JP3703956B2 - Splittable fiber and fiber sheet using the splittable fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a splittable fiber and a fiber sheet using the splittable fiber.
[0002]
[Prior art]
For example, a nonwoven fabric used as an alkaline battery separator needs to be dense so as not to cause a short circuit between electrodes. For this reason, a dense nonwoven fabric has been produced by applying an external force to a fiber web containing splittable fibers that can be divided into ultrafine fibers by an external force such as a water flow to generate the ultrafine fibers.
[0003]
As the splittable fiber, for example, as shown in a fiber cross-sectional view in FIG. 6, a fiber having an orange cross-sectional shape in which polypropylene 3 and high-density polyethylene 4 are arranged adjacent to each other has been used. Since these splittable fibers are all made of an olefin resin, they can be suitably used for applications that require alkali resistance, such as alkaline battery separators. However, since this splittable fiber is highly compatible with polypropylene 3 and high-density polyethylene 4, even if an external force such as a water stream is applied, the splittable fiber moves before it is split, and cannot be easily split. There was a problem. Such a problem is conspicuous when an external force such as a water stream is applied to a fiber web formed by a wet method using a split fiber having a short fiber length and a higher degree of freedom.
[0004]
Therefore, in order to solve this problem, a heat-fusible fiber is mixed in addition to the splittable fiber, the splittable fiber is fixed by fusion of the heat-fusible fiber, and the degree of freedom of the splittable fiber. In such a state that the pressure is lowered, an external force such as a water flow is applied to divide the material. However, since the splittable fibers are not sufficiently fixed by this method, the splitting tends to be insufficient.
[0005]
In addition, the non-woven fabric produced by dividing the splitting fiber consisting only of the polyolefin resin as described above has low hydrophilicity, so it is difficult to use it for applications that require hydrophilicity, or a separate hydrophilization treatment. There is also a problem that it is complicated.
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve these problems, and an object thereof is to provide a splittable fiber excellent in splitting property and hydrophilicity, and a fiber sheet using the splitting fiber.
[0007]
[Means for Solving the Problems]
The splittable fiber of the present invention includes an ethylene copolymer composed of methacrylic acid and ethylene, and a high melting point polymer having a higher melting point than the ethylene copolymer, and the ratio of methacrylic acid in the ethylene copolymer is 1 to 20 mass%. The ethylene copolymer and the high melting point polymer are disposed adjacent to each other, and at least the ethylene copolymer is exposed on the surface.
[0008]
As described above, the splittable fiber of the present invention contains an ethylene copolymer, and the ethylene copolymer as described above has a low melting point, and the degree of freedom of the splittable fiber can be eliminated by fusing the ethylene copolymer. It can be easily divided by external force. In addition, an ethylene copolymer containing methacrylic acid is excellent in fusion power and hydrophilicity.
[0009]
Since the fiber sheet of the present invention contains the above-described splittable fiber ethylene copolymer in a fused state, it is excellent in tensile strength, rigidity, and hydrophilicity. Further, another fiber sheet of the present invention is in a state where the above-mentioned splittable fibers are split, that is, in a state containing ultrafine fibers, and thus has a dense structure and excellent hydrophilicity.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The ethylene copolymer in the present invention is composed of methacrylic acid and ethylene, and acts as a fusing component that is easily fused in the stage before dividing the splittable fiber, thereby imparting hydrophilicity. Acts as a component, and in some cases, acts as a fusion component for fusing the ultrafine fibers after splitting the split fibers to generate ultrafine fibers.
[0012]
The ethylene copolymer in the present invention contains methacrylic acid . The ethylene copolymer of the present invention may be one in which ethylene and methacrylic acid are alternately contained, one that is randomly contained, one that is contained in a block, or a mixture thereof. However, it can be used in the present invention.
[0013]
The ratio of methacrylic acid in the ethylene copolymer needs to be 1 to 20 mass% . When the ratio of methacrylic acid is less than 1 mass%, the fusing power tends to be too low, and when the ratio of methacrylic acid exceeds 20 mass%, the melting point becomes too low and it is used for applications requiring heat resistance. More preferably 3 to 18 mass%, and most preferably 5 to 16 mass%. In addition, the ratio of methacrylic acid in this ethylene copolymer can be measured by FT-IR (Fourier transform infrared spectrometer).
