JP6829134B2 - Porous hollow fiber - Google Patents

Description

The present invention relates to a porous hollow fiber and a sea-island type composite fiber used for producing the same.

Polyester fibers have various excellent properties including mechanical properties, and are used in various uses and fields including clothing applications. However, polyester fibers are said to be harder in texture, less water-absorbent, and less preferable in terms of tactile sensation than natural fibers, and these problems have been solved by changing the cross-sectional shape of the fibers. ..

In garment applications, hollow fibers having a hollow cross-sectional shape are used in order to obtain high fabric strength while being lightweight. In order to obtain hollow fibers, the spinneret is made hollow, or a composite fiber (usually called conjugate spinning) device is used, and a polyvinyl alcohol resin is used for the fiber center (core). A composite fiber with a core-sheath structure that uses polyester resin for the outer periphery (sheath), and the polyvinyl alcohol resin in the core is eluted after spinning and winding, leaving the polyester fiber in the sheath to create a hollow fiber with a high hollow ratio. It has been proposed to obtain (eg, Patent Document 1). However, in the method of obtaining hollow fibers by making the spinneret into a hollow shape, spinning breakage is likely to occur, and it is difficult to carry out stable production. On the other hand, in the method of obtaining hollow fibers from composite fibers having a core-sheath structure, although it is relatively easy to increase the hollow ratio, the area per discharge hole of the spinneret becomes huge and the core portion. It is difficult to control the position of the resin component of the resin component, and it is difficult to obtain a uniform fiber. In particular, it is difficult to completely elute the resin component of the core portion of long fibers. So far, good porous hollow fibers in which many hollow portions are uniformly formed in the yarn length direction and the yarn cross-section direction have not been obtained.

By the way, in Japanese Patent Application Laid-Open No. 9-241941 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2001-115334 (Patent Document 3), a core portion having a hollow cross section orthogonal to the fiber axis and a core portion outside the core portion. A hollow fiber having a shape including a fin portion protruding from the surface and extending along the length direction of the core portion has been proposed. However, with this shape, the porosity in the multifilament state is low, resulting in poor lightness.

Further, Japanese Patent Application Laid-Open No. 2008-57060 (Patent Document 4) also describes hollow fibers, but since these hollow fibers have a small number of fins and a highly deformed cross section, the silk of the fibers The factor (strength x √ elongation) becomes low, fluffing occurs frequently in the drawing process, and the hollowness ratio and void ratio greatly decrease due to the deformation of the fiber cross section.

Japanese Unexamined Patent Publication No. 2002-173824 Japanese Unexamined Patent Publication No. 9-241941 Japanese Unexamined Patent Publication No. 2001-115334 Japanese Unexamined Patent Publication No. 2008-57060

An object of the present invention is to provide a porous hollow fiber having a uniform diameter of the hollow portion even if the proportion of the hollow portion is large, and which is lightweight and has high heat retention.

The present invention is also a sea-island type composite fiber used to obtain a porous hollow fiber having a uniform diameter of the hollow part even if the proportion of the hollow part is large, which is lightweight and has high heat retention, and is an island in the sea-island type composite fiber. Provided is a sea-island type composite fiber capable of easily removing island components even if the content ratio of the components is high, having sufficient mechanical strength to withstand practical use, and being able to obtain porous hollow fibers having an extremely large number of hollow portions. The purpose is to do.

[Perforated hollow fiber]
That is, the present invention is a porous hollow fiber obtained by removing the island component from a plurality of sea-island type composite fibers having an easily soluble polymer as an island component and a poorly soluble polymer as a sea component. The number of hollow portions observed in the fiber cross section perpendicular to the length direction is 100 or more per porous hollow fiber, the distance between the hollow portions adjacent to each other is 100 nm or more, and each of the hollow portions The diameter is in the range of 10 to 1000 nm, the variation in the diameter of the hollow portion (CV value) is 30% or less, and the poorly soluble polymer forms an oligomer by the esterification reaction of the dicarboxylic acid component and the diol component. Then, it is a polyester produced by subjecting an oligomer to a polycondensation reaction, and the polyester contains 0.5 to 2.0 mol% of an alkali metal compound and / or an alkaline earth metal compound with respect to the total dicarboxylic acid component. It is a porous hollow fiber, which is contained in such an amount and contains a phosphorus compound represented by the following chemical formula (I) in an amount satisfying the following formula (1).

0.80 <P [molar] / M [molar] ≤ 2.0 ... (1)
(In the above formula (1), P represents the number of moles of the phosphorus compound, and M represents the number of moles of the alkali metal compound and / or the alkaline earth metal compound.)

[Kaijima type composite fiber]
The present invention is also a sea-island type composite fiber containing an easily soluble polymer as an island component and a poorly soluble polymer as a sea component, and is observed in a fiber cross section perpendicular to the fiber length direction of the composite fiber. The number of island components is 100 or more, the distance between adjacent island components is 100 nm or more, the diameter of each of the island components is in the range of 10 to 1000 nm, and the variation in the diameter of the hollow portion (CV value). ) Is 30% or less, and the poorly soluble polymer is a polyester produced by forming an oligomer by an esterification reaction of a dicarboxylic acid component and a diol component and then subjecting the oligomer to a polycondensation reaction. Contains an alkali metal compound and / or an alkaline earth metal compound in an amount of 0.5 to 2.0 mol% with respect to the total dicarboxylic acid component, and the phosphorus compound represented by the following chemical formula (I) is as follows. It is a sea-island type composite fiber characterized in that it is contained in an amount satisfying the formula (1).

