JP2005200792A - Hygroscopic conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hygroscopic conjugate fiber having excellent hygroscopicity, causing no outer layer cracking even under high-temperature wetting conditions in scouring, dyeing, etc., and having excellent dimensional stability in the fiber axis direction in water absorption. <P>SOLUTION: The hygroscopic conjugate fiber is a conjugate fiber having a fiber crosssectional shape composed of three layers in which a non-water swellable elastomer is arranged in the outer layer, a water-swellable polymer in the intermediate layer and a non-water swellable polymer having no elasticity in the inner layer. A polymer having 20-100% water absorption swelling ratio is used in the intermediate layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hygroscopic composite fiber that is excellent in hygroscopicity, does not cause outer layer cracking even during refining or dyeing, and has excellent dimensional stability in the fiber axis direction during water absorption.

  Synthetic fibers such as polyester fibers and nylon fibers are widely used as clothing and industrial fiber materials because of their excellent mechanical strength and wrinkle resistance. However, synthetic fibers have such excellent characteristics, but when used as an inner, lining, or sports clothing material, they have a low hygroscopic property, which causes unpleasant feeling such as sweating.

  As a method for imparting the hygroscopic performance of such a synthetic fiber, for example, it is conceivable to include a hygroscopic compound in the synthetic fiber. However, simply blending the hygroscopic compound is insufficient in durability, and the synthesis When a fiber product made of fibers is used for a long period of time, there is a problem that the hygroscopic compound is dropped and the hygroscopic performance is lowered.

  On the other hand, it has been proposed to provide a core-sheath composite fiber in which a hygroscopic polymer is arranged in the core and a thermoplastic polymer is arranged in the sheath (Patent Document 1). However, when these composite fibers are exposed to high-temperature and wet conditions such as refining and dyeing that are generally performed, a phenomenon occurs in which the hygroscopic polymer in the core portion swells greatly and the sheath portion breaks without being able to withstand this. .

In addition, when the sheath crack occurs in this way, the hygroscopic polymer not only drops off from the sheath, but the sheath portion is broken everywhere in the fiber, so when water is absorbed, the fiber is not only in the fiber cross-sectional direction but also in the fiber axis direction. In addition, the dimensional stability when this is made into a textile product such as a fabric becomes extremely poor.
JP-A-8-81831

  The present invention has been made against the background of the above prior art, and its purpose is excellent in hygroscopicity, no outer layer cracking occurs even in high-temperature wet conditions such as scouring and dyeing, and dimensions in the fiber axis direction during water absorption. An object of the present invention is to provide a hygroscopic composite fiber having excellent stability.

  The present inventors have found that the above object can be achieved when a composite fiber composed of three layers is skillfully combined with polymers having different water swellability and elastic properties.

  Thus, according to the present invention, a composite fiber having a three-layer fiber cross-sectional shape, a non-water-swellable elastomer as an outer layer, a water-swellable polymer as an intermediate layer, and a non-water-swellable property without elasticity as an inner layer There is provided a hygroscopic composite fiber characterized in that a polymer is disposed and the water absorption swelling ratio of the intermediate layer is in the range of 20 to 100%.

  The hygroscopic conjugate fiber of the present invention is excellent in hygroscopicity, does not crack in the outer layer even in high temperature wet conditions such as scouring and dyeing, and does not extend in the fiber axis direction even when absorbed, and is excellent in dimensional stability. Therefore, it is possible to obtain a fiber product that is extremely practical from the composite fiber.

  The hygroscopic conjugate fiber of the present invention is a conjugate fiber having a fiber cross-sectional shape consisting of three layers, a non-water swellable elastomer as an outer layer, a water-swellable polymer as an intermediate layer, and a non-water swell without elasticity as an inner layer It is important to be a hygroscopic conjugate fiber in which a water-soluble polymer is disposed and the water absorption swelling ratio of the intermediate layer is in the range of 20 to 100%. Thereby, it is excellent in hygroscopicity, it does not generate | occur | produce an outer layer crack also in high temperature wet conditions, such as scouring and dyeing | staining, and can be excellent in the dimensional stability to the fiber axis direction at the time of water absorption. Hereinafter, each requirement will be described in detail.