[0014]
In addition to the ethylene copolymer as described above, the splittable fiber of the present invention contains a high melting point polymer having a higher melting point than the above-mentioned ethylene copolymer. This high melting point polymer maintains the fiber shape of the splittable fiber without fusing when the ethylene copolymer is fused, and forms a fine fiber that is generated by splitting, so that a fiber sheet having a dense structure is produced. be able to.
[0015]
This high melting point polymer has a higher melting point than the ethylene copolymer because the fiber shape needs to be maintained even at a temperature at which the ethylene copolymer is fused. The high melting point polymer preferably has a melting point that is 10 ° C. or more higher than that of the ethylene copolymer, more preferably has a melting point that is 20 ° C. or more, and most preferably has a melting point that is 30 ° C. or more. The melting point in the present invention refers to a temperature giving an extreme value of a melting absorption curve obtained by heating from room temperature at a temperature rising temperature of 20 ° C./min using a differential calorimeter.
[0016]
As the high melting point polymer, for example, a polymer that can be melt-spun such as high-density or low-density polyethylene, polypropylene, polymethylpentene, polyester, polyamide, or polystyrene can be preferably used. Among these, polyethylene, polypropylene, or polymethylpentene has high compatibility with ethylene copolymer and is difficult to be divided by external force, but it is combined with ethylene copolymer as described above, and the ethylene copolymer is fused and fixed. It can be easily divided by applying an external force later. In addition, when using polyethylene as a high melting-point polymer, it is preferable to use high-density polyethylene with a higher melting point. Moreover, the high melting point polymer does not need to be one type, and may be a mixture of two or more types, or may be different for each high melting point polymer constituting the ultrafine fiber.
[0017]
The mixing mass ratio of such an ethylene copolymer and a high melting point polymer is preferably 20:80 to 80:20. If the ratio of the ethylene copolymer is less than 20 mass%, the fusion force tends to be reduced, and if it exceeds 80 mass%, the ratio of the high melting point polymer is too small and the amount of ultrafine fibers is reduced, and the dense fiber sheet. Is more preferably 30:70 to 70:30, and most preferably 40:60 to 60:40.
[0018]
In the splittable fiber of the present invention, an ethylene copolymer and a high melting point polymer are arranged adjacent to each other, and at least the ethylene copolymer is exposed on the surface. Therefore, the splittable fiber is fixed by fusing the ethylene copolymer, and an external force is applied to the splittable fiber, so that the ultrafine fiber can be generated by peeling at the boundary between the ethylene copolymer and the high melting point polymer. . In addition, when the fiber surface consists only of an ethylene copolymer, the ethylene copolymer can be destroyed by an external force, and at the same time, it can be peeled off at the boundary between the ethylene copolymer and the high melting point polymer to generate ultrafine fibers.
[0019]
The ethylene copolymer and the high-melting polymer are only required to be adjacent to each other, and the arrangement state is not particularly limited. For example, as shown in FIG. 2 are adjacent to each other, as shown in FIG. 2, the cross-sectional shape is a tear-shaped ethylene copolymer or high-melting polymer 2 and the cross-sectional shape is a ginkgo-shaped high-melting polymer or ethylene copolymer 1 adjacent to each other. 3, a state where the high melting point polymer or ethylene copolymer 1 is divided into a fan shape by the ethylene copolymer or high melting point polymer 2 extending from the fiber axis, or as shown in FIG. 4, the ethylene copolymer 1 and There is a state in which the high melting point polymer 2 is laminated in layers and adjacent to each other. Among these, the splitting fibers of the embodiment shown in FIGS. 1 to 3 that are easy to split regardless of the external force acting from any direction are suitable, the ratio of the ethylene copolymer exposed on the fiber surface is high, and the fusion force The splitting fiber of the embodiment shown in FIG. 2 or FIG. 3 is more suitable.
[0020]
Note that the splittable fiber may have a circular cross-sectional shape as shown in FIGS. 1 to 4 or a non-circular shape such as a substantially square shape as shown in FIG. Other examples of the non-circular cross-sectional shape include an elliptical shape, an oval shape, a T shape, a Y shape, a + shape, a hollow shape, and a polygonal shape.
