KR102334183B1 - Hygroscopic exothermic fiber - Google Patents

Abstract

An object of the present invention is to provide a fiber exothermic to moisture absorption which has a rapid rise in initial temperature with respect to heat absorption by moisture and has a high level of bulkiness. A composite fiber comprising a cross-linked structure and a surface layer having a carboxyl group of Na salt type or K salt type, and a central portion of a side-by-side structure composed of two types of acrylonitrile-based polymers having different acrylonitrile content, in the cross section of the composite fiber It is a moisture absorption exothermic fiber, characterized in that the area occupied by the surface layer portion is 5% or more and less than 20%, and the saturated moisture absorption in an environment of 20°C and 65% relative humidity is 20% or more.

Description

Hygroscopic exothermic fiber

The present invention relates to a moisture absorption exothermic fiber that has a rapid rise in initial temperature with respect to the moisture absorption exothermic property, and further has a high level of bulkiness, and can realize a comfortable and warm environment for the human body at an early stage.

As the moisture absorption exothermic fiber, crosslinked acrylate-based fibers are most widely used in the medical field or the industrial material field. Such crosslinked acrylate-based fibers have harmonizing functions such as pH buffering properties, antistatic properties, and water retention properties, high moisture absorption, high moisture absorption rate, high moisture absorption difference, or temperature and humidity control functions derived therefrom. It is known to have (for example, Patent Documents 1 and 2).

However, since the crosslinked acrylate fiber has a high moisture absorption, it has the characteristics that bulkiness and shape stability are reduced by the moisture absorbed therein. For this reason, card processing was difficult, and it was in a situation where development to the use which requires bulkiness, such as batting, etc. was not advanced.

In response to this situation, the applicant has claimed that an acrylonitrile-based fiber having a side-by-side structure composed of two types of acrylonitrile-based polymers is crosslinked with a nitrogen-containing compound and hydrolyzed to obtain a crosslinked acrylate-based fiber. A fiber was proposed (Patent Document 3). Although this fiber has both heat absorption and bulkiness at a practical level, since it has high bulkiness and uses polyvalent metal salt type crosslinked acrylate fibers such as Mg and Ca, high temperature in a short time after moisture absorption for heat absorption. There was a problem that the user could not immediately realize warmth when it was difficult to rise with the futon and used it for the batting of the futon, and there was room for further improvement.

Patent Document 1: Japanese Patent Laid-Open No. 7-216730 Patent Document 2: Japanese Patent Laid-Open No. Hei 5-132858 Patent Document 3: WO2015/041275 Publication

The present invention has been devised to solve the problems of the prior art including such patent document 3, has a rapid rise in initial exothermic temperature with respect to moisture absorption exothermic property, and furthermore, a moisture absorption exothermic fiber having a high level of bulkiness. is to provide.

As a result of intensive studies to achieve the above object, the present inventors adopted a Na salt or K salt type as a crosslinked polyacrylate-based fiber to increase initial moisture absorption exotherm, and bulky, which is a drawback of Na salt type or K salt type By adopting a specific composite structure in which the surface layer portion that exhibits heat absorption by heat is small, and a technology to increase the amount of carboxyl groups in the surface layer, the low property is supplemented to maintain high bulkiness while maintaining high initial temperature due to heat absorption by moisture. Found that it can be done, and came to the completion of the present invention.

Specifically, as a crosslinked polyacrylate fiber, an alkali metal salt type of Na salt type or K salt type, which is superior to the polyvalent metal salt type of Mg salt type or Ca salt type with respect to heat absorption by heat, is adopted, and the central part is formed with two specific types of acrylonitrile. A side-by-side structure made of a polymer-based polymer, the surface layer portion that exhibits heat absorption by absorption is reduced as much as possible to obtain a composite structure with increased bulkiness, and hydrolysis treatment is performed in the formation of the surface layer portion with a lower concentration than conventional alkali metal compounds It has been found that by carrying out under the loose conditions of and subsequent acid treatment under strict conditions at high temperatures than before, high hygroscopic exotherm can be expressed by allowing carboxyl groups to exist at a higher concentration than before even in a narrow surface layer portion.

