JP4204734B2 - Porous fiber composite and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel porous fiber composite having a large number of cellular voids, and more particularly to a novel porous layer having a fiber layer having a large number of cellular voids and a fiber fusion dense layer on at least one surface thereof. It relates to a fiber composite.
[0002]
[Prior art]
Conventionally, many surface treatments have been performed to modify the surface of a textile product to provide a new function. Typical examples include moisture permeability and waterproofing and artificial leather. Moisture permeable and waterproof processing expresses a function by a film formed by coating a resin on the fabric surface. Artificial leather is made into a product by impregnating a non-woven fabric with a urethane-based resin solution to form a microporous structure, and further providing a resin layer on the surface or polishing.
JP-A-8-85181 discloses an absorbent film excellent in ink absorbability, that is, a synthetic paper. The synthetic paper is obtained by thermocompression bonding of an unstretched fiber web and stretching the pressure-bonded unstretched fiber web layer, thereby forming a fine crater film surface on at least one surface and forming a fibrous porous layer inside. Is.
In each of the above prior arts, the surface of a fabric or nonwoven fabric is resin-processed or thermocompression-bonded to form a dense layer, and the porous fiber layer having a cellular void portion, which is the object of the present invention, is formed. It is a fiber structure that is different from the fiber molding that it has.
[0003]
The present applicant invented a porous fiber molded body having a novel cellular void, and filed Japanese Patent Application Nos. 11-293679, 11-316483 and 11-366430. Yes. The porous fiber molded body obtained in these inventions has a cellular void portion, and its porosity is much larger than that of fabrics and nonwoven fabrics, and has excellent performance in heat insulation, sound absorption, liquid absorption, etc. Indicates. In order to adjust these performances of the porous fiber structure according to the application, it has been found that a structure having a dense layer on its surface is necessary.
[0004]
[Problems to be solved by the invention]
The present invention provides a novel porous fiber composite having a fiber layer having a large number of cellular voids and a fiber fusion dense layer on at least one surface thereof, and a method for producing the same.
[0005]
[Means for Solving the Problems]
That is, the first invention includes a fiber layer containing a large number of cellular voids containing a wet heat-adhesive fiber in an amount of 10 to 100% by weight and having a major axis of about 1 mm to about 30 mm, which is formed by fusing and fixing the fiber. A porous fiber composite comprising a breathable fiber fusion dense layer having the same fiber composition as the fiber layer on at least one surface of the fiber layer.
[0006]
In the second invention, the fiber layer is composed of a fiber support layer and a wet heat adhesive fiber standing on the fiber support layer, and a breathable fiber is provided at the opposite end of the fiber support layer of the standing fiber. A porous fiber composite having the structure of the first invention in the form of a sheet having a fused dense layer.
[0007]
A third invention is a sheet-like porous fiber composite having a structure of the first invention, wherein the fiber layer is composed of fibers arranged substantially parallel to the plane of the fiber layer.
[0008]
A fourth invention is a fiber bundle in which the fiber layer is converged, and has a cylindrical shape having the structure of the first invention having a breathable fiber fusion dense layer on a circumferential surface in the length direction of the fiber bundle. It is a porous fiber composite.
[0009]
A fifth invention is the porosity described in any one of the first to fourth inventions, wherein the wet heat adhesive fiber is a fiber in which an ethylene vinyl alcohol copolymer is present on at least a part of the fiber surface. It is a fiber composite.
[0010]
In a sixth aspect of the present invention, a fiber layer containing 10 to 100% by weight of a wet heat adhesive fiber is immersed in water, heat-treated while generating bubbles in the fiber layer to form a cellular void, A fiber layer having a large number of cellular voids, wherein a fiber fusion dense layer is formed by thermocompression bonding at least one surface of the fiber layer, and the same fiber as the fiber layer on at least one surface of the fiber layer This is a method for producing a porous fiber composite having a breathable fiber fusion dense layer composed of a composition.