  According to the study by the present inventors, it has been found that when the water absorption swelling rate of the water-swellable polymer in the intermediate layer is less than 20%, the desired high moisture absorption performance cannot be obtained. On the other hand, if the water absorption swelling ratio exceeds 100%, the polymer has excellent hygroscopicity, but the intermediate layer becomes excessively swollen in steps such as refining and dyeing, and outer layer cracking occurs.

  In the hygroscopic conjugate fiber of the present invention, the polymer of the intermediate layer is covered with the non-water-swellable elastomer of the outer layer, so that the outer layer does not crack even if the polymer absorbs water and swells, and the fiber surface There is no feeling of stickiness, and a textile product excellent in comfort can be obtained.

  Furthermore, since the non-swellable polymer that does not have elasticity is arranged in the inner layer, the composite fiber does not expand in the fiber axis direction even if it absorbs water, and can be made into a fiber product having excellent dimensional stability. it can.

  In the composite fiber, the ratio of the inner layer / intermediate layer / outer layer is preferably in the range of (10-50) / (30-70) / (20-60) by weight ratio. High dimensional stability in the fiber axis direction at the time of water absorption while ensuring the ratio of the intermediate layer and the outer layer exhibiting the effects described above, particularly the intermediate layer exhibiting hygroscopicity, by setting the ratio of the inner layer to 10 to 50%. Sex can be obtained. When emphasizing hygroscopicity, the ratio of the inner layer is preferably in the range of 20 to 40%. Further, by setting the ratio of the intermediate layer in the range of 30 to 70%, more preferably in the range of 50 to 70%, the ratio of the inner layer and the outer layer having the above-described effects can be ensured, and excellent moisture absorption performance can be expressed. . Furthermore, by ensuring that the ratio of the outer layer portion is 20 to 60%, while maintaining the ratio of the inner layer and the intermediate layer, particularly the intermediate layer that exhibits hygroscopicity, there is obtained a textile that has no stickiness and is excellent in comfort. Can do. When emphasizing hygroscopicity, the ratio of the outer layer is preferably in the range of 20 to 40%.

  As the water-swellable polymer constituting the intermediate layer, for example, a polyether ester polymer having polybutylene terephthalate as a hard segment and polyoxyethylene glycol as a soft segment is preferable.

  The polybutylene terephthalate which is a hard segment preferably contains at least 70 mol% of butylene terephthalate units. The content of butylene terephthalate is more preferably 80 mol% or more, and still more preferably 90 mol% or more.

  As will be described in detail later, the polybutylene terephthalate is preferably copolymerized with the metal sulfonate metal salt represented by the general formula (1) described above in terms of obtaining higher hygroscopicity, Other than this, other components may be copolymerized as long as the achievement of the object of the present invention is not substantially impaired. As other copolymerization components, dicarboxylic acid components include, for example, naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenyloxyethanedicarboxylic acid, β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, adipic acid, sebacic acid, Examples thereof include aromatic and aliphatic dicarboxylic acid components such as 1,4-cyclohexanedicarboxylic acid. Furthermore, trifunctional or higher polycarboxylic acids such as trimellitic acid and pyromellitic acid may be used as a copolymerization component. Examples of the diol component include aliphatic, alicyclic, and aromatic diol components such as trimethylene glycol, ethylene glycol, cyclohexane-1,4-dimethanol, and neopentyl glycol. Furthermore, a trifunctional or higher functional polyol such as glycerin, trimethylolpropane, or pentaerythritol may be used as a copolymerization component.

  On the other hand, polyoxyethylene glycol which is a soft segment preferably contains at least 70 mol% of oxyethylene glycol units. The content of oxyethylene glycol is more preferably 80 mol% or more, and still more preferably 90 mol% or more. For example, propylene glycol, tetramethylene glycol, glycerin and the like may be copolymerized with the polyoxyethylene glycol within a range in which the achievement of the object of the present invention is not substantially impaired.

  The number average molecular weight of the polyoxyethylene glycol is preferably 400 to 8000, and particularly preferably 1000 to 6000.

  In the present invention, the ratio of the hard segment to the soft segment is preferably in the range of 70:30 to 30:70, more preferably in the range of 60:40 to 40:60, based on the weight. When the hard segment ratio exceeds 70%, the hygroscopicity of the composite fiber tends to be low. On the other hand, if the hard segment ratio is less than 30%, the melt viscosity is too low and the polymer has poor spinnability, and the composite fiber of the present invention tends to be difficult to mold.

