JP2000160432A - Fiber from which superfine fibers can be generated, superfine fibers generated therefrom and fiber sheet using the superfine fibers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber capable of generating superfine fibers which are not pressed and adhered to each other even when cut, are homogeneously dispersed, and are useful for producing filter materials, etc., by enabling the generation of the superfine fibers that contain high melting point polypropylene having a melting point of a prescribed value or larger and have a fiber diameter of a specified value or smaller. SOLUTION: This fiber can generate superfine fibers which contain high melting point polypropylene having a melting point of >=166 deg.C and have a fiber diameter of <=5 μm. The superfine fiber-generable fiber has a sea-island like fiber cross section. The high melting point polypropylene is contained in the island component 1, and the island component 1 has a diameter of <=2 μm. A value obtained by dividing the standard deviation of the diameter of the island component 1 by the average diameter of the island component 1 is >=0.2. The superfine fibers generated from the super fine fiber-generable fibers are preferably used for preparing fiber sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microfiber-generating fiber, a microfiber generated from the fiber, and a fiber sheet using the microfiber.

[0002]

2. Description of the Related Art Since ultrafine fibers having a fiber diameter of about 5 μm or less have a small fiber diameter, finer solids can be separated when used as a fiber constituting a filtering material. As described above, it is considered that the separation performance is further improved if the fiber diameter of the ultrafine fibers is small. Therefore, it is preferable to use ultrafine fibers having a small fiber diameter as the fibers constituting the filtering material. The ultrafine fibers preferably contain polypropylene which is excellent in chemical resistance and electret properties.

[0003] A suitable filter medium (nonwoven fabric) containing polypropylene microfibers is, for example, spinning a sea-island fiber having polypropylene as an island component, cutting it into a predetermined length, dissolving and removing the sea component, and then fiber web. Can be manufactured by bonding the fiber webs after preparing the fiber web. However, according to this method, the smaller the fiber diameter of the polypropylene ultrafine fiber, the more the island components tend to be pressed together when cutting the sea-island fiber, so that a fiber web having a uniform formation cannot be obtained. However, there is a problem that a filter material (nonwoven fabric) having a uniform texture cannot be obtained. Such a tendency was remarkable when the diameter of the island component was 2 μm or less.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to produce ultra-fine fibers which do not crimp even when cut, ultra-fine fibers generated therefrom, and ultra-fine fibers. An object is to provide a fiber sheet using fibers.

[0005]

The ultrafine fiber generating fiber of the present invention is an ultrafine fiber generating fiber containing a high melting point polypropylene having a melting point of 166 ° C. or more, and is capable of generating an ultrafine fiber having a fiber diameter of 5 μm or less. Fiber. This melting point is 16
It has been found that high melting point polypropylene having a melting point of 6 ° C. or higher has high crystallinity, and thus has high rigidity.

[0006] Since the ultrafine fibers of the present invention contain high-melting-point polypropylene, which is generated from the above-mentioned ultrafine fiber-generating fibers, even if the ultrafine fibers are cut, they do not adhere to each other, or the cut ultrafine fibers adhere to each other. That is not what you do. Therefore, they can be uniformly dispersed.

[0007] Since the fiber sheet of the present invention contains the above-mentioned ultrafine fibers, the fiber sheet is excellent in texture, in which the ultrafine fibers are uniformly dispersed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The ultrafine fiber-generating fiber of the present invention contains a high melting point polypropylene having a melting point of 166 ° C. or higher. Since the melting point of general polypropylene is about 160 ° C., the high melting point polypropylene constituting the ultrafine fiber generating fiber of the present invention has higher crystallinity.
It is considered that the higher the crystallinity of the high melting point polypropylene, the higher the stiffness and the less likely to be pressure bonding during cutting. Therefore, the melting point is more preferably 168 ° C. or higher. The high melting point polypropylene may contain an olefin component such as ethylene as a copolymer component.

The melting point in the present invention refers to a temperature at which a maximum value of a melting endothermic curve obtained by using a differential scanning calorimeter at a heating rate of 10 ° C./min from room temperature is obtained. When there are two or more maximum values, the maximum value at the highest temperature is defined as the melting point.

