JP2003221727A - Hollow fiber, composite fiber, and method for treating fiber structure containing composite fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow fiber having a porous hollow portion excellent in water absorption, light weight, swelling feeling and the like, and a fiber structure containing the fiber. SOLUTION: This is a porous hollow fiber having a hollow portion number (α1) and a hollow ratio (α2) satisfying the following formulas (1) to (3), and the surface of the fiber has a groove or a streak communicating with the hollow portion. Porous hollow fiber with pinholes. α1 ≧ 5 (1) 3 ≦ α2 ≦ 65 (2) 0.15 ≦ α1 × α2 / 100 ≦ 350 (3)

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous hollow fiber and a fiber structure containing the same. Specifically, there are streak-shaped pinholes of varying size on the fiber surface, which are excellent in water absorption, lightweight, excellent in swelling, and have a good feeling, especially hollow fibers. The present invention relates to a hollow fiber and its fiber structure.

[0002]

2. Description of the Related Art Synthetic fibers such as polyester and polyamide are widely used not only for clothing but also for industrial purposes due to their excellent physical and chemical properties, and have industrially important value. There is. Since the above synthetic fibers have low hygroscopicity and water absorbency, their use in applications such as underwear, inner garments, sheets, and towels that require hygroscopicity and water absorbency has been limited. Examples of the method of imparting hygroscopicity or water absorption to synthetic fibers include a method of post-treating polyester fiber with a hydrophilic treatment agent, a method of imparting hygroscopicity or water absorption by making the surface or the inside of polyester fiber porous. Is proposed. However, these methods do not sufficiently improve the hygroscopicity and water absorption of the synthetic fiber, and in the case of the fiber to which hydrophilicity is imparted by the post-treatment, the hygroscopicity and water absorbing ability imparted by repeated washing decrease. There was a drawback to do.

Further, it has been widely practiced to hollow the fibers in order to reduce the weight of the synthetic fibers and improve the heat retaining property.
As a method for producing a hollow fiber, it is generally well known to produce using a hollow spinning nozzle, but in such a method, after spinning, the surface tension of the resin in a molten state until it solidifies and There is a problem that the deformed cross section is collapsed due to the take-up tension during spinning or the hollow part is easily crushed, and particularly when trying to develop a porous hollow shape, even if a fiber is provided with a porous hollow structure immediately after spinning. However, the porous hollow portion was crushed and disappeared, or the ratio of the hollow portion was easily reduced, and it was substantially impossible to obtain a fiber having a porous hollow portion.

In view of the above problems, the applicant of the present invention has
In P1134307, a thermoplastic water-soluble polyvinyl alcohol is used as an island component, and a fiber structure composed of sea-island type composite fibers containing another thermoplastic polymer as a sea component is treated with water to dissolve and remove the water-soluble polyvinyl alcohol. Therefore, a method for producing a porous hollow fiber without crushing the hollow portion is proposed. The porous hollow fiber obtained there is excellent in lightness and heat retention, but there is room for improvement in water absorption in the application field where high water absorption is required.

[0005]

The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a hollow fiber having excellent water absorbency, lightness, repulsion feeling and, in some cases, good bulging feeling, and hollow fibers. The purpose is to provide a fiber structure. Another object of the present invention is to provide a composite fiber for rationally producing such a hollow fiber without causing wastewater treatment and environmental problems, and further to provide a method for producing a hollow fiber using the composite fiber. That is.

[0006]

That is, according to the present invention, the number of hollow parts (α1) and the hollow ratio (α2) are expressed by the following formulas (1) to (1).
A porous hollow fiber satisfying (3), characterized in that a groove-shaped or streak-shaped pinhole communicating with the hollow portion is present on the surface of the fiber, and α1 ≧ 5 (1 ) 3 ≦ α2 ≦ 65 (2) 0.15 ≦ α1 × α2 / 100 ≦ 350 (3) In the present invention, the thermoplastic polymer is used as the sea component and the water-soluble thermoplastic polyvinyl alcohol polymer is used as the island component. And the number of islands (β
1) and the island area ratio (β2) satisfy the following equations (4) to (6): β1 ≧ 5 (4) 3 ≦ β2 ≦ 65 (5) 15 ≦ β1 × β2 / 100 ≦ 350 (6) Furthermore, in the present invention, the above-mentioned conjugate fiber is treated as it is or after being made into a fiber structure containing the conjugate fiber, with water,
At the same time as or after dissolving and removing at least a part of the water-soluble thermoplastic polyvinyl alcohol-based polymer of the composite fiber, the composite fiber is treated with a soluble solvent or a decomposable solvent of the thermoplastic polymer as a sea component, and the above-mentioned pinhole A method for treating a fiber structure, which is characterized by forming a structure.

The term "fibrous structure" as used in the present invention means, of course, multifilament yarns, spun yarns, woven and knitted fabrics, non-woven fabrics, papers, artificial leathers and filling materials composed of the composite fibers or hollow fibers of the present invention. Thing, natural fiber, semi-synthetic fiber,
Mixed yarns and blended yarns with other synthetic fibers, processed yarns such as plied yarns, entangled yarns and crimped yarns, mixed woven fabrics, knitted fabrics, fiber laminates, and clothing, living materials, industrial materials composed of these ,
It also includes various final products such as medical supplies.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is important that a groove-shaped or streak-shaped pinhole communicating with the hollow portion is present on the surface of the porous hollow fiber, and the presence of this pinhole is excellent. Water absorption performance is imparted. Further, as shown in FIG. 1, in order to impart excellent water absorption performance, a fiber in which a communication hole is formed from the hollow part communicating with the fiber surface as described above to another hollow part It preferably has a structure. However, when the communication holes are formed from one hollow portion toward a plurality of hollow portions at the same time, the fiber strength decreases and a problem occurs in terms of practicality. It is preferable that one communication hole is formed from one hollow portion to another hollow portion. Also, when observing the fiber cross section, there may be a case where a communication hole is formed between the hollow portions that are not in communication with the fiber surface. Such a communication hole seems to be meaningless at first glance from the viewpoint of improving water absorption. However, these hollow portions may communicate with other hollow portions communicating with the fiber surface at another position in the fiber length direction, which leads to improvement of water absorption.