In addition, FIG. 1 is a graph showing the temperature change for each elapsed time of the Na salt type or Mg salt type crosslinked polyacrylate-based fiber measured in accordance with the measurement method and conditions of ISO18782:2015 in FIG. 1 . As can be seen from FIG. 1 , it can be seen that the Na salt type is superior to the Mg salt type with respect to the initial rise temperature based on the moisture absorption exotherm of the crosslinked polyacrylate-based fiber.

That is, the present invention has been completed based on the above findings, and has the following structures (1) to (4).

(1) A composite fiber comprising a cross-linked structure and a central portion of a side-by-side structure comprising a surface layer portion having a carboxyl group of Na salt type or K salt type, and two types of acrylonitrile-based polymers having different acrylonitrile content, An area occupied by the surface layer in a cross section is 5% or more and less than 20%, and a saturated moisture absorption rate in an environment of 20°C and 65% relative humidity is 20% or more.

(2) The moisture absorption exothermic fiber according to (1), wherein the total amount of carboxyl groups is 3.5 mmol/g or more.

(3) The moisture absorption exothermic fiber as described in (1) or (2) characterized by the rising temperature measured based on ISO18782:2015 being 4-10 degreeC.

(4) The moisture absorption exothermic fiber according to any one of (1) to (3), wherein the specific volume is 15 to 50 cm 3 /g.

The moisture absorption exothermic fiber of the present invention has an initial high temperature rise due to moisture absorption exothermic property, which could not be achieved in conventional polyvalent metal salt type crosslinked polyacrylate fibers such as Mg salt type and Ca salt type, and a high level of punishment It has the effect of having both key characteristics. This effect results from the presence of a specific complex structure and a high concentration of carboxyl groups, as well as the exothermicity of hygroscopicity exhibiting a high temperature at an early stage of the crosslinked polyacrylate-based fibers of Na salt type or K salt type. The moisture absorption exothermic fiber of the present invention rapidly heats up a large amount of moist air flowing in due to its high bulkiness and high moisture absorption exotherm, which increases the temperature rapidly, so that it is possible to immediately change it into warm air with low humidity. When used as a bedding product, batting for autumn/winter outdoor clothing, the wearer can realize warmth and heat retention at a very early stage.

1 is a graph showing the temperature transition for each elapsed time of crosslinked polyacrylate fibers of Na salt type or Mg salt type measured in accordance with the measurement method and conditions of ISO18782:2015.

Hereinafter, the moisture absorption exothermic fiber of the present invention will be described in detail.

The moisture absorption exothermic fiber of the present invention is a composite comprising a cross-linked structure and a surface layer having a Na salt type or K salt type carboxyl group, and a central side-by-side structure composed of two types of acrylonitrile-based polymers having different acrylonitrile content. The fiber, characterized in that the area occupied by the surface layer in the cross section of the composite fiber is 5% or more and less than 20%, and the saturated moisture absorption in an environment of 20°C and 65% relative humidity is 20% or more. With these characteristics, both the moisture absorption exothermic property which absorbs moisture quickly and shows high heat generation property and the bulkiness property which brings about continuous heat retention are brought about at a high level.

The moisture absorption exothermic fiber of the present invention needs to be a crosslinked polyacrylate-based fiber having a carboxyl group of a monovalent metal Na salt type or K salt type. The divalent metal salt type of the Mg salt type or the Ca salt type has high heat absorption by moisture and moderately high bulkiness. there is a problem. Further, other divalent metal salt types such as the Zn salt type are not preferred because they are inferior in heat absorption to moisture and a comfortable environment cannot be obtained. Since the monovalent metal salt type of the Na salt type or the K salt type has a high initial rise temperature at the time of heat absorption by heat, warmth can be realized at an early stage. However, since crosslinked polyacrylate fibers of Na salt type or K salt type lack bulkiness in a normal fiber form and do not maintain heat retention, in the present invention, a special composite structure as described later is adopted.