0.80 <P [molar] / M [molar] ≤ 2.0 ... (1)
(In the above formula (1), P represents the number of moles of the phosphorus compound, and M represents the number of moles of the alkali metal compound and / or the alkaline earth metal compound.)

According to the present invention, it is possible to provide a porous hollow fiber having a uniform diameter of the hollow portion even if the proportion of the hollow portion is large, and is lightweight and has high heat retention.

The present invention is also used to obtain a porous hollow fiber, and even if the content ratio of the island component in the sea-island type composite fiber is high, the island component can be easily removed and has sufficient mechanical strength to withstand practical use. It is possible to provide a sea-island type composite fiber capable of obtaining a porous hollow fiber having an extremely large number of hollow portions.

It is sectional drawing of a part of the spinneret used for spinning the sea-island type composite fiber of this invention. It is sectional drawing of a part of the spinneret used for spinning the sea-island type composite fiber of this invention. It is sectional drawing explanatory view of an example of the sea-island type composite fiber of this invention.

Hereinafter, the present invention will be described in detail.

[Perforated hollow fiber]
In the porous hollow fiber of the present invention, the number of hollow portions observed in the fiber cross section perpendicular to the length direction of the fiber is 100 or more, preferably 500 or more per fiber. If the number of hollow portions is less than 100, it is not possible to obtain sufficient performance regarding the lightness, heat retention and soft feeling of the porous hollow fiber. If the number of hollow portions is too large, the manufacturing cost of the spinneret increases and the processing accuracy of the spinneret itself tends to decrease. Therefore, the number of hollow portions is preferably 1000 or less.

The diameter of the hollow portion of the porous hollow fiber is 10 to 1000 nm, preferably 100 to 700 nm. If the diameter of the hollow portion is less than 10 nm, the fiber structure itself becomes unstable and the hollow forming property becomes unstable, and if it exceeds 1000 nm, the heat retention characteristic of the porous hollow fiber cannot be obtained. The more uniform the diameter of the hollow portion of the porous hollow fiber, the better the quality of the fiber.

The distance between the hollow portions adjacent to each other observed in the fiber cross section perpendicular to the length direction of the fiber is 100 nm or more, preferably 200 nm or more. If it is less than 100 nm, it is not possible to sufficiently secure the mechanical strength of the porous hollow fiber obtained after dissolving and removing the island component. The distance between the hollow portion and the hollow portion adjacent to the hollow portion efficiently forms micropores penetrating into the sea component of the sea-island type composite fiber when the porous hollow fiber is manufactured, and a highly homogeneous porous hollow fiber is obtained. From the viewpoint, it is preferably less than 500 nm.

The variation in the diameter of the hollow portion (CV value) is preferably 0 to 30%, more preferably 0 to 20%, particularly from the viewpoint of uniformly forming the hollow portion in the yarn length direction and the yarn cross-section direction in the long fibers. , More preferably 0 to 15%. When the CV value is low, it means that the fiber is a uniform porous hollow fiber with little variation in fineness.

The porous hollow fiber of the present invention preferably has a tensile strength of 1.0 to 6.0 cN / dtex. By providing the tensile strength in this range, it is possible to cope with many applications requiring tensile strength.

Further, the porous hollow fiber of the present invention preferably has a cutting elongation rate of 15 to 60%. By providing a cutting elongation in this range, it has strength that can be applied and developed in various applications.

[Easy-soluble polymer]
The easily soluble polymer used for the island component of the sea-island type composite fiber used to obtain the porous hollow fiber of the present invention has higher solubility in an alkaline aqueous solution than the poorly soluble polymer used for the sea component, and is more soluble than the poorly soluble polymer. Also use a polymer that dissolves easily. This easily soluble polymer is a polymer that is easily dissolved in an alkaline aqueous solution, and includes, for example, polylactic acid, ultrahigh molecular weight polyalkylene oxide condensed polymer, polyethylene glycol compound copolymerized polyester, and polyethylene glycol compound and 5-sodium sulfoisophthalic acid. Copolymerized polyester with can be used.

Among them, in order to achieve both the solubility in alkali and the cross-sectional formation property of sea islands, the easily soluble polymer contains 6 to 12 mol% of 5-sodium sulfonic acid and 94 to 88 mol% of terephthalic acid as dicarboxylic acid. A copolymerized polyester containing 3 to 10% by weight of polyethylene glycol having a molecular weight of 4000 to 12000 and 97 to 90% by weight of diethylene glycol as a diol component is preferable. The copolymerized polyester preferably has an intrinsic viscosity of 0.4 to 0.6.

The copolymerization component 5-sodium isophthalic acid in this copolymerized polyester contributes to the improvement of the hydrophilicity and melt viscosity of the obtained copolymerized polyester, and the polyethylene glycol improves the hydrophilicity of the obtained copolymer.

The molecular weight of polyethylene glycol in this copolymerized polyester is 4000 to 12000. When the molecular weight exceeds 12000, the hydrophilicity, which is considered to be due to the higher-order structure, increases, but the reactivity with the dicarboxylic acid component decreases, and the obtained reaction product becomes a blend system, so that it is heat-resistant and spun. There will be a lack of stability. On the other hand, if the molecular weight is less than 4000, the hydrophilicity becomes insufficient and it becomes difficult to remove the island component.

