JPH0941221A - Synthetic fiber excellent in comfortableness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject synthetic fibers good in high-order processability without any process trouble in spite of its hygroscopicity and water absorptivity and especially useful as a material for clothes by including a hygroscopic component in the fibers and providing at least a part of the constituent fibers with one or more slits. SOLUTION: The synthetic fibers have a moisture absorption and desorption coefficient (ΔMR) increased to >=1.5% and are obtained by a method for compounding or blending a hygroscopic component such as a polyether ester therein, etc. At least a part of the fibers constituting the synthetic fibers are filaments or staple fibers having one or more slits and comprise multilobal cross-section yarns, etc., having 3-8 recessed and protruding parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comfortable synthetic fiber for clothing, and more particularly, it can be suitably used as a material for clothing such as inner garments, inner garments and sports clothing. It also relates to a synthetic fiber having both hygroscopic and water-absorbing properties.

[0002]

2. Description of the Related Art Thermoplastic synthetic fibers typified by polyesters and polyamides have excellent mechanical strength, chemical resistance, heat resistance, and ease of resin processing, so they are widely used mainly for clothing and industrial applications. Has been done. However, since these synthetic fibers have extremely low hygroscopicity, when used in a field such as an inner, inner garment, sports clothing, etc., which is directly worn on the skin or close to the skin, It causes stuffiness and stickiness due to sweating from the skin, and is inferior to natural fibers in terms of comfort. Therefore, it is the actual situation that the advancement to the clothing use is limited. Therefore, for example, Japanese Patent Publication No. 60-475 and Japanese Utility Model Publication No. 60-
40612, or JP-A-60-215835.
Equilibrium moisture content (moisture absorption rate)
Attempts have been proposed to obtain moisture-absorbing comfort as a cloth by various kinds of mixed fibers, mixed twists, and alignment with high-quality fibers. Although the use of these methods certainly improves comfort, its effect is not sufficient, and conversely, disperse dyes commonly used when dyeing synthetic fibers cause contamination or homogeneity. However, there is a problem in that the physical properties inherent to synthetic fibers are lost.

As a method for imparting hygroscopic properties to polyester or polyamide fibers, a method of graft-polymerizing acrylic acid or methacrylic acid to introduce a carboxyl group substituted with an alkali metal into the fiber, or acrylamide or the like. It is known to graft-polymerize a large amount of such amide compounds. Increasing the introduction amount of the carboxyl group substituted with the alkali metal increases the hygroscopic property, and the hygroscopic property higher than that of cotton can be obtained. However,
A fabric imparted with hygroscopicity by a post-processing method such as the above method is likely to cause stains due to the presence of a large amount of hygroscopic component on the fiber surface, and when the amount of introduction of a carboxyl group substituted with an alkali metal increases. However, it has not been put to practical use because it has a drawback that it becomes slimy when wet.

As described above, the method of imparting hygroscopicity in the post-processing step has various problems at the time of dyeing or in the characteristics of the obtained fabric. Moisture absorption is 10% to eliminate problems
A core-sheath type composite fiber in which the above hygroscopic resin is used as a core part and covered with polyester which is a sheath part is disclosed in JP-A-2-99612.
It has been proposed in the publication. In addition, JP-A-4-36161
No. 6 discloses a core-sheath type composite fiber in which a polyether ester amide is used for the core, and JP-A-4-361617 discloses a blend of a polyether ester amide and another thermoplastic resin for the core. A core-sheath type composite fiber is disclosed. Since these core-sheath type composite fibers cover the highly hygroscopic component with the sheath component, they have a hygroscopic property, yet have a relatively dry feel and a good texture. However, all the functions of the core-sheath composite fiber are to impart hygroscopicity, and the function of transferring moisture generated by a large amount of perspiration (water absorption) is low.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to overcome the above-mentioned problems of the prior art, to have good processability without process trouble, and to have two functions of hygroscopicity and water absorption. It is to provide a synthetic fiber having high wearing comfort.

[0006]

The above-mentioned object of the present invention is a synthetic fiber having a moisture absorption / release coefficient (ΔMR) of 1.5% or more, and at least a part of the synthetic fiber is 1 This can be achieved by a synthetic fiber having excellent comfort, which is a filament or a short fiber having one or more slits.

