JP2002155426A - Conjugate fiber and method for producing hollow fiber using the conjugate fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow fiber having excellent lightweight properties, prevention of see-through clothing, swelling feeling, soft feeling, or the like, and a fiber structure comprising the fiber. SOLUTION: A fiber structure comprising a sea-island conjugate fiber composed of a thermoplastic polymer having >2% equilibrium moisture regain as a sea component and a water-soluble thermoplastic polyvinyl alcohol-based polymer as an island component is treated with water and at least a part of the water-soluble thermoplastic polyvinyl alcohol-based polymer is dissolved and removed from the conjugate fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conjugate fiber and a fiber structure containing the same, and a hollow fiber obtained from the conjugate fiber and a fiber structure containing the same. More specifically, the present invention relates to a hollow fiber which is excellent in lightness and transparency, and has a feeling of swelling and softness and has a good feeling, particularly a porous hollow fiber and a fiber structure thereof.

[0002]

2. Description of the Related Art Synthetic fibers such as polyesters and polyamides are widely used not only for clothing but also for industrial use due to their excellent physical and chemical properties, and have industrially important value. I have. However, these synthetic fibers have a single distribution of single-fiber fineness, and because of their high single-fiber fineness and simple cross-sectional shape, they can be used as natural fibers such as silk, cotton, and hemp. The texture and gloss are monotonous in comparison. Further, the above-mentioned synthetic fiber was inferior in lightness, and was cold, had a slimy feel and was of low quality. Therefore, in order to improve the above-mentioned drawbacks of synthetic fibers, it has been widely practiced to deform the cross-sectional shape of the synthetic fibers or hollow the fibers. Normally, irregular cross-section fibers and hollow fibers produced using a modified spinning nozzle or hollow spinning nozzle are deformed due to the surface tension of the resin in the molten state before spinning and take-up tension during spinning. There is a problem that the cross section collapses or the hollow part is easily collapsed, especially when trying to express a porous hollow shape,
Immediately after spinning, even if a porous hollow structure is imparted to the fiber, the porous hollow portion is crushed and disappears, or the ratio of the hollow portion is easily reduced, and a fiber having a large number of hollow portions can be obtained by such a method. Was virtually impossible.

On the other hand, Japanese Patent Application Laid-Open No. 7-316977 discloses an alkali-resistant polymer having an easily decomposable polymer as an island component and having a water absorption of 3% or more such as a polyamide or an ethylene-vinyl alcohol copolymer as a sea component. There has been proposed a technique in which a porous fiber is obtained by decomposing and removing the easily decomposable polymer by treating it with a hot alkali aqueous solution after forming the composite fiber by using the above method. However, as these problems, wastewater treatment of alkaline decomposition products is complicated, and a great problem remains from an environmental point of view. In addition, in this method, the number of hollow portions is limited, and there is a problem that if the area of the hollow portion is increased in order to increase the lightness, the hollow portion is easily crushed and the see-through prevention is insufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a hollow fiber and a fiber structure containing the same which are excellent in lightness, sheer prevention, swelling and softness. It is to provide. Another object of the present invention is to provide a conjugate fiber for producing such a hollow fiber without causing wastewater treatment and environmental problems, and further provide a method for producing a hollow fiber using the conjugate fiber. .

[0005]

That is, according to the present invention, a thermoplastic polymer having an equilibrium moisture content exceeding 2% is used as a sea component,
A conjugate fiber containing a water-soluble thermoplastic polyvinyl alcohol-based polymer as an island component, and the above-mentioned conjugate fiber is treated with water, and the water-soluble thermoplastic polyvinyl alcohol-based polymer is at least partially dissolved and removed from the conjugate fiber. A method for producing a hollow fiber. Still further, the present invention provides a fibrous structure characterized by treating a fiber structure containing the above-mentioned conjugate fiber with water, and dissolving and removing at least a part of a water-soluble thermoplastic polyvinyl alcohol-based polymer from the conjugate fiber. And a fibrous structure containing hollow fibers obtained by such treatment.