If the copolymerization amount of polyethylene glycol in the copolymerized polyester is less than 3% by weight, the hydrophilicity is insufficient and it tends to be difficult to remove the island component with an alkaline aqueous solution, which is not preferable. On the other hand, when the copolymerization amount of polyethylene glycol exceeds 10% by weight, polyethylene glycol originally has a melt viscosity lowering effect, so that the viscosity of the obtained copolymer is too low, and an object of the present invention to provide a porous hollow fiber. Is not preferable because it tends to be difficult to achieve.

[Dissolution rate ratio]
The dissolution rate ratio (island component / sea component) of the easily soluble polymer of the island component and the poorly soluble polymer of the sea component is preferably 200 or more. When this dissolution rate ratio is less than 200, a part of the sea component in the surface layer of the fiber cross section is also dissolved while the island component in the central part of the cross section of the obtained sea island type composite fiber is dissolved in the alkaline aqueous solution. As a result, in order to completely dissolve and remove the island component, the sea component is also partially dissolved and the amount of fiber is reduced, resulting in thickness unevenness of the poorly soluble polymer and deterioration of fiber strength due to solvent erosion. At the same time, fluff and fibrils may be generated, which may deteriorate the quality of the product using the fiber, which is not preferable.

[Slightly soluble polymer]
The poorly soluble polymer used in the sea component of the sea-island type composite fiber used to obtain the porous hollow fiber of the present invention is a polymer that is not easily dissolved in an alkaline aqueous solution. This poorly soluble polymer is a polymer that satisfies the above-mentioned dissolution rate ratio with the easily soluble polymer used in combination as an island component in the sea-island type composite fiber.

In the present invention, as this poorly soluble polymer, a polyester produced by forming an oligomer by an esterification reaction of a dicarboxylic acid component and a diol component and then polycondensing the oligomer is used. The polyester contains an alkali metal compound and / or an alkaline earth metal compound in an amount of 0.5 to 2.0 mol% with respect to the total dicarboxylic acid component. Further, this polyester contains a phosphorus compound represented by the following chemical formula (I) in an amount satisfying the following formula (1).

0.80 <P [molar] / M [molar] ≤ 2.0 ... (1)
(In the above formula (1), P represents the number of moles of the phosphorus compound, and M represents the number of moles of the alkali metal compound and / or the alkaline earth metal compound.)

The alkali metal compound and / or the alkaline earth metal compound and the phosphorus compound have an action of forming micropores on the fiber surface of the sea component at the same time when the island component is dissolved and removed from the sea island type composite fiber. As a poorly soluble polymer, polyester produced by forming an oligomer by an esterification reaction of a dicarboxylic acid component and a diol component and then subjecting the oligomer to a polycondensation reaction is used, and an alkali metal compound and / or an alkaline earth metal compound and phosphorus are used. By containing the compound in this range, a solvent for removing island components is permeated in the yarn length direction and the yarn cross-sectional direction, especially in long fibers, the island components are uniformly removed, and a large number of hollow portions are formed. Can be made to.

The alkali metal element and the alkaline earth metal element of the alkali metal compound and / or the alkaline earth metal compound are preferably Li, Na, Mg, Ca, Sr, Ba, more preferably Ca, Sr, Ba, particularly preferably. Use Ca. Further, as the alkali metal compound and / or the alkaline earth metal compound, a compound that reacts with a phosphorus compound to form a metal-containing phosphorus compound is used. Specifically, salts with organic carboxylic acids are preferable, and acetic acid salts are particularly preferable because acetic acid produced as a by-product can be easily removed by the reaction. The alkali metal and / or alkaline earth metal compound may be used alone or in combination of two or more.

The value of P [molar] / M [molar] is preferably 0.80 to 2.0, more preferably 0.82 to 1.5. When the value of P [mol] / M [mol] is less than 0.80, the amount of particles formed from the phosphorus compound and the alkali metal compound and / or the alkaline earth metal compound decreases, so that the obtained polyester is melted. The formation of fine pores on the fiber surface of the sea component of the polyester fiber obtained by spinning and then reducing the amount of alkali is insufficient, and it is difficult to obtain a sufficiently porous hollow, and the alkali metal compound and / or alkaline soil in the polyester It is not preferable because the amount of the metal compound is excessive and the excess metal atomic component promotes the thermal decomposition of the polyester and impairs the thermal stability. On the other hand, if the value of P [molar] / M [molar] exceeds 2.0, the phosphorus compound becomes excessive, and the excess phosphorus compound inhibits the polymerization reaction of polyester, which is not preferable.

The alkali metal compound and / or the alkaline earth metal compound is contained in the range of 0.5 to 2.0 mol%, preferably 0.8 to 1.5 mol% with respect to the dicarboxylic acid component of the polyester described above. Add to. When the addition amount is less than 0.5 mol%, the amount of particles formed from the phosphorus compound and the alkali metal compound and / or the alkaline earth metal compound decreases, so that the obtained polyester is melt-spun and then alkali-reduced. As a result, the formation of fine pores on the fiber surface of the sea component of the polyester fiber obtained is insufficient, and a sufficient porous hollow cannot be obtained. On the other hand, when it exceeds 2.0 mol%, the particles formed from these phosphorus compounds and alkali metal compounds and / or alkaline earth metal compounds become coarse particles, and the obtained polyester is melt-spun and then alkali-reduced. The fine pores of the sea component of the polyester fiber obtained in the above process are also coarse, and although a porous hollow is obtained, the thread strength of the remaining sea component is excessively reduced, and the yarn-making property in the melt spinning process is also improved. It gets worse significantly.

