, and 5,6-dihydroxyindoline hydrobromide; even more preferably one or two selected from the group consisting of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid; and even more preferably a combination of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.

[0019] When 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid are used in combination, from the viewpoint of providing higher photothermal performance and other functionalities, and efficiently imparting functionality, the molar ratio is preferably in the range of 50:50 to 99:1, more preferably in the range of 80:20 to 99:1, and even more preferably in the range of 85:15 to 95:5. The molar ratio of 5,6-dihydroxyindole to 5,6-dihydroxyindole-2-carboxylic acid can be quantified by reverse-phase HPLC.

[0020] The melanin precursor can be commercially available. Alternatively, it can be obtained by previously reported enzymatic or chemical methods. For example, it can be produced by referring to the method described in Japanese Patent Publication No. 4578221 as an enzymatic method, or by referring to the method described in Japanese Patent Publication No. 7212628 as a chemical method.

[0021] Suitable solvents for the melanin precursor solution include, from the viewpoint of solubilizing the melanin precursor, water; lower alcohols such as ethanol and isopropyl alcohol; low molecular weight diols and triols with 6 or fewer carbon atoms such as ethylene glycol, propylene glycol, 1,3-butylene glycol, and glycerin; and buffer solutions such as phosphate buffer and acetate buffer. One or more solvents can be used. Among these, water, ethanol, or mixtures thereof are preferred from the viewpoint of cost. From the viewpoint of preservation, the ethanol concentration is preferably 5% by mass or more, more preferably 10% by mass or more, and also preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less in the solvent.

[0022] The content of melanin precursor in the melanin precursor solution is preferably 0.05 mM or more, more preferably 0.1 mM or more, and even more preferably 1 mM or more, from the viewpoint of imparting functionality such as photothermal performance. Furthermore, there is no particular upper limit, but from the viewpoint of cost relative to functionality, it is preferably 120 mM or less, more preferably 67 mM or less, and even more preferably 40 mM or less. The content of melanin precursor in the melanin precursor solution is preferably 0.05 to 120 mM, more preferably 0.1 to 67 mM, and even more preferably 1 to 40 mM.

[0023] In addition to the melanin precursor and solvent, the melanin precursor solution may optionally contain additives such as oxidases like tyrosinase that catalyze the oxidation reaction of the melanin precursor, surfactants, stabilizers, buffers, fragrances, texture enhancers, chelating agents, solubilizers, and preservatives. Furthermore, antioxidants such as sodium ascorbate and sodium sulfite may be optionally included to control the oxidation rate of the melanin precursor. The amount of additives can be appropriately set within a range that does not impair the objective of the present invention.

[0024] The pH (at 20°C) of the melanin precursor solution is preferably 2 or higher, more preferably 4 or higher, and even more preferably 6 or higher, from the viewpoint of promoting oxidation of the melanin precursor, and preferably 13 or lower, more preferably 12 or lower, and even more preferably 11 or lower, from the viewpoint of suppressing the decomposition of melanin. The pH (at 20°C) of the melanin precursor solution is preferably 2 to 13, more preferably 4 to 12, and even more preferably 6 to 11.

[0025] In this specification, applying the melanin precursor solution to a fiber means bringing the melanin precursor solution into contact with the fiber. The means of applying the melanin precursor solution are not particularly limited and may include immersing the fiber in the melanin precursor solution, directly coating the fiber with the melanin precursor solution, or spraying the fiber with the melanin precursor solution. Preferably, the method is to immerse the fiber in the melanin precursor solution. This may be done under standing conditions or under stirring conditions. Furthermore, the application method may be repeated multiple times, for example, two or three times.

[0026] The amount of melanin precursor solution used should be sufficient to impart functionality such as photothermal performance to the fibers, and can be appropriately determined depending on the form of use. For example, in a method of immersing fibers in melanin precursor solution, the bath ratio of the melanin precursor solution, i.e., the mass ratio of melanin precursor solution to fibers, is preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more, from the viewpoint of ease of immersion, and preferably 100 or less, more preferably 80 or less, and even more preferably 60 or less, from the viewpoint of cost. The mass ratio of melanin precursor solution to fibers is preferably 4 to 100, more preferably 6 to 80, and even more preferably 8 to 60.