The moisture absorption exothermic fiber of the present invention is a composite comprising a cross-linked structure and a surface layer having a Na salt type or K salt type carboxyl group, and a central side-by-side structure composed of two types of acrylonitrile-based polymers having different acrylonitrile content. As the fiber, it is necessary that the area occupied by the surface layer portion in the cross section of the composite fiber is 5% or more and less than 20%. In the moisture absorption exothermic fiber of the present invention, it has a composite structure consisting of a central part and a surface layer part around it, and by making the hard structure in the central part as large as possible, it contributes to the improvement of bulkiness, and a crosslinked structure and Na salt type or K in the surface part It is characterized by the presence of a salt-type carboxyl group to perform the role of high heat absorption by moisture. In the present invention, since the area occupied by the surface layer portion in the cross section of the moisture absorption exothermic fiber is reduced to less than 20% as much as possible, it is considered that high heat absorption by moisture cannot be realized, Since it is increasing, high moisture absorption exotherm can be expressed. However, if the area occupied by the surface layer portion is less than 5%, it is not preferable because sufficiently high heat absorption by moisture cannot be exhibited. The moisture absorption exothermic fiber of the present invention may have 3.5 mmol/g or more with respect to the total amount of carboxyl groups, and up to a maximum of about 10 mmol/g. In reality, substantially all of this amount of carboxyl groups exists in the surface layer part. In addition, it is possible to achieve a moisture absorption rate of 20% or more, further 30% or more, up to a maximum of about 70% with respect to the moisture absorption rate specified in Examples to be described later.

The moisture absorption exothermic fiber of the present invention uses an acrylonitrile-based fiber as a raw material fiber, and the acrylonitrile-based fiber can be produced from an acrylonitrile-based polymer by a known method. As for the acrylonitrile-type polymer, it is preferable that acrylonitrile is 50 weight% or more, More preferably, it is 80 weight% or more. When there is little content of acrylonitrile, a crosslinked structure decreases and there exists a possibility that fiber physical property may fall. The crosslinked structure can be introduced into the fiber by reacting the nitrile group of the acrylonitrile-based polymer with a nitrogen-containing compound such as a hydrazine-based compound.

The moisture absorption exothermic fiber of the present invention has a composite structure in which two types of acrylonitrile-based polymers having different acrylonitrile content are joined side-by-side. By arranging two types of acrylonitrile polymers having a difference in the acrylonitrile content as described above side-by-side, there is a difference in the degree of shrinkage during hydrolysis treatment, and crimping can be expressed as a result. It can contribute to the improvement of bulkiness. Further, in order to sufficiently improve the bulkiness, the difference in the content of acrylonitrile between the two types of acrylonitrile-based polymers is preferably 1 to 8% by weight, more preferably 1 to 5% by weight, and the two types of acrylonitrile-based polymers. It is preferable that the composite ratio (weight ratio) of a polymer is 20/80-80/20, Furthermore, it is 30/70-70/30.

A crosslinked structure is introduced into the surface layer portion with respect to the fibers of the composite structure as described above. Although a conventionally well-known crosslinking agent may be used for introduction|transduction of a crosslinked structure, it is preferable to use a nitrogen-containing compound from the point of introduction efficiency of a crosslinked structure. As the nitrogen-containing compound, it is preferable to use an amino compound or a hydrazine-based compound having two or more primary amino groups. Examples of the amino compound having two or more primary amino groups include diamine compounds such as ethylenediamine and hexamethylenediamine, diethylenetriamine, 3,3'-iminobis(propylamine), N-methyl-3,3' -triamine compounds such as iminobis(propylamine), triethylenetetramine, N,N'-bis(3-aminopropyl)-1,3-propylenediamine, N,N'-bis(3-aminopropyl ) tetramine-based compounds such as -1,4-butylenediamine, polyamine-based compounds having two or more primary amino groups as polyvinylamine, polyallylamine, and the like are exemplified. Moreover, as a hydrazine type compound, hydrazine hydrazine, hydrazine sulfate, hydrazine hydrochloride, hydrazine hydrobromic acid, hydrazine carbonate, etc. are illustrated. Moreover, although the upper limit of the number of nitrogen atoms in 1 molecule is not specifically limited, It is preferable that it is 12 or less, More preferably, it is 6 or less, Especially preferably, it is 4 or less. When the number of nitrogen atoms in one molecule exceeds the said upper limit, a crosslinking agent molecule becomes large and it may become difficult to introduce|transduce a crosslinked structure into a fiber. The conditions for introducing the crosslinked structure are not particularly limited, and may be appropriately selected in consideration of the reactivity of the crosslinking agent and the acrylonitrile-based fiber to be employed, the amount of the crosslinked structure, and the like. For example, when using a hydrazine-based compound as a crosslinking agent, the above-mentioned acrylonitrile-based fiber is immersed in an aqueous solution to which the above-mentioned hydrazine-based compound is added so as to have a hydrazine concentration of 0.1 to 10% by weight, and then 80 to 150°C, 2 The method of processing in - 10 hours, etc. are mentioned.

