TWI739033B - Moisture-absorptive acrylonitrile fiber, method for producing said fiber, and fiber structure containing said fiber - Google Patents

Abstract

The present invention provides a moisture-absorptive acrylonitrile fiber constituted from a polymer which does not substantially have a crosslink structure by a covalent bond, wherein carboxyl groups uniformly exist over the fiber, wherein a content of the carboxyl groups in the fiber is 0.2 to 4.5 mmol/g, wherein a saturated moisture-absorption rate of the fiber at 20℃ and 65% RH is 5% by weight or more, and wherein a degree of swelling in water is 10 times or less. This moisture-absorptive acrylonitrile fiber is produced without a step for introducing the crosslink structure, and has sufficient fiber physical properties. Therefore, the fiber can be continuously produced. Also, the fiber has a high moisture-absorptive property and does not exhibit an increase in red color through uses. Further, the fiber is easily provided with a shrinking property, an easy-de-crimping property, a voluminous property, and a water-repelling property.

Description

Hygroscopic acrylic fiber, method for manufacturing the fiber, and fiber structure containing the fiber

The present invention relates to a hygroscopic acrylic fiber, a method for manufacturing the fiber, and a fiber structure containing the fiber.

Due to the increasing awareness of comfort in recent years, the development of materials with hygroscopic properties is required, and the development is also vigorously carried out in the fiber field. For example, a crosslinked acrylic fiber obtained by chemically modifying acrylic fiber is known (Patent Document 1). The fiber contains a cross-linked structure and a carboxyl group, and has excellent moisture absorption performance or moisture absorption and heat generation performance. However, the crosslinked acrylic fiber has the following problems (i) and (ii).

(i) First, the cross-linked acrylic fiber exhibits a light pink to dense pink color due to the hydrazine cross-linked structure of the fiber, which has the disadvantage that the application field is limited.

Regarding such a problem, Patent Document 2 and Patent Document 3 respectively disclose that acid treatment A is performed after cross-linking treatment with a hydrazine-based compound, and acid treatment B is performed after hydrolysis treatment with an alkali, and the degree of redness can be greatly reduced.

However, even in cross-linked acrylic fibers whose whiteness is improved by the above-mentioned method, there are some Heat, washing, etc., and the degree of redness increases. In addition, in the above-mentioned method, the number of manufacturing steps increases, and the manufacturing cost increases. Therefore, it is still difficult to expand its use.

In the conventional cross-linked acrylic fiber, the color red is caused by the cross-linked structure formed by the reaction of cyano group and hydrazine. However, since the crosslinked acrylic fiber contains a large amount of highly hydrophilic carboxyl groups, if there is no crosslinked structure, it is difficult to maintain fiber physical properties due to swelling or dissolution in water. Therefore, it is not easy to remove the cross-linked structure that is the root cause of the color red, and so far there has been almost no review.

In addition, in fibers using copolymers of acrylonitrile and methacrylic acid, it is difficult to improve the hygroscopicity while suppressing the degree of water swelling.

In addition, in the production of (ii) cross-linked acrylic fiber, in addition to the step of introducing the cross-linked structure of hydrazine and the step of hydrolysis for introducing the carboxyl group, there is also the need to remove the residue of the reagent used in the reaction after each step The steps of things. Moreover, each of these steps requires high temperature and long time. Therefore, it is difficult to manufacture the fiber by continuous processing, and it has been performed by batch processing with low productivity from the past. Therefore, the conventional crosslinked acrylic fiber system has low productivity and high manufacturing cost. In addition, this fiber generates heat due to moisture absorption, and therefore, in a state where the moisture absorption is close to saturation, further heat generation cannot be expected.

Also, with regard to acrylic fibers having a carboxyl group, acrylic fibers composed of an acrylonitrile-based polymer containing a monomer having a carboxyl group such as acrylic acid as a copolymerization component are known. However, if acrylic acid is copolymerized in a large amount, spinning becomes difficult, so it is difficult to exhibit high moisture absorption sex. In addition, it is easy to dissolve under alkaline conditions such as alkaline soaping in dyeing, etc., which becomes a problem when it is oriented for clothing use.

The above-mentioned cross-linked acrylate-based fibers imparted with hygroscopicity are those with many manufacturing steps and low productivity, or those with difficulty in improving hygroscopicity. In addition, such fibers can also be used for clothing materials that require heat retention based on their moisture absorption and heat generation properties, but only heat generation due to moisture absorption may be insufficient. In addition, since such fibers have a cross-linked structure, it is difficult to further impart functions such as shrinkage, ease of crimp removal, bulkiness, and water repellency.

Prior art literature Patent literature

Patent Document 1 Japanese Patent Application Laid-Open No. 5-132858

Patent Document 2 JP 2010-216051 A

Patent Document 3 JP 2009-114556 A

The present invention was created in view of the current state of the prior art, and its purpose is to provide a hygroscopic acrylic fiber that can be continuously produced in a simpler step than in the past. In addition, the object of the present invention is to provide an acrylic fiber which has almost no red color, not only has high moisture absorption and heat generation, but also can be further imparted with shrinkage, ease of crimp removal, bulkiness, water repellency, etc., as required The function.

In order to achieve the above-mentioned object, the inventors conducted a dedicated review. As a result, it was found that the spinning dope in which the acrylonitrile polymer is dissolved is spun from the nozzle, and then it is obtained by passing through the various steps of coagulation, water washing, and stretching. The undried fiber is hydrolyzed, and even if it is an acrylonitrile polymer fiber that does not have a cross-linked structure, it can have both hygroscopicity and practical fiber properties, and has less color red. It can be continuously produced, and if necessary, it can be added to the fiber. The functions of shrinkage, ease of crimp removal, bulkiness, and water repellency have completed the present invention.

That is, the present invention is constituted by the following (1) to (15).

(1) A hygroscopic acrylic fiber, which is a hygroscopic acrylic fiber composed of a polymer that does not substantially have a cross-linked structure formed by covalent bonds, and is characterized in that the carboxyl groups are uniformly Existing in the entire fiber, the amount of carboxyl groups in the fiber is 0.2 to 4.5 mmol/g, the saturated moisture absorption rate of the fiber at 20°C×65%RH is 5 wt% or more, and the water swelling degree is 10 times or less.

(2) A hygroscopic acrylic fiber, which is a hygroscopic acrylic fiber composed of a polymer that does not substantially have a cross-linked structure formed by covalent bonds, and is characterized in that it has a surface layer The core-sheath structure of the core part and the center part, the surface part contains a polymer containing carboxyl groups, the center part contains an acrylonitrile polymer, the amount of carboxyl groups in the fiber is 0.2~4.5mmol/g, and the fiber is at 20℃×65%RH The saturated moisture absorption rate is 5 wt% or more, and the water swelling degree is 10 times or less.

(3) The hygroscopic acrylic fiber as described in (1), which further contains 0.1 to 15% by weight of metal oxide.

(4) The hygroscopic acrylic fiber as described in (3), wherein the metal oxide is titanium oxide.

(5) The hygroscopic acrylic fiber described in (1) has a boiling water shrinkage rate of 5-50%.

(6) The hygroscopic acrylic fiber described in (1) has a crimp reduction coefficient of 0.7 or less after boiling water treatment.

(7) The hygroscopic acrylic fiber described in (1) has a crimp ratio of 7% or more.

(8) The hygroscopic acrylic fiber as described in (1), which further contains a water-repellent agent, and the time from being left standing in water to being submerged is 10 minutes or more.

(9) A fiber structure characterized by containing the hygroscopic acrylic fiber as described in any one of (1) to (8).

(10) A method for producing a hygroscopic acrylic fiber as described in (1), which is characterized by comprising: spinning a dope containing an acrylic polymer from a nozzle, then coagulating, washing, and stretching. In each step, the undried fiber obtained by hydrolysis.

(11) A method for producing hygroscopic acrylic fiber as described in (3) or (4), characterized by comprising: spinning a spinning dope containing an acrylonitrile polymer and a metal oxide from a nozzle , After coagulation, washing and stretching, the undried fiber obtained by hydrolysis.

(12) A method for producing a hygroscopic acrylic fiber as described in (5), characterized by comprising: spinning a dope containing an acrylic polymer from a nozzle, then coagulating, washing, and stretching. In each step, the undried fiber obtained by hydrolysis is then stretched.

(13) A method for producing a hygroscopic acrylic fiber as described in (6), characterized by comprising: spinning a dope containing an acrylic polymer from a nozzle, and then coagulating, washing, and stretching. In each step, the undried fiber obtained by hydrolysis is heat-treated in a tensioned or stretched state, and then crimp is imparted.

(14) A method for producing a hygroscopic acrylic fiber as described in (7), which is characterized by comprising: spinning dope (A) containing an acrylonitrile polymer and containing the dope (A) The spinning dope (B) of the acrylonitrile polymer composed of different monomers contained in the acrylonitrile polymer is compounded, and after spinning out from the nozzle, it undergoes the steps of coagulation, water washing, and extension, and hydrolyzes the resulting fiber Dry the fiber.

(15) A method for producing a hygroscopic acrylic fiber as described in (8), which is characterized by comprising: spinning a dope containing an acrylic polymer from a nozzle, then coagulating, washing, and stretching. In each step, the undried fiber obtained by hydrolysis is then treated with a water-repellent agent.