  In the present invention, it is preferable that an organic sulfonic acid metal salt represented by the following general formula (1) is copolymerized with the polyether ester polymer. Thereby, a moisture absorption rate can further be improved.

  In the formula, R1 is an aromatic hydrocarbon group or an aliphatic hydrocarbon group, preferably an aromatic hydrocarbon group having 6 to 15 carbon atoms or an aliphatic hydrocarbon group having 10 or less carbon atoms. Particularly preferred R 1 is an aromatic hydrocarbon group having 6 to 12 carbon atoms, particularly a benzene ring. M1 is an alkali metal or alkaline earth metal, and n is 1 or 2. Among them, those in which M1 is an alkali metal (for example, lithium, sodium or potassium) and n is 1 are preferable. X1 represents an ester-forming functional group, and X2 represents the same or different ester-forming functional group as X1, or represents a hydrogen atom, but is preferably an ester-forming functional group. The ester-forming functional group may be any group that reacts with and bonds to the main chain or terminal of the polyether ester, and specifically includes the following groups.

（上記式中、Ｒ’は低級アルキル基またはフェニル基を示し、ａおよびｄは１〜１０の整数を示し、ｂは２〜６の整数を示す。）

(In the above formula, R ′ represents a lower alkyl group or a phenyl group, a and d represent an integer of 1 to 10, and b represents an integer of 2 to 6.)

  Preferable specific examples of the organic sulfonic acid metal salt represented by the general formula (1) include sodium 3,5-dicarbomethoxybenzenesulfonate, potassium 3,5-dicarbomethoxybenzenesulfonate, 3,5-dicarboxylate. Lithium carbomethoxybenzenesulfonate, sodium 3,5-dicarboxybenzenesulfonate, potassium 3,5-dicarboxybenzenesulfonate, lithium 3,5-dicarboxybenzenesulfonate, 3,5-di (β-hydroxyethoxy) Carbonyl) sodium benzenesulfonate, potassium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate, lithium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate, 2,6-dicarbomethoxynaphthalene 4-sulphonic acid sodium rim, 2,6 -Potassium dicarbomethoxynaphthalene-4-sulfonate, lithium 2,6-dicarbomethoxynaphthalene-4-sulfonate, sodium 2,6-dicarboxynaphthalene-4-sulfonate, 2,6-dicarbomethoxysphthalene -1-sodium sulfonate, 2,6-dicarbomethoxynaphthalene-3-sodium sulfonate, 2,6-dicarbomethoxynaphthalene-4,8-sodium disulfonate, 2,6-dicarboxynaphthalene-4,8 Examples thereof include sodium disulfonate, sodium 2,5-bis (hydroethoxy) benzenesulfonate, α-sodium sulfosuccinic acid, and the like. The said organic sulfonic acid metal salt may be used individually by 1 type, or may be used together 2 or more types.

  In the present invention, it is further obtained that the organic sulfonic acid metal salt represented by the following general formula (2) can be copolymerized to easily increase the intrinsic viscosity of the polyetherester polymer and improve the spinnability. It is preferable in that the moisture absorption rate of the polyether ester polymer can be remarkably increased.

  In the formula, R2 is an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and is the same as the definition of R1 in the above general formula (1), M2 is an alkali metal or an alkaline earth metal, and the above general formula ( It is the same as the definition of M1 in 1). Preferable specific examples of such organic sulfonic acid metal salts include sodium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate, potassium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate, 3,5 -Li (β-hydroxyethoxycarbonyl) benzenesulfonic acid lithium and the like are exemplified.

  If the copolymerization amount of the organic sulfonic acid metal salt is too large, the intrinsic viscosity does not increase due to the increase in viscosity due to the ionic crosslinking effect at the time of polymerization, and the polymer becomes poor in spinnability. It is preferable to set it as the range of 0.1-20 mol% on the basis of all the acid components. Conversely, even if the amount of copolymerization is too small, the moisture absorption rate tends to decrease, and it is more preferably in the range of 0.5 to 15 mol%.

  The polyether ester polymer used in the present invention is obtained by subjecting a raw material containing, for example, dimethyl terephthalate, tetramethylene glycol, and polyoxyethylene glycol to a transesterification reaction in the presence of a transesterification catalyst to produce bis (ω-hydroxybutyl) terephthalate. And / or forming an oligomer, and then performing melt polycondensation under high temperature and reduced pressure in the presence of a polycondensation catalyst and a stabilizer.