[0021]
Further, the ethylene copolymer 1 and the high-melting point polymer 2 that are constituent units of the ultrafine fibers may be any number, but the fiber diameter of the ultrafine fibers that are generated by division is 0.1 so that a dense fiber sheet can be formed. It suffices if the number is ˜15 μm. In the present invention, when the cross-sectional shape of the fiber is non-circular, the diameter of a circle having the same area as the cross-sectional area is regarded as the fiber diameter.
[0022]
In the splittable fiber of the present invention, at least the ethylene copolymer is exposed on the surface so that the splittable fiber can be fused and fixed. In addition, it is preferable that both the ethylene copolymer 1 and the high-melting-point polymer 2 are exposed on the surface so that they can be more easily divided by an external force. In this case, it is preferable that the exposure rate of the ethylene copolymer 1 is 30% or more (the exposure rate of the high melting point polymer 2 is 70% or less), and 40% or more (high melting point) so that fusion by the ethylene copolymer 1 is likely to occur. The exposure rate of polymer 2 is more preferably 60% or less. In addition, this exposure rate means the percentage of the exposed area with respect to a fiber surface area.
[0023]
In addition, the splittable fiber of the present invention preferably has a recess 5 on the fiber surface so as to be more excellent in splittability, and particularly preferably has a recess 5 at the boundary between the ethylene copolymer 1 and the high melting point polymer 2 (FIG. 7). reference). As described above, when the depression 5 is provided at the boundary between the ethylene copolymer 1 and the high melting point polymer 2, even if the entire fiber surface is covered with the ethylene copolymer 1, it can be easily divided by an external force. In addition, when both the ethylene copolymer 1 and the high melting point polymer 2 are exposed on the fiber surface, they can be more easily divided. In addition, this "dent" means the state depressed from the smooth fiber surface, and is discontinuous in the fiber length direction and the circumferential direction. Such a depression can be easily confirmed by an electron micrograph.
[0024]
The fineness of such a splittable fiber is not particularly limited, but is preferably 50 μg / m to 600 μg / m so that ultrafine fibers having the above-described fiber diameter can be easily generated. Further, the splittable fiber may be a filament or a staple cut to a length of about 1 to 160 mm. In addition, even if it is a splittable fiber having a length of about 1 to 30 mm, which is difficult to split because of the high degree of freedom of the fiber, the splitting property is excellent.
[0025]
In the ethylene copolymer and / or high melting point polymer, for example, a hygroscopic agent, a matting agent, a pigment, a flame retardant, a stabilizer, an antistatic agent, a coloring agent, a dyeing agent, a conductive agent, a hydrophilizing agent, a deodorizing agent, Alternatively, various functions can be added by mixing functional substances such as antibacterial agents.
[0026]
Such a splittable fiber of the present invention can be easily spun by using a conventional compound spinning apparatus. For example, when the ethylene copolymer is composed of an ethylene-methacrylic acid copolymer and the high melting point polymer is composed of polypropylene, any polymer can be easily spun by setting the melt spinning temperature to 220 to 300 ° C., preferably 250 to 270 ° C. .
[0027]
The undrawn yarn thus composite-spun can be drawn 1 to 8 times at a temperature not lower than room temperature and not higher than the melting point of the ethylene copolymer to produce a split fiber having a fineness of about 50 μg / m to 600 μg / m. it can. In addition, when using this splittable fiber as a raw material of a dry-type nonwoven fabric or as a spun yarn, it is preferable to mechanically or thermally impart about 5-50 pieces / inch.
[0028]
In addition, the splittable fiber having the depression 5 on the fiber surface that is suitable in the present invention can be obtained by, for example, stretching an undrawn yarn 2 to 8 times (preferably 2.3 to 6 times), an ethylene copolymer and / Alternatively, it can be produced by mixing a solvent-extractable resin in a high melting point polymer and extracting and removing the solvent-extractable resin after spinning. Among these, the former method is more preferable because it is easy to produce a splittable fiber having a depression 5 at the boundary between an ethylene copolymer and a high melting point polymer, and can be easily produced only by adjusting the stretching conditions. .
[0029]
Since one of the fiber sheets of the present invention contains the above-described splittable fiber ethylene copolymer in a fused state, it is excellent in tensile strength, rigidity, and hydrophilicity. Moreover, since another fiber sheet contains the above-described splittable fiber in a divided state, it has a dense structure and is excellent in hydrophilicity. In addition, a woven fabric, a knitted fabric, a nonwoven fabric etc. can be illustrated as a fiber sheet. Among these, the nonwoven fabric has an irregular fiber structure and requires more tensile strength, rigidity, or denseness. Therefore, when the above-described splitting fibers are used as the fibers constituting the nonwoven fabric, particularly excellent effects are exhibited. . Therefore, it demonstrates below based on a nonwoven fabric.