The hygroscopic acrylic fiber of the present invention does not substantially have a crosslinked structure formed by covalent bonds. Therefore, since it does not have a hydrazine cross-linked structure, the hygroscopic acrylic fiber of the present invention has almost no color red. In addition, since the hygroscopic acrylic fiber of the present invention does not require a crosslinking introduction step during production, the production steps can be drastically reduced. As a result, it can be continuously produced using ordinary acrylic fiber production equipment, and the productivity is high. In addition, the hygroscopic acrylic fiber of the present invention maintains practical fiber properties even without cross-linking treatment, so it is suitable for continuous production. In terms of function, it not only has hygroscopicity but also has light-to-heat conversion performance. , Shrinkage, ease of crimp removal, bulkiness and water repellency.

The form of the invention

The hygroscopic acrylic fiber of the present invention is different from the conventional hygroscopic acrylic fiber, and is characterized in that it does not substantially have a crosslinked structure formed by a covalent bond. Therefore, the cross-linking introduction step is not required, and as a result, the manufacturing steps can be drastically reduced, and the production can be performed in a simpler step than in the past. Therefore, it is not limited to batch processing like the conventional production of crosslinked acrylic fibers, and continuous production is possible. In addition, it is possible to suppress or prevent the fiber from being colored red or the degree of redness increasing with the passage of time. Furthermore, as desired, the hygroscopic acrylic fiber of the present invention can have light-to-heat conversion performance, shrinkage, ease of crimp removal, bulkiness and water repellency. In addition, in the present invention, the term "substantially not having a crosslinked structure formed by a covalent bond" refers to those having a <solubility in aqueous sodium thiocyanate solution> of 95% or more, which will be described later.

Regarding the suppression of the color red of the hygroscopic acrylic fiber of the present invention, in the expression method of JIS Z8781-4, a ^* indicating the degree of red can be made 2 or less, and it is possible to further make a ^* 0 or less. As ^{the lower limit of a*} , since other colors other than red become thicker if it is too low, it is preferably -4, and more preferably -3.

In addition, the hygroscopic acrylic fiber of the present invention contains a carboxyl group, and the content thereof is 0.2 to 4.5 mmol/g, preferably 0.5 to 4.0 mmol/g, in the value obtained by the method described later. More preferably, it is 0.5 to 3.5 mmol/g. In addition, when the hygroscopic acrylic fiber of the present invention In the case of a core-sheath structure, it is preferably 0.2 to 2 mmol/g, more preferably 0.5 to 1.0 mmol/g. When the amount of carboxyl groups is less than the lower limit of the above range, the moisture absorption performance described below may not be obtained. When the amount exceeds the upper limit, the hydrophilicity of the fiber is too high, exceeding the water swelling degree described below, violently swelling or dissolving in water, and handling becomes difficult.

The hygroscopic acrylic fiber of the present invention has a saturated moisture absorption rate under an environment of 20° C. and a relative humidity of 65%, which has a saturated moisture absorption rate of 5% by weight or more, preferably 10% by weight or more, and more preferably 15% by weight or more. When the saturated moisture absorption rate is less than the above lower limit, even if it is applied to various fiber structures, it is difficult to impart meaningful moisture absorption performance. Regarding the upper limit, from the viewpoint of maintaining fiber physical properties, it is preferably 35% by weight or less, and more preferably 30% by weight or less.

The hygroscopic acrylic fiber of the present invention has a degree of water swelling determined by the method described later of 10 times or less, preferably 8 times or less, and more preferably 5 times or less. The hygroscopic acrylonitrile fiber of the present invention is as described above, and does not have a cross-linked structure formed by covalent bonds. If the water swelling degree exceeds 10 times, the fiber becomes brittle and part of it falls off, or it may dissolve as the case may be. , Processing becomes difficult. There is no particular limitation on the lower limit, but the hygroscopic acrylic fiber of the present invention is generally 0.05 from the viewpoint that the saturated moisture absorption rate in an environment of 20°C and a relative humidity of 65% is 5% by weight or more. Times more.

Relative to the weight of the polymer constituting the fiber, the hygroscopic acrylic fiber of the present invention may contain 0.1 to 15% by weight of metal oxide, preferably 0.2 to 10% by weight. In order to obtain sufficient light-to-heat conversion properties, it is preferable to make the amount of metal oxide contained in the fiber the above Above the lower limit of the range, but when the upper limit is exceeded, the fiber physical properties will decrease, which may not be able to withstand textile processing or practical use.

The aforementioned metal oxides are not particularly limited as long as they have photothermal conversion properties. Examples include compounds such as oxides such as Si, Ti, Zn, Al, Fe, and Zr. Those that are insoluble in water may be used alone. One type selected from these can be used, or two or more types can be used in combination. In addition, the oxide system of Si, Ti, Zn, Al, and Zr not only has light-to-heat conversion properties, but also exhibits the effect of improving the color and whiteness of the fiber. It may be less than 50 in the whiteness evaluation method described below. High-end color white. Among them, titanium oxide is particularly good in terms of color white improving effect, safety, and price.

In addition, the particle size of the metal oxide is not particularly limited, and the average primary particle size is preferably in the range of 1 to 1000 nm, and more preferably in the range of 50 to 600 nm. When the average primary particle size is less than the lower limit of the above range, there is a possibility that a large amount of dust will fly or clogging of the spinning nozzle due to aggregation during fiber production. When the upper limit is exceeded, the physical properties of the fiber may be impaired.

In addition, the boiling water shrinkage rate of the hygroscopic acrylic fiber of the present invention is preferably 5%-50%, more preferably 8%-45%, and particularly preferably 12%-40%. In order to impart meaningful shrinkage performance even when applied to various fiber structures, it is preferable to make the boiling water shrinkage ratio more than the lower limit of the above-mentioned range, but when the upper limit is exceeded, it is difficult to maintain practical fiber properties.

In addition, the hygroscopic acrylic fiber of the present invention has a crimp reduction coefficient after boiling water treatment determined by the method described below, preferably 0.7 or less, more preferably 0.6 or less, and particularly preferably 0.5 or less. The volume The shrinkage reduction factor means that the smaller the value, the easier it is to remove the curl. When the curl reduction factor is greater than the above upper limit, even if it is applied to various fiber structures, it is difficult to give meaningful design properties due to curl removal. . On the other hand, with regard to the lower limit, since it is difficult to completely eliminate the curl, it is usually 0.05 or more.

In addition, the crimp ratio of the hygroscopic acrylic fiber of the present invention is preferably 7% or more, more preferably 10% or more. The crimp rate is specified in JIS L1015. The higher the crimp rate, the easier it is for fibers and fibers to become entangled, and become bulky when it becomes a fiber assembly such as web, nonwoven fabric, and woven yarn. If the crimp ratio is lower than the above lower limit, the connection between the fibers in the carding step will be poor, and the bulkiness when forming a fiber assembly will be low. Full thickness shape. On the other hand, with regard to the upper limit, if the crimp ratio is too high, the entanglement of the fibers will become too strong. Since the opening of the carding step becomes difficult and the fiber structure is tight and difficult to bulk, it is preferably 40 % Or less, more preferably 20% or less.

As the bulkiness of the hygroscopic acrylonitrile fiber of the present invention, when it is used for quilts or clothing cotton, the specific volume mentioned later is preferably 35 cm ³ /g or more, more preferably 40 cm ³ /g or more, It is particularly preferable to have 45 cm ³ /g or more. On the other hand, with regard to the upper limit, if the specific volume is too large, only a small amount of force is applied, which will simply cause distortion, which may cause insufficient shape retention. Therefore, it is preferably 100 cm ³ /g or less, and more preferably 80 cm ³ /g or less.

The hygroscopic acrylic fiber of the present invention may contain a water repellent, and the time from being placed on water to being submerged at that time is preferably 10 minutes or more, more preferably 15 minutes or more, and particularly preferably 20 minutes or more. To the end When the time to full submersion is less than 10 minutes, there is insufficient water repellency, which may cause problems in comfort. In addition, the upper limit is not particularly limited. When the time to submerge is 20 minutes or more, there will be no submergence afterwards.

In addition, in the hygroscopic acrylic fiber of the present invention, it is preferable that the carboxyl group is uniformly present in the entire fiber. Here, the term "homogeneously present in the entire fiber" means that the coefficient of variation CV of the magnesium content in the fiber section measured by the measurement method described later is 50% or less. If the carboxyl group is locally present, the part will easily become brittle due to moisture absorption. Since the carboxyl group is uniformly present in the entire fiber, it suppresses embrittlement even if it absorbs moisture and water, and even if it does not have a cross-linked structure, it is easy to obtain fiber properties that can withstand practical use. From such a viewpoint, the above-mentioned CV value is preferably 30% or less, more preferably 20% or less, and particularly preferably 15% or less.

However, depending on the required physical properties or applications, the hygroscopic acrylic fiber of the present invention may adopt a core-sheath structure in which only carboxyl groups are substantially uniformly present on the fiber surface. At this time, the core-sheath structure is composed of a surface layer portion containing a carboxyl group-containing polymer and a center portion containing an acrylonitrile-based polymer. In this way, by having a core-sheath structure including the center part and the surface layer part surrounding it, since the practical fiber properties that are hard and elastic at the center part are obtained, the moisture absorption speed can be significantly increased in the surface layer part with a high carboxyl group concentration. .

The occupied area of the surface layer in the cross section of the fiber of the core-sheath structure is preferably 20 to 80%, more preferably 30 to 70%. If the occupancy area of the surface layer is small, there is a risk that the hygroscopicity and other functions may not be fully exhibited. If the area occupied by the surface layer portion is large, the center portion becomes thinner, and practical fiber properties may not be obtained.

As the state of the carboxyl group, when higher moisture absorption performance is required, the counter ion is preferably a cation other than H. More specifically, the relative ion is the ratio of cations other than H, that is, the degree of neutralization is preferably 25% or more, more preferably 35% or more, and particularly preferably 50% or more.

