JP3297492B2 - Sheath-core type composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hygroscopic thermoplastic conjugate fiber having excellent mechanical properties even when absorbing moisture. More specifically, the present invention relates to a novel conjugate fiber that can exhibit excellent moisture absorption properties as a material for clothing such as an inner, lining, jacket, and sports clothing.

[0002]

2. Description of the Related Art Thermoplastic fibers typified by polyethylene terephthalate, nylon, etc. have excellent mechanical properties and heat resistance, and are excellent in wash and wear properties, so they are widely used in clothing and industrial applications. Have been.
However, since these thermoplastic fibers have extremely low hygroscopicity, there is a problem that stickiness or stuffiness at the time of sweating occurs in inners, linings, jackets, sports clothing and the like. Therefore, in these fields, natural fibers such as cotton are mainly preferred.

Some proposals have been made so far for the purpose of resolving such problems of thermoplastic fibers. For example, JP-A-4-245975 discloses grafting of acrylic acid or methacrylic acid and JP-A-4-4-1975.
JP 08164 proposes to improve the hygroscopicity by plasma treatment and grafting of polyethylene glycol. However, fibers that have been surface-treated by these methods are not practical, such as reduced dyeing fastness and light fastness, and the effect of hygroscopicity is reduced by repeated washing and the like, and is inferior in durability. .

Further, Japanese Patent Application Laid-Open Nos. Hei 1-298212, Hei 3-179024, Hei 4-222218
In Japanese Patent Application Laid-Open Publication No. H11-264, a method of imparting hygroscopicity by using a polymer as a copolymer using polyalkylene glycol or the like as a moisture absorbing component has been proposed. Although the fiber obtained by such a method has improved hygroscopic durability, in practice, it is necessary to copolymerize a large amount of a component exhibiting hygroscopicity in order to obtain satisfactory hygroscopicity. There is a drawback in that mechanical properties such as strength, which are inherent characteristics of thermoplastic fibers, are impaired. In addition, there are unfavorable problems such as a decrease in mechanical properties such as strength when moisture is absorbed and a decrease in color fastness.

In recent years, Japanese Patent Application Laid-Open No.
-99612, JP-A-4-361616,
Japanese Patent Application Laid-Open No. 4-108113 proposes a composite fiber having a hygroscopic polymer as a core component and a fiber-forming polymer as a sheath component. By using this composite fiber,
It was an excellent proposal in that problems such as slimming of the fiber surface during moisture absorption, deterioration of mechanical properties, and color fastness were solved. However, the conjugate fibers according to these proposals have a very low hygroscopic component in the core, which is completely covered with a sheath component having poor hygroscopicity. It lacked wearability. Furthermore, when these composite fibers are subjected to hydrothermal treatment during scouring and dyeing in a post-processing step, the core component swells due to moisture absorption and water absorption because the moisture absorption of the core component is extremely high, and the sheath component and It was clarified that there was a problem that excessive strain was applied to the sheath portion due to the difference in swelling and cracks were generated in the fibers.

The cracked fibers may cause fibrils in the product, dirt or the like may be adsorbed to the cracks while the garment is being worn, and may be easily stained, or may deteriorate the fastness to wet friction after dyeing. This is a major problem in terms of impairing the performance. The occurrence of cracks is more remarkable when the adhesion between the sheath component and the core component thermoplastic polymer is poor. For example, as described in JP-A-4-361616, the adhesion between the two components is improved. It turned out that this did not help.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned problems of the prior art and to provide a commercial value without impairing the inherent properties of thermoplastic fibers and without causing any process troubles or product quality problems. To provide a conjugate fiber having high moisture absorption.

[0008]

Means for Solving the Problems As a result of intensive studies on the realization of the above-mentioned object, the present inventors have found that in a composite fiber comprising a sheath component and a core component, when a hygroscopic polymer is used as a core component, The single yarn 1
By adding the function of a school to one book, all the problems of the prior art were solved, and it was found that a hygroscopic conjugate fiber excellent in practicality was obtained, and the present invention was completed.

That is, the present invention relates to a conjugate fiber comprising a hygroscopic thermoplastic polymer having a moisture absorption of 10% by weight or more at 30 ° C. and 90% RH as a core component and a thermoplastic polymer as a sheath component. In a section perpendicular to the axis,
The core component occupies 10 to 50% of the total cross-sectional area of the composite fiber, and a part of the core component is exposed at four or more locations around the surface of the composite fiber, whereby the sheath is divided into four or more parts. The conjugate fiber is characterized in that the exposed portion accounts for 10% or less of the entire circumference of the fiber cross section.