[0030]
The above-described splittable fiber preferably contains 10 mass% or more, more preferably contains 20 mass% or more, and more preferably contains 30 mass% or more so that tensile strength, rigidity, denseness, and hydrophilicity are improved. Most preferably.
[0031]
As the fibers other than the splittable fibers, ordinary fibers can be used. For example, inorganic fibers such as glass fibers and carbon fibers, natural fibers such as silk, wool, cotton, and hemp, regenerated fibers such as rayon fibers, 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 polyamide fiber Alternatively, synthetic fibers such as composite fibers composed of two or more kinds of resin components and having a crimping property, heat-fusibility, or splitting property can be used.
[0032]
A method for manufacturing a nonwoven fabric using the splittable fibers as described above will be briefly described. First, a fiber web containing the splittable fibers as described above is formed. Examples of the method for forming the fiber web include a dry method such as a card method, an air lay method, a spun bond method, and a melt blow method, and a wet method. The fiber length differs depending on the fiber web forming method, and when the former dry method is used (except for the spunbond method and the melt blow method), fibers having a length of about 20 to 160 mm are used, and the latter wet method is used. When forming, fibers having a length of about 1 to 30 mm are used. Further, after forming these fiber webs, different types of fiber webs may be laminated, such as laminating fiber webs having different production methods.
[0033]
Subsequently, by applying an external force to the fiber web, the splittable fiber can be split to generate ultrafine fibers. The high melting point polymer constituting the splittable fiber is made of polyethylene, polypropylene, or polymethylpentene. As described above, when the compatibility between the ethylene copolymer and the high melting point polymer is high (particularly when the fiber length is about 1 to 30 mm), heat treatment is performed before applying external force, and only the ethylene copolymer is fused. Thus, it is preferable to eliminate the degree of freedom of the splittable fibers.
[0034]
This heat treatment is preferably carried out at a temperature which is at least 10 ° C. higher than the melting point of the polyethylene copolymer and lower than the melting point of the high melting point polymer. Moreover, it is preferable to carry out under no pressure so that the polyethylene copolymer is not formed into a film by this heat treatment. Such heat treatment can be performed by, for example, a dryer, a hot air dryer, a dryer with suction, or the like.
[0035]
Examples of the external force that can be applied after eliminating the degree of freedom of the splittable fiber by such heat treatment or without heat treatment include fluid flow such as needle punch, water flow, calendar, or flat plate press. Among these, a fluid flow such as a needle punch or a water flow is preferable because it can be entangled simultaneously with the splitting of the splittable fiber, and it is excellent in fluidity such as a water flow that is excellent in splittability and highly entangled. The flow is more suitable.
[0036]
As processing conditions by this suitable fluid flow, for example, a nozzle diameter of 0.05 to 0.3 mm, preferably 0.08 to 0.2 mm, a pitch of 0.2 to 3 mm, and preferably 0.4 to 2 mm. And a fluid flow having a pressure of 1 to 30 MPa, preferably 5 to 25 MPa may be ejected from the nozzle plates arranged in one or more rows. The pressure of the fluid flow may be changed, or the nozzle plate may be swung or vibrated.
[0037]
By applying such an external force, the non-woven fabric in which the split fibers are split to generate ultrafine fibers is excellent in denseness.
[0038]
The non-woven fabric in which the ethylene copolymer of the other splittable fiber is fused may be a heat-treated fiber web, but it may or may not be heat-treated to eliminate the freedom of the splittable fiber. First, after splitting the split fibers to generate ultrafine fibers, heat treatment is performed so that the ultrafine fibers made of ethylene copolymer are fused, so that the tensile strength, rigidity, and hydrophilicity are increased. An excellent nonwoven fabric can be produced.
[0039]
The heat treatment in the case of re-implementation is preferably carried out at a temperature that is 10 ° C. or more higher than the melting point of the polyethylene copolymer and lower than the melting point of the high-melting polymer, as in the first heat treatment. Moreover, it is preferable to carry out under no pressure so that the polyethylene copolymer is not formed into a film by this heat treatment. Such heat treatment can be performed by, for example, a dryer, a hot air dryer, a dryer with suction, or the like. Note that the first heat treatment condition and the second heat treatment condition may be the same, or one or more conditions may be different.