After the crosslinked structure is introduced, a hydrolysis treatment with an alkaline metal compound is performed, and the nitrile group present in the surface layer portion of the fiber is hydrolyzed to form a carboxyl group. As specific treatment conditions, in consideration of the amount of carboxyl groups described above, various conditions such as the concentration of the treatment agent, reaction temperature, and reaction time may be appropriately set, but preferably 0.5 to 10% by weight, more preferably A means of treating at a temperature of 80 to 150° C. for 2 to 10 hours in 1 to 5 wt% of an aqueous solution of a treatment agent is industrially and preferably in terms of fiber properties. In the present invention, rather than sequentially performing the above-mentioned crosslinking introduction treatment and hydrolysis treatment as described above, it is preferable to use an aqueous solution in which the respective treatment agents are mixed and simultaneously treat them collectively. Further, in the present invention, in this simultaneous treatment, it is preferable to carry out under loose conditions of an alkali metal compound of a lower concentration than before, and to carry out the subsequent acid treatment under strict conditions at high temperature than conventionally. By doing in this way, the moisture absorption exothermic fiber of the present invention can have a structure in which more carboxyl groups are present than before in a narrow surface layer portion, and a relatively hard acrylonitrile-based polymer is kept warm in the center portion.

The formed carboxyl group includes a salt-type carboxyl group whose counter ion is a cation other than a hydrogen ion, and an H-type carboxyl group whose counter ion is a hydrogen ion. In order to obtain a high moisture absorption rate, it is preferable that 50% or more of the carboxyl groups be salt-type carboxyl groups. The cation constituting the salt-type carboxyl group is an alkali metal of sodium or potassium. When magnesium, calcium, zinc, etc. which are polyvalent metal ions are employ|adopted, bulkiness is high, but since the initial rise temperature by moisture absorption is low, it is unpreferable. For example, the moisture absorption exothermic fiber of the present invention is unique to the present invention as described above with respect to the acrylonitrile-based fiber in which two types of acrylonitrile-based polymers having different acrylonitrile content are joined side by side. It is obtained when crosslinking is introduced and hydrolysis is performed under the conditions of forming a carboxyl group, and sodium or potassium is selected as the counter ion.

As a method of adjusting the ratio of the salt-type carboxyl group and the H-type carboxyl group to the above range, ion exchange treatment with a metal salt such as nitrate, sulfate, or hydrochloride, acid treatment with nitric acid, sulfuric acid, hydrochloric acid, formic acid, or the like, or an alkali metal compound The method of performing the pH adjustment process etc. by etc. is mentioned.

In the moisture absorption exothermic fiber of the present invention, the area occupied by the surface layer portion in the cross section is 5% or more and less than 20%, preferably 10% or more and less than 20%. When the area of the surface layer is less than the above range, it is not possible to sufficiently make a carboxyl group exist in a fiber, and high heat absorption by moisture cannot be exhibited. In addition, when the above range is exceeded, the fibers are easily cut off due to moisture absorption, causing a problem in bulkiness. Since the area occupied by the surface layer of the fiber of the present invention is very small, and the area of the center where carboxyl groups are not substantially present occupies most of the area, the bulkiness of the fiber due to moisture absorption or decrease in bulkiness by adopting the Na salt type or K salt type The influence is small, and high bulkiness can be achieved. In addition, as shown in FIG. 1, the cross-linked polyacrylate-based fibers of Na salt type or K salt type have high heat absorption by hygroscopicity (especially the initial rise temperature) compared to divalent metal salts such as Mg salt type. In the invention, the features can be enjoyed as they are.

Since the moisture absorption exothermic fiber of the present invention is composed of the above-described cross-linked polyacrylate-based fiber of Na salt type or K salt type having a special composite structure, the range of 6.0 to 40% within 5 minutes under an environment of 20°C x 65% RH can be easily achieved. In particular, the moisture absorption exothermic fiber of the present invention can realize a high moisture absorption exothermic effect (high rise temperature) within the first 5 minutes when human skin comes into contact.