[0010] Such a high melting point polypropylene is preferably contained at 5 mass% or more, preferably at least 10 mass%, in the ultrafine fiber-generating fiber so as not to be pressed when cutting the ultrafine fiber-generating fiber. Is more preferred. Note that 90mass is used so that ultrafine fibers can be generated.
It is preferably at most s%.

[0011] The fiber capable of generating ultrafine fibers of the present invention contains the above-mentioned high melting point polypropylene, but the state of existence of the high melting point polypropylene is not particularly limited. For example, as shown in FIG. 1, a state where the island component exists as an island component 1 or a sea component 2 of a sea-island fiber having a sea-island fiber cross-sectional shape, and as shown in FIG. As shown in FIG. 3, a state existing as the first component 3 or the second component 4, a state existing as the first component 3 or the second component 4 of the multiple bimetallic fiber having a fiber cross-sectional shape in which resin components are laminated, and the like. There is. Among these, it is preferable that the high melting point polypropylene is contained in the island component of the sea-island fiber having a sea-island fiber cross-sectional shape capable of generating an ultrafine fiber having a smaller fiber diameter.

In the case of sea-island fibers, the diameter of the island component is equal to the diameter of the first component or the second component in the case of orange fibers and multiple bimetal fibers so that ultrafine fibers having a fiber diameter of 5 μm or less can be generated. Is 5 μm or less. In the present invention, since high-melting-point polypropylene is contained, even if the diameter (island component, first component, second component) is 2 μm or less, it can be cut without pressure bonding. In addition,
In the present invention, when the cross-sectional shape of the ultrafine fiber, the island component, the first component or the second component is non-circular, the diameter or diameter of these fibers refers to the diameter of a circle having the same cross-sectional area.

When the high melting point polypropylene is present as an island component of sea-island fibers or as a first component or a second component of an orange fiber or a multi-bimetal fiber, these components (island component, first component or second component) are used. Component) may be composed solely of high melting point polypropylene, or may include a polymer other than high melting point polypropylene.
For example, a polymer having a lower melting point than the high melting point polypropylene is contained in addition to the high melting point polypropylene, and the low melting point polymer is composed of these components (the island component, the first component or the second component).
When at least a part of the surface of the fiber sheet is constituted, after the ultrafine fibers composed of the island component, the first component or the second component are generated from the ultrafine fiber-generating fibers, the low melting point polymer is adhered to the fiber sheet to thereby produce the fiber sheet. Can be given strength and the fibers can be fixed. Further, in addition to the high melting point polypropylene, the high melting point polypropylene includes a polymer having a different shrinkage rate due to heat, and when the polymers having different shrinkage rates are unevenly distributed (for example, a laminated shape and an eccentric shape),
Island component, first component or second component
After the generation of the ultrafine fibers composed of the components, crimping can be developed by heat treatment to impart flexibility and stretchability to the fiber sheet.

[0014] The melting point of the above-mentioned low melting point polymer is lower than the melting point of the high melting point polypropylene by 10 ° C or more (that is, 1 ° C) so that the high melting point polypropylene does not melt during bonding.
56 ° C. or lower), preferably 20 ° C. or lower (that is,
146 ° C. or less). Examples of such a low-melting polymer include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, polyethylene such as copolymerized polyethylene,
There are copolymerized polypropylene and polybutylene succinate.

[0015] The low melting point polymer forms at least a part of the surface of the island component, the first component or the second component so that the polymer can be bonded. The low-melting polymer has a surface 3 of the island component, the first component or the second component so as to have excellent adhesion.
It preferably accounts for 0% or more, and more preferably 60% or more. When the proportion of the high-melting-point polypropylene is low, it tends to be easily pressed when cut, so that the high-melting-point polypropylene is preferably contained at 25 mass% or more in the island component, the first component or the second component.