In the present invention, in order to provide comfort, particularly when sweating, the synthetic fiber has a moisture absorbing / releasing function of ΔMR 1.5% or more, and at least a part of the synthetic fiber is composed. It is a filament or a short fiber having one or more slits, and needs to have water absorption due to a capillary phenomenon.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The moisture absorbing / releasing function of the synthetic fiber of the present invention will be described below. The hygroscopic component preferably used in the synthetic fiber of the present invention is a polyether ester,
Polyether amide, polyether imide amide, and polyether ester amide are preferable, and polyether ester amide is particularly preferable. Each of these hygroscopic components has a moisture absorption / release coefficient ΔMR described later of 5% or more,
It has high hygroscopicity.

Here, the polyether ester amide is a block copolymer having an ether bond, an ester bond and an amide bond in the same molecular chain. More specifically, one or more polyamide-forming components (A) selected from lactams, aminocarboxylic acids, salts of diamines and dicarboxylic acids, and polyether esters composed of dicarboxylic acids and poly (alkylene oxide) glycols. It is a block copolymer polymer obtained by polycondensation reaction of the forming component (B). Examples of the polyamide-forming component (A) of the polyether ester amide of the present invention include lactams such as caprolactam, enantolactam, dodecanolactam and undecanolactam, aminocaproic acid, 11-
Ω of aminoundecanoic acid, 12-aminododecanoic acid, etc.
-Aminocarboxylic acid, nylon 66, nylon 610,
There are nylon salts of diamine-dicarboxylic acid, which is a precursor of nylon 612 and the like, and these can be used alone or in combination of two or more. A preferred polyamide-forming component (A) is ε-caprolactam, nylon 66 salt.

On the other hand, the polyether ester component (B) which constitutes the soft segment of the polyether ester amide comprises dicarboxylic acid and poly (alkylene oxide) glycol. As dicarboxylic acids,
Dicarboxylic acids having 4 to 20 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecadiic acid, and other aliphatic dicarboxylic acids, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid Aromatic dicarboxylic acids such as acids, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and the like,
One kind or a mixture of two or more kinds can be used. Preferred dicarboxylic acids are adipic acid, sebacic acid, dodecadic acid, terephthalic acid, isophthalic acid. As the poly (alkylene oxide) glycol, polyethylene glycol, poly (1,2- and 1,3-propylene oxide) glycol, poly (tetramethylene oxide) glycol, poly (hexamethylene oxide) glycol, ethylene oxide and propylene oxide or Examples thereof include random or block copolymerization with tetrahydrofuran, and polyethylene glycol is particularly preferable. The number average molecular weight of poly (alkylene oxide) glycol can be used in the range of 300 to 10,000, preferably 500 to 4000.

The polyether ester amide block copolymer preferably used for the hygroscopic component of the present invention is obtained by polycondensing the above-mentioned polyamide-forming component (A) and polyether ester-forming component (B). . (A) and (B) are industrially preferable methods.
Examples of the polycondensation method include heating polycondensation under reduced pressure. In this case, in order to obtain a polymer having a high degree of polymerization and little coloring, for example, antimony oxide, titanic acid ester or the like is used as a polycondensation catalyst, phosphoric acid or phosphoric acid. It is preferable to add an ester or the like as a color preventing agent. The weight ratio of (A) to (B) in the polyether ester amide can be effectively utilized in the range of 99: 1 to 5:95, preferably 80:20 to 10:90.

The polyether ester amide is a hygroscopic component that is preferably used in the present invention, and is blended or composited with other fiber-forming polymer, but it is arranged in the core portion as a core-sheath type composite fiber. Is preferred. By arranging it in the core part, it is possible to impart a moisture absorbing / releasing function while maintaining the dry feeling of the surface. The composite ratio of the hygroscopic component is preferably 5 to 50% by weight based on the total weight of the fiber. More preferably 10 to 40% by weight, especially preferably 15 to
30% by weight. The range is determined from the viewpoint of high-order processability such as sufficient hygroscopicity and the tendency of fiber surface cracking due to swelling in hot water atmosphere such as dyeing.