[0011]
According to a seventh aspect of the present invention, after forming a fiber fusion dense layer by thermocompression bonding at least one surface of a fiber layer containing 10 to 100% by weight of wet heat adhesive fiber, the fiber layer is immersed in water, A fiber layer having a large number of cellular voids formed by heat treatment while generating bubbles in the layer, and the same fiber as the fiber layer on at least one surface of the fiber layer This is a method for producing a porous fiber composite having a breathable fiber fusion dense layer composed of a composition.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The porous fiber composite used in the present invention contains wet heat adhesive fibers. The wet heat adhesive fiber referred to in the present invention is a fiber containing a polymer component that is softened with hot water of about 95 to 100 ° C. and adheres to itself or other fibers. An example of such a polymer is an ethylene vinyl alcohol copolymer. The ethylene vinyl alcohol copolymer refers to a copolymer obtained by copolymerizing ethylene alcohol with 10 mol% or more and 60 mol% or less with polyvinyl alcohol. In particular, those obtained by copolymerizing ethylene residues of 30 mol% or more and 50 mol% or less are preferred from the viewpoint of wet heat adhesion. The vinyl alcohol portion has a saponification degree of 95 mol% or more. Due to the large number of ethylene residues, a unique property of having wet heat adhesiveness but not hot water solubility is obtained. The degree of polymerization can be selected as necessary, but is usually about 400 to 1500. After forming the desired porous fiber molded body, the ethylene vinyl alcohol copolymer can be partially crosslinked for post-processing such as dyeing or fiber modification.
Examples of the other polymer include a copolymer having acrylamide as one component, and polylactic acid.
[0013]
The wet heat adhesive fiber of the present invention may be a fiber made of the copolymer, a composite fiber with another thermoplastic polymer, or a fiber coated with the copolymer on another thermoplastic polymer. . The thermoplastic polymer needs to have a melting point higher than that of an ethylene vinyl alcohol copolymer in terms of heat resistance, dimensional stability, etc., for example, a crystalline thermoplastic polymer having a temperature of 150 ° C. or higher is preferable. Examples thereof include polyester, polyamide, and polypropylene.
[0014]
Polyesters include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, phthalic acid, α, β- (4-carboxyphenoxy) ethane, 4,4-dicarboxydiphenyl, 5-sodium sulfoisophthalic acid, etc. Acids: Aliphatic dicarboxylic acids such as azelaic acid, adipic acid, sebacic acid or their esters; ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl Examples thereof include fiber-forming polyesters composed of diols such as glycol, cyclohexane-1,4-dimethanol, polyethylene glycol, and polytetramethylene glycol, and 80 mol% or more of the structural units are ethylene terephthalate units. preferable.
Examples of the polyamide include an aliphatic polyamide and a semi-aromatic polyamide mainly composed of nylon 6, nylon 66, and nylon 12, and may include a polyamide containing a small amount of the third component.
[0015]
In a composite fiber composed of an ethylene vinyl alcohol copolymer and another thermoplastic polymer, the composite ratio is the former: the latter (weight ratio) = 10: 90 to 90:10, particularly 30:70 to 70:30. Is preferable from the viewpoint of spinnability. In addition, the composite form is not particularly limited as long as it is a conventionally known composite form, such as a core-sheath type, an eccentric core-sheath type, a multi-layer bonding type, a side-by-side type, a random composite type, a radial bonding type, a fine fiber division type, and the like. Can be mentioned. The cross-sectional shape of these fibers is not limited to a round cross-section or a solid cross-sectional shape that is a solid cross-sectional shape, and may be various cross-sectional shapes such as a hollow cross-sectional shape.
Moreover, in the fiber which coated the ethylene vinyl alcohol type copolymer on the other thermoplastic fiber, this copolymer is a fiber which coat | covered 1/4 or more of the surface of the other fiber, Preferably it is 1/3 or more.
[0016]
The porous fiber composite having the fiber fusion dense layer of the present invention needs to contain 10 to 100% by weight, preferably 50 to 100% by weight of the wet heat adhesive fiber. When the wet heat adhesive fiber is less than 10% by weight, the adhesion between the fibers becomes insufficient, the formation of the fiber fusion dense layer is insufficient, the breaking strength is low, and this is not practically preferable. Furthermore, the formation of cellular voids becomes insufficient.
The fiber layer having a cellular void portion of the present invention has fibers constituting the fiber layer arranged in a random web shape, arranged substantially parallel to the plane of the fiber layer, and a fiber support layer. Any of fibers made up of the support layer may be used.
[0017]
The porous fiber layer of the present invention has cellular voids in the fiber layers having the above-described various fiber arrangements. The cellular void portion is a void portion formed inside the porous fiber layer, and is a space region formed by moving the fibers constituting the fiber layer and fusing and fixing the fibers in that state. The shape includes various irregular shapes such as a spherical shape and a cloud shape, and the size ranges from about 1 mm to about 30 mm in the major axis, and preferably has a wide distribution of about 2 mm to about 10 mm. The cellular void portion is an independent or continuous shape, and when viewed microscopically in an enlarged photograph, there is also a void that is continuous with micropores between fibers over several tens of centimeters.