In the present invention, the groove-shaped or streak-shaped pinhole formed on the fiber surface has a form as shown in the side view photograph of the fiber of FIG. 2, for example, and is parallel to the fiber axis. It is preferable that at least one fiber is present in 5 mm of the single fiber, the length in the fiber axis direction is 1 mm or less, the width is ½ or less of the diameter of the single fiber, and the fibers are formed at substantially non-uniform intervals. . If the number of fibers is less than 1 per 5 mm, the water absorption is insufficient. Further, when the length of the pinhole is longer than 1 mm, and when the width is larger than 1/2 of the single fiber diameter, the fiber strength becomes low, which causes problems in practical use and is not suitable. The upper limit of the number of pinholes depends on the length and width of the pinholes, but if the number is too large, the fiber strength decreases, so it is preferably about 30/5 mm or less. The lower limit of the length of the pinhole is not particularly limited, but if it is too small, the water absorption will not be improved, so it is preferably about 10 μm or more. Further, the lower limit of the width of the pinhole is about 1 for the same reason as the case of the length.
It is desirable that the thickness is at least μm.

Further, in the present invention, it is preferable that 20% or more of the many hollow portions communicate with the fiber surface by the pinholes as described above.

In the hollow fiber of the present invention, it is important that the number (α1) of hollow parts and the hollow ratio (α2)% satisfy the following formulas (1) to (3) at the same time as having a specific pinhole. is there. α1 ≧ 5 (1) 3 ≦ α2 ≦ 65 (2) 0.15 ≦ α1 × α2 / 100 ≦ 350 (3) The relationship between the number of hollow parts (α1) and the hollow ratio (α2)% is α1
With <5,3> α2, 0.15> α1 × α2 / 100, lightweightness, a bulging feeling and a sufficient repulsion feeling cannot be obtained. Also,
When α2> 65 and α1 × α2 / 100> 350, it is not suitable because it becomes difficult to fibrillate and there is a problem in practical use because the fiber strength is low. Therefore, preferably α1 ≧ 8,
5 ≦ α2 ≦ 50, 0.4 ≦ α1 × α2 / 100 ≦ 100
Is desired.

The pinhole-containing porous hollow fiber of the present invention as described above is produced by dissolving and removing the island component from a specific sea-island type composite fiber. For example, the sea component is made of polyester. When the island component of the water-soluble thermoplastic polyvinyl alcohol polymer is eluted from the sea-island type composite fiber in which the island component is composed of the water-soluble thermoplastic polyvinyl alcohol polymer, the expansion of the polyvinyl alcohol by water is caused. By using pressure to form extremely fine grooves on the fiber surface, and by dissolving or decomposing a part of the thermoplastic polymer that constitutes the sea component with a solvent or a decomposing agent, the fine groove parts are formed. It is formed as a pinhole.

The cross section of the conjugate fiber of the present invention is, for example, one in which several circular island components made of a water-soluble thermoplastic polyvinyl alcohol polymer are surrounded by a sea component made of a polyester polymer. In addition, a large number of small island components having an irregular shape that is not circular are surrounded by sea components.

In the present invention, the composite ratio of the island component and the sea component is not particularly limited, but the composite ratio is appropriately selected depending on the number of hollow portions and the hollow ratio of the finally obtained hollow fiber. Can be changed. Preferably island: sea
= 2: 98 to 65:35, and further 5:95 to 60: 4
It is preferably 0. Further, the shape of each island component is not limited at all, and may be circular, elliptical, or any other irregular shape. Furthermore, the island component may be continuous or discontinuous in the fiber axis direction. Further, the cross-sectional shape of the composite fiber is not particularly limited, and in addition to the circular cross-section, for example, a flat shape, an elliptical shape, a rectangular shape such as a triangle to an octagon, a T shape, and 3 to 8 are available.
The shape may be any shape such as a multi-leaf shape such as a leaf shape. Further, the conjugate fiber of the present invention may contain optional additives such as a fluorescent whitening agent, a stabilizer, a flame retardant and a colorant, if necessary.

Next, the water-soluble thermoplastic polyvinyl alcohol polymer (hereinafter sometimes simply referred to as PVA) used as the island component of the composite fiber of the present invention will be described. The PVA used in the present invention includes not only a homopolymer of polyvinyl alcohol but also, for example, copolymerized, terminal modified, and modified polyvinyl alcohol having a functional group introduced by a post reaction.

The PVA used in the present invention has a viscosity average degree of polymerization (hereinafter simply referred to as a degree of polymerization) of preferably 200 to 500, more preferably 230 to 470, and even more preferably 250 to 4
50 is particularly preferred. If the degree of polymerization is less than 200, sufficient spinnability may not be obtained during spinning, and fiber formation may be difficult. If the degree of polymerization exceeds 500, the melt viscosity will be too high,
In some cases, the polymer cannot be discharged from the spinning nozzle. In addition, a so-called low polymerization degree PV having a polymerization degree of 500 or less
By using A, not only the dissolution rate can be increased when the composite fiber is dissolved in the aqueous solution, but also the shrinkage when the composite fiber is dissolved can be reduced.

The degree of polymerization (P) of PVA is JIS-K67.
It is measured according to 26. That is, it is obtained by the following formula from the intrinsic viscosity [η] (dl / g) measured in water at 30 ° C. after re-saponifying PVA and purifying it. P = ([η] × 10 ³ /8.29) ^{(1 / 0.62) When the} degree of polymerization is within the above range, the object of the present invention can be more suitably achieved.

The PVA used in the present invention has a saponification degree of 9
It is preferably from 0 to 99.99 mol%. More preferably 93 to 99.98 mol%, and further 94 to 99.9.
7 mol% is preferable, and 96 to 99.96 mol% is particularly preferable. If the degree of saponification is less than 90 mol%, the thermal stability of PVA may be poor, and satisfactory melt spinning may not be possible due to thermal decomposition or gelation, and the water solubility of PVA may decrease depending on the type of copolymerization monomer described below. There is a case. On the other hand, PVA having a saponification degree of more than 99.99 mol% tends to have low solubility and cannot be stably produced, which makes stable fiber formation difficult.

Further preferred PVA for use in the present invention
Indicates that the molar fraction of the central hydroxyl group of the three-chain hydroxyl group by triad display to the vinyl alcohol unit is 70-
It is preferably 99.9 mol%, has a melting point of 160 ° C. to 230 ° C., and contains 0.0003 to 1 part by mass of alkali metal ion in terms of sodium ion based on 100 parts by mass of PVA.