[0016] The high-melting-point polypropylene constituting the ultrafine fiber-generating fiber of the present invention or a polymer other than the polymer having a lower melting point than the high-melting-point polypropylene (for example, the polymer constituting the sea component of sea-island fiber, orange fiber or multi-bimetallic fiber) As the polymer constituting the first or second component, for example, when removing the polymer such as when removing the sea component of the sea-island fiber, a high-melting polypropylene (a polymer having a lower melting point than the high-melting polypropylene) may be used. (Including low melting point polymer if included) is 5 mass
% Of a solvent that can be removed by only 95% by mass or less with respect to a solvent that removes only less than 95% by mass. When an orange fiber or a multi-bimetallic fiber is split by an external force, a high melting point polypropylene (lower than a high melting point polypropylene) When a polymer having a melting point is contained, a polymer having a low melting point is also included) and a poorly compatible polymer can be used. More specifically, in the former case, polyester (polyethylene terephthalate, polyethylene terephthalate-based copolymer, polybutylene terephthalate, polybutylene terephthalate-based copolymer, polyglycolic acid, glycolic acid Copolymers, polylactic acid, lactic acid copolymers, etc.) and polyethylene (low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polyethylene copolymer) can be combined. Among these, polylactic acid and intrinsic viscosity (60:40 (weight ratio) mixed solvent of phenol and 1,1,2,2-tetrachloroethane), which are relatively easy to stretch and can increase the crystallinity of polypropylene by a stretching step, are used. It is preferable to use a polyester having a value of about 0.6 or less (measured with an Ostwald viscometer at 30 ° C.). In the latter case, polyamide (nylon 6, nylon 66, nylon copolymer, etc.),
Polyester (polyethylene terephthalate, polyethylene terephthalate copolymer, polybutylene terephthalate, polybutylene terephthalate copolymer, polyglycolic acid, glycolic acid copolymer, polylactic acid, lactic acid copolymer, etc.) can be combined.

[0017] When the diameters of the ultrafine fibers generated from the fibers capable of generating the ultrafine fibers of the present invention are substantially the same, the nonwoven fabric in which the ultrafine fibers are dispersed has a uniform pore diameter and is excellent in separation performance and the like. Preferably, the diameter of the island component, the first component or the second component is substantially the same. In other words, the island component,
The value obtained by dividing the standard deviation value of the diameter of the first component or the second component by the average value of the diameters of the island component, the first component or the second component is 0.2 or less (preferably 0.18 or less). Is preferred. The average value of the diameters of the island component, the first component, or the second component is obtained by taking an electron micrograph of an ultrafine fiber-generating fiber or a generated ultrafine fiber.
The average value of the diameters of at least 00 (n) island components, the first component or the second component is measured, and the standard deviation value is a value obtained by calculating the measured diameter (χ) from the following formula. . Standard deviation = {(nΣχ ² − (Σχ) ² ) / n (n−1)} ^1/2 n: Number of measured island components, first component or second component χ: Each island component, first component Or the diameter of the second component

The cross-sectional shape of the ultrafine fiber-generating fiber of the present invention does not need to be circular, but is non-circular (for example, elliptical,
Oval, T-shaped, Y-shaped, + -shaped, hollow, polygonal, etc.), and when the ultrafine fiber-generating fiber is sea-island fiber, the cross-sectional shape of the island component is also circular. It need not be, and is non-circular (eg, elliptical, elliptical, T-shaped, Y-shaped,
+, Hollow, polygonal, etc.). Also,
In the polymer (for example, high melting point polypropylene) constituting the microfiber-generating fiber, a hygroscopic agent, a matting agent, a pigment,
Various functions can be added by mixing functional substances such as a flame retardant, a stabilizer, an antistatic agent, a colorant, a dye, a conductive agent, a hydrophilic agent, a deodorant, or an antibacterial agent.

The fineness of the ultrafine fiber-generating fiber is not particularly limited, but is suitably about 0.8 to 10 denier. Also, the fiber length is not particularly limited,
When generating ultra-fine fibers constituting the wet nonwoven fabric,
About 0.5 to 30 mm is appropriate, and when generating ultra-fine fibers constituting the dry nonwoven fabric, 25 to 160 mm
The degree is appropriate.

[0020] Such a microfiber-generating fiber of the present invention comprises:
Spinning can be carried out using a conventional composite spinning method and / or mixed spinning method. For example, sea-island fibers in which the island component is made of high-melting polypropylene and the sea component is made of polylactic acid,
After spinning at a melt spinning temperature of 210 to 245 ° C., the fiber can be drawn to produce a fiber capable of generating ultrafine fibers. In addition, you may cut | disconnect after extending | stretching so that a nonwoven fabric etc. may be easily manufactured using the fiber which can generate the ultrafine fiber of this invention. Since the ultrafine fiber-generating fiber of the present invention contains high melting point polypropylene, it is possible to obtain ultrafine fiber-generating short fibers that are not pressed at the cut portion. As this cutting method, for example, a known method such as a guillotine cutter, a rotary cutter, and a press cutter can be used. When the ultrafine fiber-generating fiber is used as a raw material of a dry nonwoven fabric or as a spun yarn, it is preferable to mechanically or thermally apply a crimp of about 5 to 50 pieces / inch.