Examples of cations include alkali metals such as Li, Na, and K, alkaline earth metals such as Be, Ca, and Ba, metals such as Cu, Zn, Al, Mn, Ag, Fe, Co, Ni, and NH ₄ Cations such as amines, amines, etc., multiple types of cations can also be mixed. Among them, Li, Na, K, Mg, Ca, Zn, etc. are preferred.

In addition, in the above case, it can also exhibit excellent deodorizing performance against acid gases such as acetic acid and isovaleric acid, and aldehydes such as formaldehyde. In addition, if it is Mg or Ca ions, the flame retardancy is high, and if it is Ag or Cu ions, it is possible to obtain high antibacterial performance.

On the other hand, increasing the relative ion of H as a carboxyl group can enhance the deodorizing performance, antiviral performance, and antiallergic performance of ammonia, triethylamine, pyridine and other amine gases.

The above-mentioned hygroscopic acrylic fiber of the present invention can be obtained by subjecting the acrylic fiber in an undried state to a hydrolysis treatment. When imparting shrinkage to the fiber, it is subjected to a stretching treatment after hydrolysis. In addition, when imparting ease of crimp removal to the fiber, after hydrolysis, heat treatment is applied in a stretched or stretched state, and then crimp is imparted. Hereinafter, the representative manufacturing method of the hygroscopic acrylic fiber of the present invention will be described in detail.

First, the raw material is acrylic fiber, but the acrylic polymer system constituting the fiber preferably contains 40% by weight or more of acrylonitrile (hereinafter also referred to as AN) in the polymerization composition, and more preferably 50% by weight or more. Particularly preferably, it is 85% by weight or more. In addition to AN homopolymers, AN-based polymers can also be copolymers of AN and other monomers. As other monomers, monomers containing sulfonic acid groups such as vinyl halides and vinylidene halides, (meth)acrylates, methallylsulfonic acid, p-styrenesulfonic acid, etc., and their salts, propylene Amide, styrene, vinyl acetate, etc. are not particularly limited as long as they are monomers that can be copolymerized with AN. In addition, the description of (methyl) means both the term with and without the methyl.

Next, such an AN-based polymer is used to perform fiberization by wet spinning. However, as the solvent, if an inorganic salt such as sodium thiocyanate is used, it is as follows. First, the above-mentioned AN-based polymer is dissolved in a solvent to prepare a spinning dope. To this spinning dope, metal oxides are added as needed. After the spinning dope is spun from the nozzle, it goes through the steps of coagulation, water washing, and stretching, so that the water content of the stretched undried fiber (hereinafter, also referred to as gel-like acrylic fiber) becomes 20 to 250 weight %, preferably 25 to 130% by weight, more preferably 30 to 100% by weight.

Here, when a gel-like acrylic fiber in an undried state is used as the raw fiber to be hydrolyzed, the carboxyl group can be uniformly present in the entire fiber as described above. On the other hand, when the undried gel-like acrylic fiber is further heat-treated to make it densified, or the fiber that has been further relaxed after densification is used as the raw material fiber and subjected to hydrolysis treatment, It can be a core-sheath structure in which carboxyl groups are locally present on the surface of the fiber.

In addition, for the purpose of imparting bulkiness, and in order to further increase the crimp ratio, it is effective as a means of forming a raw fiber composited with two or more acrylonitrile polymers having different monomer compositions. For example, two types of acrylonitrile-based polymers (a) and (b) that differ in the polymerization ratio of acrylonitrile can be used to produce spinning dope (A) and (B) containing the respective polymers. These two types of spinning dope are extruded from the same hole of the spinneret, and the acrylonitrile-based fiber compounded with the two types of acrylonitrile-based polymer is used as a means of raw fiber. By adopting such a method, curling based on the difference in the degree of shrinkage of each acrylonitrile-based polymer is exhibited.

The composite structure of the acrylonitrile-based polymer may be one that is joined in parallel, or one that is randomly mixed, but it is preferably one that joins two kinds of acrylonitrile-based polymers in parallel. At this time, in order to obtain sufficient crimp ratio, the difference between the acrylonitrile polymerization ratios of the two acrylonitrile polymers is preferably 1 to 10%, more preferably 1 to 5%, a composite of the two acrylonitrile polymers The ratio is preferably 20/80 to 80/20, more preferably 30/70 to 70/30.

When the gelatinous acrylic fiber is used as the raw material fiber, when the water content of the gelatinous acrylic fiber is less than 20% by weight, the agent does not penetrate into the fiber during the hydrolysis treatment described later, and the carboxyl group cannot be formed in the fiber. The situation generated in the whole. When it exceeds 250% by weight, the fiber contains a lot of water, and the fiber strength is too low, and the spinnability is impaired. When paying more attention to the strength of the fiber, it should be set in the range of 25 to 130% by weight. In addition, there are many methods to control the moisture content of the gelatinous acrylonitrile fiber within the above range, but for example, the temperature of the coagulation bath is preferably -3~15°C, preferably -3~10°C, and the elongation ratio is preferably 5 ~20 times, preferably about 7~15 times.

Furthermore, when the gelatinous acrylic fiber is further heat-treated, for example, by alternately performing a dry heat treatment at 110°C and a wet heat treatment at 60°C, the voids inside the fiber disappear and a densified fiber is obtained. Furthermore, by performing autoclave treatment at 120°C for 10 minutes, a fiber with a somewhat relaxed fiber structure was obtained. If these fibers are used as a raw material and subjected to the hydrolysis treatment described later, the reaction proceeds from the surface layer of the fiber, and it is easy to obtain a structure such as a core-sheath structure. Furthermore, as the reaction progresses, the degree of water swelling tends to increase easily, and it may become difficult to handle the resulting fiber.

Gel-like acrylic fibers or fibers subjected to further heat treatment are subsequently subjected to hydrolysis treatment. As a means of such a hydrolysis treatment, a means of heat treatment in the state of being impregnated or immersed in an alkaline aqueous solution of alkali metal hydroxide, alkali metal carbonate, ammonia, etc., or an aqueous solution of nitric acid, sulfuric acid, hydrochloric acid, or the like can be mentioned. As the specific treatment conditions, it is sufficient to consider the range of the amount of carboxyl groups mentioned above, and appropriately set various conditions such as the concentration of the treatment agent, the reaction temperature, and the reaction time. However, the impregnation is generally 0.5-20% by weight, preferably 1.0-15% by weight. % Of the treatment agent and extruded, in a humid and hot environment, at a temperature of 100~140℃, preferably 110~135℃, and set within the range of 10~60 minutes of processing conditions. It is industrial and fiber physical properties. It is also more appropriate. Within the above range, the higher the processing temperature, the higher the crimp rate tends to be. Furthermore, the so-called hot and humid environment refers to an environment filled with saturated steam or superheated steam. This treatment hydrolyzes the nitrile groups in the gel-like acrylic fiber to generate carboxyl groups.

In the fiber subjected to the hydrolysis treatment as described above, cations such as alkali metal or ammonium corresponding to the kinds of alkali metal hydroxides, alkali metal carbonates, ammonia, etc. used in the hydrolysis treatment are generated as counter ions The salt type carboxyl group, but then, if necessary, the relative ion of the carboxyl group can be converted. If ion exchange treatment is performed for an aqueous solution of metal salts such as nitrate, sulfate, hydrochloride, etc., it can become a salt-type carboxyl group with a desired metal ion as a counter ion. Furthermore, by adjusting the pH or metal salt concentration of the aqueous solution ‧ types, it is also possible to mix the relative ions of different species or adjust their ratio.

The fibers subjected to the hydrolysis treatment or the fibers further subjected to the ion exchange treatment as described above can be given shrinkage by subsequent stretching treatment. The extension ratio is usually set at 1.1~2.0 times. If the stretching ratio is less than 1.1 times, the shrinkage will be low, and if it is more than 2.0 times, the fiber physical properties will be poor. In addition, the extension treatment is performed under heating, but the temperature is preferably lower than the temperature of the above-mentioned hydrolysis treatment. The heating means may be moist heat such as steam or dry heat such as dry heat rolls.

In addition, the fibers subjected to the hydrolysis treatment or the fibers further subjected to the ion exchange treatment as described above are then subjected to heat treatment in a tensioned or stretched state, which can be given subsequent post-processing treatments for spinning and the like. And the need for curling. Here, in the provision of crimping, a generally used mechanical crimping method can be adopted. The fiber thus obtained can be subjected to heat treatment such as boiling water treatment to remove crimping.

In addition, the fibers subjected to post-hydrolysis treatment as described above can be treated with a water-repellent agent. In this case, relative to the fiber, that is, the weight of the fiber before the water-repellent treatment, preferably contains 0.2 to 5.0% by weight of the water-repellent agent. , And more preferably contain 0.3 to 3.0% by weight. When the water repellent contained in the fiber is less than the lower limit of the above range, sufficient water repellency may not be obtained, and when it exceeds the upper limit, the hand feeling and spinning process passability may deteriorate.

As the above-mentioned water-repellent agent, fluorine-containing silicone, fluorine-containing compound, amino modified silicone, epoxy modified silicone, etc. can be used alone or in combination of two Used above. Among them, the fluorine-containing polysiloxane has a high water-repellent effect and is particularly good.

The method of applying the water-repellent agent is not particularly limited, but for example, the water-repellent agent dispersion can be used to impregnate the hydrolyzed fibers in the water-repellent dispersion, and then apply the water-repellent dispersion to the water-repellent dispersion by an extrusion method or spraying the hydrolyzed fibers. The method and so on.

