Photothermal heating performance-imparting composition

Abstract

To provide a photothermal heating performance-imparting composition and a photothermal heating performance-imparting method that make it possible to impart to a target such as natural fibers a photothermal heating performance having durability against washing.SOLUTION: A photothermal heating performance-imparting composition comprising a melanin precursor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photothermal performance-imparting composition, a photothermal performance-imparting method, and a method for producing a photothermal fiber or photothermal leather. [Background technology]

[0002] In the clothing industry, the market size is expanding for clothing with various functionalities, such as antibacterial, deodorizing, quick-drying, heat-retaining, shape-stable, and UV protection properties. Clothing with thermal functions is particularly popular for winter wear. Typical thermal functional fiber products include fibers that absorb moisture and generate heat when sweating, as well as synthetic fibers with ceramic particles kneaded into their cores that have photothermal properties that convert light into heat. There has also been a report of a wool fabric with photothermal properties being produced 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 ultraviolet absorbing functions, radical scavenging functions, antioxidant functions, etc. Because melanin is a highly safe substance derived from living organisms, it is widely used as an ultraviolet absorber, antioxidant, pigment, etc. in cosmetics, foods, plastic products, etc.

[0004] In vivo, melanin is biosynthesized by the oxidation of the substrate compound tyrosine, catalytically catalyzed by the melanin-producing enzyme tyrosinase, to produce dihydroxyindoles (e.g., 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid) via dopa and dopaquinone, followed by polymerization of these dihydroxyindoles. When using melanin as a dye, it is difficult to penetrate and dye an object using melanin, a high-molecular-weight compound, directly. Therefore, melanin precursors, such as dihydroxyindoles, are used as dyes to form melanin within the object. For example, a method for dyeing cotton fibers or 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 or dark brown can be obtained, but the function of melanin within fibers remains unknown. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-42480 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-46658 [Patent Document 3] Japanese Patent Application Publication No. 9-87977 Summary of the Invention [Problem to be solved by the invention]

[0006] Functional clothing made from natural fibers is in demand for consumers with sensitive skin. While coating functional particles with a binder is considered as a way to impart photothermal properties to natural fibers, this method is not practical in terms of durability and changes in texture of the fibers. Furthermore, the method described in Patent Document 1 has the problem that functionality is easily lost when washed with laundry detergent. Therefore, the present invention relates to providing a new composition for imparting photothermal performance and a method for imparting photothermal performance that can impart photothermal performance with durability to washing to a target object such as natural fibers. [Means for solving the problem]

[0007] The present inventors have discovered that by using a melanin precursor to generate melanin inside an object, it is possible to impart high photothermal performance to the object, and that the imparted photothermal performance has excellent durability against washing.

[0008] That is, the present invention relates to the following 1) to 3). 1) A photothermal performance-imparting composition containing a melanin precursor. 2) A method for imparting photothermal properties to an object, comprising applying a composition containing a melanin precursor to the object. 3) A method for producing fibers or leather imparted with photothermal properties, which comprises applying a composition containing a melanin precursor to the fibers or leather. [Effects of the Invention]

[0009] According to the present invention, it is possible to impart photothermal performance that is robust to washing to objects such as textiles and leather. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Photoheat-generating composition) The photoheat-imparting composition of the present invention contains a melanin precursor, which is a compound that is polymerized by air oxidation and converted into melanin. In the present invention, examples of melanin precursors include tyrosine, dopa, dopaquinone, dihydroxyindoles, etc. One or a combination of two or more melanin precursors can be used. Among these, from the viewpoint of efficiently imparting photothermal performance, one or more selected from tyrosine and dihydroxyindoles are preferred, and one or more selected from dihydroxyindoles are more preferred. Dihydroxyindoles include compounds represented by the following general formula (1) and salts thereof.

[0011] [ka]

[0012] (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 represents a hydrogen atom or -COOR (where R is a hydrogen atom, a methyl group, or an ethyl group). 3 represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group.

[0013] From the viewpoint of ease of penetration into the target object, it is preferable that the dashed line portion in general formula (1) contains a π bond. From the same viewpoint, in general formula (1), R 1 is preferably a hydroxyl group, and R 2 is preferably a hydrogen atom or -COOR (R is a hydrogen atom, a methyl group, or an ethyl group), more preferably a hydrogen atom or -COOH. 3 is preferably a hydrogen atom.