In the present invention, the central hydroxyl group of the 3-chain hydroxyl group represented by triad display of polyvinyl alcohol means a 500 MHz proton NMR (JEOL GX-500) apparatus in PVA d6-DMSO solution at 65 ° C.
It means a peak (I) reflecting the tacticity of triad of hydroxyl protons measured. Peak (I)
Is the sum of isotacticity chain (4.54 ppm), heterotacticity chain (4.36 ppm) and syndiotacticity chain (4.13 ppm) in the triad of hydroxyl groups of PVA, and all vinyl alcohol units are represented. Since the peak (II) of the hydroxyl group in 4) appears in the region of chemical shift of 4.05 ppm to 4.70 ppm, the molar fraction of the central hydroxyl group of the 3-chain hydroxyl group by the triad display with respect to the vinyl alcohol unit of the present invention is 100 × (I ) / (II).

Hydroxyl group 3 by PVA triad display
When the content of the central hydroxyl group in the chain is less than 70 mol%, the crystallinity of the polymer is lowered and the fiber strength is lowered, and at the same time, the fibers are stuck to each other during melt spinning and unwinding after winding may occur. is there. In addition, water solubility may not be obtained. When the content of the central hydroxyl group of the hydroxyl group 3 chain according to the triad representation of PVA is higher than 99.9 mol%, the melting point of the polymer is high, so that the melt spinning temperature needs to be raised. As a result, during melt spinning The heat stability of the polymer is poor, and decomposition, gelation, and polymer coloring are likely to occur.

Further, the PVA of the present invention is ethylene-modified P
In the case of VA, the effect of the present invention is further enhanced by satisfying the following formula. -1.5 × Et + 100 ≧ mol fraction ≧≧ -Et + 85 Here, the mole fraction (unit: mol%) represents the mole fraction of the central hydroxyl group of the hydroxyl group 3 chain by the triad notation to the vinyl alcohol unit, and Et is It represents the ethylene content (unit: mol%) contained in the vinyl alcohol polymer.

Therefore, the content of the central hydroxyl group of the 3-chain hydroxyl group by the triad display of PVA used in the present invention is more preferably 72 to 99 mol%, and 74 to 97 mol%.
Is more preferable, and 76 to 95 mol% is particularly preferable.

By controlling the amount of the central hydroxyl group of the three-chain hydroxyl group of polyvinyl alcohol used in the present invention, various physical properties related to water such as water solubility and hygroscopicity of PVA, strength, elongation, elastic modulus, etc. It is possible to control various physical properties related to melt spinning properties such as melting point, melt viscosity and the like. It is considered that this is because the central hydroxyl group of the triad hydroxyl group 3 chain is rich in crystallinity and expresses the features of PVA.

Melting point (Tm) of PVA used in the present invention
Is preferably 160 to 230 ° C., 170 to 2
27 degreeC is more preferable, 175-224 degreeC is further more preferable, 180-220 degreeC is especially preferable. Melting point 160
When the temperature is lower than 0 ° C, the crystallinity of PVA is lowered, the fiber strength of the conjugate fiber is lowered, and at the same time, the thermal stability of the conjugate fiber is deteriorated, and the fiber cannot be formed. On the other hand, the melting point is 2
If it exceeds 30 ° C., the melt spinning temperature becomes high, and the spinning temperature and the decomposition temperature of PVA are close to each other, so that the sea-island type composite fiber composed of PVA and polyester may not be stably produced. The melting point of PVA was measured by using DSC in nitrogen after heating up to 250 ° C. at a heating rate of 10 ° C./min.
It means the temperature at the peak top of the endothermic peak showing the melting point of PVA when cooled to room temperature and heated again to the temperature rising rate of 10 ° C./250° C.

The PVA used in the present invention is obtained by saponifying the vinyl ester unit of the vinyl ester polymer. As the vinyl compound monomer for forming the vinyl ester unit, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples thereof include vinyl versatate, and of these, vinyl acetate is preferable from the viewpoint of obtaining PVA.

The PVA used in the present invention may be a homopolymer or a modified PVA having a copolymerized unit introduced, but from the viewpoint of melt spinning property, water solubility and fiber physical properties, the copolymerization is performed. It is preferable to use a modified polyvinyl alcohol in which a unit is introduced. Examples of the type of copolymerizable monomer include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene, acrylic acid and salts thereof, methyl acrylate, ethyl acrylate, and n-acrylic acid. Acrylic esters such as propyl and i-propyl acrylate, methacrylic acid and salts thereof, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate and i-propyl methacrylate, acrylamide, N- Acrylamide derivatives such as methyl acrylamide and N-ethyl acrylamide, methacrylamide derivatives such as methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl Vinyl ether, vinyl ethers such as n- butyl ether, ethylene glycol vinyl ether, 1,3
-Hydroxy group-containing vinyl ethers such as propanediol vinyl ether and 1,4-butanediol vinyl ether, allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, and hexyl allyl ether; monomers having an oxyalkylene group; Vinylsilyls such as vinyltrimethoxysilane, isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decene-1. -Ol, 3-methyl-3-buten-1-ol and other hydroxy group-containing α-olefins, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or itaconic anhydride A monomer having a carboxyl group derived from Nsuruhon acid, allylsulfonic acid, methallyl sulfonic acid, 2-acrylamido-2
Monomers having a sulfonic acid group derived from methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, Examples include monomers having a cationic group derived from N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine and the like. The content of these monomers is usually 20 mol% or less.

Among these monomers, α-olefins such as ethylene, propylene, 1-butene, isobutene and 1-hexene, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, Vinyl ethers such as i-propyl vinyl ether and n-butyl vinyl ether, hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether, allyl acetate, propyl allyl ether, butyl Allyl ether,
Allyl ethers such as hexyl allyl ether, monomers having an oxyalkylene group, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, Monomers derived from hydroxy group-containing α-olefins such as 9-decen-1-ol and 3-methyl-3-buten-1-ol are preferred.

In particular, ethylene, propylene, 1-butene, from the viewpoint of copolymerizability, melt spinnability and water solubility of fibers,
More preferred are α-olefins having 4 or less carbon atoms of isobutene, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether. The unit derived from α-olefins and / or vinyl ethers having 4 or less carbon atoms is 0.1 to 0.1% in PVA.
20 mol% is preferably present, more preferably 1 to 20 mol%, further preferably 4 to 15 mol%,
6 to 13 mol% is particularly preferable. Further, when the α-olefin is ethylene, the physical properties of the fiber become high, so it is preferable to use a modified PVA in which an ethylene unit is introduced in an amount of 4 to 15 mol%, more preferably 6 to 13 mol%.