The term "fiber structure" as used in the present invention means not only a multifilament yarn, a spun yarn, a woven or knitted fabric, a nonwoven fabric, a paper, an artificial leather, a filling material, but also a multifilament yarn or a spun yarn composed solely of the conjugate fiber or hollow fiber of the present invention. , Natural fiber, semi-synthetic fiber,
Processed yarns such as blended yarns, blended yarns, twisted yarns, entangled yarns and crimped yarns with other synthetic fibers, interwoven fabrics, interwoven fabrics, fiber laminates, and clothing, living materials, and industrial materials composed of these ,
It also includes various end products such as medical supplies.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the conjugate fiber of the present invention, the sea component is composed of a thermoplastic polymer having an equilibrium moisture content exceeding 2%, and the island component is composed of a water-soluble thermoplastic polyvinyl alcohol-based polymer. It is important that the condition of the sea-island of the composite fiber is not particularly limited as long as such conditions are satisfied. The number of islands can be set according to the application, but the present invention is exerted when obtaining hollow fibers having a high hollow ratio or hollow fibers having a large number of hollow portions. The value of the number of islands is not particularly limited, but is preferably in the range of 5 to 1500, more preferably 20 to 1300, and still more preferably 30 to 1
The number is preferably 000, more preferably 30 to 600. If the number of islands is less than 5, the prevention of see-through is insufficient, and a problem arises in that the hollow portion is liable to be crushed by increasing the area of the hollow portion in order to increase the lightness. If the number of islands exceeds 1500, fiberization becomes difficult. The shape of each island component is not limited at all, and may be a circle, an ellipse, or another irregular shape. Further, the island component may be continuous or discontinuous in the fiber axis direction. When a representative example of the composite fiber of the present invention is shown by a cross-sectional view thereof,
For example, those shown in FIGS. 1 to 6 can be mentioned. The composite fiber of FIG. 1 has a form in which a small island component 2 made of a water-soluble thermoplastic polyvinyl alcohol-based polymer is surrounded by a sea component 1 made of a thermoplastic polymer having an equilibrium moisture content exceeding 2%. The composite fiber of FIG. 2 has a large island component 2 and a small island component 2 composed of a water-soluble thermoplastic polyvinyl alcohol polymer at the center of the fiber cross section, and a sea component 1 composed of a thermoplastic polymer having an equilibrium moisture content exceeding 2%. In FIG. 3, the shape of the many smaller island components 2 in FIG. 1 is an irregular shape that is not circular. 4 to 6 show a fiber cross-section having a triangular cross-section.

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 determined according to the number of hollow portions and the hollow ratio of the finally obtained hollow fiber. Can be changed. However, if the proportion of the island component is too small, the effect of reducing the weight as the hollow fiber is not sufficiently exhibited, while if the proportion of the hollow portion is too large, the hollow fiber has practical fiber physical properties. Island: sea = 2: 98-6 preferably
The ratio is preferably 5:35, more preferably 5:95 to 60:40. The cross-sectional form of the conjugate fiber is not particularly limited. In addition to the circular cross-sections shown in FIGS. 1 to 3, for example, flat, elliptical, triangular (FIGS. 4, 5, 6) to octagons such as octagons,
An arbitrary shape such as a T-shape or a multi-leaf shape such as a 3 to 8 lobe shape can be adopted. Further, the conjugate fiber of the present invention can contain optional additives such as a fluorescent whitening agent, a stabilizer, a flame retardant, and a coloring agent, if necessary.

Next, the water-soluble thermoplastic polyvinyl alcohol-based polymer (hereinafter sometimes abbreviated simply as PVA) used for the island component of the conjugate 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, a modified polyvinyl alcohol having a functional group introduced by copolymerization, terminal modification, and post-reaction.

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

The degree of polymerization (P) of PVA is determined according to JIS-K67.
26 is measured. That is, it is obtained by the following equation from the intrinsic viscosity [η] (dl / g) measured in water at 30 ° C. after re-saponification and purification of PVA. P = ([η] × 10 ³ /8.29) ^{(1 / 0.62) When the} degree of polymerization is in 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%, further 94 to 99.9.
7 mol% is preferable, and 96 to 99.96 mol% is particularly preferable. When the degree of saponification is less than 90 mol%, the thermal stability of PVA is poor, and satisfactory melt spinning may not be performed due to thermal decomposition or gelation. In addition, the water solubility of PVA is reduced depending on the type of a copolymerized monomer described below. May be. On the other hand, PVA having a degree of saponification of more than 99.99 mol% tends to have low solubility and cannot be produced stably, making stable fiber formation difficult.

Further preferred PVAs for use in the present invention
Means that the molar fraction of the central hydroxyl group of three hydroxyl groups in the triad display with respect to the vinyl alcohol unit is 70 to
It is preferable that the melting point is 99.9 mol%, the melting point is 160 ° C to 230 ° C, and the alkali metal ion is contained in an amount of 0.0003 to 1 part by mass in terms of sodium ion with respect to 100 parts by mass of PVA.

In the present invention, the central hydroxyl group of the triad of the hydroxyl group in polyvinyl alcohol triad is defined as a 500 MHz proton NMR (JEOL GX-500) apparatus in a d6-DMSO solution of PVA at 65 ° C.
It means the peak (I) reflecting the tacticity of the triad of the hydroxyl proton by measurement. Peak (I) is the sum of the triad-represented isotacticity (4.54 ppm), heterotacticity (4.36 ppm) and syndiotacticity (4.13 ppm) of the hydroxyl group of PVA, Since the peak (II) of the hydroxyl group in the vinyl alcohol unit of the formula (1) appears in the chemical shift range of 4.05 ppm to 4.70 ppm, the mole fraction of the central hydroxyl group of the three hydroxyl groups in triad notation with respect to the vinyl alcohol unit of the present invention is: It is represented by 100 × (I) / (II).