Hereinafter, the present invention will be described in detail. In the composite fiber of the present invention, the thermoplastic polymer forming the sheath component is not particularly limited as long as it is a fiber-forming polymer. For example, a line represented by polyethylene terephthalate, polybutylene terephthalate, polyethylene 2, 6 naphthalate, or the like is used. Polyesters or copolymers thereof, polyamides such as nylon 4, nylon 6, nylon 66, nylon 610, nylon 612, or copolymers thereof, and polyolefins such as polypropylene, polyethylene, or the like. And the like.

Further, these polymers may contain a third component such as a heat stabilizer, a matting agent, and an antistatic agent, if necessary, as long as the effects of the present invention are not impaired. Generally, polyethylene terephthalate, nylon 6, nylon 66, or the like is used for clothing because of its advantages such as dyeability and heat resistance. Since these thermoplastic polymers constituting the sheath component generally have poor hygroscopicity, they retain sufficient mechanical properties even when wet, and thus are preferable.

On the other hand, the thermoplastic polymer used as the core component in the present invention must have a moisture absorption of 10% by weight or more at 30 ° C. and 90% RH. The moisture absorption rate is a moisture absorption rate at 30 ° C. and 90% relative humidity (RH) with respect to the polymer at the time of absolute drying, which is measured by a method described later. Specific examples of the hygroscopic thermoplastic polymer that forms the core component include copolymers of block alkyl ether glycol, block polyether amide, block polyester ether amide, and the like, and metal salts of sulfoisophthalic acid. And polyesters and polyamides obtained by copolymerizing the above, and mixtures of these with thermoplastic polymers.

Further, a mixture of a non-thermoplastic polymer such as an acrylic acid derivative such as sodium polyacrylate, polymethacrylic acid and polyacrylamide with a thermoplastic polymer, poly (N-vinylpyrrolidone) and its copolymer, polyvinyl alcohol, Preference is also given to copolymers, grafts of polycaprolactone and cellulose, or mixtures of these with general-purpose thermoplastic polymers. In particular, the hygroscopic thermoplastic polymer preferably contains 10% by weight or more of polyalkylene glycol. If necessary, the esterified product can be made to exhibit hygroscopicity by hydrolysis with an alkali after being made into a conjugate fiber or further after weaving. In particular, in the case of using a polyacrylic acid-based polymer exhibiting extremely high hygroscopicity and water absorption, the volume expands several times during moisture absorption and water absorption, so that it is mixed with a general-purpose thermoplastic elastomer as a mixed polymer. It is preferred to use.

The hygroscopic thermoplastic polymer may be a thermoplastic elastomer mixed with a hygroscopic polymer. The hygroscopic polymer used in the present invention is not necessarily limited to a thermoplastic polymer having a moisture absorption of 10% by weight or more at 30 ° C. and 90% RH. If the moisture absorption of the thermoplastic polymer forming the core component is less than 10% by weight, the improvement of the moisture absorption of the conjugate fiber is insufficient, and the object of the present invention cannot be achieved. The higher the moisture absorption of the hygroscopic thermoplastic polymer, the lower the proportion of the core component in the conjugate fiber. Therefore, the moisture absorption of the thermoplastic polymer forming the core component is preferably 15% by weight or more, and more preferably 15% by weight or more. It is preferably at least 20% by weight.

In the present invention, it is preferable that the thermoplastic polymer of the sheath component and the core component has good adhesiveness to each other. If the adhesion of both components is poor, if necessary, improve the adhesion by mixing and / or copolymerizing a compatibilizer for both components with either or both of the sheath component and the core component. Is possible. For example, when the sheath component is a polyamide-based polymer and the core component is a polyester-based polymer, good adhesion is exhibited as long as a polyalkylene glycol and / or metal sulfoisophthalate is copolymerized on the polyester side. Further, when the sheath component is a polyester-based polymer and the core component is a polyamide-based polymer, a polyetheresteramide obtained by copolymerizing a polyamide with a polyalkylene glycol exhibits good adhesiveness.