In addition, since the moisture absorption exothermic fiber of the present invention is made of the above-described cross-linked polyacrylate fiber of Na salt type or K salt type having a special composite structure, a specific volume in the range of 50 to 100 cm 3 /g can be achieved. Such high bulkiness is caused by the high bulkiness of crosslinked polyacrylate fibers of Na salt type or K salt type having a special complex structure. When a specific volume is low, since sufficient air does not flow in, there exists a possibility that heat retention may become inadequate. When the specific volume is high, mold breakage is easily caused only by applying a slight force, and there is a fear that the shape retaining property is insufficient.

The moisture absorption exothermic fiber of the present invention, alone or in combination with other materials, can form a fiber structure by a conventionally known method. As the external form of such a fiber structure, there are cotton, thread, letter, woven fabric, nonwoven fabric, pile fabric, paper-shaped material, and the like. As the content of the moisture absorption exothermic fiber of the present invention in the structure, it is substantially uniformly distributed by mixing with other materials, or in the case of a structure having a plurality of layers, any one layer (even in single or plural) in which the moisture absorption exothermic fiber of the present invention is concentrated and present, and in each layer, the moisture absorption exothermic fiber of the present invention is distributed in a specific ratio, and the like.

In the fiber structure, other materials that can be used together with the moisture absorption exothermic fiber of the present invention include, for example, natural fibers, organic fibers, semi-synthetic fibers, and synthetic fibers. can be employed. Specific examples of the material for use include cotton, hemp, silk, wool, nylon, rayon, polyester, and acrylic fibers. In addition, the raw material used together may be raw material, such as down feather, resin, and particle|grains.

For example, if the fibrous structure is for batting, a combination with polyester is suitable. Specifically, it is a batting containing 40 to 90% by weight of polyester fibers and 10 to 60% by weight of crosslinked polyacrylate fibers of Na salt type and/or K salt type, and is of Na salt type and/or K salt type. The crosslinked polyacrylate fiber has a crosslinked structure and a surface layer having a Na salt type and/or a K salt type carboxyl group, and a central part of a side-by-side structure composed of two types of acrylonitrile polymers having different acrylonitrile content. As a composite fiber, the area occupied by the surface layer in the cross section of the composite fiber is 5% or more and less than 20%, The batting characterized by the above-mentioned is provided.

As described above, the moisture absorption exothermic fiber of the present invention, as a fiber structure, can be used in combination with other materials, if necessary, to enjoy the advantages of heat absorption heat and high bulkiness that can be realized at an early stage, and low humidity at an early stage, which is not previously available. I have the comfort that I can realize the warmth of. For this reason, bedding products (quilts, mattresses, pillows, etc.) or outer clothing for autumn and winter using the moisture absorption and exothermic fibers of the present invention absorb moisture emitted from the human body and heat up at an early high temperature, thereby warming immediately, and It is possible to continuously realize the warmth by the thermal insulation due to the high bulkiness.

Example

Although the present invention has been specifically described with reference to the following examples, the present invention is not limited thereto. In addition, unless otherwise indicated, the ratio in an Example is shown on a weight basis. The evaluation method of the characteristic in an Example is as follows.

(1) Amount of carboxyl groups

About 1 g of a fiber sample is immersed in 50 ml of 1 mol/L hydrochloric acid aqueous solution for 30 minutes. Then, the fiber sample is 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 (when the bath pH is less than 4, it is washed again with water). Next, about 0.2 g of a sufficiently dried fiber sample is precisely weighed (W1 [g]), 100 ml of water is added, and 15 ml of 0.1 mol/L sodium hydroxide aqueous solution, 0.4 g of sodium chloride and phenolphthalein are further added. Add and stir. After 15 minutes, the sample fiber and the filtrate are separated by filtration, and then the sample fiber is washed with water until the coloration of phenolphthalein disappears. The mixture of the washing water and the filtrate at this time is titrated with 0.1 mol/L hydrochloric acid aqueous solution until the color of phenolphthalein disappears, and the consumption of hydrochloric acid aqueous solution (V1 [ml]) is calculated. From the obtained measured value, the total amount of carboxyl groups is computed by the following formula.