Examples of the PVA used in the present invention include known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is carried out without solvent or in a solvent such as alcohol is usually adopted. Examples of the alcohol used as the solvent during the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol. As the initiator used for the copolymerization, α, α′-azobisisobutyronitrile, 2,2′-azobis (2,2
4-dimethyl-valeronitrile), benzoyl peroxide,
Known initiators such as azo-based initiators such as n-propyl peroxycarbonate or peroxide-based initiators may be mentioned. The polymerization temperature is not particularly limited, but is 0 ° C to 1
A range of 50 ° C is suitable.

The content ratio of the alkali metal ion in the PVA used in the present invention is preferably 0.0003 to 1 part by mass, and 0.0003 to 0.8 part by mass in terms of sodium ion based on 100 parts by mass of PVA. A part is more preferable, 0.0005 to 0.6 part by mass is further preferable, and 0.0005 to 0.5 part by mass is particularly preferable. When the content ratio of the alkali metal ion is less than 0.0003 parts by mass, sufficient water solubility may not be exhibited and undissolved matter may remain. Further, when the content of alkali metal ions is more than 1 part by mass, decomposition and gelation during melt spinning may be remarkable and fiber formation may not be possible. Examples of alkali metal ions include potassium ion and sodium ion.

In the present invention, the method for incorporating a specific amount of alkali metal ions into PVA is not particularly limited, and P
A method of adding an alkali metal ion-containing compound after polymerizing VA, and when saponifying a vinyl ester polymer in a solvent, by using an alkaline substance containing an alkali ion as a saponification catalyst, an alkali metal ion is added to PVA. PVA obtained by blending and saponifying
Examples of the method include controlling the content of alkali metal ions contained in PVA by washing the above with a washing liquid, but the latter is preferable. The content of alkali metal ions can be determined by the atomic absorption method.

Examples of the alkaline substance used as the saponification catalyst include potassium hydroxide and sodium hydroxide. The molar ratio of the alkaline substance used in the saponification catalyst is preferably 0.004 to 0.5, and particularly preferably 0.005 to 0.05, based on the vinyl acetate unit. The saponification catalyst may be added all at once at the beginning of the saponification reaction, or may be additionally added during the saponification reaction. As the solvent for the saponification reaction, methanol, methyl acetate, dimethyl sulfoxide,
Examples include dimethylformamide. Among these solvents, methanol is preferable, and the water content is 0.001 to
Methanol controlled to 1 mass% is more preferable, methanol whose water content is controlled to 0.003 to 0.9 mass% is more preferable, and methanol whose water content is controlled to 0.005 to 0.8 mass% is particularly preferable. . Examples of the washing liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, water and the like, and among these, methanol, methyl acetate, water alone or a mixed liquid is more preferable. The amount of the cleaning liquid is set so as to satisfy the content ratio of the alkali metal ions, but normally 300 to 10,000 parts by mass is preferable with respect to 100 parts by mass of PVA, and 500.
〜5000 parts by mass is more preferred. As the cleaning temperature,
5-80 degreeC is preferable and 20-70 degreeC is more preferable.
The washing time is preferably 20 minutes to 10 hours, more preferably 1 hour to 6 hours.

Further, in the present invention, P as described above is used.
Even if VA is used, PVA is generally inferior in melt fluidity at high temperature as compared with a general-purpose thermoplastic resin, and therefore, if necessary, polyethylene glycol, propylene glycol and its oligomer, butylene glycol and its Oligomer, polyglycerin derivative, glycerin derivative in which alkylene oxide such as ethylene oxide and propylene oxide is added to glycerin, derivative in which alkylene oxide such as ethylene oxide and propylene oxide is added to sorbitol, polyhydric alcohol such as pentaerythritol and its derivative , PO /
It is preferable to add a plasticizer such as an EO random copolymer to PVA at a ratio of 1 to 30% by mass, preferably 2 to 20% by mass, from the viewpoint of improving the spinnability. Then, in order to obtain good plasticization and spinnability, thermal decomposition hardly occurs in the fiberizing step, in order to obtain an alkylene oxide adduct of sorbitol,
Polyglycerin alkyl monocarboxylic acid ester, PO
It is preferable to add 1 to 30% by mass, preferably 2 to 20% by mass of a plasticizer such as / EO random copolymer, and particularly 1 to 30% of sorbitol ethylene oxide.
Compounds with a mole addition are preferred.

The thermoplastic polymer constituting the sea component of the composite fiber of the present invention is not particularly limited as long as it is a fiber-forming thermoplastic polymer, and examples thereof include polyolefin-based heavy polymers such as polyethylene, polypropylene and polymethylpentene. Polyester such as coalesced polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polypropylene terephthalate, polylactic acid, polyphenylene sulfide, polyarylate, polycarbonate, polymethylmethacrylate, polyvinyl chloride, polyvinylidene chloride, polyurethane, polybutadiene, hydrogenated polybutadiene , Polyisoprene, hydrogenated polyisoprene, a copolymer of an aromatic vinyl monomer and a diene monomer, or a hydrogenated product thereof, wherein the basic skeleton has an ethylene content of 25 to 70 mol%. Ethylene is a saponification degree of 95% or more -
Examples thereof include vinyl alcohol copolymers, polyamides such as Ny-6 and Ny-66, and semi-aromatic polyamides synthesized from aromatic dicarboxylic acids and aliphatic diamines. Especially in the polyester system, isophthalic acid,
Copolymerization with 5-sodium sulfoisophthalic acid, sebacic acid, adipic acid or the like is a preferred direction from the viewpoint of easy removal of the island component PVA. Further, an additive may be contained in the thermoplastic polymer constituting the sea component.

In the present invention, it is preferable to add fine particles to the thermoplastic polymer of the sea component in terms of quality stability. 0.5 to 0.5% of the fine particle inert material having an average particle size of 100 mμm or less
Contains 10% by weight. As the fine particles to be added, for example, silica sol, fine particle silica, alumina sol, fine particle alumina, ultrafine particle titanium oxide, calcium carbonate sol,
Fine-grained calcium carbonate, modified silica sol with improved dispersion stability, or a colloid of other fine-grained inert substances having a refractive index close to that of polyester fiber is used. If the fine particles are added in an amount of more than 10% by weight, the fiber forming processability becomes poor and it is not suitable.

