JP4529145B2 - Slow moisture absorption and release cross-linked acrylic fiber - Google Patents

Description

【００４７】
実施例１および２は、式１〜式３を満たしており、図１からも安定に発熱が持続すると考えられる。これに対して、比較例１においては、飽和吸湿率が高いが、初期の短時間で多量に吸湿し、その後吸湿速度が遅くなるため、持続的な発熱という点については劣ると考えられる。また、比較例２および３においては、吸湿速度は遅いものの、飽和吸湿率が小さく、比較的短時間で飽和に近い吸湿率に達してしまっているため、持続的な発熱は期待できないものと考えられる。【Technical field】
[0001]
The present invention relates to a slow-absorbing and releasing moisture-crosslinking acrylic fiber. In particular, the present invention relates to a fiber that has a high saturated moisture absorption rate and can generate heat continuously by absorbing moisture gradually.
[Background]
[0002]
In recent years, with increasing demands for comfort in living environments, clothing and bedding are required to have a humidity control function and a high heat retention function. A fiber having moisture absorption / release properties is promising as a material that can meet such a demand because it generates heat during moisture absorption. Cotton, wool, rayon, acetate, cross-linked acrylic fiber, etc. are known as hygroscopic and hygroscopic fibers. Among them, cross-linked acrylic fiber is actively researched as having excellent moisture control and hygroscopic properties. Has been done.
[0003]
For example, Patent Document 1 discloses a cross-linked acrylic fiber having a controlled absorption / desorption rate. The fiber is characterized by having harmonious functions such as a temperature control / humidity control function, pH buffering property, antistatic property, water retention, etc., and a saturated moisture absorption rate in an atmosphere of 20 ° C. × 65% RH is 15 to 15%. In applications that require a high moisture absorption, such as sports clothing, which is as low as 35%, it is not fully satisfactory. In addition, since the saturated moisture absorption rate is low, the calorific value is small and it is difficult to obtain a large heat retention effect.
[0004]
In this regard, Patent Document 2 discloses a cross-linked acrylic fiber that has a high moisture absorption rate of 39 to 89% in a saturated moisture absorption rate at 20 ° C. and 65% RH, and has a high moisture absorption rate. It is described that the fiber has a high hygroscopic calorific value of 130 to 800 cal per gram of dry weight. However, since the fiber has a high moisture absorption rate, most of the heat generation occurs within a short time in the initial stage of moisture absorption. For this reason, there is not much sustainability of heat generation, and it is difficult to obtain a heat retaining effect for a long time.
[Patent Document 1]
Japanese Patent Laid-Open No. 9-59872 [Patent Document 2]
JP-A-9-158040 [Disclosure of the Invention]
[Problems to be solved by the invention]
[0005] As described above, cross-linked acrylic fibers so far have characteristics such as temperature control / humidity control functions, pH buffering properties, antistatic properties, harmonious functions such as water retention, high moisture absorption rate, and high moisture absorption rate. However, it did not take much consideration into the sustainability of heat generation and heat retention. An object of the present invention is to provide a crosslinked acrylic fiber that has a high saturated moisture absorption rate and that gradually absorbs moisture and is excellent in sustainability of moisture absorption heat generation.
[Means for Solving the Problems]
[0006] As a result of diligent studies to achieve the above-mentioned object, the present inventor has reached the present invention shown below.
[0007]
[1] crosslinked structure and 5.4 ~10mmol / g of a salt-type carboxyl group, and 5.4 mmol / g or more is Mg salt type carboxyl groups crosslinked acrylic absorbing of the salt type carboxyl group Wet fiber, saturated moisture absorption at 20 ° C. × 95% RH (a (%)), saturated moisture absorption at 20 ° C. × 50% RH (b (%)), and 20 ° C. × 95% RH × 60 minutes The moisture absorption rate (c (%)) of the above satisfies the following formulas (1) to (3).
a (%) ≧ 60 (1)
a−b (%) ≧ 30 (2)
c / a ≦ 0.5 (3)
[2] The relationship of the following equation (4) between 20 ° C. × 95% RH × 90 minutes moisture absorption (d (%)) and 20 ° C. × 95% RH × 180 minutes moisture absorption (e (%)) The sustained-absorption / release moisture-crosslinking acrylic fiber according to [1], wherein
e / d ≧ 1.5 (4)

[3] The sustained-absorbing / releasing acrylic fiber according to [1] or [2], wherein the degree of swelling is 1.5 g / g or less.