In the conjugate fiber of the present invention, the ratio of the core component to the total cross-sectional area of the composite fiber in the cross section perpendicular to the fiber axis is 10% to 50%, and a part of the core component is conjugate. It has a cross-sectional structure exposed at four or more places around the surface of the fiber, whereby the sheath is divided into four or more parts.

FIG. 1 schematically shows the cross-sectional shape of the conjugate fiber of the present invention. FIG. 1 is a cross-sectional view schematically illustrating a case where the number of core components exposed on the fiber surface is four, FIG. 2 is an example in the case of six locations, and FIG. 3 is an example in the case of eight locations. . There are four or more core components exposed on the fiber surface, and usually 4 to 8 locations are employed. FIG. 4 is an enlarged cross-sectional view of a portion of the exposed core component in FIG. 1, and FIG. 5 shows a cross-sectional shape of a conventionally known composite fiber for comparison.

The present inventors have previously described Japanese Patent Application Laid-Open No. H4-1268.
In Japanese Patent Publication No. 14, a composite fiber of easily peelable split fibers having a similar cross-sectional shape for a different purpose from the present invention was proposed. In a conjugate fiber having such a special cross-sectional shape, when a polymer having high moisture absorption and water absorption is provided in the core component, only the core component partially sandwiched between the sheath components and exposed on the fiber surface when water is absorbed. Have swelled and spread, and have lost water, they have narrowed, and have been found to deform as if the gaps in the schoolhouse were slightly open and closed. It is conceivable that the composite fiber of the present invention absorbs the expansion distortion due to water absorption by this school-like deformation.

On the other hand, in the case of the conventionally known composite fiber shown in FIG. 5, when a high moisture-absorbing or water-absorbing polymer is provided as the core component, the core component expands when the composite fiber absorbs water and expands with the sheath component. Excessive strain is applied to the sheath due to the difference, and cracks occur in the sheath. FIG. 6 shows that the composite fiber of FIG.
Fig. 3 schematically shows a state in which a part of a sheath is cleaved.
In the conjugate fiber of the present invention, the ratio of the core component to the total cross-sectional area of the cross section of the conjugate fiber needs to be 10% to 50%. If the ratio of the core component is less than 10%, even if a polymer having a high moisture absorption rate is used as the core component, the moisture absorption rate of the entire fiber is insufficient, and the object of the present invention is not achieved. If the ratio of the core component is more than 50%, the mechanical properties and dyeing fastness of the conjugate fiber are reduced, and the object of the present invention is not achieved. More preferably, the ratio of the core component to the total cross-sectional area of the cross section of the composite fiber is 20% to 40%.

In the present invention, the core component has a shape in which a part of the core component is exposed on the fiber surface, and there are four or more exposed parts around the fiber surface. The exposed portion accounts for 10% or less of the entire circumference of the fiber cross section. If the ratio of the exposed portion to the entire perimeter exceeds 10%, when the core component absorbs and absorbs moisture, the texture of the fiber becomes slim and the dyeing fastness of the fiber decreases. The ratio of the exposed portion is preferably as small as possible, but is preferably 2% to 8%, more preferably 2% to 5% from the viewpoint of fiber-forming properties.

Hereinafter, the method for producing the conjugate fiber of the present invention will be described. The conjugate fiber of the present invention can be obtained by arranging the thermoplastic polymer for the sheath component and the hygroscopic polymer for the core component using a known conjugate spinning machine. More specifically, it can be produced according to the method for producing a conjugate fiber disclosed in JP-A-4-126814. That is, when the two components merge in the spinneret, the sheath component is supplied from the horizontal direction to the core component flowing in the vertical direction. The number of sheath components is supplied corresponding to the number of core components exposed on the fiber surface.

The ratio of the core component to the total cross-sectional area of the composite fiber cross section is determined by the supply ratio of each polymer of the sheath component and the core component. The ratio of the peripheral length occupied by the core component exposed on the fiber surface to the total peripheral length of the fiber cross section is determined by the melt viscosity ratio of both components. Specifically, it is achieved by adjusting the melt viscosity at the spinning temperature so that the ratio of the sheath component / core component becomes 1 or more, preferably 1.5 or more. The method of spinning and winding of the conjugate fiber of the present invention comprises:
The fiber spun from the spinneret can be easily obtained by a conventionally known spinning and drawing method. Also, a spin draw take-up method in which the fiber is spun and stretched continuously without being wound up, and a spin take-up method in which the fiber is spun at a speed of about 5000 m / min or more and wound up without being stretched to obtain a practically usable fiber. It can also be obtained by a method.

