JP7210949B2 - Moisture-releasing and cooling fiber and fiber structure containing said fiber - Google Patents

Description

The present invention relates to a moisture-releasing cooling fiber and a fiber structure containing the fiber.

Moisture-releasing cooling refers to the process in which the temperature of a substance decreases (i.e., cools down) by depriving the substance of the heat of vaporization when the moisture adsorbed in the substance evaporates and transpires (i.e., releases moisture). ) refers to phenomena. When fibers having moisture-releasing and cooling properties are used for applications such as clothing and bedding, a cooling effect on the human body can be expected.

For example, Patent Document 1 discloses a fabric containing a polyester fiber processed by polymerizing a hydrophilic compound on the fiber surface, wherein the temperature rise due to moisture absorption heat generation is 0 compared to the fabric containing the fiber before processing. 0.5° C. or higher, and a moisture-dissipating heat-generating/moisture-dissipating cooling fabric having a temperature drop of 0.5° C. or higher due to moisture-dissipating cooling.

Further, Patent Document 2 discloses a fabric made of 60% by weight or more of hydrophobic synthetic fibers, in which highly moisture-absorbing and releasing organic fine particles made of an acrylic polymer having a salt-type carboxyl group and a crosslinked structure are graft-polymerized on the fiber surface. Moisture wicking and releasing fabrics are disclosed which are characterized by being bound by a sintering agent, and the fabrics are said to have a moisture releasing and cooling effect.

Furthermore, FIG. 5 of Patent Document 3 and paragraphs [0005] to [0007] of Patent Document 4 disclose that crosslinked acrylate fibers have a moisture releasing and cooling action.

JP-A-2002-88653 JP-A-2002-38375 JP-A-9-59872 Japanese Patent Application Laid-Open No. 2004-218111

However, the technique of each of the documents described above has a problem that the moisture-dissipating cooling effect is difficult to feel because the moisture-dissipating cooling effect is small or does not last. The present invention was invented in view of the current state of the prior art, and its object is to provide a fiber having a high moisture-releasing and cooling effect that can be maintained, and a fiber structure containing the fiber.

The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have found that the following means can provide a large and sustained moisture-releasing and cooling effect, and have completed the present invention.

(1) A core-sheath fiber having a surface layer portion mainly composed of a polymer having a crosslinked structure and a carboxyl group, and a core portion mainly composed of an acrylonitrile-based polymer, and having a numerical value A represented by the following formula 3: is 0.050 or more and less than 0.080, and the cooling temperature (ΔT ₃₀ ) determined by the following evaluation method is 1.5° C. or more.
[Formula 3] A = Amount of carboxyl groups possessed by the fiber [mmol/g] / Percentage of area occupied by "a surface layer portion mainly composed of a polymer having a crosslinked structure and a carboxyl group" in the cross section of the fiber [%]
(Evaluation method)
A fiber is used as a card web, and 2.5 g is cut from the card web and folded into a size of 16 cm x 9 cm to obtain a measurement sample. The measurement sample is left for 16 hours in an atmosphere of 35° C. and 90% relative humidity. Next, an electronic thermometer sensor is inserted into the center of the measurement sample, transferred to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and the temperature indicated by the electronic thermometer after 30 minutes (t ₃₀ [° C.]) to read. From this result, ΔT ₃₀ is obtained by the following formula 1.
[Formula 1] ΔT ₃₀ [°C] = 20-t ₃₀

(2) The moisture-releasing cooling fiber according to (1), wherein the cooling temperature (ΔT ₅ ) determined by the following evaluation method is 1.0°C or higher.
(Evaluation method)
A fiber is used as a card web, and 2.5 g is cut from the card web and folded into a size of 16 cm x 9 cm to obtain a measurement sample. The measurement sample is left for 16 hours in an atmosphere of 35° C. and 90% relative humidity. Next, insert an electronic thermometer sensor into the center of the measurement sample, move it to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and the temperature indicated by the electronic thermometer after 5 minutes (t ₅ [° C.]) to read. From this result, _ΔT5 is obtained by the following equation 2.
[Formula 2] ΔT ₅ [°C] = 20-t ₅

( 3 ) A fiber structure characterized by containing 5% by mass or more of the moisture-releasing cooling fiber according to (1) or ( 2 ).