【The invention's effect】
[0008]
The slow moisture-releasing and cross-linking acrylic fiber of the present invention has characteristics that were not found in conventional cross-linked acrylic fibers, that is, the saturated moisture absorption rate is very high, and it generates heat continuously by gradually absorbing moisture. It is what has. The slow-absorbing and releasing moisture-crosslinking acrylic fiber of the present invention having such characteristics can be suitably used for applications requiring a humidity control function and a high heat retaining function such as autumn / winter clothing, bedding, or sports clothing such as ski wear.
[Brief description of the drawings]
[0009]
FIG. 1 shows moisture absorption curves of fibers of Examples 1 and 2 and Comparative Examples 1 to 3.
BEST MODE FOR CARRYING OUT THE INVENTION
[0010]
The present invention is described in detail below. First, in the present invention, the functional group having the counter ion bonded to “—COO ⁻ ” is “carboxyl group”, the counter ion of the carboxyl group is hydrogen ion, “H type”, and other ions It is expressed as “salt type”. For example, “—COOH” is expressed as “H-type carboxyl group”.
[0011]
The controlled moisture absorption / release crosslinked acrylic fiber of the present invention has a saturated moisture absorption rate (a (%)) at 20 ° C. × 95% RH, a saturated moisture absorption rate (b (%)) at 20 ° C. × 50% RH, and 20 ° C. The moisture absorption rate (c (%)) of x95% RH x 60 minutes satisfies the following formulas (1) to (3).
a (%) ≧ 60 (1)
a−b (%) ≧ 30 (2)
c / a ≦ 0.5 (3)
[0012]
Here, as shown in the formula (1), in the fiber of the present invention, a (%) is 60% or more, preferably 65% or more, more preferably 70% or more. Although the fiber of the present invention absorbs and releases moisture gradually, the higher the final moisture absorption rate, the longer the duration of moisture absorption heat generation. That is, if a (%) is small, continuous heat generation cannot be expected.
[0013]
Further, the left side of the formula (2) indicates the difference in saturated moisture absorption between 95% RH and 50% RH, and the larger the value, the higher the moisture absorption performance in the realistic humidity range of the environment actually used. Represents that. The fiber of the present invention has this value of 30% or more, preferably 35% or more, more preferably 40% or more. If this value is 30% or more, an effect of suppressing the feeling of stuffiness when the moisture in the clothes increases due to sweating is expected.
[0014]
C (%) is the moisture absorption rate when 60 minutes have passed after the fibers were dried at 105 ° C. × 16 hours and then placed in a constant temperature and humidity chamber adjusted to 20 ° C. × 95% RH. * It is calculated | required from the difference of the fiber weight when 60 minutes passes at 20 degreeC x 95% RH after drying for 16 hours. Therefore, the left side of Equation (3) indicates how much moisture is absorbed in the first hour when the saturated moisture absorption rate of the fiber is 1, and the smaller the value, the slower the moisture absorption. . This value is 0.5 or less, preferably 0.4 or less, more preferably 0.3 or less, and the slow-absorbing / releasing crosslinked acrylic fiber of the present invention absorbs moisture slowly. Fever gradually occurs and becomes persistent. When the value of c (%) is small, it becomes difficult to realize moisture absorption heat generation. Therefore, from the viewpoint of obtaining effective heat generation, c (%) is 5% or more, preferably 7% or more. desirable.
[0015]
Moreover, the sustained moisture-releasing and cross-linking acrylic fiber of the present invention has a cross-linked structure and a salt-type carboxyl group. The salt-type carboxyl group is a part related to the moisture absorption / release performance of the crosslinked moisture-absorbing acrylic fiber of the present invention, and the saturated moisture absorption rate can be increased as the amount thereof is increased. However, on the other hand, the hydrophilicity of the fiber is also increased, so that water swelling becomes intense, the strength is lowered and the shape is lost, and in some cases, the phenomenon such as elution into water may occur. Conversely, if the amount of the salt-type carboxyl group is too small, a sufficient saturated moisture absorption rate cannot be obtained. Accordingly, the amount of the salt-type carboxyl group is preferably determined so as to satisfy the above formulas (1) to (3) in consideration of the above matters. Generally, 1-10 mmol / g is preferable, More preferably, it is 3-10 mmol / g, More preferably, it is 3-8 mmol / g.