[0040]
The fiber sheet of the present invention that can be produced as described above is dense and excellent in tensile strength, rigidity, and hydrophilicity. For example, base materials for artificial leather such as gloves, outer garments, and bags, and cores for clothing. It can be used for various applications such as ground, padding, leak-proof sheets, masks, battery separators, air or liquid filters, wallpaper, automotive interior materials, partition base materials, wipers and the like. In addition, post-processing such as dyeing processing, buffing processing, pigment coloring processing with binder, stagnation processing, electret processing, hydrophilization processing (when further hydrophilicity is required) to suit various applications, for various applications Can be implemented to suit.
[0041]
Examples of the present invention will be described below, but the present invention is not limited to the following examples.
[0042]
【Example】
(Example 1)
In a conventional composite spinning apparatus, ethylene-methacrylic acid copolymer (the ratio of methacrylic acid in the ethylene copolymer is 15 mass%, melting point 90 ° C.) is 260 ° C., while polypropylene (melting point 160 ° C.) as a high melting point polymer is 260 ° C. Then, it was extruded from a nozzle at a composite mass ratio of ethylene copolymer and polypropylene of 50:50 to obtain a wound yarn having a fineness of 311 μg / m.
[0043]
Next, the wound yarn was stretched 2.4 times at 55 ° C. and then cut to produce a split fiber having a fineness of 144 μg / m and a fiber length of 10 mm. As shown in FIG. 2, the cross-sectional shape of the splittable fiber is such that eight ginkgo-shaped ethylene copolymers and eight tear-shaped polypropylenes are adjacent to each other, and both the ethylene copolymer and the polypropylene are exposed on the surface (ethylene Further, the copolymer had an exposure rate of 50%), and had many depressions 5 at the boundary between the ethylene copolymer and polypropylene (see FIG. 8). This splittable fiber could generate ultrafine fibers having a fiber diameter of 3.6 μm made of ethylene copolymer and ultrafine fibers having a fiber diameter of 3.6 μm made of polypropylene.
[0044]
Next, a fiber web was formed by a conventional wet method using 100% by mass of the splittable fiber. Next, this fiber web was heat-treated for 5 minutes with a hot air dryer set at 110 ° C. to fuse only the ethylene copolymer (see FIG. 9).
[0045]
Next, this fused fiber web was placed on a net having an opening of 0.147 mm, and a pressure of 9.3 mm was applied to the fused fiber web from a nozzle plate arranged with a diameter of 0.13 mm and a pitch of 0.6 mm. A water flow of 8 MPa was ejected, the fiber web was then inverted, and a water flow of pressure 9.8 MPa was ejected from the same nozzle plate to split and split the split fibers.
[0046]
Then, the entangled fiber web was heat-treated for 5 minutes with a hot air dryer set at 110 ° C., and only the ultrafine fibers made of ethylene copolymer were fused to obtain an area density of 40 g / m ² and a thickness of 0.2 mm. A non-woven fabric was produced. When this nonwoven fabric was observed with an electron micrograph, the splittable fibers were sufficiently divided and had a dense structure (see FIG. 10).
[0047]
(Example 2)
Exactly the same as in Example 1, after obtaining a wound yarn having a fineness of 489 μg / m, the wound yarn was stretched 2.4 times at 55 ° C. and then cut to obtain a fineness of 222 μg / m and a fiber length of 10 mm. Splittable fibers were produced. As shown in FIG. 2, the cross-sectional shape of the splittable fiber is such that eight ginkgo-shaped ethylene copolymers and eight tear-shaped polypropylenes are adjacent to each other, and both the ethylene copolymer and the polypropylene are exposed on the surface (ethylene The copolymer had an exposure rate of 50%), and had many depressions 5 at the boundary between the ethylene copolymer and polypropylene (see FIG. 7). This splittable fiber could generate ultrafine fibers having a fiber diameter of 4.4 μm made of ethylene copolymer and ultrafine fibers having a fiber diameter of 4.4 μm made of polypropylene.