The moisture-releasing and cooling fiber of the present invention has a characteristic that the moisture-releasing and cooling effect is large and the effect can be maintained. The moisture-releasing and cooling fiber of the present invention having such properties is suitable as a material for, for example, summer clothing (underwear, T-shirts, hats, etc.), or summer bedding (side material and batting of skin comforter, bed pad). can be used.

The present invention will be described in detail below. The moisture-releasing cooling fiber of the present invention exhibits a cooling temperature _ΔT30 of 1.5° C. or higher, preferably 2.0° C. or higher, as determined by the evaluation method described later. That is, the moisture-releasing cooling fiber of the present invention maintains a temperature lower than the ambient temperature by 1.5° C. or more even after 30 minutes from the start of moisture releasing. Due to such characteristics, the fiber structure using the moisture-releasing cooling fiber of the present invention can be made excellent in the sustainability of the cooling effect. Furthermore, if the ΔT ₆₀ is preferably 1.0° C. or higher, more preferably 1.5° C. or higher, the cooling effect can be further improved in durability.

Further, the moisture-releasing cooling fiber of the present invention desirably exhibits a cooling temperature _ΔT5 of 1.0° C. or higher, preferably 1.5° C. or higher, as determined by the evaluation method described later. The fact that the cooling temperature ΔT ₅ is 1.0° C. or more indicates that the fibers are cooled to a temperature that is 1.0° C. or more lower than the ambient temperature 5 minutes after the start of moisture release. Due to such properties, a fiber structure using such fibers can obtain a rapid cooling effect.

The moisture-releasing and cooling fiber of the present invention includes a surface layer portion (hereinafter also simply referred to as "surface layer portion") mainly composed of a polymer having a crosslinked structure and a carboxyl group, and a core mainly composed of an acrylonitrile polymer. A core-sheath fiber having a portion (hereinafter also simply referred to as a “core portion”) can be mentioned. Here, the term "main component" indicates that it is the most abundant component in each of the surface layer portion and the central portion, and in normal cases, each polymer preferably contains 90 It accounts for 95% by mass or more, more preferably 95% by mass or more. Here, the acrylonitrile-based polymer that constitutes the central portion may have a crosslinked structure.

In such a core-sheath fiber, moisture absorbed by the fiber is released by the highly hydrophilic carboxyl group. Makes it easier to get the cooling effect. Conversely, even if carboxyl groups are present in the central part, the moisture absorbed in the central part cannot be released unless it moves a long distance to the fiber surface, so it is difficult to contribute to the cooling effect.

In addition, by forming the central portion of the acrylonitrile-based polymer, the physical properties of the fibers do not become too low, making it easier to perform spinning processing and improving the durability during use. For this reason, in such a core-sheath fiber, it is possible to increase the content ratio in the fiber structure, and it is possible to exhibit a more excellent moisture-releasing and cooling effect.

Furthermore, in the core-sheath fiber described above, the numerical value A represented by the following formula 3 is preferably 0.050 or more and less than 0.080, and more preferably 0.055 or more and less than 0.070.
[Formula 3] A = amount of carboxyl groups [mmol/g] / ratio of area occupied by the surface layer in the cross section of the fiber [%]

Here, the numerical value A is a numerical value that correlates with the concentration of carboxyl groups in the surface layer of the fiber. . Therefore, the larger the numerical value A, the more moisture can be contained in the surface layer of the fiber, and the faster the moisture can be released.

In order to obtain such effects, the numerical value A is preferably 0.050 or more, more preferably 0.055 or more. However, if the numerical value A is 0.080 or more, the surface layer of the fiber becomes tacky due to moisture absorption, and the fibers tend to stick to each other. sometimes.

In addition, the moisture-releasing cooling fiber of the present invention has a saturated moisture absorption rate in an atmosphere of 35°C and 90% relative humidity, and is saturated in the above atmosphere and moved to an atmosphere of 20°C and 45% relative humidity. The difference in moisture absorption after 30 minutes of exposure is preferably 10 percentage points or more, more preferably 12 percentage points or more, and still more preferably 14 percentage points or more. The larger the difference in moisture absorption rate, the higher the moisture release rate. If the difference is less than 10 percentage points, the cooling temperature described above may not be obtained sufficiently.