[0016]
Further, an H-type carboxyl group may be present in addition to the salt-type carboxyl group, but the total amount with the salt-type carboxyl group is 10 mmol / g or less from the viewpoint of water swelling and elution described above. It is desirable.
[0017]
Mg is most suitable as the salt type of the salt type carboxyl group. In particular, good performance can be obtained when the Mg salt-type carboxyl group is contained at 2 mmol / g, preferably 2.5 mmol / g or more. A salt-type carboxyl group other than the Mg salt type or an H-type carboxyl group may coexist. Examples of the salt type carboxyl group other than the Mg salt type include alkali metals such as Li, Na, and K, alkaline earth metals such as Be, Ca, and Ba, Cu, Zn, Al, Mn, Ag, Fe, Co, Ni, and the like Other metals, organic cations such as NH ₄ , amine and the like. Further, even when Mg is not used, as long as the above formulas (1) to (3) are satisfied by using a plurality of salt-type carboxyl groups other than the Mg salt-type and H-type carboxyl groups in combination. Can be adopted.
[0018]
The crosslinked structure of the gradual moisture-releasing and cross-linking acrylic fiber of the present invention is a part mainly responsible for maintaining the form of the fiber. As described above, increasing the amount of salt-type carboxyl groups to enhance moisture absorption / release characteristics causes phenomena such as “disintegration of shape” and “the polymer itself elutes in water”, but it has a crosslinked structure. Thus, such a phenomenon can be suppressed. Such a crosslinked structure is obtained by, for example, copolymerizing a monomer having a reactive functional group with a polymer constituting the fiber, spinning it into a fiber, and then reacting with the reactive functional group. It can form by making the compound (henceforth a crosslinkable compound) react.
[0019]
Here, the combination of the monomer having a reactive functional group and the crosslinkable compound is not particularly limited, but a nitrile group-containing monomer such as acrylonitrile or methacrylonitrile and a hydrazine such as hydrazine hydrate or hydrazine sulfate. A combination with a compound is a typical example.
[0020]
Further, the gradual moisture-releasing and cross-linking acrylic fiber of the present invention has a moisture absorption rate (d (%)) of 20 ° C. × 95% RH × 90 minutes and a moisture absorption rate (e (%) of 20 ° C. × 95% RH × 180 minutes. It is desirable that the relationship of the following formula (4) is established between
e / d ≧ 1.5 (4)
[0021]
Here, d (%) and e (%) are numerical values obtained in the same manner as c (%) described above, with the elapsed time being 90 minutes or 180 minutes, respectively. That is, e / d represents how many times the moisture absorption rate after the lapse of 180 minutes is greater than the moisture absorption rate after the lapse of 90 minutes. In the fiber of the present invention, this numerical value is 1.5 or more, preferably 1.7 or more. When this numerical value is close to 1, it means that the difference between d (%) and e (%) is small. Almost no moisture is absorbed in 90 minutes from 90 minutes after the start of moisture absorption, and 90 minutes after the start of moisture absorption. It means that it is already close to saturation at the time. In such a case, almost no continuous heat generation can be expected. Further, when e / d is about 2 or more, the moisture absorption rate between 90 minutes and 180 minutes after the start of moisture absorption is about the same or more than the moisture absorption rate up to 90 minutes after the start of moisture absorption. It can be expected that it will absorb moisture and generate heat continuously. Note that d (%) is 7% or more, preferably 10% or more, from the viewpoint of obtaining effective heat generation as in the case of c (%) described above.
[0022]
Further, it is desirable that the gradual moisture-releasing and cross-linking acrylic fiber of the present invention has a degree of swelling of 1.5 g / g or less, preferably 1.3 g / g or less as measured by the method described later. If the degree of swelling exceeds 1.5 g / g, the fiber dimensions are likely to change due to moisture absorption, and spinning and subsequent processing into a knitted or woven fabric may be difficult.