[Kaijima type composite fiber]
The present invention is also a sea-island type composite fiber. That is, the present invention is also a sea-island type composite fiber containing an easily soluble polymer as an island component and a poorly soluble polymer as a sea component, and is observed in a fiber cross section perpendicular to the fiber length direction of the composite fiber. The sea-island type is characterized in that the number of island components to be formed is 100 or more, the distance between adjacent island components is 100 nm or more, and the diameter of each of the island components is within the range of 10 to 1000 nm. It is a composite fiber.

This sea-island type composite fiber can be used to obtain the above-mentioned porous hollow fiber. In this sea-island type composite fiber, the number of island components needs to be 100 or more, preferably 500 or more. If it is less than 100, the number of island components of the porous hollow fiber obtained from the sea-island type composite fiber is also less than 100, and it is not possible to obtain sufficient performance in terms of lightness, heat retention and softness of the porous hollow fiber. If the number of island components is too large, the manufacturing cost of the spinneret increases and the processing accuracy of the spinneret itself tends to decrease. Therefore, the number of island components is preferably 1000 or less.

In the sea-island type composite fiber, the distance between the island components adjacent to each other is 100 nm or more, preferably 200 nm or more. In the porous hollow fiber obtained when the interval is less than 100 nm, the interval between the island components adjacent to each other is also less than 100 nm, and the mechanical strength of the porous hollow fiber obtained after the island components are dissolved and removed cannot be sufficiently secured.

The diameter of each of the island components is 10 to 1000 nm, preferably 100 to 700 nm. If the diameter of the island component is less than 10 nm, the porous hollow fiber structure itself obtained from the sea-island type composite fiber becomes unstable and the hollow forming property becomes unstable, and if it exceeds 1000 nm, the heat retention characteristic of the porous hollow fiber can be obtained. Absent. The more uniform the diameter of the hollow portion of the porous hollow fiber, the better the quality of the fiber.

The mass ratio of the sea component to the island component (sea component: island component) is preferably 30:70 to 80:20, more preferably 40:60 to 70:30. Within this range, it is possible to easily dissolve and remove the island component when obtaining the porous hollow fiber, and it is possible to obtain a porous hollow fiber having sufficient mechanical strength that can withstand practical use after the dissolution and removal of the island component. ..

The sea-island type composite fiber passes through the center of the diameter (r) of the island component and the fiber cross section from the viewpoint of obtaining a porous hollow fiber having mechanical strength that can withstand practical use in the fiber cross section perpendicular to the fiber length direction. When four straight lines are drawn with an angular interval of 45 degrees from each other, the minimum value (S _min ) of the interval between the island components on these four straight lines, and the interval between the fiber diameter (R) and the island component. It is preferable that the maximum value (S _max ) of the above satisfies the relationship of the following formulas (I) and (II).
0.001 ≤ S _{min /} r ≤ 1.0 (I)
S _{max /} R ≤ 0.15 (II)
It is more preferable that these satisfy the following formulas (III) and (IV).
0.01 ≤ S _{min /} r ≤ 0.7 (III)
S _{max /} R ≤ 0.08 (IV)

When these conditions are satisfied, the high-speed spinnability at the time of producing the sea-island type composite fiber can be maintained well, the draw ratio can be increased, high mechanical strength can be obtained, and adjacent island components can be stuck to each other. Can be prevented.

In the measurement of the distance between island components, if the central part of the sea-island type composite fiber is formed by the sea component, the distance between adjacent island components via the sea component of this central part is excluded from the measurement. To do.

[Manufacturing method of sea-island type composite fiber]
The sea-island type composite fiber of the present invention can be produced, for example, by the following method.

First, the easily soluble polymer and the poorly soluble polymer are melt-spun so that the former is an island component and the latter is a sea component. As the spinneret used for melt spinning, one having a group of hollow pins or a group of micropores for forming an island component can be used. Specifically, for example, the island component flow extruded from a hollow pin or micropores and the sea component flow supplied from a flow path designed to fill the space between them are merged, and this combined fluid flow is gradually narrowed. While extruding from the discharge port, a spinneret for forming a sea-island type composite fiber is used.

An example of a preferably used spinneret is shown in FIGS. 1 and 2. FIG. 1 is a cross-sectional explanatory view of a part of a spinneret used for spinning the sea-island type composite fiber of the present invention. FIG. 2 is a cross-sectional explanatory view of a part of another example of the spinneret used for spinning the sea-island type composite fiber of the present invention.

In the spinneret 1 shown in FIG. 1, the island component polymer (melt) in the distribution front island component polymer reservoir 2 is distributed in the island component polymer introduction path 3 formed by a plurality of hollow pins. Will be done. On the other hand, the sea component polymer (melt) is introduced into the pre-distribution sea component polymer reservoir 5 through the sea component polymer introduction passage 4. The hollow pin forming the island component polymer introduction path 3 penetrates the sea component polymer reservoir 5, and is the center of each inlet of the plurality of core-sheath type composite diversion passages 6 formed below the hollow pin. It opens downward in the part.