[0048]
Next, 100% by mass of this splittable fiber was used, and fiber web formation, heat treatment, hydroentanglement treatment, and heat treatment were performed in the same manner as in Example 1 to obtain an area density of 40 g / m ² and a thickness of 0. A 2 mm non-woven fabric was produced. When this nonwoven fabric was observed with an electron micrograph, the splittable fibers were sufficiently divided and had a dense structure similar to the nonwoven fabric of Example 1.
[0049]
(Example 3)
Exactly the same as in Example 1, after obtaining a wound yarn having a fineness of 311 μg / m, the wound yarn was stretched 1.6 times at 55 ° C. and then cut to obtain a fineness of 216 μg / m and a fiber length of 10 mm. Splittable fibers were produced. As shown in FIG. 2, the cross-sectional shape of the splittable fiber is such that eight ginkgo-shaped ethylene copolymers and eight tear-shaped polypropylenes are adjacent to each other, and both the ethylene copolymer and the polypropylene are exposed on the surface (ethylene The exposure rate of the copolymer was 50%). In addition, the fiber surface was a smooth state without a hollow (refer FIG. 11). Further, this splittable fiber could generate ultrafine fibers having a fiber diameter of 4.3 μm made of ethylene copolymer and ultrafine fibers having a fiber diameter of 4.3 μm made of polypropylene.
[0050]
Next, 100% by mass of this splittable fiber was used, and fiber web formation, heat treatment, hydroentanglement treatment, and heat treatment were performed in the same manner as in Example 1 to obtain an area density of 40 g / m ² and a thickness of 0. A 2 mm non-woven fabric was produced. When this nonwoven fabric was observed with an electron micrograph, a part of the split fibers that were not split were present.
[0051]
【The invention's effect】
The splittable fiber of the present invention includes an ethylene copolymer composed of methacrylic acid and ethylene, and a high melting point polymer having a higher melting point than the ethylene copolymer, and the ratio of methacrylic acid in the ethylene copolymer is 1 to 20 mass%. The ethylene copolymer and the high melting point polymer are arranged adjacent to each other, and at least the ethylene copolymer is exposed on the surface.
[0052]
As described above, the splittable fiber of the present invention contains an ethylene copolymer, and the ethylene copolymer as described above has a low melting point, and the degree of freedom of the splittable fiber can be eliminated by fusing the ethylene copolymer. It can be easily divided by external force. In addition, an ethylene copolymer containing methacrylic acid is excellent in fusion power and hydrophilicity.
[0053]
Since the fiber sheet of the present invention contains the above-described splittable fiber ethylene copolymer in a fused state, it is excellent in tensile strength, rigidity, and hydrophilicity. Further, another fiber sheet of the present invention is in a state where the above-mentioned splittable fibers are split, that is, in a state containing ultrafine fibers, and thus has a dense structure and excellent hydrophilicity.
[Brief description of the drawings]
1 is a cross-sectional view of a splittable fiber of the present invention. FIG. 2 is a cross-sectional view of another splittable fiber of the present invention. FIG. 3 is a cross-sectional view of still another splittable fiber of the present invention. FIG. 5 is a cross-sectional view of still another splittable fiber of the present invention. FIG. 6 is a cross-sectional view of a conventional splittable fiber. FIG. 7 is a schematic view of the splittable fiber of FIG. FIG. 8 is an electron micrograph of a splittable fiber (Example 1). FIG. 9 is an electron micrograph of only the ethylene copolymer of the splittable fiber (Example 1). FIG. Electron micrograph of Example 1 [FIG. 11] Electron micrograph of splittable fiber (Example 3) [Explanation of symbols]
1 Ethylene copolymer 2 High melting point polymer 3 Polypropylene 4 High density polyethylene 5 Dimple

Claims (5)

An ethylene copolymer composed of methacrylic acid and ethylene, and a high-melting polymer having a higher melting point than the ethylene copolymer, and the ratio of methacrylic acid in the ethylene copolymer is 1 to 20 mass%. Are arranged adjacent to each other, and at least the ethylene copolymer is exposed on the surface.   The splittable fiber according to claim 1, wherein the fiber surface has a depression. 3. The splittable fiber according to claim 1 , wherein the high melting point polymer is a polymer selected from polypropylene, polyethylene, and polymethylpentene. A fiber sheet comprising the splittable fiber ethylene copolymer according to any one of claims 1 to 3 in a fused state. A fiber sheet comprising the splittable fiber according to any one of claims 1 to 3 in a split state.

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