Hydroxyl group 3 by triad display of PVA
When the content of the central hydroxyl group in the chain is less than 70 mol%, the crystallinity of the polymer is reduced and the fiber strength is reduced, and at the same time, the fibers may be stuck during melt spinning and cannot be unwound after winding. is there. The content of the central hydroxyl group of three hydroxyl groups by the triad display of PVA is 99.9 mol%.
In larger cases, the melting point of the polymer is high and the melt spinning temperature needs to be raised.As a result, the thermal stability of the polymer during melt spinning is poor, and decomposition, gelation, and polymer coloring occur. Cheap.

Further, the PVA of the present invention is an ethylene-modified PVA.
In the case of VA, the effects of the present invention are further enhanced by satisfying the following expression. -1.5 × Et + 100 ≧ molar fraction ≧ −Et + 85 Here, the molar fraction (unit: mol%) represents the molar fraction of the central hydroxyl group of three hydroxyl groups in triad notation with respect to the vinyl alcohol unit, and Et is Indicates the ethylene content (unit: mol%) contained in the vinyl alcohol-based polymer.

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

In the present invention, the amount of P is controlled by controlling the amount of the central hydroxyl group in the three hydroxyl groups of the polyvinyl alcohol.
Various properties related to water such as water solubility and hygroscopicity of VA, properties related to fibers such as strength, elongation and elastic modulus, and properties related to melt spinning properties such as melting point and melt viscosity can be controlled. This is presumably because the central hydroxyl group of the triad of triads is rich in crystallinity, thereby exhibiting the characteristics of PVA.

Melting point (Tm) of PVA used in the present invention
Is preferably 160 to 230 ° C., and 170 to 2
27 ° C is more preferable, 175 to 224 ° C is further preferable, and 180 to 220 ° C is particularly preferable. 160 melting point
If the temperature is lower than ℃, the crystallinity of PVA is reduced, the fiber strength of the conjugate fiber is lowered, and at the same time, the heat stability of the conjugate fiber is deteriorated, and the fiber may not be formed into fibers. On the other hand, the melting point is 2
If the temperature exceeds 30 ° C., the melt spinning temperature becomes high, and the spinning temperature and the decomposition temperature of PVA become close to each other, so that it may not be possible to stably produce a composite fiber composed of PVA and another thermoplastic polymer. The melting point of PVA was determined by heating the sample to 250 ° C. at a rate of 10 ° C./min in nitrogen using DSC.
It means the temperature at the peak top of the endothermic peak indicating the melting point of PVA when cooled to room temperature and heated again to a heating rate of 10 ° C./250° C.

The PVA used in the present invention is obtained by saponifying a vinyl ester unit of a vinyl ester polymer. Vinyl compound monomers for forming vinyl ester units include 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 among them, vinyl acetate is preferred from the viewpoint of obtaining PVA.

The PVA used in the present invention may be a homopolymer or a modified PVA into which a copolymerized unit is introduced. From the viewpoints of melt spinnability, water solubility, and fiber properties, the copolymer is preferably a copolymer. It is preferable to use a modified polyvinyl alcohol into which a unit has been introduced. Examples of the type of the comonomer include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene, acrylic acid and salts thereof, methyl acrylate, ethyl acrylate, and n-acrylate. Acrylates such as propyl and i-propyl acrylate; methacrylic acid and its salts; methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate and i-propyl methacrylate; acrylamide; Acrylamide derivatives such as methylacrylamide and N-ethylacrylamide, methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide, 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
-Propanediol vinyl ether, hydroxy group-containing vinyl ethers such as 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, 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 -Ole, hydroxy-containing α-olefins such as 3-methyl-3-buten-1-ol, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or itaconic anhydride Having a carboxyl group derived from etc .; Nsuruhon acid, allylsulfonic acid, methallyl sulfonic acid, 2-acrylamido-2
A monomer having a sulfonic acid group derived from methylpropanesulfonic acid or the like; 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, 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 and 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-decene-1-ol and 3-methyl-3-buten-1-ol are preferred.

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

The PVA used in the present invention includes known methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or in a solvent such as an alcohol is usually employed. Examples of the alcohol used as a 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,
4-dimethyl-valeronitrile), benzoyl peroxide,
Known initiators such as an azo initiator such as n-propyl peroxycarbonate and a peroxide initiator are exemplified. The polymerization temperature is not particularly limited.
A range of 50 ° C. is appropriate.

The content ratio of alkali metal ions in the PVA used in the present invention is preferably 0.0003 to 1 part by mass, and preferably 0.0003 to 0.8 part by mass with respect to 100 parts by mass of PVA in terms of sodium ions. Part is more preferable, 0.0005 to 0.6 part by mass is more 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 solubility in water may not be exhibited and undissolved matter may remain. When the content of the alkali metal ion is more than 1 part by mass, decomposition and gelation at the time of melt spinning may be remarkable, and the fiber may not be formed. Examples of the alkali metal ion include a potassium ion and a sodium ion.