In addition, the counter ion of the carboxyl group in the polymer having a crosslinked structure and a carboxyl group is not limited to hydrogen ions, but also the cations of alkali metals such as lithium, sodium and potassium, and the cations of alkaline earth metals such as magnesium and calcium. One or more of cations, cations of other metals such as manganese, copper, zinc and silver, ammonium ions, etc. can be selected according to the required properties. When such a carboxyl group having a counter ion other than a hydrogen ion (hereinafter referred to as a salt-type carboxyl group) is present, the above-mentioned saturated moisture absorption difference becomes larger and the moisture release rate becomes larger. A large cooling effect can be expected. The amount of such salt-type carboxyl groups is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, based on the total amount of carboxyl groups. On the other hand, if the amount of salt-type carboxyl groups is too large, the fiber tends to become tacky or brittle when absorbing moisture. It is desirable to Further, when sodium ions or potassium ions are selected as counter ions, the cooling effect can be further enhanced.

Next, as a representative method for producing the moisture-releasing cooling fiber of the present invention, a method of subjecting the surface layer portion of the acrylonitrile-based fiber to a cross-linking introduction treatment and a hydrolysis treatment can be employed. The cross-linking introduction treatment may be applied not only to the surface layer portion but also to the central portion. The acrylonitrile-based fiber as a raw material can be produced from an acrylonitrile-based polymer by a known method. The acrylonitrile polymer preferably contains 50% by mass or more of acrylonitrile, more preferably 80% by mass or more, and even more preferably 85% by mass or more. As will be described later, the crosslinked structure is formed by the reaction between the nitrile groups of the acrylonitrile-based polymer and the cross-linking agent. Therefore, when the acrylonitrile content in the acrylonitrile-based polymer is small, the amount of the crosslinked structure that can be introduced decreases. , the fiber strength may be insufficient in terms of processing and practical use.

A crosslinked structure is introduced into the acrylonitrile-based fiber as described above. Although a conventionally known cross-linking agent may be used for introducing the cross-linked structure, it is preferable to use a nitrogen-containing compound from the viewpoint of the efficiency of introducing the cross-linked structure. As the nitrogen-containing compound, it is preferable to use an amino compound having two or more primary amino groups or a hydrazine-based compound. Examples of amino compounds having two or more primary amino groups include diamine compounds such as ethylenediamine and hexamethylenediamine, diethylenetriamine, 3,3'-iminobis (propylamine), N-methyl-3,3'-iminobis ( propylamine), triamine compounds such as triethylenetetramine, N,N'-bis(3-aminopropyl)-1,3-propylenediamine, N,N'-bis(3-aminopropyl)-1,4- Tetramine-based compounds such as butylenediamine, polyamine-based compounds having two or more primary amino groups such as polyvinylamine and polyallylamine are exemplified. Examples of hydrazine-based compounds include hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, hydrazine hydrobromide, and hydrazine carbonate. Although the upper limit of the number of nitrogen atoms in one molecule is not particularly limited, it is preferably 12 or less, more preferably 6 or less, and particularly preferably 4 or less. When the number of nitrogen atoms in one molecule exceeds the above upper limit, the size of the cross-linking agent molecule becomes large, which may make it difficult to introduce a cross-linked structure into the fiber. The conditions for introducing the crosslinked structure are not particularly limited, and can be appropriately selected in consideration of the reactivity between the crosslinker used and the acrylonitrile-based fiber, the amount of the crosslinked structure, and the like. For example, when a hydrazine-based compound is used as a cross-linking agent, the above-mentioned acrylonitrile-based fiber is immersed in an aqueous solution to which the hydrazine-based compound is added so that the hydrazine concentration is 0.1 to 10% by mass. ℃ for 2 to 10 hours.