By proceeding as described above, the hygroscopic acrylic fiber of the present invention can be obtained, and the above-mentioned treatments can be continuously implemented by using the existing continuous production equipment of acrylic fiber. In addition, treatments such as washing with water, drying, and cutting to a specific fiber length can be added as necessary. In the above, the case where an inorganic salt such as sodium thiocyanate is used as a solvent is explained, but in the case of using an organic solvent, the above-mentioned conditions are also the same. However, due to the different types of solvents, the temperature of the coagulation bath is selected to suit the solvent, and the moisture content of the gelatinous acrylic fiber is controlled within the above range.

In addition, in the production of the hygroscopic acrylic fiber of the present invention, a functional material may be added to the spinning dope. Examples of such functional materials include titanium oxide, carbon black, pigments, antibacterial agents, deodorants, moisture absorbents, antistatic agents, resin beads, and the like.

Here, in the hygroscopic acrylic fiber of the present invention obtained by the above-mentioned production method, it is considered that since the gel-like acrylic fiber in the undried state is hydrolyzed, it is not based on the surface of the fiber. The order is hydrolyzed, but the agent also penetrates deep into the fiber and is hydrolyzed in the entire fiber. Furthermore, from a microscopic point of view, generally speaking, in acrylonitrile The crystalline part of the AN-based polymer alignment in the fiber is mixed with the amorphous part of the disordered structure. Therefore, it is judged that the crystalline part is hydrolyzed from the outside, but the amorphous part is hydrolyzed as a whole. As a result, after the hydrolysis, it was determined microscopically that a part of the crystalline part was not subjected to hydrolysis and remained as a part with a high nitrile group concentration, and the amorphous part was a part with a high carboxyl group concentration. In addition, the surface layer of the fiber is not locally hydrolyzed, but is hydrolyzed in the entire fiber. Therefore, when metal oxides are used, the metal oxides present in the surface layer can be prevented from falling off due to hydrolysis, and the added metal can be used without waste. Oxide.

Furthermore, when the hygroscopic acrylic fiber of the present invention contains a metal oxide, its light-to-heat conversion performance is significantly higher than when the conventional fiber contains a metal oxide. Such reports have not been reported so far. Although the main reason is unknown, it is estimated that, as described above, in the hygroscopic acrylic fiber of the present invention, since the entire fiber has a relatively thick structure, light can easily reach the depths of the fiber. , The metal oxide that exists deep inside is also effectively used, and the light-to-heat conversion effect is significantly improved.

Based on the above, the structure of the hygroscopic acrylic fiber of the present invention obtained by the above-mentioned manufacturing method is inferred to be a structure in which a portion with a high carboxyl group concentration and a portion with a high nitrile group concentration are uniformly present in the entire fiber. Moreover, it is judged that because of such a structure, even if it does not have a cross-linked structure formed by covalent bonds, the decrease in fiber properties during moisture absorption and water absorption is suppressed. In addition, the hygroscopic acrylic fiber of the present invention is as described above, by using a fiber that is densified by further heat-treating the gel-like acrylic fiber in an undried state, or it will be further relaxed after being densified. The treated fiber is used as the raw fiber, and even when the core-sheath structure is adopted, The carboxyl groups are uniformly present in the surface layer part, and the center part has a hard and elastic structure. Therefore, it is considered that even if the crosslinked structure by covalent bonds is not available, the fiber physical properties are similarly lowered.

In addition, in the hygroscopic acrylic fiber of the present invention, since it has the above-mentioned structure, the characteristics of ordinary acrylic fiber remain, and furthermore, it does not have a cross-linked structure formed by covalent bonds. It can be extended even after hydrolysis, so it is judged that shrinkage can also be imparted. In addition, for the same reason, even after hydrolysis, heat treatment can be performed in a stretched or stretched state, and then crimping can be imparted. Therefore, it is judged that ease of crimping removal can also be imparted.

Furthermore, as can be seen from the above, in the above-mentioned manufacturing method, the gel-like acrylic fiber is hydrolyzed to obtain a fiber having the above-mentioned characteristics. Gel-like acrylic fiber is not used, that is, the stretched undried fiber is not used. When the dried acrylic fiber is hydrolyzed, the agent will not penetrate deep into the fiber, because it depends on the fiber surface. Order hydrolysis, so it derives a structure with more carboxyl groups in the surface part of the fiber and few carboxyl groups in the deep part of the fiber. The fiber with such a structure causes the dissolution of the fiber surface layer into water, etc., which is not practical.

The above-mentioned hygroscopic acrylic fiber of the present invention can be used as a fiber structure useful in many applications, alone or by combining with other materials. From the viewpoint of obtaining the effect of the hygroscopic acrylic fiber of the present invention, in the fiber structure, the content of the hygroscopic acrylic fiber of the present invention is preferably 5% by weight or more, more preferably 10% by weight or more, more preferably 20% by weight or more. In addition, there are no special restrictions on the types of other materials. Commonly used natural fibers, Organic fibers, semi-synthetic fibers, synthetic fibers, and inorganic fibers, glass fibers, etc. can also be used according to the application. As a specific example, cotton, hemp, silk, wool, nylon, rayon, polyester, acrylic fiber, etc. may be mentioned.

As the appearance form of the fiber structure, there are yarns, non-woven fabrics, paper-like articles, sheet-like articles, laminates, cotton-like bodies (including spherical or lumpy ones), and the like. As the form of the fiber of the present invention in the structure, there is one that is substantially uniformly distributed by mixing with other materials. , May also be plural), or distributed in a specific ratio in each layer.

The appearance or content of the fiber structure exemplified above, other materials constituting the fiber structure, and other members combined with the fiber structure can be any, depending on the type of the final product (e.g., clothing, filter, etc.). , Curtains or carpets, bedding or cushions, insoles, etc.), considering the required function, characteristics, shape, or the manner in which the hygroscopic acrylic fiber of the present invention contributes to the performance of the function, etc., are appropriately determined.

[Example]

In order to easily understand the present invention, examples are shown below, but these are exemplifications after all, and the gist of the present invention is not limited by them. In the examples, parts and percentages are expressed on a weight basis unless otherwise specified. In addition, the measurement of each characteristic is obtained by the following method.

<Solubility in sodium thiocyanate aqueous solution>

Approximately 1 g (W1[g]) of the dried sample was finely weighed, and 100 ml of 58% sodium thiocyanate aqueous solution was added, immersed at 80°C for 1 hour, filtered, washed with water, and dried. The dried sample (W2[g]) is accurately weighed, and the solubility is calculated by the following formula.

Solubility [%]=(1-W2/W1)×100

When the solubility is 95% or more, it is judged that it does not substantially have a crosslinked structure formed by a covalent bond.

<Determination of the amount of carboxyl group>

About 1 g of the sample was weighed, immersed in 50 ml of 1 mol/l hydrochloric acid for 30 minutes, washed with water, and immersed in pure water at a bath ratio of 1:500 for 15 minutes. After washing with water until the bath pH became 4 or more, it was dried with a hot air dryer at 105°C for 5 hours. About 0.2g (W3[g]) of the dried sample was carefully weighed, and 100m of water, 15ml of 0.1mol/l sodium hydroxide, 0.4g of sodium chloride, and stirring were added to it. Next, the sample was filtered using a metal mesh and washed with water. Add 2~3 drops of phenolphthalein solution to the filtrate (also including washing liquid), titrate with 0.1mol/l hydrochloric acid, and titrate according to common methods to find the amount of hydrochloric acid consumed (V1[ml]), by The formula calculates the total amount of carboxyl groups.

Total carboxyl group [mmol/g]=(0.1×15-0.1×V1)/W3

<Measurement of saturated moisture absorption>

The sample was dried with a hot air dryer at 105°C for 16 hours, and the weight was measured (W4 [g]). Next, the sample was placed in a thermo-hygrostat adjusted to the condition of 20° C.×65% RH for 24 hours. Measure so suck The weight of the wet sample (W5[g]). From the above measurement results, it is calculated by the following formula.

Saturated moisture absorption rate [%]=(W5-W4)/W4×100

<Water swelling degree>

After immersing the sample in pure water, it was dehydrated at 1200 rpm for 5 minutes using a desktop centrifugal dehydrator. After measuring the weight of the sample after dehydration (W6[g]), the sample was dried at 115°C for 3 hours, the weight (W7[g]) was measured, and the degree of water swelling was calculated by the following formula.

Water swelling degree [times]=W6/W7-1

<neutralization degree>

About 0.2g (W8[g]) of the sample after being dried by a hot air dryer at 105℃ for 5 hours on a precision scale, add 100ml of water, 15ml of 0.1mol/l sodium hydroxide, 0.4g of sodium chloride and stir in it. . Next, the sample was filtered using a metal mesh and washed with water. Add 2~3 drops of phenolphthalein solution to the obtained filtrate (including washing liquid), titrate with 0.1mol/l hydrochloric acid, and titrate according to common methods to obtain the amount of hydrochloric acid consumed (V2[ml]). The amount of H-type carboxyl groups contained in the sample was calculated by the following formula, and the degree of neutralization was determined from the result and the total amount of carboxyl groups described above.

Amount of H-type carboxyl group [mmol/g]=(0.1×15-0.1×V2)/W8

Neutralization degree [%]=[(Total carboxyl group amount-H type carboxyl group amount)/total carboxyl group amount]×100

<hue a ^* value>

Using 0.5 g of a sample that was opened and dried at 105° C. for 16 hours in a hot air dryer, the color was measured with a color difference meter CR-300 manufactured by Konica-Minolta.