[0027] Regarding the application time, from the viewpoint of allowing the melanin precursor to sufficiently penetrate the fibers and then to oxidatively polymerize within the fibers in subsequent processes to produce melanin, it is preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 2 hours or more. Furthermore, from the viewpoint of productivity, it is preferably within 24 hours, more preferably within 10 hours, and even more preferably within 2 hours.

[0028] Also, from the perspective of sufficiently infiltrating the melanin precursor into the fiber and then sufficiently oxidatively polymerizing it inside the fiber to form melanin in the subsequent process, the application temperature is preferably 5°C or higher, more preferably 10°C or higher, still more preferably 15°C or higher. Also, from the perspectives of operability and safety, it is preferably 90°C or lower, more preferably 40°C or lower, still more preferably 30°C or lower.

[0029] In a specific embodiment of the present invention, it is preferable to carry out Step 1 under anaerobic conditions from the perspective of more sufficiently infiltrating the melanin precursor into the fiber, then sufficiently oxidatively polymerizing it inside the fiber to form melanin in the subsequent process, and exhibiting high functionality. Specifically, it is preferable to make the oxygen concentration 10% or lower, more preferably 5% or lower, still more preferably 2% or lower, by, for example, passing nitrogen.

[0030] <Step 2> This step is a step of performing an oxidation promotion treatment on the melanin precursor after Step 1. The melanin precursor is polymerized by air oxidation to be converted into melanin, but by performing an oxidation promotion treatment, it is possible to impart functions such as excellent photothermal performance to the fiber. Examples of the oxidation promotion treatment include a method of bringing an oxidizing agent, an oxidation catalyst, a metal salt, or a buffer into contact with the fiber to which the melanin precursor solution has been applied.

[0031] Examples of oxidizing agents include peroxides such as peracids or salts thereof, such as persulfuric acid, percarbonate, and superphosphate; halogen acids or salts thereof, such as chloric acid, bromic acid, and iodic acid; and perhalic acids or salts thereof, such as perchloric acid, perbromic acid, and periodic acid. Examples of oxidation catalysts include laccase, catechol oxidase, peroxidase, copper-supported catalysts, and platinum-supported catalysts. Examples of metal salts include copper salts such as copper chloride and copper sulfate; iron salts such as iron chloride, iron sulfate, iron phosphate, and iron nitrate; zinc salts such as zinc chloride, zinc sulfate, and zinc nitrate; and nickel salts such as nickel chloride and nickel sulfate. A buffer solution with a pH (at 25°C) of 7 or higher is preferred. From the viewpoint of improving functionality, the pH of the buffer solution is preferably 7 or higher, more preferably 8 or higher, and even more preferably 9 or higher. From the viewpoint of fiber modification, it is preferably 13 or lower, more preferably 12 or lower, and even more preferably 11 or lower. Examples of buffer solutions include sodium carbonate buffer, ammonium chloride buffer, Tris buffer, phosphate buffer, borate buffer, and acetate buffer. In particular, from the viewpoint of promoting the oxidation of melanin precursors and imparting functionalities such as photothermal properties, it is preferable to use at least one selected from sodium carbonate buffer, ammonium chloride buffer, Tris buffer, and phosphate buffer.

[0032] The treatment time for the oxidation acceleration treatment is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more, from the viewpoint of sufficiently oxidizing and polymerizing the melanin precursor to produce highly functional melanin. From the viewpoint of productivity, it is preferably within 5 hours, more preferably within 3 hours, and even more preferably within 2 hours.

[0033] Furthermore, the temperature for the oxidation acceleration treatment is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, from the viewpoint of sufficiently oxidizing and polymerizing the melanin precursor to produce highly functional melanin. Also, from the viewpoint of operability and safety, it is preferably 90°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower.

[0034] After performing the oxidation promotion treatment of the melanin precursor, it is preferable to perform washing with water, drying, etc. as necessary. By this, the melanin generated from the melanin precursor on the fiber surface portion can be removed, and color fading due to friction can be suppressed. According to the present invention, a processing fiber excellent in such functionality is obtained by imparting photothermal performance, antibacterial performance, deodorizing performance, and antistatic performance to the fiber. Therefore, the processing fiber of the present invention is useful for clothing and the like.