After the introduction of the crosslinked structure, hydrolysis treatment with an alkaline metal compound is applied to hydrolyze the nitrile groups present in the surface layer of the fiber to form carboxyl groups. As specific treatment conditions, various conditions such as the concentration of the treatment agent, reaction temperature, and reaction time may be appropriately set in consideration of the above-described carboxyl group concentration. More preferably, the treatment is carried out in an aqueous solution of 1 to 5% by weight of the treatment agent at a temperature of 80 to 150° C. for 2 to 10 hours, which is industrially preferable and fiber physical. Here, rather than performing the above-described cross-linking introduction treatment and hydrolysis treatment in order, it is preferable to simultaneously treat them collectively using an aqueous solution in which each treatment agent is mixed. Furthermore, in this simultaneous treatment, it is preferable to perform the acid treatment under milder conditions at a lower concentration of the alkali metal compound than before, and to perform the subsequent acid treatment under more severe conditions at a higher temperature than before. The thus-obtained moisture-releasing and cooling fiber can have a structure in which more carboxyl groups are present in the surface layer portion than before, and the relatively hard acrylonitrile-based polymer is preserved in the central portion.

Counter ions of the formed carboxyl group include those described above. Methods for adjusting the desired counter ion include ion exchange treatment with metal salts such as nitrates, sulfates, and hydrochlorides, acid treatment with nitric acid, sulfuric acid, hydrochloric acid, formic acid, etc., or pH adjustment treatment with alkaline metal compounds, etc. There is a method of applying.

A fiber structure containing the moisture-releasing cooling fibers of the present invention can be formed using the moisture-releasing cooling fibers of the present invention alone or in combination with other fibers. When combined with other fibers, the moisture-releasing cooling fiber of the present invention is preferably used in an amount of 5% by mass or more, more preferably 10% by mass or more, from the viewpoint of effect expression. If the usage rate is less than 5% by mass, uniform mixing may become difficult. Other fibers that can be combined include, for example, feathers, wool, animal hair, silk, cotton, polyester fibers, polypropylene fibers, polyethylene fibers, polyamide fibers, polyurethane fibers, acrylic fibers, and cellulosic fibers. can.

The form of the fiber structure of the present invention includes batting, thread, knitted fabric, woven fabric, pile fabric, non-woven fabric, and the like. More specifically, innerwear, pants, shirts, uniforms, cut and sewn denim, pajamas, bathrobes, leggings, socks, stockings, supporters, stomach wraps, gloves, handkerchiefs, towels, scarves, stoles, mufflers, masks, face masks, Hats, pillows, pillowcases, sheets, towel blankets, bed pads, mats, rugs, carpets and the like can be mentioned. The content form of the moisture-releasing and cooling fibers in the fiber structure of the present invention is, for example, the case of being distributed substantially uniformly, the case of being concentrated in a specific place, or the case of being distributed at a specific ratio for each place. can be considered.

EXAMPLES Examples are shown below to facilitate understanding of the present invention, but these are merely illustrative and the gist of the present invention is not limited by these.

<Method for evaluating cooling temperature>
A card web is used as a sample fiber, and 2.5 g is cut from the card web and folded into a size of 16 cm×9 cm to obtain a measurement sample. The measurement sample is left for 16 hours in an atmosphere of 35° C. and 90% relative humidity. Next, insert an electronic thermometer sensor into the center of the measurement sample, move it to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and after a certain period of time (n [minutes]), the temperature indicated by the electronic thermometer ( t _n [°C]). From this result, _ΔTn is obtained by the following formula.
_ΔTn [°C] ₌ 20-tn

<Calculation of numerical value A>
1. Percentage of cross-sectional area of the surface layer in the cross-section of the fiber The sample fiber is placed in a dyeing bath containing 2.5% cationic dye (Nichilon Black G 200) and 2% acetic acid with respect to the fiber mass, and the bath ratio is 1:80. and boiled for 30 minutes, then washed with water, dehydrated and dried. The obtained dyed fiber is thinly sliced perpendicular to the fiber axis, and the cross section of the fiber is observed with an optical microscope. At this time, the central portion made of the acrylonitrile-based polymer is dyed black, and the surface layer portion having many carboxyl groups is green because the dye is not sufficiently fixed. In the fiber cross section, measure the diameter (L1) of the fiber and the diameter (L2) of the central part dyed black bordering on the part where the color starts to change from green to black, and use the following formula to calculate the surface layer cross-sectional area of the fiber Calculate the ratio to the cross-sectional area. An average value of 10 samples is taken.
Percentage of surface layer cross-sectional area in fiber cross section [%] = [1-{(L2/2) ² π/(L1/2) ² π}] × 100