[0014] Examples of the compound represented by 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, and 5-acetoxy-6-hydroxyindole-2-carboxylic acid. Examples thereof include 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, and 5-acetoxy-6-hydroxyindoline-2-carboxylic acid. Examples of salts of the compound represented by general formula (1) include hydrochloride, hydrobromide, sulfate, phosphate, acetate, propionate, lactate, citrate, etc. of the compound, and among these, hydrobromide is preferred from the viewpoint of availability. In general formula (1), R 2 is —COOH, the salt of the compound represented by general formula (1) is its carboxylate (R 2 -COO - X + (X + Na + , K. + Alkali metal ions such as Ca + , Mg + and cations such as alkaline earth metal ions, and ammonium ions).

[0015] From the viewpoint of ease of penetration into the target object, the compound represented by general formula (1) or a salt thereof 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.

[0016] When 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid are used in combination, from the viewpoint of imparting higher and more efficient photothermal performance, 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.

[0017] Commercially available melanin precursors can be used. Alternatively, they can be obtained by previously reported enzymatic or chemical methods. For example, they can be produced by referring to the enzymatic method described in Japanese Patent No. 4578221 and the chemical method described in Japanese Patent No. 7212628.

[0018] The content of the melanin precursor in the photothermal performance-imparting composition of the present invention is preferably 2 mM or more, more preferably 5 mM or more, and even more preferably 10 mM or more from the viewpoint of imparting high photothermal performance. The upper limit is not particularly limited, but from the viewpoint of cost, it is preferably 120 mM or less, more preferably 67 mM or less, and even more preferably 40 mM or less.

[0019] The photothermal performance-imparting composition of the present invention preferably further contains a solvent from the viewpoint of solubilizing the melanin precursor. Examples of the solvent include water; lower alcohols such as ethanol and isopropyl alcohol; low-molecular-weight diols and triols having 6 or less 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 a combination of two or more solvents can be used. Among these, water, ethanol, or a mixture thereof is preferred from the viewpoint of cost. From the viewpoint of antiseptic properties, the ethanol concentration in the solvent is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0020] In addition to the melanin precursor and solvent, the photoheat-imparting composition of the present invention may contain, as necessary, additives such as oxidases such as tyrosinase that catalyze the oxidation reaction of the melanin precursor, surfactants, stabilizers, buffers, fragrances, texture improvers, chelating agents, solubilizers, and preservatives. Furthermore, in order to control the oxidation rate of the melanin precursor, the composition may contain antioxidants such as sodium ascorbate and sodium sulfite. The content of the additives may be appropriately set within a range that does not impair the object of the present invention.

[0021] The form of the photoheat-imparting composition of the present invention is not particularly limited, and examples thereof include a liquid (e.g., a suspension, a solution), a gel, a paste, a solid, etc., but from the viewpoint of ease of penetration of the melanin precursor into the target object, a liquid form is preferred.

[0022] The pH (20°C) of the photoheat-generating performance-imparting composition of the present invention is preferably 2 or higher, more preferably 4 or higher, and even more preferably 6 or higher, from the viewpoint of promoting the oxidation of melanin precursors, and is preferably 12 or lower, more preferably 10 or lower, and even more preferably 7 or lower, from the viewpoint of suppressing the decomposition of melanin.

[0023] As shown in the examples described below, by using a melanin precursor to generate melanin inside an object, it is possible to impart high photothermal performance and washability to the object. That is, it is believed that the melanin generated by oxidative polymerization of the melanin precursor is fixed inside the object, for example, inside fibers, and imparts photothermal performance to the object. Therefore, in the present invention, a melanin precursor is used to impart photothermal performance to an object. Furthermore, by applying a composition containing a melanin precursor to an object, it is possible to impart photothermal performance to the object.

[0024] In the present invention, the term "photothermal performance" refers to the ability to absorb light, such as sunlight, and convert it into heat.