[0035] Regarding the above-described embodiment, the present invention further discloses the following method for manufacturing a processing fiber.

[0036] <1> A method for manufacturing a processing fiber, including step 1 of applying a melanin precursor solution to a fiber, and step 2 of performing an oxidation promotion treatment of the melanin precursor after step 1.

[0037] <2> The method for manufacturing a processing fiber according to <1>, wherein the melanin precursor contains one or more selected from tyrosine, a compound represented by the following general formula (1) as dihydroxyindoles, or a salt thereof.

[0038]

[0039] (In the formula, the broken line indicates the presence or absence of a π bond. R 1 represents a hydroxyl group or an acetoxy group. R 2 represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group, or an ethyl group). R 3) represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group.) <3> A method for producing processed fibers according to <1> or <2>, wherein the melanin precursor contains one or two selected from the group consisting of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid. <4> A method for producing processed fibers according to any one of <1> to <3>, wherein the content of the melanin precursor in the melanin precursor solution of step 1 is 0.05 mM or more. <5> A method for producing processed fibers according to any one of <1> to <4>, wherein step 1 is carried out under anaerobic conditions. <6> A method for producing processed fibers according to any one of <1> to <5>, wherein the oxidation promotion treatment of step 2 is a treatment in which at least one selected from an oxidizing agent, an oxidation catalyst, a metal salt, and a buffer is brought into contact with the fiber to which the melanin precursor solution has been applied. <7> A method for producing processed fibers according to any one of <1> to <6>, wherein the pH of the melanin precursor solution in step 1 at 20°C is 2 to 13. <8> A method for producing processed fibers according to any one of <1> to <7>, wherein the amount of melanin precursor solution used in step 1 is 4 to 100 by mass relative to the fiber. <9> A method for producing processed fibers according to any one of <1> to <8>, wherein the time for applying the melanin precursor solution in step 1 is 0.5 hours or more and 24 hours or less. <10> A method for producing processed fibers according to any one of <1> to <9>, wherein the temperature at which the melanin precursor solution in step 1 is applied is 5°C or more and 90°C or less. <11> A method for producing processed fibers according to any one of <5> to <10>, wherein the oxygen concentration when step 1 is carried out under anaerobic conditions is 10% or less. <12> A method for producing processed fibers according to any one of <1> to <11>, wherein the time for the oxidation acceleration treatment in step 2 is 5 minutes or more and 5 hours or less. <13> A method for producing processed fibers according to any one of <1> to <12>, wherein the temperature for the oxidation acceleration treatment in step 2 is 5°C or more and 90°C or less. <14> A method for producing processed fibers according to any one of <1> to <13>, wherein a water washing treatment is performed after the oxidation acceleration treatment in step 2.

[0040] <Experimental Materials> - Cotton knit fabric (unspun cotton knit, 6cm x 6cm) was purchased from Tanigashira Shoten. Wool: Wool serge fabric purchased from Irozome Co., Ltd. was used. - Dihydroxyindole (DHI) was prepared according to the method of prior art (Patent No. 7212628, Kao Corporation). Details are as follows.