<Titanium Oxide Content and Titanium Oxide Retention Rate>

From the peak intensity of the sample measured by the fluorescent X-ray analyzer, the content of titanium oxide contained in the fiber (C1[%]) is measured. Regarding the titanium oxide retention rate, the dried titanium oxide content (C2[%]) of the gel-like acrylonitrile fiber before the hydrolysis treatment in the production step of the sample was measured with the same device as described above, and it was calculated by the following formula out.

Titanium oxide retention rate (%)=C1/C2×100

<Light-to-heat conversion>

Put 5 g of a cotton-like sample in a cylindrical tube with an inner diameter of 2 cm, and perform hot pressing at 80° C. for 10 minutes to make a measurement sample with a diameter of 2 cm and a thickness of 5 mm. Place the sample for measurement in a room at 25°C to stabilize the temperature, and irradiate it with an incandescent electric lamp (SUN CLIP DX-II (AC100V, 600W), manufactured by Hakubao Photo Industry) for 5 minutes from a vertical position 1 m above the vertical. Measure the temperature (°C) of the sample with a thermal imager.

<Whiteness>

Using Hitachi U-3000 spectrophotometer, using alumina (Al ₂ O ₃ ) as a reference, measure the reflectance (X%, Y%, Z%) of the sample at 595nm, 553nm, and 453nm, using the following formula Find the degree of whiteness. The smaller the value, the greater the degree of whiteness.

White degree=0.817×((X-Z)/Y)×100)-3.71

<Boiling water shrinkage>

The sample fiber was left to stand for 24 hours in an environment of 20° C.×65% RH to adjust the humidity, and the fiber length (L1) was measured. Next, the sample fiber was shrunk in boiling water for 30 minutes, the fiber length (L2) after shrinkage was measured, and the boiling water shrinkage rate was calculated according to the following formula.

Boiling water shrinkage (%)=(L1-L2)/L1×100

<Curl reduction factor>

For the sample where the sample fiber is placed in an environment of 20℃×65%RH for 24 hours to adjust the humidity, according to the method of JIS L 1015:2010 "8.12.1 crimp number", count the applied initial load (0.18mN×fineness) (tex)) The number of hills and valleys between 25mm (A), the number of crimping (B) is calculated by the following formula.

Rolling number (B)=A/2

In addition, the sample fiber was treated in boiling water for 30 minutes to obtain a fiber removed by crimping. With respect to the fiber removed by this crimping, the number of crimps (C) was obtained by humidity control and measurement in the same manner as described above. Using the number of crimping (B) and the number of crimping (C) obtained as above, calculate the crimping reduction coefficient according to the following formula.

Curl reduction factor (%)=C/B×100

<Curl rate>

Measure and calculate according to JIS L1015.

<Specific volume (bulky)>

From the carded fleece produced by the method described in the item of "Carding Machine Passability" below, a plurality of pieces of 10 cm×10 cm were cut out and used as test pieces. The test piece was placed in a constant temperature and humidity machine, and allowed to stand for 24 hours in an environment of 20° C.×65% RH, and layered so as to be 10.0 to 10.5 g. An acrylic plate (size 10 cm x 12 cm, weight 42 g) was placed on the laminated test piece, a 500 g weight was placed for 30 seconds, and then the weight was removed and left for 30 seconds. Repeat this operation 3 times, remove the weight, measure the height of the four corners of the stacked test piece after 30 seconds, find the average value [cm], and calculate the specific volume using the following formula.

Specific volume [cm ³ /g]=10×10×average value of four corners [cm]/weight of laminated test piece [g]

<Carding machine passability>

50 g of sample fibers with a fiber length of 70 mm were used in a room adjusted to a temperature of 30 ± 5° C. and 50 ± 10% RH, using a sample roll carding machine (model SC-300L) manufactured by Daiwa Machinery Co., Ltd. to make a carded fleece. The shape of the obtained fleece was evaluated using the following criteria.

○: The entanglement is sufficient, and a fleece net without unevenness is obtained.

△: The entanglement is slightly insufficient, and there is unevenness in the fleece.

X: The entanglement is obviously insufficient, the fibers are not connected to each other, and the fleece cannot be obtained.

<Content of Water Repellent>

As shown in the following formula, the amount of water repellent adhering to the fiber is calculated based on the decrease in the solid content of the water repellent dispersion before and after the water repellent treatment. Furthermore, the solid content ratio of the water-repellent dispersion liquid is measured by the method of the following items, and the fiber weight before water-repellent treatment is measured by the same method as the item "W4" of the item "Measurement of saturated moisture absorption rate" .

The content of the water repellent in the fiber [%]={(The proportion of solid content before treatment [%] × the amount of dispersion before treatment [g]) (the proportion of solid content after treatment [%] × the amount of dispersion after treatment [g] )}/Fiber weight before water repellent treatment [g]×100

<Solid content ratio of water repellent dispersion>

The weight before and after drying by a hot air dryer at 120°C x 1 hour was measured and calculated by the following formula.

The proportion of solid content of the water repellent dispersion [%]=weight after drying [g]/weight before drying [g]×100

<Settling time of fiber in pure water>

Place the fiber-opened sample in a thermo-hygrostat adjusted to the condition of 20°C×65%RH for 24 hours. 1 g was sampled from this sample, placed in pure water, and the time from the standing to sinking in the water was measured, in units of 1 minute, to 20 minutes.

<Distribution of carboxyl groups in fiber structure>

The fiber sample was immersed in an aqueous solution of magnesium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber at 50°C for 1 hour to perform ion exchange treatment. The carboxyl groups were washed and dried. The opposite ion becomes magnesium. For the magnesium salt type fiber sample, the energy dispersive X-ray spectrometer (EDS) is used for the fiber section from the outer edge to the center. Then, at approximately equal intervals, select 10 measurement points, and measure the magnesium content of each measurement point. From the obtained values at each measurement point, use the following formula to calculate the coefficient of variation CV [%].

Coefficient of variation CV[%]=(standard deviation/average)×100

<Proportion of the area occupied by the surface layer in the cross section of the core-sheath structure fiber>

The sample fiber was immersed in a dyeing bath containing 2.5% of cationic dye (Nichilon Black G 200) and 2% of acetic acid relative to the weight of the fiber at a bath ratio of 1:80, and then boiled for 30 minutes. Washing, dehydrating, and drying. The resulting dyed fiber was sliced thinly perpendicular to the fiber axis, and the fiber section was observed with an optical microscope. At this time, the center system composed of the acrylonitrile-based polymer is dyed black, and a large amount of surface layer dyes having carboxyl groups are insufficiently fixed and become green. In the fiber section, measure the fiber diameter (D1) and the diameter of the blacked center portion (D2) with the part that changes color from green to black as the boundary (D2), and calculate the surface layer area ratio by the following formula. In addition, the average of the surface layer area ratios of the 10 samples was used as the surface layer area ratio of the sample fiber.

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

<Determination of moisture content of undried fiber after stretching>

After immersing the stretched undried fiber in pure water, use a centrifugal dehydrator (Type H-770A manufactured by Japan Centrifuge Co., Ltd.) to accelerate 1100G (G means gravitational acceleration), dehydration for 2 minutes. After measuring the weight after dehydration (as W8 [g]), the undried fiber was dried at 120°C for 15 minutes, and the weight (as W9 [g]) was measured, and it was calculated by the following formula.

The moisture content of the undried fiber after stretching (%)=(W8-W9)/W8×100

<Example 1A>

10 parts of AN-based polymer composed of 90% AN and 10% methyl acrylate dissolved in 90 parts of 44% sodium thiocyanate aqueous solution was spun out in a coagulation bath at -2.5°C. It was coagulated, washed with water, and stretched 12 times to obtain a gel-like acrylic fiber with a water content of 35%. The fiber was immersed in a 2.5% sodium hydroxide aqueous solution, and after extrusion, it was subjected to hydrolysis treatment at 123° C.×25 minutes in a humid and hot environment, washed with water, and dried to obtain the hygroscopic acrylic fiber of Example 1A. Table 1 shows the evaluation results of the obtained fibers.

<Examples 2A~5A>

Except in the formulation of Example 1A, the concentration of the aqueous sodium hydroxide solution was changed to 7.5% in Example 2A, 10% in Example 3A, and 15% in Example 4A. Except changing to 20% in 5A, the same operation was performed to obtain hygroscopic acrylic fibers of Examples 2A to 5A. Table 1 shows the evaluation results of the obtained fibers.

<Example 6A>

The hygroscopic acrylic fiber of Example 3A was immersed in an aqueous nitric acid solution, adjusted to a bath pH of 5.0, and heated at 60°C for 30 minutes. Then, it washed with water and dried to obtain the hygroscopic acrylic fiber of Example 6A. Table 1 shows the evaluation results of the obtained fibers.

<Example 7A>

Except that in the formulation of Example 6A, instead of the hygroscopic acrylic fiber of Example 3A, the hygroscopic acrylic fiber of Example 5A was used, and the same operation was performed to obtain the hygroscopic acrylic fiber of Example 7A. Nitrile fiber. Table 1 shows the evaluation results of the obtained fibers.

<Comparative Example 1A>

10 parts of AN-based polymer composed of 90% AN and 10% methyl acrylate dissolved in 90 parts of 44% sodium thiocyanate aqueous solution was spun out in a coagulation bath at -2.5°C. After coagulation, water washing, and 12-fold stretching, it is dried in an environment of dry ball/wet ball=120°C/60°C to obtain raw fiber. The raw fiber was treated in a 35% hydrazine aqueous solution at 100°C for 3 hours under the conditions shown in Table 1, and then treated in a 5% sodium hydroxide aqueous solution at 90°C for 2 hours, and then dehydrated. It is washed with water and dried to obtain fiber with cross-linked structure and carboxyl group. Table 1 shows the evaluation results of the obtained fibers.