In the present invention, the method for incorporating a specific amount of alkali metal ions into PVA is not particularly limited.
A method of adding a compound containing an alkali metal ion after polymerizing VA, and a method of saponifying a polymer of a vinyl ester in a solvent, using an alkali substance containing an alkali ion as a saponification catalyst to thereby form an alkali metal ion in PVA. And PVA obtained by saponification
Is washed with a washing liquid to control the content of alkali metal ions contained in PVA. The latter is more preferable. The content of the alkali metal ion can be determined by an atomic absorption method.

The alkaline substance used as the saponification catalyst includes potassium hydroxide or sodium hydroxide. The molar ratio of the alkaline substance used in the saponification catalyst is preferably from 0.004 to 0.5, more preferably from 0.005 to 0.05, based on the vinyl acetate unit. The saponification catalyst may be added all at once in the early stage 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,
Dimethylformamide and the like. Among these solvents, methanol is preferable, and the water content is 0.001 to 0.001.
Methanol controlled at 1% by mass is more preferable, methanol controlled at a water content of 0.003 to 0.9% by mass is more preferable, and methanol controlled at a water content of 0.005 to 0.8% by mass is particularly preferable. . Examples of the washing liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, and water, and among them, methanol, methyl acetate, and water alone or a mixed liquid are more preferable. The amount of the cleaning solution is set so as to satisfy the content ratio of the alkali metal ion, and is usually preferably 300 to 10000 parts by mass with respect to 100 parts by mass of PVA.
5,000 parts by mass is more preferred. As the washing temperature,
5-80 degreeC is preferable and 20-70 degreeC is more preferable.
The washing time is preferably from 20 minutes to 10 hours, more preferably from 1 hour to 6 hours.

Also, in the present invention, P
Even if VA is used, PVA is generally inferior in melt fluidity at high temperatures as compared with general-purpose thermoplastic resins. Therefore, if necessary, polyethylene glycol, propylene glycol and its oligomer, butylene glycol and its Oligomers, polyglycerin derivatives, glycerin derivatives in which alkylene oxides such as ethylene oxide and propylene oxide are added to glycerin, sorbitol, derivatives in which alkylene oxides such as ethylene oxide and propylene oxide are added, polyhydric alcohols such as pentaerythritol and derivatives thereof , PO /
It is preferable to mix 1 to 30% by mass, preferably 2 to 20% by mass of a plasticizer such as an EO random copolymer with PVA from the viewpoint of improving spinnability. Then, in the fiberization step, thermal decomposition hardly occurs, and in order to obtain good plasticization and spinnability, an alkylene oxide adduct of sorbitol, polyglycerin alkyl monocarboxylate,
It is preferable to mix a plasticizer such as a PO / EO random copolymer in an amount of 1 to 30% by mass, preferably 2 to 20% by mass.
Compounds with molar addition are preferred.

The thermoplastic polymer constituting the sea component of the conjugate fiber of the present invention is not particularly limited as long as it has an equilibrium moisture content of more than 2%.
Polyamide such as ethylene-vinyl alcohol copolymer or Ny-6 or Ny-66 having a saponification degree of 5% to 70% by mole and a semiaromatic polyamide synthesized from an aromatic dicarboxylic acid and an aliphatic diamine. (PA-9T, PA-
9MT). These polymers may be modified by copolymerization or the like or may contain additives as long as the equilibrium moisture content is within a range satisfying the requirements of the present invention.

The conjugate fiber of the present invention comprises the PVA as described above.
Is an island component, and is not particularly limited as long as it is a spinning technique capable of forming a cross-sectional form using a thermoplastic polymer having an equilibrium moisture content of more than 2% as a sea component.
In a system of a combination of a polymer which does not react with and gelate, for example, a mixed spinning method is possible, and PVA as an island component and a thermoplastic polymer as a sea component are mixed with 1
It can be melt-kneaded by two extruders and subsequently discharged from the same spinning nozzle to be wound and fiberized. In the method by composite spinning, PVA and a thermoplastic polymer are melt-kneaded by different extruders, respectively.
VA can be turned into an island component, and the thermoplastic polymer can be turned into a sea component, discharged from a sea-island composite spinning nozzle, wound up, and fiberized.

The fiberization conditions need to be set according to the combination of the polymers and the composite cross-sectional shape, but it is desirable to determine the fiberization conditions mainly by paying attention to the following points. (1) In general, PVA is inferior in melt fluidity at high temperatures, and is a polymer that easily self-crosslinks and gels due to the presence of a stagnant portion. It is important that a stagnant portion hardly occurs in the polymer flowing portion inside the body). (2) The spinneret temperature is Mp to Mp + 80 when the melting point of a polymer having a high melting point among the polymers constituting the conjugate fiber is Mp.
° C is preferable, and the shear rate (γ) is 1,000 to 25,000 sec ^-1 ,
It is preferable to spin with a draft V10 to 500. (3) From the viewpoint of the combination of the composite polymers, the composite spinning is performed by combining the polymers having similar melt viscosities as measured by the die temperature during spinning and the shear rate at the time of passing through the nozzle. It is preferable from the viewpoint.