[0023]
Next, a typical method for producing the above-described sustained moisture-releasing and releasing crosslinked acrylic fiber of the present invention will be described below, but the method of producing the fiber of the present invention is not limited to this.
[0024]
First, the acrylic fiber used as a starting material may be a fiber formed of an AN polymer containing 40% by weight or more, preferably 50% by weight or more, more preferably 80% by weight or more of acrylonitrile (hereinafter referred to as AN). That's fine. The form may be any form such as short fibers, tows, yarns, knitted fabrics, non-woven fabrics, etc., and may be intermediate products or waste fibers. The AN polymer may be either an AN homopolymer or a copolymer of AN and another monomer, but as a copolymer component other than AN, sulfonic acid groups such as methallyl sulfonic acid and p-styrene sulfonic acid -Containing monomers and salts thereof, carboxylic acid group-containing monomers such as (meth) acrylic acid and itaconic acid and salts thereof, monomers such as styrene, vinyl acetate, (meth) acrylic acid esters and (meth) acrylamides There is no particular limitation as long as it is a monomer copolymerizable with AN.
[0025]
The acrylic fiber is subjected to a cross-linking treatment with a hydrazine compound and is formed into a cross-linked acrylic fiber in the sense that it is no longer dissolved in the solvent of the acrylic fiber, and at the same time, the nitrogen content increases. The means for introducing the crosslinking is not particularly limited, but a means capable of adjusting the increase in nitrogen content by this treatment to preferably 0.1 to 10% by weight, more preferably 1 to 10% by weight is desirable. . In addition, as a means for adjusting the nitrogen content to 0.1 to 10% by weight, a means for treating the hydrazine compound in an aqueous solution having a concentration of 5 to 60% by weight at a temperature of 50 to 120 ° C. within 5 hours is industrial. Is preferable.
[0026]
The hydrazine-based compound used here is not particularly limited, but besides hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, hydrazine bromate, hydrazine carbonate, etc., ethylenediamine, guanidine sulfate, guanidine hydrochloride, Examples thereof include compounds containing a plurality of amino groups such as guanidine phosphate and melamine.
[0027]
The fiber that has undergone the cross-linking introduction treatment with the hydrazine compound may be subjected to an acid treatment after sufficiently removing the hydrazine compound remaining in the treatment. Examples of the acid used here include aqueous solutions of mineral acids such as nitric acid, sulfuric acid, and hydrochloric acid, and organic acids, but are not particularly limited. The conditions for the acid treatment are not particularly limited, but the treated fibers are usually immersed in an aqueous solution having an acid concentration of 5 to 20% by weight, preferably 7 to 15% by weight, at a temperature of 50 to 120 ° C. for 0.5 to 10 hours. An example is given.
[0028]
The fiber subjected to the cross-linking introduction treatment with the hydrazine-based compound or the fiber further subjected to the acid treatment is subsequently hydrolyzed with an aqueous alkaline metal salt solution. As a result of this treatment, CN groups remaining without being involved in the cross-linking introduction treatment with the hydrazine compound of the acrylic fiber, or when the acid treatment is carried out after the cross-linking introduction treatment, the remaining CN groups and some acids Hydrolysis of the amide group generated by hydrolysis by treatment proceeds to form a carboxyl group. In addition, since the formed carboxyl group couple | bonds with the metal ion derived from the alkaline metal salt used for a hydrolysis process, most are salt type carboxyl groups. Examples of the alkaline metal salt used here include alkali metal hydroxides, alkaline earth metal hydroxides, and alkali metal carbonates. The conditions for the hydrolysis treatment are not particularly limited, but the means for treating in an aqueous solution of 1 to 10% by weight, more preferably 1 to 5% by weight, at a temperature of 50 to 120 ° C. within 1 to 10 hours is industrial, fiber properties. Is preferable.