In particular, when the hygroscopic polymer of the core component is an amorphous polymer having low crystallinity or a polymer having a low melting point, a high-speed spin take-up method can be used to obtain a good yarn-making without the fusion of filaments. Sex is achieved. The conjugate fiber of the present invention is used at 30 ° C. and 90% RH for clothing.
It is preferable from the viewpoint of practical performance to have a moisture absorption of 8% by weight or more. The reason for this is to provide comfort when wearing the garment. That is, the temperature and humidity inside the clothes when the clothes are actually worn, especially 30 to 36 ° C., 8 in the clothes close to the human body.
The practical performance required of the hygroscopic fiber is to immediately transfer the moisture in the clothes to the outside air, to eliminate the stuffiness of the human body and to provide comfort.

To provide this comfort, 30 ° C., 90%
The moisture absorption of the fiber at RH is important. Almost comfort is achieved when the moisture absorption is about 8% by weight or more.
More preferably, if it is 10% by weight or more, comfort close to cotton, which is a representative of natural fibers, can be obtained. Furthermore, when the human body sweats, it exhibits a high water absorption of about 40% by weight or more, but the conjugate fiber of the present invention has a great feature that it satisfies these requirements. Further, the conjugate fiber of the present invention has a low humidity range, for example, 6%.
At 5% RH, about 1% by weight compared to natural fiber
It is characterized by a low moisture absorption of 5% by weight. Such moisture absorption characteristics support that the clothing is preferable as a wash and wear property.

[0025]

The present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention. In addition, each characteristic value in an Example was calculated | required by the following method. (A) Moisture absorption rate The sample was conditioned for 24 hours in a thermo-hygrostat (trade name: PR-2C, manufactured by Tabai Espec) under the conditions of 30 ° C. and 90% RH.
The moisture absorption was calculated from the weight of the absolutely dry sample and the weight of the humidity control sample by the following equation. Moisture absorption (%) = Weight after humidity control-Weight when absolutely dried / Weight when absolutely dried x 100 (B) Water absorption After immersing the sample in water for 30 minutes or more, use a dehydrator of a household electric washing machine. Dehydrated for 5 minutes. The water absorption was determined from the weight of the absolutely dried sample and the weight of the sample after dehydration according to the following equation. Water absorption (%) = weight after water absorption-weight when absolutely dry / weight when absolutely dry x 100

(C) Presence or absence of cracks Five samples of 5 g were taken from the sample for every 5000 m of yarn length to prepare a single-knit fabric. Each was subjected to boiling water treatment at 98 ° C. for 30 minutes, and then conditioned at 20 ° C. and 65% RH for 24 hours. Each yarn was loosened from the knitted fabric and pulled out, and the cross section of all single yarns of the yarn was inspected with an optical microscope to check for the occurrence of cracks.
The case where there was no crack in all the single yarns was evaluated as ○, and the case where cracks occurred even in one single yarn was evaluated as ×. (D) Ratio of Fiber Cross-section to Total Perimeter Occupied by Exposed Core Component The cross-section of the conjugate fiber was photographed with an optical microscope, and the total perimeter and exposed perimeter were measured from a 1200-times photograph. I asked.

(E) Strength [Dry Strength] A sample conditioned at 20 ° C. and 65% RH for 24 hours was subjected to TENSILONUTM-2-20 manufactured by Toyo Baldwin Co., Ltd.
Initial length 20cm, tensile speed 20c by die tension tester
m. [Wet Strength] The sample was immersed in water for 30 minutes or more, and immediately measured by a tensile tester.

(F) Slime The sample was knitted with a one-piece knitting machine, subjected to ordinary scouring and drying, and then subjected to a sensory test of texture by five skilled textile engineers to make a judgment. Preparation of hygroscopic polymer [A] Block polyester ether amide According to the specification of Japanese Patent Application No. 4-55225, an average molecular weight of 14
90 polyethylene glycol, 192 parts, average molecular weight 1
830 of polyoxytetramethylene glycol 48 parts,
24 parts of adipic acid, 173 parts of caprolactam and 12 parts of hexamethylene-adipate were added to pentaerythrityl-
Using tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] as a catalyst, 25
Polymerized under reduced pressure at 0 ° C to obtain a polyethylene glycol content of 5
0% of the block polyester ether amide was obtained. The relative viscosity of this polymer (30 ° C. in meta-cresol, polymer concentration 0.5%) was 2.1, and the moisture absorption at 30 ° C. and 90% RH was 24% by weight.