[0025] The object to which the photoheat-generating performance-imparting composition of the present invention is applied is not particularly limited as long as it requires or is desired to be imparted with photoheat-generating performance. Preferred examples include fibers, leather, and blends thereof. A preferred embodiment of the present invention is a photoheat-generating performance-imparting composition that imparts photoheat-generating performance to fibers or leather. Examples of fibers include natural fibers such as cotton, silk, hemp, wool, mulberry, mitsumata, and gampi; synthetic fibers such as nylon, polyester, and acrylic; regenerated cellulose fibers such as rayon; and cellulose fibers such as paper. Natural fibers such as cotton, silk, hemp, wool, mulberry, mitsumata, and gampi are preferred, and cotton, silk, hemp, and wool are more preferred. From the viewpoint of strength as clothing, the fiber thickness is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. From the viewpoint of ease of penetration of melanin precursors, the fiber thickness is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. Examples of leather include cowhide, pigskin, snakeskin, horseskin, goatskin, and crocodile leather.

[0026] The photoheating temperature after photoheating performance is imparted by the photoheating performance-imparting composition of the present invention is preferably 7° C. or higher, more preferably 9° C. or higher. That is, the photoheating performance-imparting composition of the present invention is used, for example, to increase the photoheating temperature of an object to preferably 7° C. or higher, more preferably 9° C. or higher. The photoheating temperature is the temperature that rises upon irradiation with light, and can be measured by the method described in the examples below.

[0027] (Method for imparting photothermal properties) The method of the present invention for imparting photothermal properties to an object comprises applying a composition containing a melanin precursor to the object, thereby producing and fixing melanin within the object, and imparting high photothermal properties and durability to the object. Examples of the object are as described above.

[0028] The application method is not particularly limited, and may be any of a method of immersing an object in the composition containing the melanin precursor, a method of directly applying the composition containing the melanin precursor to the object, or a method of spraying the composition containing the melanin precursor onto the object. A method of immersing an object in a liquid composition containing the melanin precursor is preferred. This may be done while the composition is standing or under stirring. The application method may also be repeated multiple times, for example, two or three times.

[0029] The amount of the composition containing the melanin precursor to be used may be any amount that can impart photothermal properties to the object, and can be determined appropriately depending on the form of use. For example, in a method of immersing an object in a composition containing a liquid melanin precursor, the bath ratio of the composition, i.e., the mass ratio of composition to object, 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 is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less from the viewpoint of cost.

[0030] The application time is preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 2 hours or more, from the viewpoint of sufficient oxidation of the melanin precursor, and is preferably within 24 hours, more preferably within 10 hours, and even more preferably within 2 hours, from the viewpoint of productivity.

[0031] The application temperature is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, from the viewpoint of sufficient oxidation of the melanin precursor, and is preferably 90°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower, from the viewpoint of operability and safety.

[0032] After applying the composition containing the melanin precursor to the object, the object is washed with water, dried, etc. as needed. As a result, the melanin produced from the melanin precursor is fixed inside the object, and the object is endowed with photothermal properties, thereby obtaining an object endowed with photothermal properties. The content of the melanin precursor in the composition, the pH of the composition, etc. are the same as those described above in the section on the photoheat-generating composition.

[0033] (Method for manufacturing photothermal fiber or photothermal leather) The method for producing fibers or leather imparted with photothermal properties of the present invention includes applying a composition containing a melanin precursor to fibers or leather. This causes melanin to be produced and fixed inside the fibers or leather, resulting in fibers or leather imparted with photothermal properties. The fibers or leather imparted with photothermal properties of the present invention (photothermal fibers or photothermal leather) have photothermal properties that are highly fast to washing, making them useful as light-absorbing and heat-generating materials for clothing, etc. Examples of fibers or leather and application means are as described above.

[0034] In relation to the above-described embodiments, the present invention further discloses the following photothermal performance-imparting composition, method for imparting photothermal performance, and method for producing fiber or leather imparted with photothermal performance. <1> A photothermal performance-imparting composition containing a melanin precursor. <2> The melanin precursor contains tyrosine and one or more dihydroxyindoles selected from the group consisting of compounds represented by the following general formula (1) and salts thereof: <1> The photoheat-generating composition according to claim 1,

[0035] [ka]