The polypropylene resin used has a molecular weight distribution (weight-average molecular weight / number-average molecular weight) such that the polypropylene constituting the ultrafine fiber-generating fiber of the present invention has a high melting point of 166 ° C. or higher. Is 6
It is preferable to use the following (preferably 5 or less), a stretching temperature of 90 ° C. or higher and a temperature as high as possible without melting the polymer, or a combination of a polymer other than the polypropylene resin with one having excellent stretchability. The weight average molecular weight and the number average molecular weight were determined using 1,2,4-trichlorobenzene as a solvent at a temperature of 180 ° C.
Can be measured as a polystyrene equivalent molecular weight by GPC method (gel permeation chromatography).

[0022] The fibers capable of generating ultrafine fibers having substantially the same diameter as the above-mentioned island component, first component or second component can be obtained by a known composite spinning method. For example, sea-island fibers having substantially the same diameter of the island component can be produced by a method in which the island component is extruded while the spinneret regulates the spinneret into the sea component, and is compounded.

Since the ultrafine fibers of the present invention contain high-melting-point propylene generated from the above-described ultrafine fiber-generating fibers, the ultrafine fibers do not adhere to each other even when cut,
The cut ultrafine fibers are not crimped.
Therefore, they can be uniformly dispersed. The method of generating the ultrafine fibers differs depending on the fibers capable of generating the ultrafine fibers.
ss% or more removable polymer and 5%
When it is made of high melting point propylene that can be removed only by mass% or less, ultra-fine fibers made of high melting point polypropylene can be generated by being immersed in the solvent bath. And a poorly compatible polymer, it is possible to generate ultrafine fibers by applying an external force such as a fluid flow, a calender roll, or a flat press.

[0024] The fiber sheet of the present invention contains ultrafine fibers generated from the above-mentioned ultrafine fiber-generating fibers. Since the ultrafine fibers generated from the above-described ultrafine fiber-generating fibers can be uniformly dispersed, a fiber sheet (particularly, a nonwoven fabric) containing the ultrafine fibers is excellent in formation. When the ultrafine fibers are in a bonded state, the fiber sheet is excellent in tensile strength and rigidity. When the ultrafine fibers are in a state of crimping, the fiber sheet is excellent in flexibility or stretchability. Examples of the mode of the fiber sheet include a woven fabric, a knitted fabric, a nonwoven fabric, and a composite thereof.

[0025] In the fiber sheet of the present invention, the ultrafine fibers as described above are excellent in performance due to the presence of the ultrafine fibers, for example, excellent in separation performance, flexibility, and denseness.
It is preferably contained at least 10 mass%,
as%, more preferably 30% or more.
Most preferably, it is contained at least ss%.

As the fibers other than the ultrafine fibers, normal fibers can be used. For example, inorganic fibers such as glass fibers and carbon fibers, natural fibers such as silk, wool, cotton and hemp, and recycled fibers such as rayon fibers are used. Fiber, semi-synthetic fiber such as acetate fiber, polyamide fiber, polyvinyl alcohol fiber, acrylic fiber, polyester fiber, polyvinyl chloride fiber, polyvinylidene chloride fiber, polyurethane fiber, polyethylene fiber, polypropylene fiber, polymethylpentene fiber, aromatic Synthetic fibers such as polyamide fibers or composite fibers composed of two or more resin components and exhibiting crimping properties, heat bonding properties, or splitting properties can be used.

[0027] The fiber sheet of the present invention can be produced by a conventional method. For example, a wet nonwoven fabric containing ultrafine fibers generated from the above-mentioned ultrafine fiber-generating fibers can be manufactured as follows. First, an ultrafine fiber as described above is prepared. If this ultrafine fiber is not a short fiber,
For example, the sheet is cut to a desired length by a known method such as a guillotine cutter, a rotary cutter, and a press cutter.