  As the transesterification catalyst, an alkali metal salt such as sodium, an alkaline earth metal salt such as magnesium or calcium, or a metal compound such as titanium, zinc or manganese is preferably used.

  As the polycondensation catalyst, it is preferable to use a germanium compound, an antimony compound, a titanium compound, a cobalt compound, or a tin compound. The amount of the catalyst used is not particularly limited as long as it is a necessary amount for proceeding the transesterification reaction and polycondensation reaction, and a plurality of catalysts can be used in combination.

  On the other hand, as the non-water-swellable elastomer constituting the outer layer, among the following polyurethane elastomers, polyester elastomers, polyamide elastomers, polyolefin elastomers and the like, those having a water absorption swelling ratio of 5% or less are preferable.

  Specifically, as the polyurethane-based elastomer, a polyester and / or poly (alkylene) glycol having a molecular weight of 1000 to 3000 and / or a poly (alkylene) glycol, a diisocyanate, and a glycol and / or diamine which is a chain extender are optionally added. Preferable examples include thermoplastic polyurethane obtained by further adding a polycarbonate having a terminal hydroxy group and reacting them. Examples of the polyester used here include polyesters of dicarboxylic acids such as adipic acid and sebacic acid and diols such as ethylene glycol, diethylene glycol, butylene glycol and diethylene glycol, and also poly (oxyalkylene). Examples thereof include homopolymers such as glycol, poly (oxyethylene) glycol, poly (oxypropylene) glycol, and poly (oxybutylene) glycol, and block copolymers and random copolymers thereof. As the isocyanate, 2,4-tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, dicyclohexyl-4,4'-diisocyanate and the like are selected. As the chain extender, ethylene glycol, propylene glycol, 1,4-β-hydroxyethoxybenzene, ethylenediamine, propylenediamine, or the like is used.

  As the polyester-based elastomer, a dicarboxylic acid component mainly composed of terephthalic acid, a glycol component mainly composed of 1,4-butanediol, and a poly (oxyalkylene) glycol having a number average molecular weight of 400 to 4000 are used as components. The polyether ester block copolymer is exemplified.

  Moreover, as a polyamide-type elastomer, the copolymer of a lauryl lactam, poly (oxyethylene) glycol, and a dicarboxylic acid component is illustrated, for example.

  Examples of the polyolefin-based elastomer include thermoplastic elastomers in which polyethylene, polypropylene and polystyrene are used as the hard segment and ethylene / propylene rubber is used as the soft segment as the soft segment.

  In the present invention, among the above elastomers, a polyester-based elastomer, particularly a polyether ester elastomer having polybutylene terephthalate as a hard segment and polytetramethylene terephthalate as a soft segment can have a water absorption swelling rate of 5% or less. And it is preferable at the point which can carry out composite spinning with the water-swellable polymer mentioned above, and can obtain the target composite fiber stably.

  Further, as non-swellable polymers having no elasticity constituting the inner layer, polyalkylene terephthalates such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are heat resistant, strength, dimensional stability, etc. From this viewpoint, polyethylene terephthalate is particularly preferable.

  The hygroscopic conjugate fiber of the present invention can be produced, for example, by the following method. That is, the pellets constituting the outer layer, the intermediate layer, and the inner layer are dried, melted separately, led to a known three-layer composite spinning pack, a composite flow is formed in the die apparatus, and the pellets are spun from the discharge holes. Put out. The spun yarn is wound at 500 to 3000 m / min to obtain an undrawn yarn. The obtained undrawn yarn is drawn 1.1 to 5.0 times at a yarn temperature of 50 to 180 ° C. using a plate heater, a slit heater, a hot roller or the like. This spinning and drawing may be performed continuously without taking out the undrawn yarn once.