As the fiber-forming thermoplastic polymer of the present invention, any of polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6 and nylon 66, polyesters such as polyethylene terephthalate and polybutylene terephthalate can be used. However, it is preferable to use polyamide and polyester in terms of high interfacial mutual adhesion with polyetheresteramide. Further, the fiber-forming thermoplastic polymer is preferably an atmospheric dyeable polymer capable of lowering the hot water treatment temperature in the dyeing step and suppressing the swelling of the polyether ester amide. It is particularly preferable to use a modified polyester such as a polyester obtained by copolymerizing polyamide such as nylon 6 or nylon 66 or a poly (alkylene oxide) glycol, a polyester obtained by copolymerizing a 5-sodium sulfoisophthalic acid component. A small amount of the hygroscopic component of the present invention may be mixed in the fiber-forming thermoplastic polymer, but it is preferably suppressed to 10% by weight or less.

In addition, the moisture absorbing / releasing synthetic fiber of the present invention includes
Sodium polyacrylate, poly-N-vinylpyrrolidone, polyacrylic acid and its copolymer, polymethacrylic acid and its copolymer, polyvinyl alcohol and its copolymer, polyacrylamide and its copolymer, crosslinked polyethylene oxide polymer A moisture-absorbing or water-absorbing substance such as or a general-purpose thermoplastic resin such as polyamide, polyester, or polyolefin may be contained to such an extent that the object of the present invention is not impaired. Further, in addition to pigments such as titanium oxide and carbon black, conventionally known antioxidants, anti-coloring agents, light stabilizers, antistatic agents, etc. may be added to the moisture-absorbing and desorbing synthetic fibers and the fiber-forming thermoplastic polymer. Of course good.

The synthetic fiber of the present invention comprises a hygroscopic component and a fiber-forming thermoplastic polymer. Examples of the combined form include a core-sheath type, an eccentric core-sheath type, and a sea-island type, but the core-sheath type is particularly preferable.

Further, in the core-sheath type composite fiber, a hollow portion may be provided inside the fiber. The hollow portion is preferably formed at the hygroscopic component or at the interface between the hygroscopic component and the fiber-forming polymer.

The synthetic fiber of the present invention can be obtained by the following method. For example, polyamide (sheath part) and polyetheresteramide (core part) are separately melted, introduced into a spinning pack, a core-sheath composite flow is formed in a spinneret device, and spun from a discharge hole. The spun filament yarn is taken up at a predetermined speed, once wound up in a package, and the obtained undrawn yarn is drawn by a usual drawing machine. Further, after the spun yarn is taken up, it may be continuously drawn as it is and wound up (a direct spinning drawing method), or a method of obtaining a desired fiber performance at a high speed of 4000 m / min or more may be adopted. Good. As the direct spinning and drawing method, for example, spun yarn is
A method of taking it off at 00 to 5000 m / min, followed by stretching and heat setting at 3000 to 7000 m / min can be mentioned.

Next, the slit will be described. Here, the slit means a concave portion on the surface of the fiber, and means a portion sandwiched between the apparent convex portion and the convex portion. When the synthetic fiber of the present invention is made into a cloth, it has a water-transporting function due to a large number of capillary voids in the synthetic fiber. For that purpose, at least a part of the synthetic fiber must be a filament or a short fiber having one or more slits, and the slits are preferably formed continuously in the fiber longitudinal direction. .

The synthetic fiber of the present invention is more preferably a mixed fiber state of a fiber having a slit and a fiber having no slit. As the mixed fiber ratio, it is preferable that the fibers having no slits account for 20 to 80% by weight of the total amount of the mixed fiber.

As shown in FIG. 1, it is more preferable that the fiber cross-sectional shape is a multi-lobal cross section having 3 to 8 concave portions and convex portions. Among the multi-lobal cross-sections, penta-lobal cross-section (5 lobes) or hexa-lobal cross-section (6
Leaves) are particularly preferred. Further, the higher the degree of irregularity of the cross section, the better the water absorption performance, and it is preferable that the degree of irregularity is in the range of 1.3 to 5.0 from the viewpoint of forming capillary voids and good spinnability. More preferably, the degree of irregularity is in the range of 1.8 to 4.0. Here, the degree of irregularity means the radius ratio R1 / R of the circumscribed circle R1 and the inscribed circle R2 of the irregularly shaped cross section as shown in FIG.
Say two.