Next, the ultrafine fibers (and other fibers, if necessary) are converted to a conventional wet method (for example, a horizontal long net system, an inclined wire long net system, a circular net system, or a long net / circular net combination system). ) To form a fiber web. The fibrous webs can then be combined to produce a wet nonwoven. Examples of the bonding method include (1) a method of entanglement by a fluid flow such as a water flow, (2) a method of bonding with ultrafine fibers, and optionally mixed thermoadhesive fibers, and (3) a method of applying or spraying a binder. And bonding methods. In addition, these coupling methods can be used together.

[0029] The fiber sheet of the present invention has an excellent texture in which ultra-fine fibers are uniformly dispersed, and therefore has various uses, for example,
Interlining for clothing, cotton filling for clothing, interior materials, gas or liquid filtering materials, various cleaning sheets, civil engineering sheets, battery separators, base materials for adhesive materials, base materials for wallpapers, base fabrics for synthetic leather, It can be used as a base cloth for artificial leather, a moisture-permeable waterproof cloth, and the like. The fiber sheet of the present invention is dyed, colored with a pigment, raised, laminated, formed,
Various functions can be added by embossing or performing a chemical or physical surface treatment to suit various applications.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The melt index of polypropylene is a value measured according to JIS K6758, and the melt index of polyethylene is a value measured according to ASTM D1238.

[0031]

(Example 1) Using a conventional composite spinning apparatus capable of spinning sea-island fibers (25 islands of sea-island fibers can be spun),
Poly-L-lactic acid as a sea component and polypropylene as an island component (melt index: 65, molecular weight distribution: 5.
1) was extruded under the conditions of a gear pump ratio of 75:25 and a temperature of 240 ° C., and an undrawn yarn having a fineness of 4.2 denier was spun. Next, the undrawn yarn was drawn 3.4 times at a temperature of 90 ° C., and then cut with a guillotine cutter to obtain a fineness of 1.2%.
Denier, short fiber capable of generating ultrafine fibers having a fiber length of 3 mm (cross section: circular, diameter of the island component: 1.7 μm or less, value obtained by dividing the standard deviation of the diameter of the island component by the average value of the diameter of the island component:
0.085 (the number of measurements: 100), and the cross-sectional shape of the island component: circular. Observation of the cross section of the ultrafine fiber-producing short fiber by an electron micrograph revealed that the fiber had a cut surface without pressure bonding.

Next, the short fibers capable of generating ultra-fine fibers are heated at a temperature of 8
It was immersed in a 1 M sodium hydroxide aqueous solution at 0 ° C. for 30 minutes to decompose and remove poly-L-lactic acid as a sea component, and the average fiber diameter was 1.2 μm. Polypropylene ultra-short fibers (cross section: circular) having a value of 0.085 (measured number: 100) divided by the average fiber diameter of the fibers were produced. The melting point of this polypropylene ultrafine short fiber was measured using a differential scanning calorimeter, and was found to be 170.3.
° C. Next, when this polypropylene ultrafine short fiber was dispersed in water containing a copolymer of acrylamide and sodium acrylate (thickener) and polyoxyethylene nonylphenyl ether (surfactant), there was no fiber lump. , And could be uniformly dispersed.

Example 2 Using a conventional composite spinning apparatus capable of spinning sea-island fibers (25 islands of sea-island fibers can be spun), poly-L-lactic acid was used as the sea component, and polypropylene (melt index) was used as the island component. : 65, molecular weight distribution: 5.
1) was extruded under the conditions of a gear pump ratio of 50:50 and a temperature of 240 ° C., and an undrawn yarn having a fineness of 4.1 denier was spun. Next, the undrawn yarn was drawn 3.3 times at a temperature of 90 ° C., and then cut with a guillotine cutter to obtain a fineness of 3.4.
Denier, short fibers capable of generating ultrafine fibers having a fiber length of 3 mm (cross section: circular, diameter of the island component: 3.5 μm or less, value obtained by dividing the standard deviation of the diameter of the island component by the average value of the diameter of the island component:
0.053 (the number of measurements: 100), and the cross-sectional shape of the island component: circular). Observation of the cross section of the ultrafine fiber-producing short fiber by an electron micrograph revealed that the fiber had a cut surface without pressure bonding.