Carboxyl group amount [mmol/g] = (0.1×15-0.1×V1)/W1

(2) 20℃×65% RH moisture absorption

About 2.5 g of the fiber sample was dried with a hot air dryer at 105° C. for 16 hours to measure the weight (W2 [g]). Next, the fiber sample is placed in a thermo-hygrostat adjusted to a temperature of 20°C and 65% RH for 5 minutes. The weight of the fiber sample absorbed in this way is measured (W3 [g]). From these measurement results, 20 degreeC x 65% RH moisture absorption is computed by the following formula.

20℃×65% RH moisture absorption[%]=(W3-W2)/W2×100

(3) cost

After opening 50 g of a fiber sample lightly, it is opened with a card machine, and laminated|stacked. Six test pieces are cut out to have a size of 10 cm x 10 cm, put in a vat, and left in a constant temperature and humidity chamber for 24 hours or more. Take out from the thermo-hygrostat, superimpose so that the mass is 10.0 g to 10.5 g, and the prepared test piece is accurately weighed. A 10 cm x 10 cm acrylic plate is placed on the test piece, a 500 g weight is placed on it for 30 seconds, and then this weight is removed and left to stand for 30 seconds. After repeating this operation 3 times, removing 500 g of weight and leaving it to stand for 30 second, the height of four corners is measured and the average value is calculated|required, and specific volume is computed by the following formula.

Specific volume (cm 3 /g) = 10 × 10 × Measured average value of the heights of the four corners of the sample (mm) / 10 / mass of the test piece (g)

(4) Percentage of area occupied by the surface layer

The sample fiber was immersed in a dyeing bath containing 2.5% cationic dye (Nichilon Black G 200) and 2% acetic acid based on the fiber weight so that the bath ratio was 1:80, and after boiling for 30 minutes, Wash, dehydrate and dry. The obtained dyed fiber is sliced thinly perpendicular to the fiber axis, and the fiber cross section 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 a large number of carboxyl groups is green because the dye is not sufficiently fixed. In the cross section of the fiber, the diameter (D1) of the fiber and the diameter (D2) of the central portion that is dyed black with the portion starting to change color from green to black as a boundary is measured, and the surface layer area ratio by the following formula to calculate In addition, let the average value of the surface layer part area ratio of 10 samples be the surface layer part area ratio of the sample fiber.

Surface layer area ratio (%)=[{((D1)/2) ² π-((D2)/2) ² π}/((D1)/2) ² π]×100

(5) rising temperature

In accordance with ISO18782:2015, the rising temperature of the sample fiber was measured.

[Example 1]

Acrylonitrile 90 wt%, acrylic acid methyl ester 10 wt% Acrylonitrile polymer Ap (intrinsic viscosity [η] = 1.5 in dimethylformamide at 30°C), acrylonitrile 88 wt%, vinyl acetate 12 wt% An acrylonitrile-based polymer Bp ([η]=1.5) was dissolved in an aqueous solution of 48 wt% of rhodan soda, respectively, to prepare a spinning dope. Each spinning dope is induced so that the composite ratio (weight ratio) of Ap/Bp becomes 50/50 in the composite spinning apparatus according to Japanese Patent Publication No. 39-24301, and spinning, washing, stretching, and crimping according to a conventional method , heat treatment was performed to obtain a side-by-side type raw material fiber in which the polymers Ap and Bp having a single fiber fineness of 3.3 dtex were combined.

The raw material fibers were simultaneously subjected to crosslinking introduction treatment and hydrolysis treatment at 100°C for 2 hours in an aqueous solution containing 0.5% by weight of hydrazine water and 1.4% by weight of sodium hydroxide, and 120°C×3 in 8% by weight aqueous nitric acid solution. It was treated with time and washed with water. The obtained fiber was immersed in water, adjusted to pH 9 by adding sodium hydroxide, washed with water, and dried to obtain a Na salt type crosslinked polyacrylate type fiber having a Na salt type carboxyl group (surface layer area 13%). Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers. In addition, in the measurement of the infrared absorption of these fibers, there ^{is absorption in the vicinity of 2250 cm -1} derived from the nitrile group, and hydrolysis of the nitrile group is progressing in the fiber surface layer part, but it is confirmed that the nitrile group remains in the center of the fiber became

[Example 2]