From the lower end of the island component polymer introduction path 3, the island component polymer flow is introduced into the central portion of the core-sheath type composite diversion passage 6, and the sea component polymer flow in the sea component polymer reservoir 5 is a core-sheath type. A core-sheath type composite flow is introduced into the composite diversion passage 6 so as to enclose the island component polymer flow, and the island component polymer flow is the core and the sea component polymer flow is the sheath, and a plurality of core-sheath type composite flows are formed. It is introduced into the funnel-shaped merging passage 7, and in the merging passage 7, the sheath portions of the plurality of core-sheath type composite flows are joined to each other to form a sea-island type composite flow. The sea-island type complex flow gradually decreases its horizontal cross-sectional area while flowing down the funnel-shaped merging passage 7, and is discharged from the discharge port 8 at the lower end of the merging passage 7.

In the spinneret 11 shown in FIG. 2, the island component polymer reservoir 2 and the sea component polymer reservoir 5 are connected by an island component polymer introduction passage 13 composed of a plurality of through holes, and the island component is formed. The melt of the island component polymer in the polymer reservoir 2 is distributed into a plurality of island component polymer introduction passages 13, through which the island component polymer stream is introduced into the sea component polymer reservoir 5. , It penetrates through the sea component polymer (melt) housed in the sea component polymer reservoir 5, flows into the core-sheath type composite diversion passage 6, and flows down the central portion thereof.

On the other hand, the sea component polymer in the sea component polymer reservoir 5 flows down into the core-sheath type composite diversion passage 6 so as to surround the island component polymer flow flowing down the central portion thereof. As a result, a plurality of core-sheath type composite flows are formed in the plurality of core-sheath type composite diversion passages 6 and flow down into the funnel-shaped confluence passage 7, and the sea-island type composite flow is formed in the same manner as the spinneret of FIG. It is formed and flows down while reducing its horizontal cross-sectional area, and is discharged through the discharge port 8.

The sea-island type cross-sectional composite fiber discharged from the spinneret is solidified by cooling air and wound at a speed of preferably 400 to 6000 m / min, more preferably 1000 to 3500 m / min to obtain an unstretched sea-island type composite fiber. When the spinning speed is 400 m / min or less, the productivity is insufficient and not preferable, while when the spinning speed is 6000 m / min or more, the spinning stability is poor and not preferable.

Therefore, the present invention is a step of melting and extruding an island component made of an easily soluble polymer and a sea component made of a poorly soluble polymer from a spinneret for a sea island type composite fiber in order to produce a sea island type composite fiber. A method for producing a sea-island type composite fiber, which comprises a step of taking the extruded sea-island type composite fiber at a spinning speed of 400 to 6000 m / min in this order.

The obtained unstretched sea-island type composite fiber is made into a stretched sea-island type composite fiber having a desired tensile strength, cutting elongation and heat shrinkage property through a separate drawing step, or is constant without being wound once. It is taken up by a roller at a speed, and then wound up after passing through a drawing step to obtain a stretched sea-island type composite fiber.

Specifically, this drawing step is described by preheating the sea-island type composite fiber on a preheating roller having a temperature of, for example, 60 to 220 ° C., preferably 60 to 190 ° C., more preferably 75 to 180 ° C., and for example, 1.2 to 1.2 to Stretching is performed at a stretching ratio of 6.0 times, preferably 2.0 to 5.0 times. In this case, heat setting is preferable, and heat setting is performed with a set roller having a temperature of, for example, 120 to 220 ° C, preferably 130 to 200 ° C.

If the preheating temperature is insufficient, the desired high-magnification stretching cannot be achieved. Further, if the heat setting temperature is too low, the shrinkage rate of the obtained drawn fibers is too high, which is not preferable. On the other hand, if the heat setting temperature is too high, the physical properties of the obtained drawn fibers are significantly deteriorated, which is not preferable.
In this way, the sea-island type composite fiber of the present invention can be obtained.

FIG. 3 is an explanatory cross-sectional view of an example of the sea-island type composite fiber of the present invention. It is composed of a sea component 22 forming a matrix and a large number of island components 23 arranged apart from each other in the sea component 22.

In order to measure the distance between the island components in the sea-island type composite fiber of the present invention, four straight lines 25- are passed through the center 24 of the cross section 21 of FIG. 3 and are spaced 45 degrees from each other. Draw 1,25-2,25-3,25-4, measure the spacing of the island components on these four straight lines, determine the maximum spacing S _max and the minimum spacing S _min, and average the island component spacing. Calculate the value _Save . In FIG. 3, since the island components on the four straight lines are mainly described, the description of other island components is omitted in FIG.

[Manufacturing method of porous hollow fiber]
The porous hollow fiber of the present invention can be obtained by performing a weight loss treatment for dissolving and removing island components from the above-mentioned sea-island type composite fiber. The island component can be dissolved and removed, for example, by immersing it in an aqueous sodium hydroxide solution. The concentration of the aqueous sodium hydroxide solution is, for example, 1 to 10% by weight, preferably 2 to 6% by weight. The temperature at which the sea-island type composite fiber is immersed therein is, for example, 60 to 97 ° C, preferably 80 to 95 ° C.