[0036] (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 represents a hydrogen atom or -COOR (where R is a hydrogen atom, a methyl group, or an ethyl group). 3 represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group. <3> The melanin precursor contains one or two selected from the group consisting of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid. <1> or <2> The photoheat-generating performance-imparting composition according to claim 1. <4> The content of melanin precursor in the photothermal performance-imparting composition is 2 mM or more. <1> ~ <3> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <5> The photoheat-generating composition has a pH of 2 or more and 12 or less at 20°C. <1> ~ <4> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <6> It gives light-generating properties to textiles or leather. <1> ~ <5> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <7> Furthermore, it contains an oxidase that catalyzes the oxidation reaction of melanin precursors. <1> ~ <6> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <8> When 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid are used in combination as melanin precursors, the molar ratio of 5,6-dihydroxyindole to 5,6-dihydroxyindole-2-carboxylic acid is 50:50 to 99:1. <3> ~ <7> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <9> The fiber that imparts photothermal performance is one or more selected from the group consisting of cotton, silk, hemp, wool, paper mulberry, mitsumata, and gampi. <6> ~ <8> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <10> The leather to which photothermal performance is imparted is one or more types selected from the group consisting of cowhide, pigskin, snakeskin, horseskin, goatskin and crocodile leather. <6> ~ <9> 10. The photoheat-imparting composition according to claim 1, wherein the photoheat-imparting composition is a photoheat-imparting composition according to any one of claims 1 to 9. <11> A method for imparting photothermal properties to an object, comprising applying a composition containing a melanin precursor to the object. <12> The means for applying the composition containing a melanin precursor to the object is a method of immersing the object in the composition containing a melanin precursor, or a method of directly applying or spraying the composition containing a melanin precursor to the object. <11> The method described. <13> A method for producing fibers or leather imparted with photothermal properties, comprising applying a composition containing a melanin precursor to the fibers or leather. [Example]

[0037] <Experimental materials> ·fiber Cotton, wool, and silk were purchased from Okadaya Co., Ltd. (https: / / www.okadaya.co.jp / shop / c / c10 / ). Cotton: Fabric OEKO-TEX sheeting (ECO6600) In the treatment experiment, white fabric was used, and black fabric was used as a comparison example. Wool: Raw material, Wool Soft Jersey (32 - 1266), Color: Ivory Silk: Raw material, Silk Spun Twill 24 momme (KBTH241), Color: Natural color Japanese paper: Handmade Japanese paper for dyeing was used (Blue Bear Dyeing Co., Ltd.). · Leather Cowhide (Tochigi Leather Co., Ltd., Product number it - x14) was used. · 5,6 - Dihydroxyindole (DHI) It was prepared according to the method of the prior art document (Japanese Patent No. 7212628). Details are as follows. · Tyrosinase manufactured by SIGMA (Product number T3825) was used.

[0038] <Preparation method of DHI>[[]] A stirrer with a semi - lunar blade was installed in a 5L three - necked glass flask to serve as a reactor. 2L of water was charged into the reactor, and nitrogen gas was passed through the upper part of the flask. DOPA was added to the reactor so that it became 0.33 wt%, and it was dissolved by stirring at 200 rpm. At this time, the liquid temperature was adjusted to 35°C by a water bath. A solution in which 16.8 wt% of potassium hexacyanoferrate(III) and 7.2 wt% of potassium hydrogen carbonate were dissolved in water was used as the oxidizing agent solution. 0.288 mL of the oxidizing agent solution was added to the reactor charged with the DOPA aqueous solution, and reacted for 4 hours to obtain an aqueous DHI solution. The pH was adjusted to 5.0 by adding a 10 wt% phosphoric acid solution to the aqueous DHI solution. The following procedures were performed in a glove box with an oxygen concentration of 0.1% or less, using nitrogen aeration. The DHI aqueous solution was filtered through a 0.2 μm PES filter. The filtered DHI aqueous solution was added to a 5 L glass bottle, and 2 L of ethyl acetate was added as an extractant. The glass bottle was then manually shaken to agitate the solution and perform extraction. The glass bottle was then left to stand, and 1.5 L of the resulting upper layer (ethyl acetate layer) was collected in another glass bottle. 0.7 L of wash water (salt concentration: 8.33 wt%, dipotassium hydrogen phosphate and potassium dihydrogen phosphate dissolved in water, dipotassium hydrogen phosphate / potassium dihydrogen phosphate (mass ratio) = 5.12) was added, and the glass bottle was manually shaken to agitate the solution and perform washing. The glass bottle was then left to stand, and 1.0 L of the resulting upper layer (ethyl acetate layer) was collected in a recovery 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 product to adjust the DHI concentration to 1 wt%. A 6N aqueous solution of sodium hydroxide was then added dropwise to adjust the pH to 8, resulting in a 1% DHI solution.