[B] Block polyether ester 63 parts of dimethyl terephthalate, 44 parts of ethylene glycol, 0.03 part of manganese acetate, 0.1 part of antimony trioxide according to Example 1 of JP-A-53-24353. After transesterification by a conventional method, phosphorous acid 0.1
Parts, polyethylene glycol 37 having an average molecular weight of 6000
The polymerization was performed at 265 ° C. under reduced pressure to obtain a block polyetherester having a polyethylene glycol content of 40% by weight. The intrinsic viscosity of this polymer (30 ° C. in O-chlorophenol, polymer concentration 1.0%) is 0.92, 3
The moisture absorption at 0 ° C. and 90% RH was 18% by weight.

[C] Blocked polyetheramide 31.5 parts of polyethylene glycol diammonium adipate comprising polyethylene glycol diamine having an average molecular weight of 1100 and adipic acid, 57.1 parts of hexamethylene-adipate, and 21.1 parts of caprolactam were constantly used. Pressure polymerization according to the polyethylene glycol content 28
% By weight of the block polyetheramide was obtained. The relative viscosity of this polymer was 2.4, the moisture absorption at 30 ° C. and 90% RH was 21% by weight.

[D] sulfoisophthalic acid copolymerized polyester 92 parts of polyethylene glycol having an average molecular weight of 2,000,
Bishydroxyethyl sulfoisophthalate Na salt 45
9 parts, polyethylene glycol 24 having an average molecular weight of 200
9 parts of lithium acetate dihydrate 0.33 part was polymerized under reduced pressure using antimony trioxide as a catalyst to obtain a block copolymer. Next, 135 parts of dimethyl terephthalate, 99 parts of ethylene glycol, and 0.064 part of manganese acetate tetrahydrate were added, and a transesterification reaction was carried out by a conventional method, followed by polymerization under reduced pressure using antimony trioxide as a catalyst. 135 parts of a block copolymer was added and copolymerized. The intrinsic viscosity of this polymer was 0.51, 30 ° C., and the moisture absorption at 90% RH was 26% by weight.

[E] Sodium polyacrylate A styrene-butylene elastomer "ToughTech" (grade number M1943; manufactured by Asahi Kasei Kogyo Co., Ltd.) was added to a sodium polyacrylate-based hygroscopic polymer "Sunwet".
(Grade number IM-5000MPS; Sanyo Chemical Co., Ltd.)
Was mixed as a hygroscopic polymer. The moisture absorption of this polymer at 30 ° C. and 90% RH is 1
It was 8% by weight.

[0033]

Example 1 Nylon 6 having a relative viscosity of 2.4 as a sheath component
And spinning was performed with a twin-screw extruder using the block polyester ether amide of [A] as the hygroscopic polymer of the core component. At the time of spinning, with respect to the vertical flow of the core component, the sheath component flowed from the horizontal direction toward the center of the core component in six normal lines to obtain a composite fiber having a cross-sectional shape shown in FIG. (Details of the spinning method are described in
The melt viscosity ratio of the sheath component and the core component at this time was about 1.5.

The number of holes in the spinneret is 48, and the spinning temperature is 2
Extruded at 60 ° C. and discharge rate of 27.7 g / min.
It was wound up without being stretched at 0 m / min to obtain a composite fiber of 50d / 48f. The fibers shown in Table 1 were obtained by varying the mixing ratio of the sheath component and the core component. The spinning conditions were all good. Table 1 shows the physical properties of the obtained conjugate fiber. FIG. 7 shows NO. 3 shows a micrograph of a fiber of a fiber cross section of No. 3.

As in Example 1, nylon 6 was used as a sheath component.
Was spun with a twin-screw extruder using the block polyetheresteramide of [A] as a core component. At the time of spinning, the hygroscopic polymer of [A] was disposed as a core component of a conventionally known composite fiber shown in FIG. The physical properties of this composite fiber are shown in Table 1 as NO. FIG. As is clear from Table 1, the conjugate fiber of the present invention has high hygroscopicity without impairing the inherent properties of the sheath component such as mechanical properties and dyeability. On the other hand, NO. The composite fiber of No. 8 had cracks due to moisture absorption and lacked practicality.