In the present invention, the melting point Tm of PVA is a peak temperature of a main endothermic peak observed by a differential scanning calorimeter (DSC: for example, TA3000 manufactured by Mettler). The shear rate (γ) is calculated as γ = 4Q / πr ³ when the nozzle radius is r (cm) and the amount of polymer discharged per single hole is Q (cm ³ / sec). 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, when the spinneret temperature is lower than the melting point Tm of PVA,
A cannot be spun because A does not melt. On the other hand, if the temperature exceeds Tm + 80 ° C., the PVA tends to gel due to thermal decomposition or self-crosslinking, so that the spinnability decreases. In addition, if the shear rate is lower than 1,000 sec ^-1 , the thread is easily broken, and the
If it is higher than 00 sec ^-1, the back pressure of the nozzle will be high, and the spinnability will be poor. When the draft is lower than 10, the fineness unevenness becomes large and it becomes difficult to stably spin. When the draft is higher than 500, the yarn is easily broken.

The yarn discharged from the spinning nozzle is wound up at high speed without stretching or stretched as required.
Stretching is performed at a temperature equal to or higher than the glass transition point (Tg) at a stretching ratio of elongation at break (HDmax) × 0.55 to 0.9 times. Stretching ratio is HD
If it is less than max × 0.55, a conjugate fiber having sufficient strength cannot be obtained stably, and if it exceeds HDmax × 0.9, it is easy to break the yarn. The stretching may be carried out once after being wound up after being discharged from the spinning nozzle, or may be carried out subsequent to the stretching. In the present invention, any method may be used. The stretching is usually performed by hot stretching, and may be performed using any of hot air, a hot plate, a hot roller, a water bath and the like. The stretching temperature is appropriately set according to the composite combination polymer.

In the stretching step, the larger the absolute value of the stretching ratio, the more easily fluffing and yarn breakage occur.
Fiberization conditions with low draw ratio or known high-speed spinning
A method using only winding is preferable.

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

The cross-sectional shape of the conjugate fiber in the present invention is not particularly limited. The shape of the spinning nozzle can be a perfect circle, hollow or irregular cross-section. To a perfect circle.

The conjugate fiber of the present invention can control the shrinkage behavior of the conjugate fiber upon dissolution of PVA, which is an island component, in water depending on the production conditions. When it is intended to reduce the value, it is desirable that the conjugate fiber be subjected to a heat treatment.
This heat treatment may be performed simultaneously with the drawing or may be performed separately from the drawing in the fiberizing step involving the drawing. When the heat treatment temperature is increased, the maximum shrinkage rate of the hollow fiber obtained by dissolving the island component PVA can be lowered. However, the dissolution temperature of the island component PVA in water tends to increase. It is desirable to set the heat treatment conditions while observing the balance with the maximum shrinkage in the processing step, and the glass transition point of the island component PVA is approximately
It is preferable to set conditions within the range of (Tm-10) ° C.

The heat treatment may be performed by applying shrinkage to the drawn composite fiber. When shrinking composite fiber, PV in water
The shrinkage of the composite fiber until A dissolution is reduced. The applied shrinkage is preferably 0.01 to 5%, more preferably 0.1 to 0.5%, and particularly preferably 1 to 4%. When the applied shrinkage is 0.01% or less, the effect of reducing the maximum shrinkage rate of the conjugate fiber upon dissolution of PVA is not substantially obtained. It is not possible to add shrinkage stably due to sagging.

In the present invention, the fact that PVA is "water-soluble" means that PVA is dissolved at a temperature of 40 ° C. or higher regardless of the length of time required for dissolution. By changing the type of PVA and the production conditions of the composite fiber, the dissolution temperature of the PVA island component is 30 ° C. or more in the present invention.
Although it is possible to obtain a composite 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 comprising a PVA island component having a melting temperature of 40 ° C. or higher.

The melting temperature may be appropriately adjusted according to the melting temperature of PVA or the glass transition point of the thermoplastic polymer constituting the sea component of the conjugate fiber in the wet state. Becomes shorter. In the case of dissolving using hot water, if the glass transition point of the thermoplastic polymer serving as a sea component is 70 ° C. or higher, hot water treatment at a high temperature and high pressure of 100 ° C. or higher is most preferable. The aqueous solution is usually soft water, but may be an alkaline aqueous solution or an acidic aqueous solution, or may contain a surfactant or the like.