<Comparative Example 2A>

Dissolve 10 parts of AN polymer composed of 88% AN and 12% methacrylic acid in 90 parts of 44% sodium thiocyanate aqueous solution. The spinning dope is spun according to a common method, coagulated, washed with water, and stretched, and then dried to obtain acrylic fibers with carboxyl groups. Table 1 shows the evaluation results of the obtained fibers.

<Comparative Example 3A>

The acrylic fiber of Comparative Example 2A was heat-treated at 90° C. for 30 minutes with a soda ash 1 g/l aqueous solution, washed with water, and dried to obtain acrylic fiber with neutralized carboxyl groups. Table 1 shows the evaluation results of the obtained fibers.

<Comparative Example 4A>

Except that in the formulation of Comparative Example 3A, the treatment temperature of the 1g/l aqueous solution of soda ash was changed to 100°C, the same operation was performed to obtain acrylic fibers having neutralized carboxyl groups. Table 1 shows the evaluation results of the obtained fibers.

As shown in Table 1, the hygroscopic acrylic fibers of Examples 1A to 7A, although they do not have a cross-linked structure formed by covalent bonds, have a saturated moisture absorption rate of 5 at 20℃×65%RH. % Or more and water swelling degree of 10 times or less. In addition, the fiber a ^* is in the range of -4~2, and the color red has been suppressed.

In contrast, the conventional cross-linked acrylic fiber of Comparative Example 1A has a cross-linked structure, and although it shows good characteristics in terms of saturated moisture absorption and water swelling degree, the degree of redness is strong. Regarding the acrylic fiber of Comparative Example 2A, since the carboxyl group is not neutralized, the saturated moisture absorption rate is low. Although the fiber of Comparative Example 3A was neutralized with the acrylic fiber of Comparative Example 2A, the improvement of the saturated moisture absorption rate was insufficient, and on the other hand, the degree of water swelling was greatly increased. In Comparative Example 4A, due to the enhancement of the neutralization reaction conditions, although the saturated moisture absorption rate is increased, the water swelling is too high, and the fibers will gel.

<Example 1B>

After dissolving 10 parts of AN-based polymer composed of 90% AN and 10% methyl acrylate in 90 parts of 44% sodium thiocyanate aqueous solution, add 0.25 parts by weight of the spinning stock solution of titanium oxide, It was spun in a coagulation bath at -2.5°C, coagulated, washed with water, and stretched 12 times to obtain a gel-like acrylic fiber with a water content of 35%. The fiber was immersed in a 2.5% sodium hydroxide aqueous solution, and after extrusion, it was subjected to a hydrolysis treatment at 123°C×25 minutes in a hot and humid environment, washed with water, and dried to obtain the hygroscopic acrylic fiber of Example 1B.

<Examples 2B~4B>

Except that in the formulation of Example 1B, the concentration of the aqueous sodium hydroxide solution was changed to 7.5% in Example 2B, 10% in Example 3B, and 20% in Example 4B, similarly The operation was performed to obtain the hygroscopic acrylic fibers of Examples 2B to 4B.

<Example 5B>

The hygroscopic acrylic fiber of Example 3B was immersed in an aqueous nitric acid solution, adjusted to a bath pH of 5.0, and heated at 60°C for 30 minutes. Then, water washing and drying were performed to obtain the hygroscopic acrylic fiber of Example 5B.

<Example 6B>

The hygroscopic acrylic fiber of Example 4B was immersed in an aqueous nitric acid solution, adjusted to a bath pH of 5.0, and heated at 60°C for 30 minutes. Then, it washed with water and dried to obtain the hygroscopic acrylic fiber of Example 6B.

<Example 7B>

Except that in the formulation of Example 1B, the addition amount of titanium oxide was changed to 0.05 parts by weight, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 7B.

<Example 8B>

Except for the formulation of Example 1B, the addition amount of titanium oxide was changed to 0.05 parts by weight, and the concentration of the sodium hydroxide aqueous solution was changed to 20%, and the same operations were performed to obtain the hygroscopic acrylic fiber of Example 8B .

<Example 9B>

Except for changing the addition amount of titanium oxide to 0.5 parts by weight in the formulation of Example 1B, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 9B.

<Example 10B>

Except that in the formulation of Example 1B, the addition amount of titanium oxide was changed to 0.5 parts by weight, and the concentration of the sodium hydroxide aqueous solution was changed to 20%, the same operation was performed to obtain the hygroscopic acrylonitrile system of Example 10B fiber.

<Example 11B>

Except for changing the addition amount of titanium oxide to 1 part by weight in the formulation of Example 1B, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 11B.

<Example 12B>

Except that in the formulation of Example 1B, the addition amount of titanium oxide was changed to 1 part by weight, and the concentration of the sodium hydroxide aqueous solution was changed to 20%, the same operation was performed to obtain the hygroscopic acrylonitrile system of Example 12B fiber.

<Comparative Example 1B>

Except that titanium oxide was not added in the formulation of Example 4B, the same operation was performed to obtain a hygroscopic acrylic fiber containing no metal oxide in Comparative Example 1B.

<Comparative Example 2B>

Except that titanium oxide was not added in the formulation of Example 6B, the same operation was performed to obtain a hygroscopic acrylic fiber containing no metal oxide in Comparative Example 2B.

<Comparative Example 3B>

After dissolving 10 parts of AN-based polymer composed of 90% AN and 10% methyl acrylate in 90 parts of 44% sodium thiocyanate aqueous solution, add 0.25 parts by weight of the spinning stock solution of titanium oxide, It is spun in a coagulation bath at -2.5°C, coagulated, washed with water, and stretched 12 times, and then dried in an environment of dry ball/wet ball=120°C/60°C to obtain raw fiber. The raw fiber was treated in a 35% hydrazine aqueous solution at 100°C for 3 hours, and then in a 2.5% sodium hydroxide aqueous solution at 90°C for 2 hours, then dehydrated, washed, and dried to obtain a crosslinked structure and carboxyl group. The fiber.

<Comparative Example 4B>

Except for setting the concentration of the sodium hydroxide aqueous solution to 5% in Comparative Example 3B, the same operation was performed to obtain a fiber having a crosslinked structure and a carboxyl group in Comparative Example 4B.

<Comparative Example 5B>

10 parts of AN polymer composed of 88% AN and 12% methacrylic acid are dissolved in 90 parts of 44% sodium thiocyanate aqueous solution, spinning out according to common methods, coagulating, washing, After stretching, it is dried to obtain acrylic fiber having a carboxyl group.

<Comparative Example 6B>

The acrylic fiber of Comparative Example 2B was heat-treated at 90° C. for 30 minutes with a soda ash 1 g/l aqueous solution, washed with water, and dried to obtain acrylic fiber with neutralized carboxyl groups.

<Comparative Example 7B>

Except that in the formulation of Comparative Example 6B, the treatment temperature of the 1g/l aqueous solution of soda ash was changed to 100°C, the same operation was performed to obtain acrylic fibers having neutralized carboxyl groups.

<Comparative Example 8B>

10 parts of AN-based polymer composed of 90% AN and 10% methyl acrylate dissolved in 90 parts of 44% sodium thiocyanate aqueous solution was spun out in a coagulation bath at -2.5°C. After coagulation, washing with water, and 12-fold stretching, a gel-like acrylic fiber with a water content of 35% was obtained. The fiber was heat-treated at 123°C×25 minutes in a humid and hot environment, washed with water, and dried to obtain an acrylic fiber of Comparative Example 8B.

<Comparative Example 9B>

Except for adding 0.25 parts by weight of titanium oxide to the spinning dope in the formulation of Comparative Example 8B, the same operation was performed to obtain the acrylic fiber of Comparative Example 9B.

Table 2 shows the evaluation results of the fibers obtained in the above-mentioned Examples and Comparative Examples.

As shown in Table 2, the hygroscopic acrylic fibers of Examples 1B to 12B do not have a cross-linked structure formed by covalent bonds, but have a saturated moisture absorption rate of 5 at 20℃×65%RH. % Or more and water swelling degree of 10 times or less. In addition, the temperature rise caused by the light-to-heat conversion of these fibers is large. Furthermore, these fibers have a high degree of whiteness due to the use of titanium oxide as a metal oxide.

On the other hand, since the fibers of Comparative Examples 1B and 2B do not contain metal oxides, the photothermal conversion function due to metal oxides cannot be obtained. In addition, regarding the degree of whiteness, it is also in a lower level than that of each example containing titanium oxide.

The conventional cross-linked acrylic fibers of Comparative Examples 3B and 4B have a cross-linked structure. Although they show good characteristics in terms of saturated moisture absorption and water swelling, the retention rate of metal oxides is low, and the The problem of falling off is big. Furthermore, as mentioned above, the steps are complicated, and high temperature and long time are required in each step. Therefore, it is difficult to manufacture the fiber by continuous processing, and it has to be performed by batch processing with low productivity.

Regarding the acrylic fiber of Comparative Example 5B, since the carboxyl group is not neutralized, the saturated moisture absorption rate is low. Although the fiber of Comparative Example 6B had neutralized the acrylic fiber of Comparative Example 5B, the increase in saturated moisture absorption rate was insufficient, and on the other hand, the degree of water swelling was greatly increased. In Comparative Example 7B, due to the enhancement of the neutralization reaction conditions, although the saturated moisture absorption rate is increased, the water swelling is too high, and the fiber will be gelled.