[0036]

EXAMPLE 2 Nylon 66 having a relative viscosity of 2.4 was used as a sheath component, and the hygroscopic polymers [B], [C], [D], and [E] prepared above were used as a core component. Was spun in the same manner as in Example 1 so that the ratio to the total cross-sectional area was 30% to obtain a conjugate fiber. The perimeter occupied by the exposed portions of these fibers was 4% of the total perimeter of the fiber cross section. Table 2 shows the physical properties of the obtained composite fiber. As is clear from Table 2, each conjugate fiber had high hygroscopicity as well as good mechanical properties and dyeing characteristics.

[0037]

Example 3 Polyethylene terephthalate having an intrinsic viscosity of 0.62 (in O-chlorophenol, polymer concentration: 1.0% by weight) was used as a sheath component, and a block polyetherester of [A] was used as a hygroscopic polymer as a core component. In the same manner as in Example 1 to obtain a conjugate fiber. At this time, the ratio of the core component to the total cross-sectional area of the conjugate fiber was 30%.
The circumference occupied by the exposed portion of the composite fiber was 5% of the total circumference of the fiber cross section. 4.2g dry strength
/ D, strength when wet is 4.1 g / d, 30 ° C. 90% RH
Of 9.1% by weight at 20 ° C. It had a moisture absorption of 1.5% by weight and a water absorption of 62% at 65% RH, without cracks or sliminess due to wetting, and had good moisture absorption and wash and wear properties.

[0038]

According to the conjugate fiber of the present invention, cracks do not occur at the time of water absorption, which is a problem of the conventional conjugate fiber, the rate of adsorption and desorption of water to the core component is extremely fast, and the wash and wear property is improved. It is an absorptive fiber that retains mechanical properties such as strength, which are inherent properties of thermoplastic fibers, and fastness of dyeing, and does not cause problems such as slimy feeling and reduced strength when absorbing moisture.

Further, the conjugate fiber of the present invention is subjected to false twisting, scouring and dyeing in the same manner as conventional thermoplastic fibers, so that it can be used in a wide range of applications such as innerwear, lining, outer garments, sports clothing and the like. Is a hygroscopic fiber with high commercial value. Further, conventionally known polyester,
It is also possible to mix and weave with synthetic fibers such as nylon and natural and chemical fibers such as cotton, wool, hemp, rayon and cupra. Further, the conjugate fiber of the present invention, as short fibers, cotton,
It can be mixed with other fibers such as wool and hemp, has good hygroscopicity, and can be used in a wide range of applications.

[0040]

[Table 1]

[0041]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a cross-sectional shape of a conjugate fiber of the present invention when the number of core components exposed on the fiber surface is four.

FIG. 2 is a cross-sectional view schematically showing a cross-sectional shape of the conjugate fiber of the present invention when the number of core components exposed on the fiber surface is six.

FIG. 3 is a cross-sectional view schematically showing the cross-sectional shape of the conjugate fiber of the present invention when the number of core components exposed on the fiber surface is eight.

FIG. 4 is an enlarged cross-sectional view of a portion of the core component of FIG. 1 exposed on the fiber surface.

FIG. 5 is a cross-sectional view schematically showing a cross-sectional shape of a conventionally known composite fiber.

FIG. 6 is a cross-sectional view schematically showing a state in which a crack occurs when the conjugate fiber of FIG. 5 absorbs water.

FIG. 3 is a micrograph of a fiber shape showing a cross section of the conjugate fiber of FIG.

[Explanation of symbols]

 1: core component 2: sheath component 3: part exposed on the surface 4: crack

Claims (1)

(57) [Claims] 1. 10% by weight at 30 ° C., 90% RH
A composite fiber having a hygroscopic thermoplastic polymer having the above-described moisture absorption as a core component and a thermoplastic polymer as a sheath component.
In the cross section perpendicular to the fiber axis, the core component
Occupies 10 to 50% of the total cross-sectional area of the fiber, and
Exposed over 4 places around the surface of the composite fiber
By doing so, the sheath part is divided into four or more,
A conjugate fiber characterized in that the exposed portion is 10% or less of the entire circumference of the fiber cross section .