The present invention will be further described with reference to the following examples. The measurement and evaluation were carried out by the following methods.

(1) Melt Viscosity The polymer under test is dried, set in an orifice set at the melting temperature of a melt spinning extruder, held in a molten state for 5 minutes, and then extruded under a predetermined level of load. Shear rate and melt viscosity were plotted. The above operation was repeated under a plurality of levels of load. Based on the above data, a shear rate-melt viscosity relationship curve was created. On this curve, the melt viscosity was estimated when the shear rate was 1000 seconds ^-1 .

(2) Dissolution rate ratio Each of the polymer for the sea component and the polymer for the island component is extruded through a spinneret for manufacturing a sea-island type composite fiber having 10 discharge holes having a pore diameter of 0.3 mm and a land length of 0.6 mm (hereinafter, , "Melting spinning process"), winding at a speed of 1000-2000 m / min. This fiber was stretched and controlled so that the cutting elongation was in the range of 30 to 60% to produce a multifilament of 50 dtex / 10 f. A tubular knitting was made using this multifilament. The tube knitting was immersed in a solution temperature of 4 wt% NaOH aqueous solution at 95 ° C., and the weight loss rate ratio (dissolution rate ratio) was calculated from the dissolution time and the dissolution amount at this time. When the dissolution rate ratio of the island component polymer to the sea component polymer in the sea-island type composite fiber was 200 or more, it was evaluated as "good", and when it was less than 200, it was evaluated as "poor".

(3) Spinnability In the melt spinning step of (2) above, the case where continuous operation was possible for 7 hours or more was evaluated as "good", and the other cases were evaluated as "poor".

(4) Thread physical characteristics A tubular knitted fabric having a mass of 1 g or more was produced using Kaishima composite fibers. The knitted fabric was immersed in a 4 wt% NaOH aqueous solution at a liquid temperature of 95 ° C. to remove island components. The tube knitting was unwound to obtain a fiber bundle. A load-elongation curve chart of the obtained fiber bundle was prepared at room temperature under the conditions of an initial sample length of 100 mm and a tensile speed of 200 m / min. From this chart, the tensile strength (cN / dtex) and the cutting elongation (%) of the fiber bundle were determined. "Good" when the tensile strength is 1.5 cN / dtex or more and the cutting elongation rate is 15% or more, and "Defective" when the tensile strength is less than 1.5 cN / dtex or the cutting elongation rate is less than 15%. It was judged.

(5) Intrinsic Viscosity Measured at 35 ° C. using orthochlorophenol as a solvent.

(6) Observation of cross section of thread The fiber under test was cut so as to obtain a cross section perpendicular to the length direction, and the cross section was photographed at a magnification of 30,000 using a transmission electron microscope TEM. Using this electron micrograph, the diameter R of the composite fiber and the diameter r of the island component were measured. In the electron micrograph, four straight lines passing through the center point of the composite fiber and intersecting each other at an angle of 45 degrees were drawn, and the maximum spacing S _min and the maximum spacing S _max between the island components on the straight lines were measured. The average interval _Save between the island components was calculated.

(7) Variation in diameter of porous hollow portion (CV value)
The island component was removed from the test sea-island type composite fiber using a solvent, and the obtained porous hollow fiber bundle was observed with a transmission electron microscope (TEM) at a magnification of 30,000 times to measure the diameter of the porous hollow portion. The standard deviation (σ) and the average diameter (r) of the hollow portion were calculated, and the variation (CV value) was calculated by the following formula.
CV value = (standard deviation σ / average diameter r of hollow portion) × 100 (%)
The hollow portion average diameter (r) is an average value of the major axis and the minor axis of the hollow portion measured by observing the cross section of the hollow fiber using a TEM at a magnification of 30,000 times.

(8) Homogeneity of Porous Hollow Fiber The test sea-island type composite fiber was treated with a solvent for island components, and when a mass reduction corresponding to the island component content ratio was observed, the dissolution treatment was stopped and the obtained fiber bundle was obtained. The cross section of the hollow portion was observed by TEM, and the uniformity of the hollow portion was evaluated as "uniform" and "non-uniform" based on the uniformity of the cross section of the single fiber.

(9) Weight reduction rate (%)
The texture (g / m ² ) and the fabric thickness (mm) of the tubular knitted fabric using 10 filaments of polyester fiber 56dtex composed of a normal solid cross section were measured, and a reference curve for the texture with respect to the fabric thickness was created. .. The weight reduction rate (%) was defined as the reduction rate of the basis weight at the same thickness value of the reference curve when the same tubular knitted cloth was prepared.

(10) Cloth heat retention In a constant temperature and humidity environment with a temperature of 20 ° C. and a humidity of 60% RH, a 200 W ref lamp light source is used as an energy source, light is irradiated from a height of 50 cm, and the temperature of the back surface of the cloth is thermocoupled 180 seconds later. Measured in pairs. When the temperature was 30 ° C. or higher, it was judged to be good, and when it was less than 30 ° C., it was judged to be defective.