The composite fiber of the present invention is a PVA as described above.
Is an island component and is not particularly limited as long as it is a spinning technology capable of forming a cross-sectional morphology in which a thermoplastic polymer is a sea component, and a system of a combination of polyester that does not gel with the PVA of the island component during heat melting. In this case, for example, a method by mixed spinning is possible, in which PVA as an island component and a thermoplastic polymer as a sea component are melt-kneaded by one extruder and then discharged from the same spinning nozzle and wound. It can be taken and made into fibers. In the method using composite spinning, PVA and polyester are melt-kneaded by different extruders, respectively, and then PVA is made an island component and the thermoplastic polymer is made a sea component, and the mixture is discharged from a sea-island type composite spinning nozzle. It can be rolled up and made into fibers.

The fiberizing conditions need to be set according to the combination of polymers and the composite cross-sectional shape, but it is desirable to mainly determine the fiberizing conditions in consideration of the following points. (1) Generally, PVA is a polymer that is inferior in melt fluidity at high temperature and self-crosslinks in the presence of a retention part and easily gels. Therefore, as much as possible, an extrusion zone of a polymer and a jet pack (assembly of composite spinning parts) It is important to make it difficult for the retention part to occur in the polymer fluidized part inside the body. (2) The spinneret temperature is Mp to Mp + 80, where Mp is the melting point of the polymer having the highest melting point among the polymers constituting the composite fiber.
℃ is preferable, shear rate (γ) 1,000 to 25,000 sec ^-1 ,
It is preferable to carry out spinning with a draft V10 to 500. (3) From the viewpoint of the combination of the polymers to be composited, it is possible to improve the spinning stability by combining the polymers whose melt viscosities are close to each other when measured by the spinneret temperature during spinning and the shear rate when passing through the nozzle. It is preferable from the aspect.

The melting point Tm of PVA in the present invention is the peak temperature of the main endothermic peak observed by a differential scanning calorimeter (DSC: TA3000 manufactured by Mettler). The shear rate (γ) is calculated by γ = 4Q / πr ³ when the nozzle radius is r (cm) and the polymer discharge amount per single hole is Q (cm ³ / sec). Further, the draft V is calculated by V = 5A · πr ² / 3Q when the take-up speed is A (m / min).

In producing the conjugate fiber of the present invention, if the spinneret temperature is lower than the melting point Tm of PVA, the PV
A cannot be spun because A does not melt. On the other hand, when the temperature exceeds Tm + 80 ° C., PVA is apt to cause thermal decomposition or gelation due to self-crosslinking, resulting in deterioration of spinnability. If the shear rate is lower than 1,000 sec ^-1 , thread breakage will occur easily,
If it is higher than 00 sec ^-1, the back pressure of the nozzle becomes high and the spinnability deteriorates. When the draft is lower than 10, the fineness unevenness becomes large and it becomes difficult to spin stably, and when the draft is higher than 500, the yarn is easily broken.

The yarn discharged from the spinning nozzle is wound at a high speed as it is without stretching, or is stretched if necessary.
Stretching is performed at a temperature equal to or higher than the glass transition point (Tg) at a breaking elongation (HDmax) × 0.55 to 0.9 times. Draw ratio is HD
If it is less than max × 0.55, a composite fiber having sufficient strength cannot be obtained stably, and if it exceeds HDmax × 0.9, yarn breakage tends to occur. Stretching may be carried out after being once wound after being discharged from the spinning nozzle, or may be carried out subsequent to the stretching. In the present invention, either may be adopted. Stretching is usually hot stretching and may be performed using any of hot air, hot plate, hot roller, water bath and the like. In the drawing step, the larger the absolute value of the draw ratio, the more easily fluffing and fiber breakage occur. Therefore, it is preferable to use the high-speed spinning to low-draw ratio fiberization conditions or the known high-speed spinning / winding only method.

The stretching temperature is appropriately set according to the complex combination polymer, but since the polyvinyl alcohol used in the present invention has a high crystallization rate, the unstretched yarn is considerably crystallized, and the plastic part of the crystalline portion is around Tg. Does not easily deform. Therefore, for example, in the case of composite with PET, even when contact heating drawing such as hot roller drawing is performed, drawing is performed at a relatively high temperature (about 70 to 100 ° C.) as a guide. In addition, when heat drawing is performed using a non-contact type heater such as a heating furnace or a heating tube, the temperature is further increased to 150
It is preferable to set the temperature condition to about 200 ° C.

However, in the present invention, as fiberizing conditions, the spinneret temperature is Tm to Tm + 80 ° C., the shear rate (γ) is 1,000 to 25,000 sec ⁻¹ , and the draft.
(V) It is important to spin at 10 to 500. .

The composite fiber of the present invention can control the shrinkage behavior of the PVA, which is an island component, when the PVA, which is an island component, is dissolved in water depending on the production conditions. When it is desired to keep the value low, it is desirable to subject the composite fiber to a heat treatment.
By performing the heat treatment, the rate of dissolution of PVA in water becomes slower, so that a feeling of swelling appears as a texture. Swelling and shrinking of PVA occur before water dissolution, and the difference in shrinkage between the sea component and PVA causes strain in the thermoplastic polymer of the sea component, and P
It is presumed that the sea component is released from the strain after the VA is dissolved and a bulge appears. This heat treatment may be carried out at the same time as the drawing in the fiberizing step involving drawing, or may be carried out separately from the drawing. It is possible to lower the maximum shrinkage rate of the hollow fiber obtained by dissolving the island component PVA by increasing the heat treatment temperature.
Since the dissolution temperature of A in water tends to be high, it is desirable to set the heat treatment conditions while looking at the balance with the maximum shrinkage ratio in the processing step of the composite fiber. Generally, the glass transition point of the island component PVA to (Tm It is preferable to set the conditions within the range of -10) ° C.

If the treatment temperature is lower than Tg, a sufficiently crystallized composite fiber cannot be obtained. For example, when the fabric is heat set, the shrinkage becomes large and the texture of the fabric is hardened, which is not preferable. . The processing temperature is (Tm-
When the temperature exceeds 10 ° C., the fibers are agglomerated, which is not preferable.