Next, the ultrafine fiber-generating short fibers are heated at a temperature of 8
It was immersed in a 1 M aqueous solution of sodium hydroxide at 0 ° C. for 30 minutes to decompose and remove poly-L-lactic acid as a sea component. The average fiber diameter was 3 μm, and the standard deviation value of the fiber diameter of the ultrafine fiber was determined. Polypropylene ultrafine short fibers (cross section: circular) having a value of 0.053 (measured number: 100) divided by the average value of the fiber diameters were produced. The melting point of this polypropylene ultra-short fiber was measured using a differential scanning calorimeter, and was 168.0.
° C. Next, when this polypropylene ultrafine short fiber was dispersed in the same manner as in Example 1, there was no lump of fiber,
It could be uniformly dispersed.

Comparative Example A polyethylene terephthalate (proprietary) using 5-sulfoisophthalic acid as a sea component as a sea component using a conventional composite spinning apparatus capable of spinning sea-island fibers (25 islands of sea-island fibers can be spun). Viscosity: 0.54)
Polypropylene as an island component (melt index: 2
1, the molecular weight distribution 6.3) was changed to a gear pump ratio of 91:39,
It was extruded under the condition of a temperature of 295 ° C., and an undrawn yarn having a fineness of 3 denier was spun. Next, the undrawn yarn is heated to a temperature of 90 ° C.
After stretching 1.9 times with a guillotine cutter, short fibers capable of generating ultrafine fibers having a fineness of 1.7 denier and a fiber length of 3 mm (cross section: circular, diameter of island component: 1.8 μm or less, island A value obtained by dividing the standard deviation value of the diameter of the component by the average value of the diameter of the island component: 0.14 (measured number: 100), and the cross-sectional shape of the island component: circular was manufactured. Observation of the cross section of the ultrafine fiber-generating short fiber by an electron microscope photograph revealed that the island component had a surface in which the island components were pressed together.

Next, the ultra-fine fiber-generating short fibers are treated at a temperature of 8
The fiber was immersed in a 1 M aqueous sodium hydroxide solution at 0 ° C. for 45 minutes to decompose and remove polyethylene terephthalate, which is a sea component. The average fiber diameter was 1.1 μm, and the standard deviation of the fiber diameter of the microfiber was determined. Polypropylene ultrafine short fibers (cross section: circular) having a value of 0.14 (measured number: 100) divided by the average value of the diameters were produced. The melting point of the polypropylene ultra-short fibers was measured using a differential scanning calorimeter, and was 164.4 ° C. Next, when the polypropylene ultra-short fibers were dispersed in the same manner as in Example 1, the fibers were not dispersed and remained in a fiber bundle shape, or were entangled into a lump and had poor dispersibility.

(Example 3) Using a conventional composite spinning apparatus capable of spinning sea-island fibers (25 islands of sea-island fibers can be spun), poly-L-lactic acid was used as the sea component, and polypropylene (melt index) was used as the island component. : 65, molecular weight distribution: 5.
1) 40 mass% and 60 mass% of high density polyethylene (melt index: 20)
It was extruded under the conditions of 0:50 and a temperature of 240 ° C., and an undrawn yarn having a fineness of 8 denier was spun. Next, this undrawn yarn is drawn 2.4 times at a temperature of 90 ° C., and then cut with a guillotine cutter to produce ultra-fine fibers having a denier of 3.5 denier and a fiber length of 3 mm (cross section: circular, island). Ingredient diameter:
1.7 μm or less, a value obtained by dividing the standard deviation value of the diameter of the island component by the average value of the diameter of the island component: 0.11 (measured number: 10
0), cross-sectional shape of island component: circular). Observation of the cross section of the ultrafine fiber-producing short fiber by an electron micrograph revealed that the fiber had a cut surface without pressure bonding.

Next, the ultra-fine fiber-generating short fibers are treated at a temperature of 8
It was immersed in a 1 M sodium hydroxide aqueous solution at 0 ° C. for 30 minutes to decompose and remove poly-L-lactic acid as a sea component, and the average fiber diameter was 1.2 μm. Polypropylene-high-density polyethylene mixed ultra-short fibers with a value of 0.11 (measured number: 100) divided by the average fiber diameter of the fibers (cross section: circular, 60% or more of the surface is occupied by high-density polyethylene) Was manufactured. When the melting points of the polypropylene component and the high-density polyethylene component of this polypropylene-high-density polyethylene mixed ultrafine fiber were measured using a differential scanning calorimeter, the polypropylene component was 168.7 ° C. and the high-density polyethylene component was 12
9.8 ° C. When this polypropylene-high-density polyethylene mixed ultrafine short fiber was dispersed in the same manner as in Example 1, there was no lump of fibers, and the dispersion was uniform.