In dissolving and removing the PVA component by subjecting the conjugate fiber of the present invention to hot water treatment, a nonionic surfactant,
A scouring agent containing an anionic surfactant or the like as a component, other additives, or the like may be included. The dissolution and removal of PVA by the above-mentioned hot water treatment may be performed on the conjugate fiber alone, or may be subjected to the hot water treatment after forming a fibrous structure containing the conjugate fiber. The temperature and the processing time during the hot water treatment vary with the fineness of the conjugate fiber, the proportion of the island component in the conjugate fiber, the distribution state of the island component, the ratio, type, and form of the thermoplastic polymer of the sea component. 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 of the method include immersing the conjugate fiber and the fibrous structure in a hot water liquid, or applying a hot water liquid to them by a method such as padding or spraying.

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

In the present invention, the PVA in the composite fiber is selectively removed by the hot water treatment, so that the equilibrium moisture content is 2%.
% Of a hollow fiber made of a thermoplastic polymer is produced. However, since PVA as an island component is excellent in hygroscopicity and moisture retention, this property is applied, and PVA is used depending on the purpose (use).
It is also possible to partially dissolve and remove A to form voids and to leave island component PVA at the same time.

The area ratio (hollow ratio) of the hollow portion in the hollow fiber of the present invention is preferably 2% or more, and if it is lower than 2%, light weight, bulkiness, heat retention, swelling and the like are sufficiently exhibited. May not. Therefore, the area ratio of the hollow portion is preferably set to 5% or more. If the area ratio of the hollow portion is too large, the fiber strength becomes insufficient.
It is desired that the area ratio is 0% or less, more preferably 50% or less.

The hollow fiber of the present invention obtained in this manner is particularly suitable for taffeta, decine, georgette, crepe, processed, etc. due to its light weight, water absorption, heat retention, flexibility, opacity, and feeling of swelling. It is suitable for forming a woven fabric such as a thread or a twill, or a knitted fabric such as a sheet of cloth, smooth, or tricot. Furthermore, it can be used not only for clothing but also for non-woven fabrics, medical applications, sanitary materials, various living materials as a filling material, and as a fiber laminate, it can be used as an interior material for automobiles, noise reduction materials, and vibration damping materials. And papermaking can also be performed.

[0047]

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

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

The 1,2-glycol bond content was measured by the method described above. The ratio of the amount of hydroxyl groups in the three chains by triad display of the PVA of the present invention was determined by the following measurement. After saponification of PVA to a saponification degree of 99.5 mol% or more, methanol was sufficiently washed, and then dissolved in d6-DMSO using PVA dried at 90 ° C. under reduced pressure for 2 days.
500 MHz proton NMR (JEOL GX-50
0) The measurement was performed at 65 ° C. by the apparatus. A peak derived from a hydroxyl group of a vinyl alcohol unit in PVA appears in a region of 4.05 ppm to 4.70 ppm of chemical shift,
This integrated value is defined as the vinyl alcohol unit amount (II). The center hydroxyl group of the three hydroxyl groups in the triad display of PVA is 4.5 ppm in the case of isotacticity chain and 4.3 ppm in the case of heterotacticity chain, respectively.
3. 6 ppm and 4 for syndiotacticity linkage.
Appears at 13 ppm. The sum of the three integrated values is defined as the central hydroxyl group amount (I) of three hydroxyl groups in triad display. The molar fraction of the central hydroxyl group of three hydroxyl groups in the PVA of the present invention with respect to the vinyl alcohol unit is represented by 100 × (I) / (II).

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

[Removal rate of PVA in hot water] With respect to the conjugate fiber of the present invention, when the melting temperature of PVA constituting the conjugate fiber in hot water is defined as Tα (° C), a temperature of (Tα + 40) ° C The treatment with hot water for 40 minutes, the washing with water for 5 minutes, and the mass loss after drying were taken as the PVA removal rate. Tα can be determined, for example, as a temperature at which a fiber of PVA alone is applied with a load of 2.2 mg / decite, suspended in water, raised in water temperature, and cut.

[Measurement of Area Ratio of Hollow Portion] A cross section of the hollow fiber yarn was taken by SEM photograph, and the cross section was calculated from the area of the porous hollow portion and the entire area of the hollow fiber.

[Evaluation of fiberization processability] The following evaluation was performed depending on how many times the fiber was cut when spinning 100 kg of fiber. ○: Within 3 times / 100kg △: 4 to 7 times / 100kg ×: 8 times or more / 100kg

[Evaluation of Hand of Woven Fabric] Lightweight feeling ○: Lightweight feeling ×: Lack of lightness See-through prevention property ○: Rich in see-through prevention property X: Lack of see-through prevention property