Na salt type crosslinked polyacrylate fibers (surface layer area 8%) were obtained in the same manner except that the concentration of sodium hydroxide used for crosslinking introduction/hydrolysis treatment was changed from 1.4 wt% to 1.2 wt% in Example 1. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 3]

Na salt type crosslinked polyacrylate fibers (surface layer area 18%) were obtained in the same manner except for changing the concentration of sodium hydroxide used for crosslinking introduction/hydrolysis treatment from 1.4 wt% to 1.6 wt% in Example 1. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 4]

A K-salt-type crosslinked polyacrylate-based fiber (13% of surface layer area) was obtained in the same manner except that potassium hydroxide was used instead of sodium hydroxide added to adjust the pH to 9 in Example 1. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 5]

A K-salt type crosslinked polyacrylate fiber (surface layer area 8%) was obtained in the same manner except that the concentration of potassium hydroxide used in the crosslinking introduction/hydrolysis treatment was changed from 1.4 wt% to 1.2 wt% in Example 4. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 6]

A K-salt-type crosslinked polyacrylate fiber (surface layer area 18%) was obtained in the same manner except that the concentration of potassium hydroxide used in the crosslinking introduction/hydrolysis treatment was changed from 1.4 wt% to 1.6 wt% in Example 4. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 7]

Na salt-type crosslinked polyacrylate-based fibers were obtained in the same manner as in Example 1, except that the composition of the acrylonitrile-based polymer Ap was changed to 92% by weight of acrylonitrile and 8% by weight of methyl acrylate. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 8]

In Example 1, except for changing the composite ratio (weight ratio) of Ap/Bp from 50/50 to 40/60, a sodium salt-type crosslinked polyacrylate-based fiber was obtained in the same manner. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Example 9]

In Example 1, except for changing the composite ratio (weight ratio) of Ap/Bp from 50/50 to 60/40, a sodium salt-type crosslinked polyacrylate-based fiber was obtained in the same manner. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Comparative Example 1]

Na salt-type crosslinked polyacrylate fibers (surface layer area 3%) were obtained in the same manner except that the concentration of sodium hydroxide used for crosslinking introduction/hydrolysis treatment was changed from 1.4 wt% to 0.5 wt% in Example 1. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Comparative Example 2]

Na salt type crosslinked polyacrylate fiber (25% of surface layer area) was obtained in the same manner except for changing the concentration of sodium hydroxide used for crosslinking introduction/hydrolysis treatment from 1.4 wt% to 1.8 wt% in Example 1. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Comparative Example 3]

Acrylonitrile-based polymer Ap (intrinsic viscosity [η] = 1.5 in dimethylformamide at 30°C) of 90 wt% of acrylonitrile and 10 wt% of methyl acrylate ester, 88 wt% of acrylonitrile, and 12 wt% of vinyl acetate An acrylonitrile-based polymer Bp ([η]=1.5) was dissolved in an aqueous solution of 48 wt% of rhodan soda, respectively, to prepare a spinning dope. Inducing each spinning dope so that the composite ratio of Ap/Bp becomes 50/50 to the composite spinning device according to Japanese Patent Publication No. 39-24301, spinning, washing with water, stretching, crimping, and heat treatment according to a conventional method Thus, a side-by-side type raw material fiber obtained by compounding the polymers Ap and Bp having a single fiber fineness of 3.3 dtex was obtained.

The raw material fibers were simultaneously subjected to crosslinking introduction treatment and hydrolysis treatment at 100°C for 2 hours in an aqueous solution containing 0.5% by weight of hydrazine water and 1.4% by weight of sodium hydroxide, and 120°C×3 in 8% by weight aqueous nitric acid solution. It was treated with time and washed with water. Ion exchange treatment was performed by immersing the obtained fiber in water, adding sodium hydroxide to adjust the pH to 9, and then immersing it in an aqueous solution in which magnesium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber was dissolved at 50° C. for 1 hour. It was carried out, and by washing and drying with water, the Mg salt type crosslinked polyacrylate type fiber (13% of surface layer area) which has an Mg salt type carboxyl group was obtained. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Comparative Example 4]

Acrylonitrile-based polymer Ap (intrinsic viscosity [η] = 1.5 in dimethylformamide at 30°C) of 90 wt% of acrylonitrile and 10 wt% of methyl acrylate ester, 88 wt% of acrylonitrile, and 12 wt% of vinyl acetate An acrylonitrile-based polymer Bp ([η]=1.5) was dissolved in an aqueous solution of 48 wt% of rhodan soda, respectively, to prepare a spinning dope. Inducing each spinning dope so that the composite ratio of Ap/Bp becomes 50/50 to the composite spinning device according to Japanese Patent Publication No. 39-24301, spinning, washing with water, stretching, crimping, and heat treatment according to a conventional method A side-by-side type raw material fiber obtained by compounding the polymers Ap and Bp having a single fiber fineness of 3.3 dtex was obtained.