[0029]
As described above, the degree of hydrolysis, that is, the amount of salt-type carboxyl groups produced is preferably 1 to 10 mmol / g, more preferably 3 to 10 mmol / g, and even more preferably 3 to 8 mmol / g. This can be easily controlled by a combination of the concentration, temperature and processing time of the drug during the above-described processing. Moreover, the CN group may or may not remain in the fiber that has undergone such hydrolysis. If the CN group remains, there is a possibility that a further function can be imparted using its reactivity.
[0030]
The fibers obtained as described above may be used as they are as the sustained-release moisture-releasing cross-linked acrylic fiber of the present invention, but usually, further, ions by metal salts such as nitrates, sulfates, and hydrochlorides. Conversion to the desired salt-type carboxyl group or H-type carboxyl group by performing an exchange treatment, acid treatment with nitric acid, sulfuric acid, hydrochloric acid, formic acid, etc., or pH adjustment treatment with an alkaline metal salt, etc. The characteristics are adjusted by mixing them to obtain the crosslinked moisture-absorbing crosslinked acrylic fiber of the present invention.
[0031]
For example, the Mg salt-type carboxyl group recommended in the present invention can be obtained by immersing the hydrolyzed fiber in an aqueous solution containing magnesium ions such as an aqueous magnesium nitrate solution. However, in this method, it is difficult to control the amount of the Mg salt-type carboxyl group to be generated, and the reproducibility is not very good.
[0032]
In order to control the amount and obtain the Mg salt-type carboxyl group with good reproducibility, first, the fiber after hydrolysis is immersed in an acid aqueous solution such as nitric acid so that all the carboxyl groups in the fiber become H-type carboxyl groups. Next, the obtained fiber is immersed in an alkaline aqueous solution containing sodium ions such as an aqueous sodium hydroxide solution to convert the H-type carboxyl group into a Na salt-type carboxyl group. At this time, the amount of carboxyl groups converted to Na salt type can be changed by adjusting the pH. Then, it can convert into Mg salt type carboxyl group by immersing in the aqueous solution which has magnesium ions, such as magnesium nitrate aqueous solution. Here, the Na salt type carboxyl group is converted to the Mg salt type carboxyl group, and the H type carboxyl group is hardly converted to the Mg salt type carboxyl group. That is, it is possible to control the amount of Mg salt type carboxyl groups through controlling the amount of Na salt type carboxyl groups by adjusting the pH.
[0033]
In addition, the controlled moisture-releasing and cross-linking acrylic fiber of the present invention was subjected to treatments other than the above-described crosslinking introduction treatment, acid treatment, hydrolysis treatment, ion exchange treatment after hydrolysis, acid treatment, and pH adjustment treatment. It does not matter if it is a thing.
[0034]
The above-described controlled moisture absorption / release cross-linked acrylic fiber of the present invention described above has a characteristic of having a high saturated moisture absorption rate and continuously absorbing moisture. Therefore, when the crosslinked moisture-absorbing / releasing acrylic fiber of the present invention is contained as a constituent fiber of the fiber structure, the amount of heat released to the outside of the fiber structure is supplemented with continuous heat generation, thereby the fiber structure. The effect which improves the heat retention of is obtained. Therefore, the gradual moisture-releasing and cross-linking acrylic fiber of the present invention can be suitably used for applications where heat retention is required.
[0035]
Examples of such fiber structures include yarns, yarns, filaments, woven fabrics, knitted fabrics, non-woven fabrics, paper-like materials, sheet-like materials, laminates, cotton-like materials, etc., but they are used for applications where heat retention is required. In general, woven fabrics, knitted fabrics, and cotton-like bodies are generally used. Specific examples include sportswear, underwear, stomach wrap, supporters, gloves, socks, stockings, pajamas, and futon cotton. Further, the fiber structure may be composed of only the slow-absorbing and releasing cross-linked acrylic fiber of the present invention, or may be composed of other materials in combination. Other materials that can be used in combination are not particularly limited, and publicly used natural fibers, organic fibers, semi-synthetic fibers, synthetic fibers, and the like are used. In addition, inorganic fibers, glass fibers, and the like can be used depending on the application. In addition, other materials used in combination are not limited to fibers, and may be materials such as resins and particles.