For example, when a yarn having a round cross section (variant degree 1.0) and a yarn composed of fibers having a degree of irregularity of 1.3 or more are mixed,
Since the multi-lobal cross section and the round cross section are adjacent to each other, capillary voids are efficiently formed between the fibers, and the water absorption is further improved.

Here, it is not always necessary that the composite fiber having the function of transferring moisture has only the composite fiber having the moisture absorbing / releasing function, and the fiber having no moisture absorbing / releasing function has the moisture transferring function. May be.

The synthetic fiber of the present invention may be in the form of filament or staple, and may be false twisted.

[0024]

The present invention will be described in more detail with reference to the following examples. Each characteristic value in the examples was obtained by the following method. A. Moisture absorption and desorption coefficient of fiber △ MR Moisture absorption rate is about 1 g of knitted fabric knitted with sample yarn and the temperature at 20 ℃ × 65% RH or 30 ℃ × 90% RH under constant temperature It was determined by the following formula from the weight change with the weight after standing for 24 hours in a humidity chamber (PR-2G manufactured by Tabai). Moisture absorption rate (%) = [(weight after moisture absorption-weight at absolute dryness) /
(Weight at absolute dryness)] × 100 From the measured moisture absorption rates under the conditions of 20 ° C. × 65% RH and 30 ° C. × 90% RH (MR1 and MR2, respectively),
Moisture absorption and desorption coefficient ΔMR (%) = MR2-MR1 is calculated. Here, the moisture absorption / desorption coefficient ΔMR is a driving force for obtaining comfort by releasing moisture in clothes when the clothes are worn to the outside, and is 30 when performing light-medium work or light-medium exercise. ℃ × 90% RH and clothes temperature represented by 20 ℃ ×
This is the difference in moisture absorption rate from the ambient temperature and humidity represented by 65% RH. In the present invention, this ΔMR is used as a parameter for evaluation of hygroscopicity, and the larger ΔMR corresponds to the higher hygroscopicity and the better wearing comfort.

B. Water Absorption Properties of Fiber The water absorption (height of water absorption) was determined according to the JIS standard Bayrek method. However, the measurement time was 5 minutes. The diffusivity (quick drying) was determined according to the JIS standard dropping method. In each of the characteristics, the case where the cotton level was higher than or equal to was judged to be acceptable. The water absorption height of cotton is 82 mm, and the diffusivity is 9.
It is 5 cm ² .

C. Presence or absence of outflow of core component after passing through higher-order process Disassemble the sample after dyeing and reduction washing, take out one composite yarn (multifilament), sample the cross section of the fiber into flakes, and use a microscope to observe single fibers. Observe the presence or absence of cracks in the fibers one by one. When there is no single yarn among the five multifilaments in which cracks occur from the core to the surface of the fiber and the core component is seen to flow out, cracks occur. A case where the number of single yarns in which the core component was generated and outflow was observed was 1-2, and a case where the number of yarns was 3 or more was indicated by x.

D. Judgment of Dyeing Spots A knitted tubular knitted fabric was soaked with a commercially available acid dye in accordance with a standard method at about 95 ° C. for 60 minutes, after which it was washed with water for about 10 minutes, air-dried, and visually compared with a standard comparative sample.
The judgment of x was made.

E. Wearing comfort A tricot knitted fabric was knitted from the sample yarn and the inner was sewn from the knitted fabric. Five test subjects wear this inner, and after resting for 1 hour in an artificial weather room under the temperature and humidity conditions of 20 ° C x 65% RH, they are placed on a block 20 cm in height.
After a 0 minute step up and down exercise, and after maintaining a resting state for 20 minutes, a questionnaire about the feeling of wearing was taken.
The number of people who answered that they were comfortable with no stuffiness and stickiness was 5 or more. ◎, 4 or more was ○, 3 was Δ, and 2 or less was ×.