(Example 4) [0039] The polypropylene-high-density polyethylene mixed ultrafine short fiber of Example 3 and a core component comprising polypropylene (melting point: 158 ° C), a sheath component (adhesive component)
Is a core-sheath composite short fiber made of high-density polyethylene (melting point: 131 ° C.) (fiber diameter 11.8 μm, fiber length 10 m)
m) was prepared.

Next, the polypropylene-high-density polyethylene mixed ultra-short fibers and the core-sheath composite short fibers were mixed at a mass ratio of 1: 1 with an acrylamide-sodium acrylate copolymer (thickener) and polyoxyethylene nonyl. After dispersing in a dispersion bath composed of water containing phenyl ether (surfactant), and forming the paper with a square-shaped papermaking machine, the temperature was adjusted to 140 ° C.
At the same time as drying at ℃, the adhesive component of the core-sheath type composite adhesive short fiber and the high-density polyethylene component of polypropylene-high-density polyethylene mixed ultra-fine short fiber were bonded to produce a nonwoven fabric. Since this nonwoven fabric had a uniform texture and a uniform pore size, it was suitable as a gas or liquid filter or a battery separator.

[0041]

According to the present invention, the fibers capable of generating ultrafine fibers of the present invention do not crimp even when cut. Further, the ultrafine fibers containing the high melting point polypropylene generated from the ultrafine fiber-generating fibers of the present invention are those in which the ultrafine fibers do not adhere to each other even when cut, or the cut ultrafine fibers do not adhere to each other. Therefore, they can be uniformly dispersed. Further, since the fiber sheet of the present invention contains the ultrafine fibers, the fine sheets are excellent in texture, in which the ultrafine fibers are uniformly dispersed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a fiber capable of generating an ultrafine fiber of the present invention.

2A is a schematic cross-sectional view of another microfiber-generating fiber of the present invention. FIG. 2B is a schematic cross-sectional view of another microfiber-generating fiber of the present invention.

FIG. 3 is a schematic cross-sectional view of another microfiber-generating fiber of the present invention.

[Explanation of symbols]

 1 island component 2 sea component 3 first component 4 second component

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) D06M 101: 20 F-term (Reference) 4L031 AA14 AB11 BA11 CA01 DA00 4L041 AA07 AA20 BA04 BA05 BA11 BA13 BA16 BA26 BA27 BA49 BC04 BD03 BD11 BD20 CA15 CA37 CA38 DD01 DD05 DD11 DD14 DD18 EE06 EE15 EE20 4L047 AA14 AA21 AA27 AB08 BA08 BA22 BB09 CB10 CC12 4L055 AF16 AF17 AF33 AF47 EA16 EA20 GA31 GA37 GA39 GA50

Claims (8)

[Claims] An ultrafine fiber containing a high melting point polypropylene having a melting point of 166 ° C. or higher, and having a fiber diameter of 5 μm.
m, capable of generating ultrafine fibers of not more than m. 2. The ultrafine fiber-generating fiber according to claim 1, wherein the ultrafine fiber-generating fiber has a sea-island fiber cross-sectional shape, and a high-melting-point polypropylene is contained in the island component. . 3. The fiber capable of generating ultrafine fibers according to claim 2, wherein the island component comprises only high melting point polypropylene. 4. The island component includes a high melting point polypropylene and a polymer having a lower melting point than the high melting point polypropylene, and the low melting point polymer forms at least a part of the surface of the island component. 3. The fiber capable of generating ultrafine fibers according to claim 2. 5. The fiber according to claim 2, wherein the island component has a diameter of 2 μm or less. 6. The method according to claim 2, wherein a value obtained by dividing a standard deviation value of the diameter of the island component by an average value of the diameter of the island component is 0.2 or less. The fiber capable of generating the ultrafine fiber according to the above. 7. An ultrafine fiber comprising a high-melting-point polypropylene, generated from the ultrafine fiber-generating fiber according to any one of claims 1 to 6. A fiber sheet comprising the ultrafine fiber according to claim 7.