【Example】
[0036]
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In addition, unless otherwise indicated, the part and percentage in an Example are shown on a weight basis. The evaluation methods of the characteristics in the examples are as follows.
[0037]
(1) Salt-type carboxyl group content (mmol / g)
About 1 g of a well-dried sample was precisely weighed (X (g)), 200 ml of water was added thereto, 1 mol / l hydrochloric acid aqueous solution was added to the solution while being heated to 50 ° C. to pH 2, and then 0.1 mol A titration curve is obtained according to a conventional method with an aqueous sodium hydroxide solution of 1 / l. The consumption amount (Y (ml)) of an aqueous sodium hydroxide solution consumed by carboxyl groups was determined from the titration curve, and the carboxyl group amount (mmol / g) was calculated by the following formula.
(Amount of carboxyl group) = 0.1 Y / X
Separately, a titration curve is obtained in the same manner without adjusting to pH 2 by adding a 1 mol / l aqueous hydrochloric acid solution during the above carboxyl group content measurement operation, and the amount of H-type carboxyl groups (mmol / g) is obtained. From these results, the salt-type carboxyl group amount was calculated by the following formula.
(Amount of salt-type carboxyl group) = (Amount of carboxyl group) − (Amount of H-type carboxyl group)
[0038]
(2) Saturated moisture absorption (%)
About 5.0 g of the sample is dried with a hot air dryer at 105 ° C. for 16 hours and weighed (W1 (g)). Next, the sample is placed in a thermo-hygrostat adjusted to either 20 ° C. × 95% RH or 20 ° C. × 50% RH for 24 hours. The weight of the sample thus absorbed is measured. (W2 (g)). From the above measurement results, calculation was performed according to the following equation.
Saturated moisture absorption (%) = (W2−W1) / W1 × 100
[0039]
(3) About 2.5 g of a moisture absorption curve sample at 20 ° C. × 95% RH is dried with a hot air dryer at 105 ° C. for 16 hours, and the weight is measured (W3 (g)). Subsequently, the sample was put into a cylindrical mesh basket (diameter 7.5 cm, height 9.8 cm) without being pressed quickly so as to be in a soft state, and the entire temperature was immediately adjusted to 20 ° C. × 95% RH. Put in a humidifier. The weight of the sample that has absorbed moisture is measured every 10 minutes (W4 (g)), with the time when the sample is placed in a thermo-hygrostat as the start of moisture absorption. From the above measurement results, the moisture absorption rate at each measurement point was calculated by the following equation to obtain a moisture absorption curve.
Moisture absorption rate (%) = (W4−W3) / W3 × 100
[0040]
(4) Swelling degree (g / g)
About 3 g of the sample is dried with a hot air dryer at 70 ° C. for 3 hours, and the weight is measured (W5 (g)). Next, after immersing the sample in a beaker containing 300 ml of water for 30 minutes, the swollen sample is dehydrated with a desktop centrifugal dehydrator (160 G × 5 minutes), and the weight of the sample is measured (W6 (g)). From the above measurement results, calculation was performed according to the following equation.
(Swelling degree) = (W6-W5) / W5
[0041]
[Example 1]
A spinning stock solution in which 10 parts of an AN polymer (intrinsic viscosity [η] = 1.2 in 30 ° C. dimethylformamide) consisting of 90% acrylonitrile (AN) and 10% vinyl acetate was dissolved in 90 parts of a 48% rhodium soda solution. After spinning and drawing according to a conventional method (total draw ratio: 10 times), after drying in an atmosphere of dry bulb / wet bulb = 120 ° C./60° C., wet heat treatment is performed to obtain a raw fiber having a single fiber fineness of 0.9 dtex. Obtained. The raw fiber was subjected to a crosslinking introduction treatment at 98 ° C. for 5 hours in a 20% aqueous solution of hydrazine hydrate and washed. The increase in nitrogen content by this treatment was 5%. In addition, the nitrogen increase amount calculated | required nitrogen content by calculating | requiring nitrogen content by the elemental analysis about the raw material fiber and the fiber after bridge | crosslinking introduction processing, and was computed from the difference. The cross-linked fiber was immersed in a 3% nitric acid aqueous solution and subjected to acid treatment at 90 ° C. for 2 hours. Then, it hydrolyzed at 90 degreeC x 2 hours in 3% sodium hydroxide aqueous solution, processed with 3.5% nitric acid aqueous solution, and washed with water. The obtained fiber is immersed in water, adjusted to pH 11 by adding sodium hydroxide, and then immersed in an aqueous solution in which magnesium nitrate corresponding to twice the amount of carboxyl groups contained in the fiber is dissolved at 50 ° C. for 1 hour. Thus, an ion exchange treatment was carried out, followed by washing with water and drying to obtain the fiber of Example 1 having an Mg salt type carboxyl group. The evaluation results of the obtained fiber are shown in Table 1 and FIG.