Reference Example 1 (Synthesis of Polyether Esteramide Block Copolymer) 340 parts of ε-caprolactam, 18 parts of terephthalic acid, 100 parts of polyethylene glycol having a number average molecular weight of 1000,
Furthermore, 0.1 part of "Irganox 1330" (manufactured by Ciba Geigy) and 0.01 of trimethyl phosphate
Was charged into a polymerization reaction vessel together with the parts, and was put under a nitrogen stream for 240
After heating and stirring at 1 ° C for 1 hour, 0.1 part of antimony trioxide was added, and the temperature was reduced under reduced pressure program at 250 ° C, 0.5 mm.
By carrying out the polymerization reaction for 4 hours under the condition of Hg or less, the proportion of the polyamide-forming component (A) is 45% by weight and the proportion of the polyetherester-forming component (B) is 55% by weight. Got united. A solution of this copolymer in orthochlorophenol (concentration: 0.
5 g / 100 ml) has a relative viscosity ηr at 25 ° C. of 2.1.
Met. MR1 of polymer alone is 6.0%, MR2
Was 17.4% and ΔMR = 11.4%.

Example 1 The polyether ester amide block copolymer synthesized in Reference Example 1 was used as the core component, nylon 6 having a relative viscosity of 2.50 in sulfuric acid as the sheath component, and 5 radial slits at a spinning temperature of 270 ° C. A core-sheath type composite spinneret having a discharge hole is discharged so that the weight ratio is 20/80 in the core / sheath part, and the spinning speed is 3000 m / min and the drawing speed is 5000 m by the direct spinning / drawing method.
The core / sheath type composite yarn of 50 denier 24 filaments was obtained by winding at a speed of about 1 / min. The cross-sectional shape of the composite fiber was pentalobal (5 leaves), and the degree of irregularity was about 1.8. The ΔMR of the tubular knitted fabric was 4.7%, which was a good hygroscopic property. Furthermore, water absorption (water absorption height) is 120m
m, the diffusivity by the dropping method was 19 cm ^2, and all the water absorption characteristics were at a high level. The composite yarn was knitted to form a tricot knitted fabric, and this knitted fabric was sewn to form an inner. This inner is soaked with a commercially available acid dye according to a standard method at about 95 ° C. for 60 minutes, then washed with water for about 10 minutes, further colored at about 80 ° C. for 10 minutes by dyeing to an appropriate color, and again washed with water for about 10 minutes. I did it. The finished product had a good appearance quality, and even when evaluated by five test subjects, no one felt stuffy or sticky, and exhibited extremely good wearing comfort.

Examples 2 to 4 and Comparative Examples 1 to 2 Tricots were knitted in the same manner as in Example 1 except that the core-sheath composite ratio of the polyether ester amide block copolymer and the polyamide was changed. Table 1 shows the results obtained by evaluating the respective properties of Example 1 in the same manner as in Example 1. In Examples 2 to 4, both the hygroscopic property and the water absorbing property were good, and cracks due to hot water treatment were not observed at all. On the other hand, in Comparative Example 1, since the proportion of the polyether ester amide as the core component was small, the hygroscopicity was low, and in Comparative Example 2, the amount of the polyether ester amide as the core component was large, so that the hygroscopicity was high but the fiber was not treated during hot water treatment. Many cracks were generated on the surface, and the polyether ester amide flowed out to the surface of the fiber, resulting in stickiness, which was not practical.

Example 5 Polyether ester amide and nylon 6 as core components
A tricot was knitted in the same manner as in Example 1 except that the mixture having a weight ratio of 80:20 was used and the weight ratio was changed to core / sheath = 30/70. Both the moisture absorption property and the water absorption property were good, and the wearing comfort was also high.

Example 6 Polyether ester amide and nylon 6 as sheath components
A tricot was knitted in the same manner as in Example 1 except that a mixture having a weight ratio of 5:95 was used. Moisture absorption characteristics,
The water absorption characteristics were good, and the wearing comfort was also high.

Example 7 A tricot was knitted in the same manner as in Example 1 except that a modified polyester obtained by copolymerizing 3 mol% of dimethyl 5-sodiumsulfoisophthalate as a sheath component was used and a cationic dye was used in the dyeing step. I stood. Both the moisture absorption property and the water absorption property were good, and the wearing comfort was also high.

Example 8 Example 1 was repeated except that a core-sheath type composite spinneret in which radial 6-slit discharge holes (15 holes) and round holes (9 holes) were arranged dispersedly as shown in FIG. A tricot was knitted in a similar manner. The mixed fiber thus obtained had the cross-sectional shape shown in FIG. 4 and had good moisture absorption characteristics. In addition, the water absorption characteristics were even better than in Example 1.