[0039] Examples 1 to 10, Comparative Examples 1 to 6 A 1% DHI solution (67 mM) was diluted with water to the concentration shown in Table 1 to prepare a DHI treatment solution. A treatment solution containing tyrosine as the active ingredient was also prepared. Tyrosine was added to 20 mM potassium phosphate buffer (pH 7.0) to a concentration of 26.2 mM, and tyrosinase was further added to a concentration of 1000 U / mL.

[0040] <Fiber treatment method> For the photoheat-generating performance-imparting compositions other than those of Comparative Example 2, the treatment solution was added to approximately 15 x 15 cm pieces of cotton, wool, silk, leather, or Japanese paper (hereinafter also referred to as fibers, etc.) in an amount 30 times the mass of the fibers, etc. (bath ratio 30), and the mixture was left to stand for 24 hours at 30°C. After the treatment, the fibers, etc. were thoroughly washed with tap water and air-dried. In Comparative Example 2, the black cotton fabric was cut to a size of approximately 15 x 15 cm.

[0041] <Photo-thermal temperature measurement> Evaluation was carried out in accordance with the light absorption heat retention test (Boken standard BQE A 036). The above-mentioned fabrics were placed 30 cm away from a PRF300W reflector lamp (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 fabric, and the temperature rise was measured from the difference between the temperature before and after irradiation. The photogenerated temperature was calculated as (temperature rise of treated fabric) - (temperature rise of untreated fabric).

[0042] <Color measurement method> The L, a, and b values ​​of the above fibers were measured using a color difference meter (CR-400, manufactured by Konica Minolta). The difference in L, a, and b values ​​from the fibers before and after dyeing was defined as Δ, and the color difference ΔE = {(ΔL) 2 +(Δa) 2 +(Δb) 2} 0.5 was calculated.

[0043] <Washing Instructions> The fabrics were washed repeatedly using a washing machine (Hitachi PS-50AS). Washing: 10L of water, 5g of detergent (Kao Corporation Attack Zero) for 10 minutes Rinse: 10L water, 5 minutes, 1 time

[0044] <Result> The temperature rises of cotton, wool, silk fabric, leather, and Japanese paper before and after the treatment were measured when irradiated with light, and the photothermal temperature was evaluated. The results are shown in Table 1.

[0045] [Table 1]

[0046] As shown in Table 1, the use of an aqueous solution containing a melanin precursor gave the target object photothermal properties. In particular, the use of DHI showed remarkable photothermal properties.

[0047] The fibers of Examples 6, 7, and 8 were washed repeatedly, and the changes in the photoheating temperature were measured. The results are shown in Table 2.

[0048] [Table 2]

[0049] Table 2 confirms that the photothermal performance is stably maintained even after cleaning.

Claims

1. A photothermal performance-imparting composition containing a melanin precursor.

2. 2. The photothermal performance-imparting composition according to claim 1, wherein the melanin precursor contains tyrosine and one or more dihydroxyindoles selected from compounds represented by the following general formula (1) or salts thereof: 【Chemistry 1】 (wherein the dashed line indicates the presence or absence of a π bond. R １ represents a hydroxyl group or an acetoxy group. ２ represents a hydrogen atom or -COOR (wherein R is a hydrogen atom, a methyl group, or an ethyl group). ３ represents a hydrogen atom, an acetyl group, a methyl group, or an ethyl group.

3. 3. The photoheat-imparting composition according to claim 1, wherein the melanin precursor comprises one or two members selected from the group consisting of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.

4. 3. The photoheat-generating composition according to claim 1, wherein the content of the melanin precursor in the photoheat-generating composition is 2 mM or more.

5. 3. The photoheat-generating performance-imparting composition according to claim 1, wherein the photoheat-generating performance-imparting composition has a pH of 2 or more and 12 or less at 20°C.

6. 3. The photothermal performance-imparting composition according to claim 1, which imparts photothermal performance to fibers or leather.

7. A method for imparting photothermal properties to an object, comprising applying a composition containing a melanin precursor to the object.

8. A method for producing fibers or leather imparted with photothermal properties, comprising applying a composition containing a melanin precursor to the fibers or leather.

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