2. About 1 g of a carboxyl group fiber sample is immersed in 50 ml of a 1 mol/l hydrochloric acid aqueous solution for 30 minutes. The fiber sample is then immersed in water at a bath ratio of 1:500. After 15 minutes, when it is confirmed that the bath pH is 4 or more, it is dried (if the bath pH is less than 4, it is washed with water again). Next, about 0.2 g of the sufficiently dried fiber sample was precisely weighed (W1 [g]), 100 ml of water was added, and 15 ml of 0.1 mol/l sodium hydroxide aqueous solution and 0.4 g of sodium chloride were added. and phenolphthalein are added and stirred. After 15 minutes, the sample fibers and the filtrate are separated by filtration, and the sample fibers are then washed with water until the color of phenolphthalein disappears. A mixture of the washing water and the filtrate at this time is titrated with a 0.1 mol/l aqueous solution of hydrochloric acid until the color of phenolphthalein disappears, and the consumption of the aqueous solution of hydrochloric acid (V1 [ml]) is obtained. From the measured values obtained, the total carboxyl group content is calculated according to the following formula.
Carboxyl group amount [mmol / g] = (0.1 × 15-0.1 × V1) / W1

3. Number A
It is calculated by the following formula using the numerical values obtained above.
Numeric value A = amount of carboxyl groups [mmol/g] / ratio of area occupied by the surface layer in the cross section of the fiber [%]

<Moisture absorption rate difference (ease of moisture release)>
About 5 g of a sufficiently dried fiber sample is precisely weighed (W1 [g]). The sample is allowed to stand at a temperature of 35° C. and a relative humidity of 90% for 16 hours, and the mass of the sample that absorbs moisture is measured (W2 [g]). The same sample is again allowed to stand under a relative humidity of 90% for 16 hours, immediately moved to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and after 30 minutes, the mass of the sample is measured (W3 [g]). . From the above measurement results, each moisture absorption rate is calculated by the following formula.
Saturated moisture absorption rate [%] at temperature of 35°C and relative humidity of 90% = (W2-W1)/W1 x 100
Moisture absorption rate [%] after 30 minutes of moving to a temperature of 20 ° C and a relative humidity of 45% = (W3 - W1) / W1 x 100
A difference in moisture absorption rate is calculated from each moisture absorption rate obtained as described above.

<Proportion of salt-type carboxyl groups>
The amount of H-type carboxyl groups is calculated in the same manner as described above for measuring the amount of carboxyl groups, except that the initial immersion in a 1 mol/l hydrochloric acid aqueous solution and the subsequent immersion in water (water washing) are not performed. By subtracting the amount of H-type carboxyl groups from the amount of carboxyl groups described above, the amount of salt-type carboxyl groups is obtained, and the ratio to the amount of carboxyl groups described above is calculated.

[Example 1]
An acrylonitrile-based polymer containing 90% by mass of acrylonitrile and 10% by mass of methyl acrylate (limiting viscosity [η] in dimethylformamide at 30°C = 1.5) was dissolved in 48% by mass of an aqueous solution of rhodan soda to obtain a spinning dope. prepared. The spinning stock solution was subjected to spinning, washing, drawing, crimping and heat treatment according to the usual methods to obtain an acrylic fiber having a single fiber fineness of 1.7 dtex.

The resulting acrylic fiber was simultaneously subjected to cross-linking treatment and hydrolysis treatment at 100° C. for 2 hours in an aqueous solution containing 0.5% by mass of hydrazine hydrate and 2.0% by mass of sodium hydroxide. % nitric acid aqueous solution at 100° C. for 3 hours and washed with water. The resulting fiber was immersed in water, sodium hydroxide was added to adjust part of the carboxyl groups to a salt form, washed with water and dried to obtain moisture-releasing and cooling fiber A with a fineness of 3.0 dtex. . Table 1 shows the evaluation results of the obtained fibers. In the infrared absorption measurement of such fibers, there is absorption around 2250 cm ⁻¹ derived from nitrile groups, and hydrolysis of nitrile groups is progressing in the surface layer of the fiber, but nitrile groups are not present in the center of the fiber. confirmed to remain.