Example 9 A tricot was knitted in the same manner as in Example 2 except that the specifications of the discharge holes were changed and the irregularity of the fiber cross section was changed. The irregularity of the fiber was 3.8, and the water absorption property was extremely excellent.

Example 10 Mixed state of a core-sheath type composite fiber having a roundness of 1.0 with a degree of irregularity and a pentalobal fiber composed of nylon 6 with a degree of variation of 1.8 (composite fiber / pentalobal fiber = 70/30) ) Was used for knitting with a tricot in the same manner as in Example 1. The moisture absorption and water absorption characteristics were good.

Comparative Example 3 A tricot was knitted in the same manner as in Example 1 except that the shape of the discharge hole was changed to a round hole. The degree of fiber irregularity is 1.
The water absorption characteristics are 0, the water absorption height is 65 mm, and the diffusivity is 9.2.
It was cm ² , and both were inferior to cotton. The wearing comfort was also insufficient.

Comparative Example 4 A tricot was knitted in the same manner as in Example 1 except that the shape of the discharge hole was changed to a radial 9-slit discharge hole.
The cross section of the obtained fiber was nonalobal (9 leaves), and the degree of irregularity was 1.5. Although this sample has a high moisture absorption property, it has a water absorption property of a water absorption height of 80 mm and a diffusivity of 9.4 cm ^2.
And both were inferior to cotton.

[0040]

[Table 1]

[0041]

Industrial Applicability The synthetic fiber obtained by the present invention has sufficient hygroscopicity and water absorption to obtain wearing comfort, and has dry touch feeling, high dyeing fastness and light fastness. ing. Further, since the fiber surface is not cracked or cracked even under a harsh atmosphere such as dyeing conditions, it can be applied to a wide range of applications.

The synthetic fiber of the present invention is used in underwear, shirts / blouses, inner garments, sportswear, slacks, outer garments,
It is suitable for lining, as well as for bedding such as sheets and futon covers, and is extremely practical.

[0043]

[Brief description of drawings]

[0044]

1 is an example of a cross-sectional view of a fiber of the present invention.

[0045]

FIG. 2 is a cross-sectional view of a fiber for explaining the irregularity of the fiber of the present invention.

[0046]

FIG. 3 is a schematic plan view showing an example of an array of ejection holes of a die used in the present invention.

[0047]

4 is a cross-sectional view of fibers showing an example of the mixed fiber of the present invention obtained from the die of FIG.

[0048]

[Explanation of symbols] 1; Tri-lobal section 2; Tetra-lobal section 3; Penta-roval section 4; Hexa-lobal section 5; Hepta-lobal section 6; Octa-lobal section

Claims (8)

[Claims] 1. A synthetic fiber having a moisture absorption and desorption coefficient (ΔMR) of 1.5% or more, and at least a part of the synthetic fiber is a filament or a short fiber having one or more slits. Synthetic fiber with excellent comfort. 2. The synthetic fiber according to claim 1, wherein the hygroscopic / desorbable synthetic fiber in which a hygroscopic component having ΔMR of 5.0% or more is mixed or blended with a fiber-forming polymer constitutes at least a part. 3. A core-sheath type composite fiber in which a hygroscopic component having a MR of 5.0% or more is arranged in a core portion and a fiber-forming polymer is arranged in a sheath portion, and a weight ratio of the core portion / sheath portion. Is 5/95 to 50 /
The synthetic fiber according to claim 1 or 2, wherein the composite fiber of 50 constitutes at least a part. 4. The synthetic fiber according to claim 3, wherein the main component of the hygroscopic component forming the core is polyetheresteramide. 5. The synthetic fiber according to claim 3, wherein the main component of the fiber-forming polymer forming the sheath is fiber-forming polyamide or fiber-forming polyester. 6. A filament having a slit or a short fiber has a multi-lobal cross section having 3 to 8 slit portions and the same number of convex portions, and is excellent in comfort, and any one of claims 1 to 5 is provided. The synthetic fiber according to item 1. 7. The synthetic fiber according to claim 1, wherein the filament having a slit or the short fiber has a degree of irregularity of 1.3 to 5.0 in a cross section of the fiber. 8. A filament or a short fiber having a slit which constitutes at least a part of a synthetic fiber has a composition ratio of 2.
The synthetic fiber according to any one of claims 1 to 7, which is 0 to 80% by weight.