The heat treatment may be carried out by shrinking the stretched composite fiber. PV in water when shrinkage is added to the composite fiber
The shrinkage rate of the composite fiber until A dissolution is small. The applied shrinkage is preferably 0.01 to 5%, more preferably 0.1 to 5%, and particularly preferably 1 to 4%. Shrinkage of 0.01
If it is less than 10%, the effect of reducing the maximum shrinkage of the composite fiber when PVA is dissolved is not substantially obtained, and the applied shrinkage is 5
If it exceeds%, the composite fiber sags during the shrinking treatment and stable shrinkage cannot be applied.

In the present invention, the fact that PVA is “water-soluble” means that it dissolves at a temperature of 40 ° C. or higher irrespective of the length of time until dissolution. Then, by changing the type of PVA and the manufacturing conditions of the composite fiber, the melting temperature of the PVA island component in the present invention is 30 ° C to
Although it is possible to obtain a conjugate fiber having a temperature of 100 ° C., in order to balance all properties of practicality and water solubility,
It is preferable to use a composite fiber composed of a PVA island component having a melting temperature of 40 ° C. or higher.

The melting treatment temperature may be appropriately adjusted according to the melting temperature of PVA and the glass transition point in the Wet state of the thermoplastic polymer constituting the sea component of the composite fiber. Of course, the higher the treatment temperature, the longer the treatment time. Becomes shorter. When it is dissolved using hot water, if the glass transition point of the thermoplastic polymer serving as the sea component is 70 ° C. or higher, hot water treatment under high temperature and high pressure of 100 ° C. or higher is most preferable. Although soft water is usually used as the aqueous solution, it may be an alkaline aqueous solution, an acidic aqueous solution, or may contain a surfactant and the like.
In particular, when an alkaline aqueous solution is used, it is possible to dissolve and remove the PVA component and form pinholes at the same time.

When the composite fiber of the present invention is treated with hot water to dissolve and remove the PVA component, a nonionic surfactant,
A scouring agent containing an anionic surfactant or the like as a component and other additives may be included. The dissolution and removal of PVA by the hot water treatment may be performed on the composite fiber alone, or may be performed after the fiber structure containing the composite fiber is formed. The temperature and the treatment time during the hot water treatment include various factors such as the fineness of the composite fiber, the ratio of the island component in the composite fiber, the distribution state of the island component, the ratio of the thermoplastic polymer of the sea component, the type, and the morphology of the fiber structure. It can be adjusted appropriately according to the requirements of. The hot water treatment temperature is 60 ° C or higher, preferably 80 ° C or higher. As a method of hot water treatment,
Examples thereof include a method of immersing the composite fiber and the fiber structure in a hot water solution, and a method of applying a hot water solution to them by a method such as a pad or spray.

In the present invention, PVA is removed from the composite fiber as an aqueous solution by the hot water treatment as described above.
Such PVA has biodegradability and is decomposed into water and carbon dioxide when treated with activated sludge or buried in soil. Further, the PVA dissolved and removed is in the state of an aqueous solution,
Continuous treatment with activated sludge almost completely decomposes within 2 days to 1 month. From the viewpoint of biodegradability, the saponification degree of the fiber is 90 to 9
9.99 mol% is preferable, 92-99.98 mol% is more preferable, 93-99.97 mol% is especially preferable. The 1,2-glycol bond content of the fiber is 1.
0 to 3.0 mol% is preferable, 1.2 to 2.5 mol% is more preferable, and 1.3 to 1.9 mol% is particularly preferable.
When the 1,2-glycol bond amount of PVA is less than 1.0 mol%, not only the biodegradability of PVA deteriorates, but also the melt viscosity is too high and the spinnability of the conjugate fiber deteriorates. is there. When the 1,2-glycol bond content of PVA is 3.0 mol% or more, the thermal stability of PVA may deteriorate and the spinnability may decrease.

The hollow fiber of the present invention has a hollow structure and at the same time has a pinhole on the fiber surface. The means for forming the pinhole on the fiber surface is, for example, that the sea component is composed of polyester. If it is present, it may be treated with alkali such as caustic soda, but is not limited thereto. The treatment conditions for forming pinholes are: when treated with an aqueous solution of caustic soda, the concentration of caustic soda is 2 to 8% by mass, and the treatment temperature is 90 to 98 ° C.
It is preferable to perform the treatment so that the weight loss rate becomes 2 to 8%.
When the sea component is polyamide, acids such as formic acid and sulfuric acid,
In the case of polyolefin, the pinholes defined in the present invention can be formed by treating with hot xylene.

The hollow fibers of the present invention thus obtained are particularly taffeta, decin, georgette, crepe, processed yarn, twill because of their water absorbency, light weight, flexibility, opacity, and swelling feeling. Suitable for woven fabrics or knitted fabrics such as soft cloth, smooth, tricot. Furthermore, it can be used not only for clothing, but also for non-woven fabrics, medical applications, sanitary materials, and various living materials such as stuffing materials. It can also be used as an interior material for automobiles, a sound deadening material, and a vibration isolator as a fiber laminate. It is also possible to make paper. A major feature of the hollow fiber of the present invention is that a specific pinhole is formed on the fiber surface, so that even a long fiber can realize excellent water absorption. In the case of short fibers, water can penetrate into the hollow portion from the cut end surface of the fibers, but in the case of long fibers which are continuous fibers, water can enter and exit only from the fiber surface, so the present invention specifies The technical significance of pinholes is extremely large.

[0053]

EXAMPLES The present invention will now be specifically described with reference to Examples.
The present invention is not limited to these examples. The parts and% in the examples relate to mass unless otherwise specified.

[PVA Analysis Method] PVA analysis method was in accordance with JIS-K6726 unless otherwise specified. The modification amount is 500 MHz proton NMR (JEOL GX-5) using modified polyvinyl ester or modified PVA.
00) Determined by measurement with a device. The content of alkali metal ions was determined by the atomic absorption method.

The ratio of the amount of hydroxyl groups in three chains by PVA triad display was determined by the following measurement. After saponifying PVA to a saponification degree of 99.5 mol% or more, it was thoroughly washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days, and then dissolved in d6-DMSO, and then 500 MHz.
65 degreeC measurement was performed with the proton NMR (JEOL GX-500) apparatus. The peak derived from the hydroxyl group of the vinyl alcohol unit in PVA has a chemical shift of 4.05 p.
It appears in the region of 4.70 ppm from pm, and this integrated value is the vinyl alcohol unit amount (II). The central hydroxyl group of the 3-chain hydroxyl group according to the triad representation of PVA appears at 4.5 ppm for the isotacticity chain, 4.36 ppm for the heterotacticity chain, and 4.13 ppm for the syndiotacticity chain. The sum of the three integrated values is defined as the central hydroxyl group amount (I) of the three hydroxyl group chains by triad display. P of the present invention
The mole fraction of the central hydroxyl group of the 3-chain hydroxyl group in the triad notation with respect to the vinyl alcohol unit of VA is 1
It is represented by 00 × (I) / (II).