[Production of Ethylene-Modified PVA] 29.0 kg of vinyl acetate and 31.0 kg of methanol were charged into a 100-L pressure reactor equipped with a stirrer, a nitrogen inlet, an ethylene inlet and an initiator inlet, and heated to 60 ° C. 3 after heating
The system was replaced with nitrogen by bubbling nitrogen for 0 minutes. Then, ethylene was introduced and charged so that the pressure in the reaction tank was 5.2 kg / cm ² (5.3 × 10 ⁵ Pa). 2, as an initiator
A solution of 2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) in methanol at a concentration of 2.8 g / L was prepared and subjected to nitrogen replacement by bubbling with nitrogen gas. After adjusting the internal temperature of the polymerization tank to 60 ° C., 170 ml of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to increase the reaction tank pressure to 5.2 kg / cm ² (5.3 × 10 ⁵ Pa) and the polymerization temperature to 60 ° C.
610 ml / hr using the above initiator solution.
AMV was continuously added to carry out polymerization. After 10 hours, when the polymerization rate reached 70%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled through to completely remove ethylene. Then, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. Methanol was added to the obtained polyvinyl acetate solution to add 200 g of a methanol solution of polyvinyl acetate (100 g of polyvinyl acetate in the solution) adjusted to have a concentration of 50%. Molar ratio (MR) to vinyl acetate unit
(0.10) of an alkaline solution (a 10% methanol solution of NaOH) was added for saponification. About 2 after alkali addition
After the system was gelled in minutes, the mixture was pulverized with a pulverizer and left at 60 ° C. for 1 hour to progress saponification.
0 g was added to neutralize the remaining alkali. After confirming the completion of the neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration and washed at room temperature for 3 hours. After repeating the above washing operation three times, the PVA obtained by centrifugal dewatering was left in a dryer at 70 ° C. for 2 days to obtain dry PVA. The saponification degree of the obtained ethylene-modified PVA was 98.5 mol%.
After the modified PVA was incinerated, the content of sodium measured by an atomic absorption spectrophotometer using a substance dissolved in an acid was 0.01 part by mass with respect to 100 parts by mass of the modified PVA. Further, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization was added to n-
After performing reprecipitation purification by precipitation in hexane and dissolution in acetone three times, drying under reduced pressure at 80 ° C. for 3 days was performed to obtain purified polyvinyl acetate. The polyvinyl acetate was dissolved in DMSO-d6, and 500 MHz proton NMR (JEOL GX-
500) at 80 ° C., the ethylene content was 8.4 mol%. After saponifying the above methanol solution of polyvinyl acetate at an alkali molar ratio of 0.5, the pulverized product was left at 60 ° C. for 5 hours to progress saponification, and then methanol soxhlet was carried out for 3 days, and then 80 ° C. And dried under reduced pressure for 3 days to obtain a purified ethylene-modified PVA. The average degree of polymerization of the PVA was determined by a conventional method, J
It was 330 when measured according to IS K6726. The amount of the 1,2-glycol bond and the content of the hydroxyl group of three hydroxyl groups of the purified PVA were 500 MHz
It was 1.7 mol% and 83%, respectively, as determined from the measurement using an MR (JEOL GX-500) apparatus as described above. 5% of the purified modified PVA
The aqueous solution was adjusted to prepare 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 measured using DSC (Mettler, TA3000) according to the method described above.
12 ° C.

Example 1 Using the modified PVA obtained above as an island component, an ethylene-vinyl alcohol copolymer having an ethylene content of 44 mol% and a saponification degree of 95% or more (“EVAL” (registered trademark)) Is used as a sea component, and the zone maximum temperature of PVA is 2
After spinning at a spinning temperature of 240 ° C. and a spinning speed of 1200 m / min using a composite spun component in which PVA melt stagnation does not occur as much as possible, the undrawn yarn is heated at 65 ° C. with a hot roller and 12 ° C.
It was brought into contact with a hot plate at 0 ° C. and stretched at a draw ratio of 2.5 to obtain a composite fiber of 83 dtex / 24f having a fiber cross section and a composite ratio as shown in Table 1.

Next, a plain woven fabric was prepared using the composite fiber as a warp and a weft. Its green density is 95/25.
4 mm, 86 wefts / 25.4 mm. Put the greige fabric in an aqueous solution containing sodium carbonate at a rate of 2 g / liter.
After immersion at 0 ° C. for 30 minutes to desizing, pre-setting was performed at 150 ° C. for about 40 seconds. Next, hot water treatment was performed with an aqueous solution containing 1 g / liter of Intor MT Conc (anionic activator, manufactured by Meisei Chemical Co., Ltd.) at a bath ratio of 50: 1, at a temperature of 90 ° C. for 60 minutes. After washing sufficiently with water, a plain fabric having a PVA removal ratio and a hollow area ratio shown in Table 1 was obtained. Table 2 shows the evaluation results of the woven fabric.

[0058]

[Table 1]

[Table 2]

From the results shown in Table 2 above, it was found that the woven fabric comprising the porous hollow fibers defined by the present invention had a very good lightness and anti-transparency, and had a soft, bulging and excellent texture.

Examples 2 and 3 Fiberization, fabric preparation and evaluation were performed in the same manner as in Example 1 except that the composite ratio, the removal rate of island components, and the like were changed. Each of the fabrics was excellent in lightness and anti-sheer properties, and had a soft and swelling texture.
(See Tables 1 and 2).