Since the acrylic fiber of Comparative Example 9B contains titanium oxide, the temperature of light irradiation becomes higher than that of Comparative Example 8B. However, the example The temperature of 1B~12B is higher after being irradiated with light, and it can be seen that in the present invention, it has a significant light-to-heat conversion effect.

<Example 1C>

Dissolve 10 parts of acrylonitrile-based polymer composed of 90% acrylonitrile and 10% methyl acrylate in 90 parts of 48% sodium thiocyanate aqueous solution and spin it in a coagulation bath at -2.5°C. After being coagulated, washed with water, and stretched 12 times, a gel-like acrylic fiber with a water content of 35% was obtained. The fiber was immersed in a 6.0% sodium hydroxide aqueous solution, squeezed so that the liquid absorption volume relative to the fiber weight was 100%, and then subjected to hydrolysis treatment at 123°C for 25 minutes in a humid and hot environment, washed with water, and dried. , With 105°C steam, applying 1.5 times extension in a moist and hot state to obtain the hygroscopic acrylic fiber of Example 1C. Table 3 shows the evaluation results of the obtained fibers.

<Examples 2C~8C>

Except for experimenting with the concentration and stretching ratio of the sodium hydroxide aqueous solution described in Table 3, the same procedure as in Example 1C was carried out to obtain hygroscopic acrylic fibers of Examples 2C to 8C. Table 3 shows the evaluation results of the obtained fibers.

<Example 9C>

Except that after the hydrolysis treatment, a treatment with a 6% nitric acid aqueous solution was applied at room temperature for 30 minutes, the operation was performed in the same manner as in Example 6C to obtain the hygroscopic acrylic fiber of Example 9C. Table 3 shows the evaluation results of the obtained fibers.

<Example 10C>

Except that in Example 3C, instead of gelatinous acrylic fiber, a densified fiber obtained by alternately performing a dry heat treatment at 110°C×2.5 minutes and a wet heat treatment at 60°C×2.5 minutes on the fiber was used twice. , The same operation was performed to obtain the hygroscopic acrylic fiber of Example 10C. Table 3 shows the evaluation results of the obtained fibers.

<Example 11C>

Except that in Example 10C, instead of the densified fiber, the fiber was further subjected to autoclave treatment at 120°C×10 minutes to relax the relaxed fiber, and the same operation was performed to obtain the hygroscopic acrylic nitrile system of Example 11C fiber. Table 3 shows the evaluation results of the obtained fibers.

<Comparative Example 1C>

Except that the stretching treatment after the hydrolysis was omitted, the same operation as in Example 2C was carried out to obtain a non-shrinkable moisture-absorbing acrylic fiber. Table 3 shows the evaluation results of the obtained fibers.

As shown in Table 3, the shrinkable hygroscopic acrylic fibers of Examples 1C to 11C are characterized by: containing 0.2 to 4.0 mmol/g of carboxyl groups, and having a saturated moisture absorption rate of 3 weight at 20℃×65%RH % Above, the boiling water shrinkage rate is 5%~50%, and the water swelling degree is 10 times or less.

<Example 1D>

Dissolve 10 parts of acrylonitrile-based polymer composed of 90% acrylonitrile and 10% methyl acrylate in 90 parts of 48% sodium thiocyanate aqueous solution and spin it in a coagulation bath at -2.5°C. After being coagulated, washed with water, and stretched 12 times, a gel-like acrylic fiber with a water content of 35% was obtained. The fiber was immersed in a 6.0% sodium hydroxide aqueous solution, squeezed so that the liquid absorption volume relative to the fiber weight was 100%, and then subjected to hydrolysis treatment at 123°C for 25 minutes in a humid and hot environment, washed with water, and dried. , Applying extension, heat treatment, and crimping step to obtain the hygroscopic acrylic fiber of Example 1D. Table 4 shows the evaluation results of the obtained fibers.

<Examples 2D~5D>

Except that in Example 1D, the concentration of the sodium hydroxide aqueous solution was changed to the value described in Table 4, the same operation was performed to obtain hygroscopic acrylic fibers of Examples 2D to 5D. Table 4 shows the evaluation results of the obtained fibers.

<Example 6D>

Except that after the hydrolysis treatment, a treatment with a 6% nitric acid aqueous solution was applied at room temperature for 30 minutes, the operation was performed in the same manner as in Example 3D to obtain the hygroscopic acrylic fiber of Example 6D. Table 4 shows the evaluation results of the obtained fibers.

<Example 7D>

Except that in Example 3D, instead of the gel-like acrylic fiber, a densified fiber obtained by alternately performing dry heat treatment at 110°C×2.5 minutes and wet heat treatment at 60°C×2.5 minutes on the fiber was used twice. , The same operation was performed to obtain the hygroscopic acrylic fiber of Example 7D. Table 4 shows the evaluation results of the obtained fibers.

<Example 8D>

Except in Example 2D, instead of gelatinous acrylic fiber, the fiber was densified by alternately performing dry heat treatment at 110°C×2.5 minutes and wet heat treatment at 60°C×2.5 minutes. Carry out autoclave treatment at 120℃×10 minutes and relax the relaxed fibers to Otherwise, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 8D. Table 4 shows the evaluation results of the obtained fibers.

<Comparative Example 1D>

Except that in Example 2D, the dry heat extension treatment after hydrolysis was omitted, the same operation was performed to obtain the moisture-absorbing acrylic fiber of Comparative Example 1D without ease of crimp removal. Table 4 shows the evaluation results of the obtained fibers.

As shown in Table 4, the ease of crimping removal of Examples 1D-8D hygroscopic acrylic fiber is characterized by: containing 0.2-4.0mmol/g carboxyl group, saturated moisture absorption rate at 20℃×65%RH It is 3% by weight or more, the crimp removal coefficient is 0.7 or less, and the water swelling degree is 10 times or less.

<Example 1E>

Acrylonitrile polymer (a) of 90% by weight of acrylonitrile and 10% by weight of methyl acrylate (the ultimate viscosity in dimethylformamide at 30°C) [η]=1.5) and 88% by weight of acrylonitrile and 12% by weight of vinyl acetate acrylonitrile polymer (b) ([η]=1.5) are each dissolved in 48% by weight of sodium thiocyanate aqueous solution , Preparation of spinning dope. In such a way that the compound ratio of (a)/(b) becomes 1/1, the respective spinning dope is guided to the compound spinning device of Japan Special Publication No. 39-24301, and spinning, washing, and stretching are performed according to common methods. , To obtain a gel-like acrylic fiber with a water content of 35%. The fiber was immersed in a 6.0% sodium hydroxide aqueous solution, squeezed so that the liquid absorption volume relative to the fiber weight was 100%, and then subjected to hydrolysis treatment at 123°C for 25 minutes in a humid and hot environment, washed with water, and dried. , And mechanical crimping was given to obtain the hygroscopic acrylic fiber of Example 1E. Table 5 shows the evaluation results of the obtained fibers.

<Examples 2E~5E>

Except that in Example 1E, the concentration of the sodium hydroxide aqueous solution was changed to the concentration described in Table 5, the same operation was performed to obtain hygroscopic acrylic fibers of Examples 2E to 5E. Table 5 shows the evaluation results of the obtained fibers.

<Example 6E>

Except that in Example 3E, the step of treating with 6% nitric acid aqueous solution at room temperature for 30 minutes was applied after the hydrolysis treatment, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 6E. Table 5 shows the evaluation results of the obtained fibers.

<Example 7E>

Except that in Example 3E, instead of the gel-like acrylic fiber, a densified fiber obtained by alternately performing a dry heat treatment at 110°C×2.5 minutes and a wet heat treatment at 60°C×2.5 minutes on the fiber was used twice. , The same operation was performed to obtain the hygroscopic acrylic fiber of Example 7E. Table 5 shows the evaluation results of the obtained fibers.

<Example 8E>

Except in Example 2E, instead of the gel-like acrylic fiber, the fiber was densified by alternately performing dry heat treatment at 110°C×2.5 minutes and wet heat treatment at 60°C×2.5 minutes for the fiber, and then Except for the relaxed fibers that were subjected to autoclave treatment at 120°C for 10 minutes to relax, the same operations were performed to obtain hygroscopic acrylic fibers of Example 8E. Table 5 shows the evaluation results of the obtained fibers.

<Examples 9E~11E>

Except having changed the temperature of the hydrolysis treatment to the temperature shown in Table 5 in Example 2E, the same operation was performed to obtain hygroscopic acrylic fibers of Examples 9E to 11E. Table 5 shows the evaluation results of the obtained fibers.

<Examples 12E, 13E>

Except that in Example 2E, the composite ratio of acrylonitrile polymer (a)/(b) was changed to the ratio shown in Table 5, the same operation was performed to obtain hygroscopic propylene of Examples 12E and 13E Nitrile fiber. Table 5 shows the evaluation results of the obtained fibers.

<Example 14E>

Except in Example 2E, after the hydrolysis treatment, the step of applying ion exchange treatment by immersing in an aqueous solution of calcium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber at 50°C for 1 hour Otherwise, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 14E. Table 5 shows the evaluation results of the obtained fibers.

<Example 15E>

Except that in Example 14, magnesium nitrate was used instead of calcium nitrate, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 15E. Table 5 shows the evaluation results of the obtained fibers.