[Melting Point] The melting point of PVA was determined by using DSC (Mettler Co., TA3000) in nitrogen and at a heating rate of 10
PVA when the temperature was raised to 250 ° C. at a rate of 10 ° C./min, cooled to room temperature, and then raised to 250 ° C. at a rate of 10 ° C./min again.
The temperature at the peak top of the endothermic peak indicating the melting point of

[Measurement of pinhole part] Measurement was carried out by SEM photograph observation. Number: 5 mm in the length direction in the single fiber was set as one unit, the number of pinholes in the unit was counted, and the average value of the number that can be confirmed when observing a total of 20 units was shown. Note that the number of pinholes was counted only in the portion that appeared in the SEM photograph, not in the number of pinholes that might be present on the back side of the fibers not shown in the photograph. Length: Calculated by dividing the total length of all pinholes counted above by the total number of pinholes. Width: The total width of all pinholes counted above was divided by the total number of pinholes, and the value was divided by the diameter of single fiber.

[Hygroscopic rate] The mass (X) of the fiber after vacuum drying at 60 ° C. for about 7 hours and the fiber were left for 1 hour in an atmosphere consisting of a saturated aqueous solution of sodium nitrite (20 ° C. × 65 RH). The moisture absorption rate was calculated from the subsequent fiber mass (Y) by the following formula. Moisture absorption rate = {(Y−X) / X} × 100

[Water absorption rate] The water absorption rate was measured according to the JIS-L-1096 method.

[Evaluation of texture (lightness, texture)] The woven fabric was evaluated by 10 panelists and evaluated according to the following criteria. ◎: 9 or more people judged that the feeling of lightness, softness and swelling was excellent ○: 7-8 people judged that the feeling of lightness, softness and swelling were excellent △: 5-6 people feeling light , Judged to be excellent in both softness and bulge x: judged to be inferior in lightness, softness and bulge for 6 or more people

[Production of ethylene-modified PVA] In a 100 L pressure reactor equipped with a stirrer, nitrogen inlet, ethylene inlet and initiator addition inlet, 29.0 kg of vinyl acetate and 31.0 kg of methanol were charged, and the temperature was raised to 60 ° C. After heating 3
The system was replaced with nitrogen by bubbling nitrogen for 0 minutes. Next, ethylene was introduced and charged so that the reactor pressure became 5.9 kg / cm ² (5.8 × 10 ⁵ Pa). 2, as an initiator
A 2.8 g / L solution of 2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) dissolved in methanol was prepared, and bubbling with nitrogen gas was performed to substitute nitrogen. After adjusting the temperature inside the polymerization tank to 60 ° C., 170 ml of the above initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to make the reactor pressure 5.9 kg / cm ² (5.8 × 10 ⁵ Pa) and the polymerization temperature 60 ° C.
Maintained at 610 ml / hr using the above initiator solution.
Then, AMV was continuously added to carry out polymerization. After 10 hours, the polymerization was stopped by cooling when the polymerization rate reached 70%. After removing the ethylene by opening the reaction tank, nitrogen gas was bubbled to completely remove the ethylene. Then, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. To 200 g of a methanol solution of polyvinyl acetate adjusted to have a concentration of 50% by adding methanol to the obtained polyvinyl acetate solution (100 g of polyvinyl acetate in the solution), 46.5 g (in polyvinyl acetate) was added. Molar ratio (MR) to vinyl acetate unit
Saponification was carried out by adding an alkaline solution of 0.10) (10% methanol solution of NaOH). About 2 after adding alkali
The gelled system was crushed with a crusher in minutes, and allowed to stand at 60 ° C. for 1 hour to allow saponification to proceed.
0 g was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left standing and washed at room temperature for 3 hours. After the above washing operation was repeated 3 times, the PVA obtained by centrifugal deliquoring was allowed to stand in a dryer at 70 ° C. for 2 days to obtain dried PVA. The degree of saponification of the obtained ethylene-modified PVA was 98.4 mol%.
The content of sodium measured by an atomic absorption spectrophotometer using the solution of the modified PVA dissolved in an acid after ashing was 0.01 parts by mass with respect to 100 parts by mass of the modified PVA. In addition, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization is n-
Precipitation in hexane and reprecipitation by dissolving in acetone were repeated three times, and then dried under reduced pressure at 80 ° C. for 3 days to obtain purified polyvinyl acetate. The polyvinyl acetate was dissolved in DMSO-d6 and subjected to 500 MHz proton NMR (JEOL GX-
The content of ethylene was 8.4 mol% when measured at 80 ° C. using 500). The above methanol solution of polyvinyl acetate was saponified at an alkali molar ratio of 0.5, and the pulverized product was allowed to stand at 60 ° C. for 5 hours to proceed with saponification, followed by methanol soxhlet for 3 days, and then at 80 ° C. The product was dried under reduced pressure for 3 days to obtain a purified ethylene-modified PVA. The average degree of polymerization of the PVA was measured by the conventional method J
It was 330 when measured according to IS K6726. The 1,2-glycol bond content of the purified PVA and the content of hydroxyl groups in the 3-chain hydroxyl group were adjusted to 500 MHz proton N.
It was 1.50 mol% and 83%, respectively, when determined as described above from the measurement by the MR (JEOL GX-500) apparatus. Furthermore, 5 of the purified modified PVA
% Aqueous solution was prepared to form a cast film having a thickness of 10 μm. After the film was dried under reduced pressure at 80 ° C. for 1 day, the melting point of PVA was 208 ° C. as measured by the above-mentioned method using DSC (Mettler, TA3000).

Example 1 Using the modified PVA obtained above as an island component, 6 mol% of isophthalic acid containing 0.045% by mass of titanium oxide
Modified polyethylene terephthalate ([η] = 0.68,
(Abbreviated as IPA6coPET hereinafter) as a sea component, a PVA zone maximum temperature of 230 ° C., and a composite spinning component that does not cause melt retention of PVA as much as possible.
After spinning at 1800C and a spinning speed of 1800 m / min, the unstretched yarn was brought into contact with a heating roller at 83 ° C and a heating plate at 140 ° C, and stretched at a draw ratio of 2.3 times, as shown in Table 1. 83dtex / 2 with different fiber cross section and composite ratio
4f composite fiber was obtained.