Hereinafter, the present invention will be described specifically by way of examples. In addition, each physical property in an Example was measured with the following method.
(1) Breaking strength / breaking elongation It measured by performing a tensile test using a Tensilon RTM-100 tensile tester manufactured by Toyo Baldwin in a constant temperature and humidity chamber adjusted to 20 ° C. and 65% RH.
(2) Moisture absorption rate Moisture absorption according to the following equation based on the weight of the humidity control sample measured immediately after the sample was conditioned for 24 hours in a constant temperature and humidity chamber adjusted to 35 ° C and 95% RH, and the weight of the absolutely dry sample. The rate was determined.
Moisture absorption rate (%) = (weight of humidity control sample−weight of absolute dry sample) × 100 / weight of absolute dry sample (3) Water absorption swelling rate of intermediate layer Constant temperature at which fiber was conditioned to 20 ° C. and 65% RH A cross-sectional photograph of the fiber cross section was taken after placing it in a constant humidity chamber for 24 hours and immediately after immersing it in hot water at 98 ° C. for 1 hour, and this photograph was magnified twice. In the cross-sectional photograph, arbitrary 10 single yarns were selected, and the cross-sectional area of each intermediate layer was measured. The cross-sectional area of the intermediate layer was determined by subtracting the cross-sectional areas of the outer layer and the inner layer from the cross-sectional area of the entire fiber. The water absorption swell ratio was calculated from the following formula, assuming that the cross-sectional area after placing it under conditions of 20 ° C. and 65% RH for 24 hours was A ₀ and the cross-sectional area immediately after being immersed in hot water of 98 ° C. for 1 hour was A ₁ .
Water absorption swelling rate of intermediate layer (%) = (A ₁ −A ₀ ) × 100 / A ₀
(4) Water absorption swelling rate in the fiber axis direction (dimensional stability)
After placing in a constant temperature and humidity chamber adjusted to 20 ° C. and 65% RH for 24 hours, 10 fibers cut to a test length of 10.0 cm were prepared, and further immersed in hot water at 98 ° C. for 1 hour. the fiber length immediately calculated from the following equation as L _1.
Fiber axis direction swelling ratio (%) = (L ₁ −10.0) × 100 / 10.0
(5) Outer layer (sheath) cracking Fiber cross-section after boiling water treatment is observed with a microscope, and there is no outer layer (sheath) cracking. The result was “slightly present”, and 4 or more of 36 filaments with an outer layer (sheath) crack observed were “present”.

[Example 1]
The water-swellable polymer constituting the intermediate layer was produced by the following method. That is, 100 parts by weight of dimethyl terephthalate, 23 parts by weight of 40% ethylene glycol solution of sodium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate (5.0 mol% based on the total acid components), polyoxy Reaction vessel containing 113.4 parts by weight of ethylene glycol (number average molecular weight 4000), 73.5 parts by weight of 1,4-butanediol (1.4 mol times the total acid component) and 0.4 parts by weight of tetrabutyl titanate as a catalyst The ester exchange reaction was carried out at an internal temperature of 200 ° C. When about 80% of the theoretical amount of methanol was distilled, 0.4 parts by weight of the above-mentioned hindered phenol stabilizer was added, and the polycondensation reaction was started by raising the temperature and reducing the pressure. The polycondensation reaction is made 30 mmHg over about 30 minutes, and further 3 mmHg over 30 minutes. Thereafter, the reaction is performed for 200 minutes at an internal temperature of 250 ° C. under a vacuum of 1 mmHg, and then further under a vacuum of 1 mmHg or less for 20 minutes at 250 ° C. For 20 minutes. The intrinsic viscosity of the produced water-swellable polyetherester polymer (PEE (1)) is 1.10, and the weight ratio of polybutylene terephthalate (hard segment): polyoxyethylene glycol (soft segment) is 50:50. there were.

  On the other hand, as a non-water-swellable elastomer constituting the outer layer, a polyether ester elastomer having polybutylene terephthalate as a hard segment and polytetramethylene terephthalate as a soft segment, the hard segment content is 38% by weight, and the elastomer 100 Polyether ester elastomer (PEEE) containing 0.2 parts by weight of hindered amine-based antioxidant and 0.2 parts by weight of benzotriazole-based ultraviolet absorber with respect to parts by weight was used.

  Furthermore, polyethylene terephthalate (PET) was used as a non-water-swellable polymer that does not have elasticity that constitutes the inner layer.

  The above-described composite fiber cap (nozzle hole diameter (nozzle diameter)) is formed by melting PEEE at 230 ° C., PEE (1) at 230 ° C., and PET at 280 ° C. D) 0.3 mm × nozzle length (L) 0.6 mm, number of holes 36 holes) so that the inner layer / intermediate layer / outer layer weight ratio is 30/50/20 and the total discharge amount is 30 g / min. Extrusion and the discharged yarn were taken up at 2000 m / min and wound up at 2050 m / min to obtain an undrawn yarn. The obtained undrawn yarn was drawn 1.75 times at 65 ° C. and further heat-treated at 150 ° C. to obtain a composite fiber consisting of three layers of 83 dtex 36 filaments. The results are shown in Table 1.