[0042]
[Example 2]
A fiber of Example 2 having an Mg salt type carboxyl group was obtained in the same manner as in Example 1, except that the pH adjustment with sodium hydroxide was changed from pH 11 to pH 8. The evaluation results of the obtained fiber are shown in Table 1 and FIG.
[0043]
[Comparative Example 1]
A fiber of Comparative Example 1 having a Na salt type carboxyl group was obtained in the same manner as in Example 1 except that the ion exchange treatment with magnesium nitrate was not performed. The evaluation results of the obtained fiber are shown in Table 1 and FIG.
[0044]
[Comparative Example 2]
In Example 1, the fiber of the comparative example 2 which has Ca salt type carboxyl group was obtained similarly except using a calcium nitrate aqueous solution instead of a magnesium nitrate aqueous solution. The evaluation results of the obtained fiber are shown in Table 1 and FIG.
[0045]
[Comparative Example 3]
After the sodium hydroxide of Example 1 was added until the pH was adjusted to about 11, the fiber was dissolved in an aqueous solution in which magnesium nitrate corresponding to 0.6 times the amount of carboxyl groups contained in the fiber was dissolved. After immersing at 50 ° C. for 1 hour, washing with water, and further immersing in 50 ° C. for 1 hour in an aqueous solution in which calcium nitrate corresponding to 0.5 times the amount of carboxyl groups is dissolved, washing with water and drying, Mg salt type carboxyl groups And a fiber of Comparative Example 3 in which Ca salt type carboxyl groups are mixed. The evaluation results of the obtained fiber are shown in Table 1 and FIG. In addition, about the ratio of Mg and Ca, the fiber was wet-decomposed and it calculated | required using the atomic absorption method.
[0046]
[Table 1]

[0047]
Examples 1 and 2 satisfy Formulas 1 to 3, and it is considered that heat generation continues stably from FIG. On the other hand, in Comparative Example 1, although the saturated moisture absorption rate is high, it absorbs a large amount in the initial short time, and then the moisture absorption rate becomes slow. In Comparative Examples 2 and 3, although the moisture absorption rate is slow, the saturated moisture absorption rate is small and the moisture absorption rate close to saturation is reached in a relatively short time. Therefore, it is considered that continuous heat generation cannot be expected. It is done.

Claims (3)

In cross-linking structure and 5.4 ~10mmol / g of a salt-type carboxyl group, and 5.4 mmol / g or more is Mg salt type carboxyl groups crosslinked acrylic moisture absorptive and desorptive fiber of the salt type carboxyl group The saturated moisture absorption rate at 20 ° C. × 95% RH (a (%)), the saturated moisture absorption rate at 20 ° C. × 50% RH (b (%)), and the moisture absorption rate at 20 ° C. × 95% RH × 60 minutes. (C (%)) satisfies the following formulas (1) to (3): A moisture absorption / release crosslinked acrylic fiber characterized by the following.
a (%) ≧ 60 (1)
a−b (%) ≧ 30 (2)
c / a ≦ 0.5 (3) The following equation (4) holds between 20 ° C. × 95% RH × 90 minutes moisture absorption (d (%)) and 20 ° C. × 95% RH × 180 minutes moisture absorption (e (%)). The sustained-release moisture-releasing crosslinked acrylic fiber according to claim 1.
e / d ≧ 1.5 (4)   The degree of swelling is 1.5 g / g or less, and the sustained-absorbing and releasing moisture-crosslinking acrylic fiber according to claim 1 or 2.

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