[Example 2]
A moisture-releasing cooling fiber B having a fineness of 2.5 dtex was obtained in the same manner as in Example 1, except that the concentration of sodium hydroxide was changed to 1.5% by mass. Table 1 shows the evaluation results of the obtained fibers.

[Example 3]
A moisture-releasing cooling fiber C having a fineness of 3.5 dtex was obtained in the same manner as in Example 1, except that the concentration of sodium hydroxide was changed to 2.5% by mass. Table 1 shows the evaluation results of the obtained fibers.

[Comparative Example 1]
A fiber D having a fineness of 4.2 dtex was obtained in the same manner as in Example 1, except that the concentration of sodium hydroxide was changed to 3.5% by mass. Table 1 shows the evaluation results of the obtained fibers.

[Comparative Examples 2 and 3]
Table 1 shows the evaluation results for rayon with a fineness of 1.4 dtex and polyester with a fineness of 1.4 dtex.

As can be seen from Table 1, the fibers of Examples 1 to 3 maintain a temperature lower than the ambient temperature by 1.5°C or more even after 30 minutes from the start of moisture release. It is cooled to a temperature 1.0° C. or more lower than the ambient temperature after a minute has elapsed, and has both rapid and sustained cooling properties. In contrast, the fiber of Comparative Example 1 was inferior in cooling properties.

[Example 4]
A spun yarn having a cotton count of 45/1 was prepared by mixing moisture-releasing cooling fiber A and polyester fiber at a ratio of 30/70. Also, a spun yarn with a cotton count of 40/1 was produced only from cotton. Next, using these spun yarns, a knitted fabric of tenjiku knitting was produced. Table 2 shows the result of measuring the cooling temperature using the knitted fabric in place of the card web in the method of measuring the cooling temperature described above and the blend ratio of each fiber in the knitted fabric.

[Comparative Example 4]
Using only the cotton spun yarn produced in Example 4, a cotton sheeting knitted fabric was produced, and the cooling temperature was measured using the knitted fabric. Table 2 shows the results.

The fiber structure of Example 4 using the cooling and moisture-releasing fibers of the present invention was superior in cooling properties to the fiber structure of Comparative Example 4, which was made of 100% cotton.

Claims (3)

A core-sheath fiber having a surface layer portion mainly composed of a polymer having a crosslinked structure and a carboxyl group, and a core portion mainly composed of an acrylonitrile-based polymer, wherein the numerical value A represented by the following formula 3 is 0.00. 050 or more and less than 0.080, and a cooling temperature (ΔT ₃₀ ) determined by the following evaluation method is 1.5°C or more.
[Formula 3] A = Amount of carboxyl groups possessed by the fiber [mmol/g] / Percentage of area occupied by "a surface layer portion mainly composed of a polymer having a crosslinked structure and a carboxyl group" in the cross section of the fiber [%]
(Evaluation method)
A fiber is used as a card web, and 2.5 g is cut from the card web and folded into a size of 16 cm x 9 cm to obtain a measurement sample. The measurement sample is left for 16 hours in an atmosphere of 35° C. and 90% relative humidity. Next, an electronic thermometer sensor is inserted into the center of the measurement sample, transferred to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and the temperature indicated by the electronic thermometer after 30 minutes (t ₃₀ [° C.]) to read. From this result, ΔT ₃₀ is obtained by the following formula 1.
[Formula 1] ΔT ₃₀ [°C] = 20-t ₃₀ 2. The moisture-releasing cooling fiber according to claim 1, wherein the cooling temperature (ΔT ₅ ) determined by the following evaluation method is 1.0° C. or higher.
(Evaluation method)
A fiber is used as a card web, and 2.5 g is cut from the card web and folded into a size of 16 cm x 9 cm to obtain a measurement sample. The measurement sample is left for 16 hours in an atmosphere of 35° C. and 90% relative humidity. Next, insert an electronic thermometer sensor into the center of the measurement sample, move it to an atmosphere with a temperature of 20 ° C. and a relative humidity of 45%, and the temperature indicated by the electronic thermometer after 5 minutes (t ₅ [° C.]) to read. From this result, _ΔT5 is obtained by the following equation 2.
[Formula 2] ΔT ₅ [°C] = 20-t ₅ A fiber structure containing 5% by mass or more of the moisture-releasing cooling fiber according to claim 1 or 2 .