[Examples 2 and 3]
A composite fiber was obtained in the same manner as in Example 1 except that the weight ratio of the inner layer / intermediate layer / outer layer was changed as shown in Table 1. The results are shown in Table 1.

[Example 4]
Water-swellable polyether ester having an intermediate layer of polybutylene terephthalate as a hard segment, polyoxyethylene glycol (number average amount 4000) as a soft segment, and a hard segment: soft segment ratio of 60:40 based on weight A core-sheath composite fiber was obtained in the same manner as in Example 2 except that the polymer (PEE (2)) was changed. The results are shown in Table 1.

[Comparative Example 1]
A composite fiber was obtained in the same manner as in Example 1 except that PET was used for the outer layer. The results are shown in Table 1.

[Comparative Example 2]
It is a core-sheath type composite fiber having a sheath as PEEE and a core as PEE (1), and melted at 230 ° C., respectively, and a base for composite fiber (nozzle hole diameter (D) 0.3 mm × nozzle length (L) 0.6 mm, Introduced into 36 holes, extruded so that the sheath / core weight ratio is 50/50, and the total discharge amount is 28 g / min, the discharge yarn is taken up at 2000 m / min and wound up at 2050 m / min, and unstretched The obtained undrawn yarn was drawn 1.75 times at 80 ° C., and further heat-treated at 150 ° C. to obtain a core-sheath type composite fiber of 84 dtex 36 filaments. Show.

  The hygroscopic composite fiber of the present invention is excellent in hygroscopicity, and does not crack in the outer layer (sheath) even in a high temperature wet state such as scouring and dyeing. In addition, the above-mentioned composite fiber does not extend in the fiber axis direction when water is absorbed, and not only has excellent dimensional stability, but also can provide a fabric having no stickiness and excellent comfort. Furthermore, for this reason, the core-sheath-type conjugate fiber of the present invention can be widely used for sports clothing, innerwear, outerwear, lining, stockings, socks, and the like.

Claims (9)

  A composite fiber having a three-layer fiber cross-sectional shape, in which a non-water-swellable elastomer is disposed in the outer layer, a water-swellable polymer is disposed in the intermediate layer, and a non-water-swellable polymer having no elasticity is disposed in the inner layer. A hygroscopic composite fiber having a water absorption swelling ratio in the range of 20 to 100%.   The hygroscopic conjugate fiber according to claim 1, wherein the ratio of the inner layer / intermediate layer / outer layer is in the range of (10-50) / (30-70) / (20-60) by weight ratio.   The hygroscopic composite fiber according to claim 1 or 2, wherein the water-swellable polymer is a polyether ester polymer having polybutylene terephthalate as a hard segment and polyoxyethylene glycol as a soft segment.   The hygroscopic composite fiber according to any one of claims 1 to 3, wherein the water-swellable polymer is a polyether ester polymer having polybutylene terephthalate as a hard segment and polyoxyethylene glycol as a soft segment. The hygroscopic composite fiber according to claim 4, wherein an organic sulfonic acid metal salt represented by the following general formula (1) is copolymerized with the polyether ester polymer.

(Wherein R1 is an aromatic hydrocarbon group or aliphatic hydrocarbon group, X1 is an ester-forming functional group, X2 is the same or different ester-forming functional group or hydrogen atom as X1, or M1 is an alkali metal or alkaline earth) Metal, n represents 1 or 2)   The hygroscopic composite fiber according to claim 5, wherein the copolymerization amount of the organic sulfonic acid metal salt is in the range of 0.1 to 20 mol% based on the acid component constituting the polyether ester polymer.   The hygroscopic composite fiber according to any one of claims 3 to 6, wherein a ratio of hard segment: soft segment of the polyether ester polymer is in a range of 30:70 to 70:30 on the basis of weight.   The hygroscopic composite fiber according to any one of claims 1 to 7, wherein the non-water-swellable elastomer is a polyether ester elastomer having polybutylene terephthalate as a hard segment and polytetramethylene terephthalate as a soft segment.   The hygroscopic conjugate fiber according to any one of claims 1 to 8, wherein the non-water-swellable polymer having no elasticity is polyalkylene terephthalate.