[0041] <Preparation Method of DHI> A stirrer with crescent-shaped blades was set up in a 5L glass three-necked flask to serve as a reactor. 2L of water was added to the reactor, and nitrogen gas was vented from the top of the flask. DOPA was added to the reactor to a concentration of 0.33 wt% and dissolved by stirring at 200 rpm. At this time, the liquid temperature was adjusted to 35°C using a water bath. An oxidizing agent solution was prepared by dissolving 16.8 wt% potassium hexacyanoferrate(III) and 7.2 wt% potassium bicarbonate in water. 0.288 mL of the oxidizing agent solution was added to the reactor containing the DOPA aqueous solution, and the reaction was carried out for 4 hours to obtain an aqueous DHI solution. The pH of the aqueous DHI solution was adjusted to 5.0 by adding a 10 wt% phosphoric acid solution. The following operations were performed in a glove box where the oxygen concentration was kept below 0.1% by venting with nitrogen. The aqueous DHI solution was filtered through a PES 0.2 μm filter. A filtered DHI aqueous solution was added to a 5L glass bottle, followed by the addition of 2L of ethyl acetate as an extractant. The solution was stirred by shaking the glass bottle by hand to perform the extraction. The glass bottle was allowed to stand, and 1.5L of the separated upper layer (ethyl acetate layer) was collected in another glass bottle. 0.7L of washing water (salt concentration: 8.33 wt%, dipotassium hydrogen phosphate / potassium dihydrogen phosphate (mass ratio) = 5.12) containing dipotassium hydrogen phosphate and potassium dihydrogen phosphate dissolved in water was added to this water, and the solution was stirred by shaking the glass bottle by hand to perform the washing. The glass bottle was allowed to stand, and 1.0L of the separated upper layer (ethyl acetate layer) was collected in a round-bottom flask. The collected ethyl acetate layer was completely evaporated using an evaporator (water bath temperature 45°C). 20 wt% ethanol was added to the dried material to adjust the concentration to 1 wt% DHI. Further adjustment to pH 8 by adding 6N sodium hydroxide aqueous solution dropwise was performed to obtain a 1% DHI solution.

[0042] <Fiber Treatment Method (Step 1)> The following operations were carried out using a glove box to avoid contact between the DHI solution and fiber samples and oxygen. DHI was diluted with distilled water to the concentrations shown in each table to prepare the DHI treatment solution. For fibers measuring 6 cm x 6 cm, the DHI treatment solution was added to achieve a bath ratio of 20, and the mixture was left to stand at 20°C for the time indicated in each table.

[0043] <Oxidation Treatment Method (Step 2)> ​​In the example, the reagents shown in each table were added to the DHI solution after Step 1 was completed, and the fibers were exposed to the air at 20°C while immersed in the DHI solution and left to stand for a predetermined time to promote oxidation. The fibers that underwent the oxidation promotion treatment were thoroughly washed with tap water and air-dried.

[0044] As a reference example, DHI adsorbed onto fibers was oxidized under atmospheric conditions. Specifically, the fibers were exposed to the atmosphere at 20°C while immersed in the DHI solution from step 1, and left for the times indicated in each table.

[0045] <Color Measurement Method> The L, a, and b values ​​of the above fibers were measured using a colorimeter (CR-400, manufactured by Konica Minolta). The difference in L, a, and b values ​​between the dyed and undyed fibers was defined as Δ, and the color difference ΔE = {(ΔL)} 2 + (Δa) 2 + (Δb) 2} 0.5 The result was calculated.

[0046] <Measurement of Photothermal Heat Generation Temperature> Evaluation was conducted according to the light absorption heat retention test (Boken standard BQE A 036). The fibers were placed 30 cm away from a reflector lamp PRF300W (Iwasaki Electric) and irradiated with light at 100 V for 10 minutes (illuminance of the irradiated surface: 12 klx). A thermocouple was placed on the back of the fiber and the temperature rise was measured from the temperature difference between the temperature before and after irradiation. The photothermal heat generation temperature was calculated as (temperature rise of treated fabric) - (temperature rise of untreated fabric).

[0047] <Antibacterial Performance Evaluation Method> The antibacterial activity of the fibers was evaluated according to JIS L1902:2015 bacterial suspension absorption method (quantitative test). Staphylococcus aureus NBRC12732 was used as the bacterial species, and the bacterial count was measured by pour plate culture. The antibacterial activity was calculated using the following formula.

[0048] Bacterial count before culturing on standard cotton cloth before treatment: C0 Bacterial count after 18 hours of culturing on standard cotton cloth before treatment: C t Bacterial count before culture in processed cotton fabric before treatment: T0 Bacterial count after 18 hours of culture in processed cotton fabric before treatment: T t Antibacterial activity = (LogC t -LogC0)-(LogT t -LogT0)

[0049] <Antistatic Evaluation Method> Following JIS L 1094 Method A, a voltage of 10 kV was applied to the test piece for 30 seconds, and the time it took for the charged voltage to be halved (half-life) was measured. In addition, following JIS L 1094 Method B, the frictional voltage was measured when the target fabric was cotton.