Then, a plain woven fabric was prepared by using the composite fiber as a warp and a weft. The machine density is 95/25.
It was 4 mm and weft 86 threads / 25.4 mm. 80 in an aqueous solution containing the greige fabric at a rate of 2 g / l sodium carbonate
After immersing at 37 ° C for 30 minutes to desizing, presetting was performed at 170 ° C for about 40 seconds. Next, hot water treatment was performed with an aqueous solution containing 1 g / liter of Intol MT Conc (anion activator, manufactured by Meisei Chemical Co., Ltd.) at a bath ratio of 50: 1, a temperature of 120 ° C., and a time of 40 minutes. Furthermore, caustic soda 40 g / liter, bath ratio 1:
Alkali weight loss treatment was carried out by immersing in 30 aqueous alkali solution of 95 ° C. for 40 minutes. After that, stain under the following conditions,
A dry finishing set was carried out by a conventional method. Dyeing method: Dianix Red BN-SE (CI Disperse Red127) 5% omf Dispersion aid: Disper TL (Meisei Chemical Industry Co., Ltd.) 1 g / l pH adjusting agent: Ammonium sulfate 1 g / l Acetic acid (48%) 1 g / l bath Ratio: 1:30 Temperature: 120 ° C. × 60 minutes Reduction cleaning Hydrosulfide 1 g / liter Amylazine (Daiichi Kogyo Seiyaku Co., Ltd.) 1 g / liter NaOH 1 g / liter Bath ratio; 1:30 Temperature; 80 ° C. × 20 minutes

Table 2 shows the evaluation results of the fiberizing processability, the number of hollow fiber pinholes, the length, the width, the water absorption, the hygroscopicity, the lightweight feeling, and the feel of the obtained plain weave. The woven fabric composed of the porous hollow fibers defined in the present invention had extremely good water absorbency and light weight feeling, and had an excellent soft and swelling texture.

[0065]

[Table 1]

[0066]

[Table 2]

Examples 2 to 5 In the same manner as in Example 1 except that the fiber cross section, the number of islands, and the composite ratio were carried out under the conditions shown in Table 1, fiberization, woven fabric production,
An evaluation was performed. All the fabrics were excellent in water absorbency and light weight, and had an excellent soft and swelling texture (see Table 2).

Examples 6 to 9 As shown in Table 1, fiberization, woven fabric preparation and evaluation were carried out in the same manner as in Example 1 except that the modified species and modified amount of the island component were changed. All the fabrics were excellent in water absorbency and light weight, and had an excellent soft and swelling texture (see Table 2).

Examples 10 to 16 As shown in Table 1, fiberization, woven fabric production and evaluation were carried out in the same manner as in Example 1 except that the type of sea component polymer, fiber cross section, number of islands and composite ratio were changed. It was All the fabrics were excellent in water absorbency and light weight, and had an excellent soft and swelling texture (see Table 2).

[Brief description of drawings]

FIG. 1 is a fiber cross-sectional view showing a pinhole of a hollow fiber of the present invention.

FIG. 2 is a side view of a fiber showing a communication hole of the hollow fiber of the present invention.

Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) D06M 11/22 D06M 9/10 (72) Inventor Nobuhiro Koga 1621 Sakata, Kurashiki-shi, Okayama F-term (Kuraray Co., Ltd.) Reference) 4L031 AB06 AB11 BA08 BA14 DA00 DA08 4L035 BB31 DD03 EE20 4L041 AA07 BA04 BA05 BA16 CA44 DD11 DD14 EE05 EE14

Claims (12)

[Claims] 1. A porous hollow fiber having a number of hollow portions (α1) and a hollow ratio (α2) satisfying the following formulas (1) to (3), wherein the surface of the fibers is in the form of grooves communicating with the hollow portions or A porous hollow fiber characterized by the presence of striped pinholes. α1 ≧ 5 (1) 3 ≦ α2 ≦ 65 (2) 0.15 ≦ α1 × α2 / 100 ≦ 350 (3) 2. Groove-shaped or streak-shaped pinholes are present in the fiber axis direction on the fiber surface, and are 1 or more per 5 mm single fiber, 1 mm or less in length, and 1/2 or less in diameter of single fiber. 2. The porous hollow fiber according to claim 1, which is present and is formed at substantially non-uniform intervals. 3. The porous hollow fiber according to claim 1 or 2, wherein there is a communicating portion between the hollow portion communicating with the fiber surface and another hollow portion. 4. The porous hollow fiber according to claim 1, wherein the thermoplastic polymer is polyester, polyolefin or polyamide. 5. The porous hollow fiber according to claim 1, which is a substantially long fiber. 6. A fiber structure containing at least a part of the porous hollow fiber according to any one of claims 1 to 5. 7. A composite fiber comprising a thermoplastic polymer as a sea component and a water-soluble thermoplastic polyvinyl alcohol-based polymer as an island component, wherein the number of island parts (β
1) and the island area ratio (β2) satisfy the following formulas (4) to (6). β1 ≧ 5 (4) 3 ≦ β2 ≦ 65 (5) 0.15 ≦ β1 × β2 / 100 ≦ 350 (6) 8. The sea-island type according to claim 7, wherein the water-soluble thermoplastic polyvinyl alcohol is a modified polyvinyl alcohol containing 0.1 to 20 mol% of an α-olefin unit having 4 or less carbon atoms and / or a vinyl ether unit. Composite fiber. 9. The sea-island type composite fiber according to claim 8, which contains 4 to 15 mol% of ethylene units and / or propylene units as α-olefin units. 10. The sea-island type composite fiber according to any one of claims 7 to 9, wherein the thermoplastic polymer is polylactic acid. 11. A fiber structure containing at least a part of the composite fiber according to any one of claims 7 to 10. 12. The fiber structure according to claim 11 is treated with water to simultaneously dissolve and remove at least a part of the water-soluble thermoplastic polyvinyl alcohol-based polymer from the sea-island type composite fiber constituting the fiber structure. Alternatively, a method for treating a fiber structure, which comprises, after dissolution and removal, treating with a soluble solvent or a decomposable solvent of a thermoplastic polymer as a sea component to form the pinhole structure according to claim 1.