(11) Raw materials Table 1 shows the raw materials used for producing the sea-island type composite fiber. The polymers listed in Table 1 are:
PET1:
Polyethylene terephthalate Ny-6: having a melt viscosity at 280 ° C. of 120 Pa · s:
Nylon 6 having a melt viscosity at 280 ° C. of 140 Pa · s
Modified PET1:
In the esterification reaction tank, 86 parts of terephthalic acid and 40 parts of ethylene glycol were esterified according to a conventional method to obtain an oligomer. 86 parts of terephthalic acid and 40 parts of ethylene glycol were continuously supplied to this oligomer over 65 minutes, and an esterification reaction was carried out at 245 ° C. Then, 0.045 parts of antimony trioxide was added, and 20 minutes later, an oligomer having an equimolar amount equal to the amount of the oligomer produced from the additionally supplied terephthalic acid and ethylene glycol was sent to the polycondensation reaction tank. Immediately after the completion of the liquid feeding, 1.0 mol% of calcium acetate was added to the polycondensation reaction tank with respect to the acid component in the polymer. After a further 5 minutes, 1.25 mol% of phenylphosphonic acid was added to the polycondensation reaction tank with respect to the acid component in the polymer. After that, the temperature is raised to 290 ° C., a polycondensation reaction is carried out in a high vacuum of 0.03 kPa or less, and the obtained polyester having an intrinsic viscosity of 0.64 dL / g is referred to as modified PET1.
Modified PET2:
Modified polyethylene terephthalate obtained by copolymerizing 4 wt% of polyethylene glycol (PEG) having an average molecular weight of 4000 with a melt viscosity at 285 ° C. and 8 mol% of 5-sodium sulfoisophthalic acid is referred to as modified PET2.

Example 1
Sea-island type composite fibers were produced using the island component polymer and the sea component polymer shown in Table 1. In this Example 1, modified PET1 and modified PET2 are used as a polymer for sea components and a polymer for island components at a weight ratio of 50:50, respectively, and both are heated and melted to form a base for spinning sea-island type composite fibers. It was extruded at a spinning temperature of 290 ° C. and wound on a take-up roller at the take-up speeds shown in Table 1. The obtained unstretched fiber bundle was roller-stretched with, and the stretched fiber bundle was heat-treated at a temperature of 150 ° C. and wound up. At this time, the spinning discharge flow rate and the draw ratio were adjusted so that the yarn count of the obtained stretch-heat-treated fiber bundle was 50 dtex / 10f.

Table 1 shows the results of measurement and evaluation of the obtained sea-island type composite fiber. In the obtained sea-island type composite fiber, the thickness of the sea component between the island components was thin, and islands having a uniform diameter were formed. The cross section of this sea-island type composite fiber was observed by TEM, and the minimum value (S _min ) between the diameter (r) of the island component and the distance between the island components and the maximum value between the diameter (R) of the sea-island type composite fiber and the distance between the island components. When the relationship of (S _max ) was examined, it was found that S _{min /} r = 0.49 and S _{max /} R = 0.1.

A tubular knitting was prepared using this sea-island type composite fiber, and the mixture was immersed in a 4% weight NaOH aqueous solution at a liquid temperature of 95 ° C. to reduce the weight by 50% by weight until the weight was reduced to 50% by weight. When the cross section of the fiber bundle constituting the tubular knitting after the weight loss treatment was observed, a porous hollow fiber having a uniform porous hollow was formed. The tensile strength of the fiber bundle after the weight loss treatment was 2.5 cN / dtex, and the cutting elongation was 45%.

Example 2
A sea-island type composite fiber was produced in the same manner as in Example 1. However, in Example 2, the same polymer for sea components and polymer for island components as in Example 1 were used, and both were used in a weight ratio of 60:40. A tubular knitting was prepared in the same manner as in Example 1, and immersed in a 4 wt% NaOH aqueous solution at a liquid temperature of 95 ° C. to reduce the fiber weight of the sea-island type composite fiber by 40 wt% to 60 wt%. Did. When the cross section of the sea-island type composite fiber after the weight reduction treatment was observed, a porous hollow fiber having a uniform porous hollow was formed. The tensile strength of the fiber bundle of the obtained porous hollow fiber was 3.0 cN / dtex, and the cutting elongation was 35%.

Example 3
A sea-island type composite fiber was produced in the same manner as in Example 1. However, in Example 3, the same polymer for sea components and polymer for island components as in Example 1 were used, and both were used in a weight ratio of 80:20. When observing the cross section of the sea-island type composite fiber, the thickness of the sea component between the island component and the inter-island component was thin, and islands having a uniform diameter were formed. By TEM observation of the cross section of this sea-island type composite fiber, the minimum value S _min of the diameter (r) of the island component and the distance between the island components, and the maximum value S _max of the diameter (R) of the sea-island type composite fiber and the distance between the island components. As a result of investigating the relationship between S _{min /} r = 0.30 and S _{max /} R = 0.01.

Using the obtained drawn yarn, a tubular knitting was prepared in the same manner as in Example 1 and immersed in a 4 wt% NaOH aqueous solution at a liquid temperature of 95 ° C. to reduce the weight of the sea-island type composite fiber by 20 wt% to 80 wt%. Weight loss processing was performed until it became. When the cross section of the obtained fiber bundle was observed, fibers having a uniform porous hollow were formed. The tensile strength of the fiber bundle after removing the island component is 3.5 cN / dtex, the cutting elongation is 50%, and the yarn count of the obtained stretch-heat-treated fiber bundle is 50 dtex / 10f. The discharge flow rate and the draw ratio were adjusted.