The raw material fibers were simultaneously subjected to crosslinking introduction treatment and hydrolysis treatment at 100°C for 2 hours in an aqueous solution containing 0.5% by weight of hydrazine water and 1.4% by weight of sodium hydroxide, and 120°C×3 in 8% by weight aqueous nitric acid solution. It was treated with time and washed with water. Ion exchange treatment was performed by immersing the obtained fiber in water, adding sodium hydroxide to adjust the pH to 9, and then immersing it in an aqueous solution in which calcium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber was dissolved at 50° C. for 1 hour. It was carried out, and the Ca salt type crosslinked polyacrylate type fiber (13% of surface layer area) which has a Ca salt type|mold carboxyl group was obtained by washing with water and drying. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers.

[Comparative Example 5]

The side-by-side raw material fiber obtained in Example 1 was simultaneously subjected to a crosslinking introduction treatment and a hydrolysis treatment at 100° C. for 1 hour in an aqueous solution containing 0.5% by weight of hydrazine water and 2.0% by weight of sodium hydroxide, It was further treated with an 8 wt% aqueous nitric acid solution at 100°C x 1 hour, and washed with water. Ion exchange treatment was performed by immersing the obtained fiber in water, adding sodium hydroxide to adjust the pH to 9, and then immersing it in an aqueous solution in which magnesium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber was dissolved at 50° C. for 1 hour. By carrying out, washing with water and drying, the Mg salt type crosslinked polyacrylate type fiber (35% of surface layer area area) which has an Mg salt type carboxyl group was obtained. Table 1 shows the details and evaluation results of the obtained crosslinked polyacrylate-based fibers. In addition, the hydrolysis treatment of Comparative Example 5 was performed under more stringent conditions than those of Example 1, and the acid treatment was performed under more loose conditions than those of Example 1.

As can be seen from Table 1, the moisture absorption exothermic fibers of Examples 1 to 9 have both high moisture absorption exothermic properties (moisture absorption rate and rising temperature) and high bulkiness (specific volume), whereas Na salt type crosslinking. Comparative Example 1 with a small surface layer area of the polyacrylate-based fiber had poor hygroscopicity, and Comparative Example 2 with a large surface layer area of the Na salt-type crosslinked polyacrylate-based fiber was inferior in bulkiness, Mg salt type crosslinked polyacrylate Comparative Examples 3 and 4 of the system fibers had a problem of poor hygroscopicity. In addition, Comparative Example 5 of Mg salt-type crosslinked polyacrylate-based fibers produced under conventional conditions and not having a special structure as in the present invention had a problem of poor hygroscopicity.

Since the moisture absorption exothermic fiber of the present invention has both high heat absorption by moisture and high bulkiness resulting in heat retention, which can be realized at an early stage, it can be used comfortably in bedding products, medical products, etc. that come into contact with human skin.

Claims (4)

A composite fiber comprising a cross-linked structure and a surface layer having a carboxyl group of Na salt type or K salt type, and a central portion of a side-by-side structure composed of two types of acrylonitrile-based polymers having different acrylonitrile content, in the cross section of the composite fiber of 5% or more and less than 20%, and a saturated moisture absorption rate of 20% or more in an environment of 20°C and 65% relative humidity. The moisture absorption exothermic fiber according to claim 1, wherein the total amount of carboxyl groups is 3.5 mmol/g or more. The moisture absorption exothermic fiber according to claim 1 or 2, wherein the rising temperature measured in accordance with ISO18782:2015 is 4 to 10°C. The moisture absorption exothermic fiber according to claim 1 or 2, characterized in that it has a specific volume of 15 to 50 cm 3 /g.

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