<Comparative Examples 1E and 2E>

Except in each of Examples 1E and 2E, as the spinning dope, only the acrylonitrile-based polymer (a) dissolved in a 48% by weight sodium thiocyanate aqueous solution was used as the spinning dope, and the usual spinning spinneret was used. Head, and in Example 1E, except that the concentration of the sodium hydroxide aqueous solution was changed to 2.0%, the same operation was performed to obtain hygroscopic acrylic fibers of Comparative Examples 1E and 2E. Table 5 shows the evaluation results of the obtained fibers.

<Comparative Examples 3E and 4E>

Except in each of Comparative Examples 1E and 2E, after the hydrolysis treatment, ions were applied by immersing in an aqueous solution of calcium nitrate equivalent to twice the amount of carboxyl groups contained in the fiber and immersing at 50°C for 1 hour. pay Except for the steps of the treatment, the same operation was performed to obtain hygroscopic acrylic fibers of Comparative Examples 3E and 4E. Table 5 shows the evaluation results of the obtained fibers.

<Comparative Example 5E>

Except that in Comparative Example 4E, magnesium nitrate was used instead of calcium nitrate, the same operation was performed to obtain a hygroscopic acrylic fiber of Comparative Example 5E. Table 5 shows the evaluation results of the obtained fibers.

As can be seen from Table 5, since Examples 1E to 15E have both hygroscopicity and crimping properties, they have high bulkiness and good carding processability. In contrast, in Comparative Examples 1E to 5E, although the moisture absorption rate is the same, the crimping or bulkiness is low, the carding processability is poor, and because the carded fleece cannot be obtained, the specific volume cannot be measured. Implement.

<Example 1F>

Dissolve 10 parts of acrylonitrile-based polymer composed of 90% acrylonitrile and 10% methyl acrylate in 90 parts of 48% sodium thiocyanate aqueous solution and spin it in a coagulation bath at -2.5°C. It is coagulated, washed with water, and stretched 12 times to obtain a gel-like acrylic fiber with a water content of 35%. The fiber was immersed in a 7.5% sodium hydroxide aqueous solution, and after squeezing, it was subjected to hydrolysis treatment at 123° C.×25 minutes in a humid and hot environment, and then washed with water. Next, it was immersed in a water-repellent dispersion (NK Guard S-09: manufactured by Nikka Chemical), and after squeezing out the excess liquid, it was dried to obtain an example having the water-repellent content shown in Table 6 1F hygroscopic acrylic fiber.

<Examples 2F and 3F>

Except that in Example 1F, the concentration of the sodium hydroxide aqueous solution was changed to 10% in Example 2F and 20% in Example 3F, the same operation was performed to obtain the moisture absorption of Examples 2F and 3F Acrylonitrile fiber.

<Example 4F>

Except that in Example 3F, the hydrolyzed and water-washed fibers were immersed in an aqueous nitric acid solution, adjusted to a bath pH of 5.0, and heated at 60°C for 30 minutes, and then a water washing step was added. The treatment was performed in the same manner to obtain Example 4F. Hygroscopic acrylic fiber.

<Example 5F>

Except for reducing the content of the water-repellent agent in Example 3F, the same operation was performed to obtain the hygroscopic acrylic fiber of Example 5F.

<Examples 6F and 7F>

Except that in Example 2F, the content of the water repellent was increased, the same operation was performed to obtain the hygroscopic acrylic fibers of Examples 6F and 7F. Furthermore, regarding the fiber of Example 7F, since the content of the water-repellent agent is high, it has a harder hand than the fibers of the other examples.

<Example 8F~10F>

Except in Example 5F, the type of water repellent was changed to Asahi Guard AG-E082 (manufactured by Asahi Glass) in Example 8F, and KF-8012 (manufactured by Shin-Etsu Chemical) in Example 9F. Except changing to X-22-9002 (manufactured by Shin-Etsu Polysiloxane) in 10F, the same operation was performed to obtain hygroscopic acrylic fibers of Examples 8F to 10F.

<Example 11F>

Except that in Example 1F, instead of the gel-like acrylic fiber, a densified fiber obtained by alternately performing dry heat treatment at 110°C×2.5 minutes and wet heat treatment at 60°C×2.5 minutes on the fiber was used twice. , The same operation was performed to obtain the hygroscopic acrylic fiber of Example 11F.

<Example 12F>

Except in Example 1F, instead of gelatinous acrylic fiber, the fiber was densified by alternately performing dry heat treatment at 110°C×2.5 minutes and wet heat treatment at 60°C×2.5 minutes for the fiber, and then The operation was performed in the same manner except that the relaxed fibers were relaxed by autoclave treatment at 120°C for 10 minutes to obtain the hygroscopic acrylic fiber of Example 12F.

<Comparative Example 1F>

Except that in Example 1F, the water repellent treatment was omitted and the concentration of the sodium hydroxide aqueous solution was changed to 2.5%, the same operation was performed to obtain a fiber of Comparative Example 1F.

<Comparative Example 2F>

Except that in Example 1F, the content of the water-repellent agent was reduced and the concentration of the sodium hydroxide aqueous solution was changed to 2.5%, the same operation was performed to obtain a fiber of Comparative Example 2F.

<Comparative Example 3F>

Dissolve 10 parts of acrylonitrile polymer composed of 88% acrylonitrile and 12% methacrylic acid in 90 parts of 48% sodium thiocyanate aqueous solution. After washing and stretching, it is dried to obtain acrylic fiber with carboxyl group. Then, in a 1g/l aqueous solution of soda ash, the neutralization treatment was performed at 90°C for 30 minutes, but the swelling degree became high, and the subsequent water-repellent treatment could not be performed.

Table 6 shows the evaluation results of the fibers obtained in the above-mentioned Examples and Comparative Examples.

As shown in Table 6, the water-repellent and moisture-absorbing acrylic fibers of Examples 1F to 12F, although they do not have a cross-linked structure formed by covalent bonds, the saturated moisture absorption rate of 20℃×65%RH is 3 % Or more, and the settling time in water is 10 minutes or more, showing that it has excellent water repellency.

On the other hand, the fiber systems of Comparative Examples 1F and 2F had low water repellency performance and were inferior to each of the Examples, and the acrylic fiber of Comparative Example 3F had a significant increase in water swelling degree, and the subsequent water repellent treatment could not be performed.

Claims (15)

A hygroscopic acrylic fiber, which is a hygroscopic acrylic fiber composed of a polymer that does not substantially have a cross-linked structure formed by covalent bonds, and is characterized in that carboxyl groups are uniformly present in the fiber In the whole, the amount of carboxyl groups in the fiber is 0.2 to 4.5 mmol/g, the saturated moisture absorption rate of the fiber at 20°C×65%RH is 5 wt% or more, and the water swelling degree is 10 times or less. A hygroscopic acrylic fiber, which is a hygroscopic acrylic fiber composed of a polymer that does not substantially have a cross-linked structure formed by covalent bonds, and is characterized in that it has a surface layer and a center The core-sheath structure of the part, the surface part contains a polymer containing carboxyl groups, the center part contains an acrylonitrile polymer, the amount of carboxyl groups in the fiber is 0.2~4.5mmol/g, and the fiber is saturated at 20℃×65%RH. The moisture rate is 5 wt% or more, and the water swelling degree is 10 times or less. Such as the hygroscopic acrylic fiber of claim 1, which further contains 0.1-15% by weight of metal oxide. The hygroscopic acrylic fiber of claim 3, wherein the metal oxide is titanium oxide. For example, the hygroscopic acrylic fiber of claim 1 has a boiling water shrinkage rate of 5-50%. For example, the hygroscopic acrylic fiber of claim 1, the crimp reduction coefficient after boiling water treatment is 0.7 or less. For example, the hygroscopic acrylic fiber of claim 1 has a crimp rate of 7% or more. Such as the hygroscopic acrylic fiber of claim 1, which further contains a water-repellent agent, and the time from being left standing on water to being submerged is 10 minutes or more. A fiber structure characterized by containing the hygroscopic acrylic fiber according to any one of claims 1 to 8. A method for producing a hygroscopic acrylic fiber according to claim 1, characterized in that it comprises: spinning the dope containing acrylic polymer from the nozzle, and then undergoing the steps of coagulation, washing and stretching, and hydrolysis The resulting undried fiber. A method for producing a hygroscopic acrylic fiber according to claim 3 or 4, which is characterized by comprising: spinning a spinning dope containing an acrylic polymer and a metal oxide from a nozzle, then coagulating, washing, and washing. In each step of extension, the undried fiber obtained is hydrolyzed. A method for producing a hygroscopic acrylic fiber according to claim 5, which is characterized in that it comprises: spinning the dope containing acrylic polymer from the nozzle, and then undergoing the steps of coagulation, washing and stretching, and hydrolysis After the obtained undried fiber, it is stretched. A method for producing a hygroscopic acrylic fiber according to claim 6, characterized in that it comprises: spinning the dope containing acrylic polymer from the nozzle, and then undergoing the steps of coagulation, washing and stretching, and hydrolysis After the resulting undried fiber is heat-treated in a tensioned or stretched state, then crimp is imparted. A method for producing a hygroscopic acrylic fiber according to claim 7, characterized in that it comprises: spinning dope (A) containing acrylic polymer and containing the same with the spinning dope (A). The acrylonitrile polymer spinning dope (B) composed of different monomers of the acrylonitrile polymer is compounded, and after spinning out from the nozzle, the undried fiber obtained is hydrolyzed through various steps of coagulation, washing and stretching. A method for producing a hygroscopic acrylic fiber according to claim 8, characterized in that it comprises: spinning the dope containing acrylic polymer from the nozzle, and then undergoing the steps of coagulation, washing and stretching, and hydrolysis The resulting undried fiber is then treated with a water-repellent agent.