Examples 4 to 6 As shown in Table 1, fiberization, fabric preparation and evaluation were performed in the same manner as in Example 1 except that the fiber cross section, the number of islands, the composite ratio, the island component removal rate, and the like were changed. Done. Each of the fabrics was excellent in lightness and anti-see-through properties, had swelling, and had a very soft feeling of tension (see Tables 1 and 2).

Examples 7 and 8 Ethylene-modified amount of island component, 1,2-glycol content,
Except that the degree of saponification was changed as shown in Table 1, fibrillation, preparation of a woven fabric, and evaluation were performed in the same manner as in Example 1. All fabrics were excellent in lightweight feeling and sheer-prevention property, had swelling, and had a very soft touch (Table 1,
2).

Examples 9 and 10 Fiberization and production of a woven fabric were carried out in the same manner as in Example 1 except that the denatured species, denaturation amount, and 1,2-glycol content of the island component were changed as shown in Table 1. An evaluation was performed. All the fabrics were excellent in lightweight feeling and see-through prevention, had swelling, and had a very soft touch (see Tables 1 and 2).

Examples 11 to 13 Fiberization, fabric preparation and evaluation were carried out in the same manner as in Example 1 except that the kind of the sea component polymer, the composite ratio, the island component removal rate, etc. were changed as shown in Table 1. Was. All of the fabrics were excellent in lightweight feeling and see-through prevention, and had a soft, bulging and excellent texture (see Tables 1 and 2).
Ny-6 in Table 1 indicates nylon 6, and PA-9
T represents a semi-aromatic polyamide synthesized from terephthalic acid and 1,9-nonanediamine, and PA-9MT represents a semi-aromatic polyamide synthesized from terephthalic acid and 2-methyl-1,8-octanediamine. Show.

Examples 14 to 16 Fiberization, fabric preparation and evaluation were carried out in the same manner as in Example 13 except that the fiber cross section, the number of islands, etc. were changed as shown in Table 1. Both fabrics are excellent in lightness and sheer prevention,
It had a soft, swelling and excellent texture (see Tables 1 and 2).

[Brief description of the drawings]

FIG. 1 is a fiber cross-sectional view showing an example of a cross-sectional shape of a conjugate fiber of the present invention.

FIG. 2 is a fiber cross-sectional view showing an example of a cross-sectional shape of the conjugate fiber of the present invention.

FIG. 3 is a fiber cross-sectional view showing an example of a cross-sectional shape of the conjugate fiber of the present invention.

FIG. 4 is a fiber cross-sectional view showing an example of a cross-sectional shape of the conjugate fiber of the present invention.

FIG. 5 is a fiber cross-sectional view showing an example of a cross-sectional shape of the conjugate fiber of the present invention.

FIG. 6 is a fiber cross-sectional view showing an example of a cross-sectional shape of the conjugate fiber of the present invention.

[Explanation of symbols]

 1: Sea component 2: Island component

Continued on the front page (72) Inventor Norihiro Koga 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Masao Kawamoto 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture F-Term Co., Ltd. F-term (reference) 4L031 AA16 AB06 AB11 BA11 CA01 DA00 DA01 DA05 4L041 AA07 AA20 BA04 BA05 BA14 BA16 BA17 BA37 BC06 BD07 BD11 BD14 BD15 BD20 CA21 CA30 CA44 CA55 CA61 DD01 DD11 DD14 DD15 EE14 EE20

Claims (7)

[Claims] 1. A conjugate fiber comprising a thermoplastic polymer having an equilibrium moisture content exceeding 2% as a sea component and a water-soluble thermoplastic polyvinyl alcohol-based polymer as an island component. 2. The conjugate fiber according to claim 1, wherein the water-soluble thermoplastic polyvinyl alcohol is a modified polyvinyl alcohol containing 0.1 to 20 mol% of α-olefin units and / or vinyl ether units having 4 or less carbon atoms. . 3. The conjugate fiber according to claim 2, which contains 4 to 15 mol% of ethylene units and / or propylene units as α-olefin units. 4. The conjugate fiber according to claim 1, wherein the content of 1,2-glycol bonds in the water-soluble thermoplastic polyvinyl alcohol is 1.0 to 3.0 mol%. 5. The conjugate fiber according to claim 1, wherein the thermoplastic polymer is an ethylene-vinyl alcohol copolymer or a polyamide having an equilibrium moisture content of more than 2%. 6. The conjugate fiber according to claim 1, wherein the conjugate fiber is treated with water, and a water-soluble thermoplastic polyvinyl alcohol-based polymer is at least partially dissolved and removed from the conjugate fiber. Method for producing hollow fibers. 7. A fiber structure containing the conjugate fiber according to any one of claims 1 to 5, which is treated with water, and at least part of a water-soluble thermoplastic polyvinyl alcohol-based polymer is dissolved and removed from the conjugate fiber. A method for treating a fiber structure.