[0050] Examples 1-8, Comparative Example 1, and Reference Example 1: Cotton fabrics were treated with DHI at the concentrations shown in Table 1, followed by oxidation treatment under various conditions. The hue and photothermal performance of the standard cotton fabrics and the obtained fibers were evaluated.

[0051]

[0052] When comparing under conditions of a DHI treatment concentration of 0.67 mM, the example in which an oxidation accelerator was added to fibers oxidized with DHI in air as in existing methods showed higher photothermal performance. The reason why a small amount of melanin showed high heat generation performance is not clear, as analysis of the melanin structure is generally difficult, but it is expected that there are differences such as a higher degree of polymerization.

[0053] In Example 9 and Reference Example 2, cotton fabrics were treated with DHI at the concentrations shown in Table 2, and then subjected to oxidation treatment under various conditions. The color and antibacterial performance of the standard cotton fabrics and the obtained fibers were evaluated.

[0054]

[0055] In Example 9, an oxidation accelerator was added to fibers that had been oxidized with DHI in air, and this demonstrated excellent antibacterial activity.

[0056] In Example 10, Comparative Example 2, and Reference Example 3, woolen cloths were treated with DHI at the concentrations shown in Table 3, and then subjected to oxidation treatment under various conditions. The hue and antistatic properties of the woolen cloths and the resulting fibers were evaluated.

[0057]

[0058] In Example 10, where an oxidation accelerator was added to fibers oxidized with DHI in air, excellent antistatic properties were observed.

Claims

1. A method for producing processed fibers, comprising step 1 of applying a melanin precursor solution to fibers, and step 2 of performing an oxidation-promoting treatment on the melanin precursor after step 1.

2. A method for producing processed fibers according to claim 1, wherein the melanin precursor contains tyrosine and one or more compounds selected from those represented by the following general formula (1) or salts thereof. (In the formula, the dashed line indicates the presence or absence of a π bond. R 1 R represents a hydroxyl group or an acetoxy group. 2 R represents a hydrogen atom, or -COOR (where R is a hydrogen atom, a methyl group, or an ethyl group). 3 (This represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group.) 3. A method for producing processed fibers according to claim 1 or 2, wherein the melanin precursor contains one or two selected from the group consisting of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.

4. A method for producing processed fibers according to any one of claims 1 to 3, wherein the content of melanin precursor in the melanin precursor solution of step 1 is 0.05 mM or more.

5. A method for producing processed fibers according to any one of claims 1 to 4, wherein step 1 is carried out under anaerobic conditions.

6. A method for producing processed fibers according to any one of claims 1 to 5, wherein the oxidation acceleration treatment in step 2 is a treatment in which at least one selected from an oxidizing agent, an oxidation catalyst, a metal salt, and a buffer solution is applied to the fibers to which the melanin precursor solution has been applied.

7. The method for producing processed fibers according to any one of claims 1 to 6, wherein the pH of the melanin precursor solution in step 1 at 20°C is 2 to 13.

8. A method for producing processed fibers according to any one of claims 1 to 7, wherein the amount of melanin precursor solution used in step 1 is 4 to 100 by mass relative to the fiber.

9. A method for producing processed fibers according to any one of claims 1 to 8, wherein the time for applying the melanin precursor solution of step 1 is 0.5 hours or more and 24 hours or less.

10. A method for producing processed fibers according to any one of claims 1 to 9, wherein the temperature at which the melanin precursor solution of step 1 is applied is 5°C or higher and 90°C or lower.

11. A method for producing processed fibers according to any one of claims 5 to 10, wherein the oxygen concentration when step 1 is carried out under anaerobic conditions is 10% or less.

12. A method for producing processed fibers according to any one of claims 1 to 11, wherein the time for the oxidation acceleration treatment in step 2 is 5 minutes or more and 5 hours or less.

13. A method for producing processed fibers according to any one of claims 1 to 12, wherein the temperature of the oxidation acceleration treatment in step 2 is 5°C or higher and 90°C or lower.

14. A method for producing processed fibers according to any one of claims 1 to 13, wherein a water washing treatment is performed after the oxidation acceleration treatment in step 2.

15. Processed fiber produced by the method for producing processed fiber according to any one of claims 1 to 14.

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