Examples 4-9
A sea-island type composite fiber was produced in the same manner as in Example 2. In Examples 4 and 7, the same polymer for sea components and polymer for island components as in Example 2 were used, the weight ratio of the two was 60:40, and the number of islands and the diameter of the islands were as shown in Table 1. The yarn was made at. The cross-sectional formability of the obtained sea-island type composite fiber was good.

Comparative Example 1
A sea-island type composite fiber was produced in the same manner as in Example 1. In Comparative Example 1, the same polymer for sea components and polymer for island components as in Example 1 were used, the weight ratio of both was 20:80, and the number of islands was 800 for spinning and stretching. The cross-sectional formability of the obtained sea-island type composite fiber was good, but the thickness of the sea component between islands was thin because the amount of sea component was too small, and after the island component was eluted by weight loss treatment with an alkaline aqueous solution. The strength of the obtained porous hollow fiber was weak, and it was not practically usable.

Comparative Example 2
A sea-island type composite fiber was produced in the same manner as in Example 1. In Comparative Example 2, the same polymer for sea components and polymer for island components as in Example 1 were used, the weight ratio of both was 90:10, and the number of islands was 800 for spinning and stretching. The cross-sectional formability of the obtained sea-island type composite fiber was good, but because the amount of sea component was too large, the thickness of the sea component between islands was thick, and the island component in the center of the fiber could not be dissolved and removed, resulting in porosity. Hollows were not formed uniformly.

Comparative Example 3
A sea-island type composite fiber was produced in the same manner as in Example 1. In Comparative Example 3, the modified PET1 was used as a polymer for sea components and PET1 was used as a polymer for island components at a weight ratio of 60:40. Although the sea-island formation was good, the weight loss rate of the island component by the alkaline aqueous solution was insufficient compared to that of the sea component, so that a considerable amount of the polymer for the sea component was reduced during the alkali weight loss. , Despite the removal of a significant portion of the marine component polymer, most of the island component polymer distributed in the central part of the composite fiber remains unreduced and is a uniform porous hollow fiber. Was not obtained.

Comparative Example 4
A sea-island type composite fiber was produced in the same manner as in Example 1. In Comparative Example 4, PET1 was used as a polymer for sea components and modified PET2 was used as a polymer for island components at a weight ratio of 60:40. Although the sea-island formation was good, since the polymer of the sea component did not contain a micropore-forming agent, even if a considerable amount of the sea component was reduced, a considerable amount of the island component was not completely removed. It remained in the central portion of the composite fiber, and a uniform porous hollow fiber could not be obtained.

According to the porous hollow fiber of the present invention, the porous hollow fiber is uniformly formed in the single fiber, and it is possible to provide a polyester-based hollow fiber having both light weight and heat retention.

Further, since the sea-island type composite fiber of the present invention can easily dissolve and remove the island component, a porous hollow can be uniformly formed in the single fiber, and it is used for producing a polyester-based hollow fiber having excellent lightness and heat retention. be able to.

1 Spinning cap 2 Polymer reservoir for island components before distribution 3 Polymer introduction path for island components formed by multiple hollow pins 4 Polymer introduction passage for sea components 5 Polymer reservoir for sea components before distribution 6 Multiple core-sheath composite diversion Passage 7 Rohto-shaped merging passage 8 Discharge port 11 Spinning spout 13 Introductory passage for island component polymer consisting of multiple through holes 21 Cross section explanatory view of an example of sea-island type composite fiber Fig. 22 Sea components forming a matrix 23 Separated from each other 24 Centers of the cross section of the spinneret 25 Straight lines that pass through the center of the cross section of the spinneret and are spaced 45 degrees from each other.

Claims (3)

It is a porous hollow fiber obtained by removing the island component from a plurality of sea-island type composite fibers having an easily soluble polymer as an island component and a poorly soluble polymer as a sea component, with respect to the length direction of the fiber. The number of hollow portions observed in the right-angled fiber cross section is 100 or more per porous hollow fiber, the distance between the hollow portions adjacent to each other is 100 nm or more, and the diameter of each of the hollow portions is 10 to 1000 nm. The variation in the diameter of the hollow part (CV value) is 30% or less, and the poorly soluble polymer produces an oligomer by the esterification reaction of the dicarboxylic acid component and the diol component, and then the oligomer is weighted. It is a polyester produced by a condensation reaction, and the polyester contains an alkali metal compound and / or an alkaline earth metal compound in an amount of 0.5 to 2.0 mol% with respect to the total dicarboxylic acid component. A porous hollow fiber, which comprises a phosphorus compound represented by the following chemical formula (I) in an amount satisfying the following formula (1).
0.80 <P [molar] / M [molar] ≤ 2.0 ... (1)
(In the above formula (1), P represents the number of moles of the phosphorus compound, and M represents the number of moles of the alkali metal compound and / or the alkaline earth metal compound.) The easily soluble polymer is selected from the group consisting of polylactic acid, ultrahigh molecular weight polyalkylene oxide condensation polymer, polyethylene glycol compound copolymerized polyester, and polyethylene glycol compound and 5-sodium sulfoisophthalic acid copolymerized polyester. The porous hollow fiber according to claim 1, which is a seed. The porous hollow fiber according to claim 1, wherein the number of hollow portions is 500 or more per one of the porous hollow fibers.