[0018]
The fiber fusion dense layer of the fiber composite of the present invention is a dense layer obtained by thermocompression bonding the surface of the porous fiber layer described above and fusing the wet heat adhesive fibers. According to scanning electron micrograph observation, the dense layer has a network structure in which wet-heat adhesive fibers are irregularly entangled and fused, and the cross section has a thickness of about 100 μm or more, preferably about 300 μm. , Has a large number of through-holes. The thickness of the dense layer and the pore diameter of the fine pores can be adjusted by the type and content of the wet heat adhesive fiber and the thermocompression bonding conditions. The dense layer of the fiber composite of the present invention is a fiber entangled layer formed by fusing the wet heat adhesive fiber component and fusing and bonding other fibers, and is a smooth and breathable layer.
[0019]
The porous fiber composite having the fiber fusion dense layer of the present invention can be formed into an arbitrary shape. The present invention is characterized by the surface structure and the internal structure, and is not limited to the external shape. Hereinafter, a method for producing a fiber composite having a typical shape will be described.
[0020]
As an example of manufacturing a sheet-like molded body, a method using a moquette as a precursor can be mentioned. Wet wet heat adhesive fibers as cut pile yarn, immersing the surface of the obtained moquette in water, irradiating with microwaves, and heating while producing bubbles from the inside of the moquette After that, a dense layer of fiber fusion is formed on the surface by pressure bonding with a thermal cylinder. In addition, after a heat cylinder is pressed on the surface of the moquette to form a dense layer of fiber fusion, the moquette is immersed in water and irradiated with microwaves to generate bubbles from the inside of the moquette. You may employ | adopt the method of heating, heating. In this method, a fiber composite structure composed of a dense fiber fusion layer and a homogeneous porous fiber layer having no cellular voids is obtained as an intermediate product. The intermediate product does not have a cellular void, but can be used as a similar product of the fiber composite of the present invention.
[0021]
The sheet-like fiber composite can be manufactured in the same manner by using the above-described moquette and using a fiber web made of ordinary long fibers or short fibers. Further, the fiber web may be an irregular fiber arrangement or a fiber arrangement substantially parallel to the fiber web plane. Depending on the arrangement of the fibers, the shape of the cellular void formed in the fiber layer tends to be an irregular shape or a shape along the plane of the fiber layer. In the present invention, various fiber webs containing wet heat adhesive fibers, which are in an intermediate treatment stage, may be referred to as precursors.
[0022]
An example of a method for producing a cylindrical porous fiber composite is a method using a fiber bundle as a precursor. A fiber bundle of about 100,000 denier containing wet heat adhesive fibers is passed while contacting the inner wall of the hollow heater. The contact pressure can be adjusted by reducing the diameter of the hollow heater. Thereby, a fiber fusion dense layer can be formed on the surface. Next, the fiber bundle is continuously or cut into a desired length, immersed in a container filled with water, and heated while generating bubbles from the fiber bundle by irradiating with microwaves, thereby forming a cell shape inside. A void is formed. Of course, the same product can be obtained by the reverse method.
[0023]
Hereinafter, the structure of the fiber composite of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of a sheet-like fiber composite having a fiber fusion dense layer of the present invention. In the porous fiber layer 1, fibers are irregularly arranged, and the cellular void 2 formed in the fiber layer has many irregular shapes. A fiber fusion dense layer 3 is provided on one surface of the fiber layer 1.
FIG. 2 is a schematic cross-sectional view showing another example of a sheet-like fiber composite having a fiber fusion dense layer of the present invention. In the porous fiber layer 1, the fibers are arranged substantially parallel to the plane of the fiber layer, and the cellular voids 2 formed in the fiber layer also have many shapes along the plane of the fiber layer. A fiber fusion dense layer 3 is provided on one surface of the fiber layer 1.
[0024]
FIG. 3 is a schematic cross-sectional view showing another example of a sheet-like fiber composite having a fiber fusion dense layer of the present invention. In the porous fiber layer 1, fibers are erected on the fiber support layer 4, and the cellular void 2 formed in the fiber layer extends along the erected fiber from the support layer to the opposite surface thereof. There are many shapes that expand sequentially. A fiber fusion dense layer 3 is provided on one surface of the fiber layer 1 (opposite side to the support layer).
FIG. 4 is a partially broken schematic view showing another example of the fiber composite having the fiber fusion dense layer of the present invention. In the porous fiber layer 1, the fibers are arranged in a cylindrical shape along the long axis, and the cellular voids 2 formed in the fiber layer are arranged in the length direction along the arranged fibers. Many shapes. A fiber fusion dense layer 3 is provided on the outer surface of the cylindrical fiber layer 1.
[0025]
FIG. 5 is an enlarged partial sectional view showing the structure of the dense layer of fiber fusion of the present invention. The fiber fusion dense layer 3 is formed by coating fibers 5 other than wet heat adhesive fibers such as polyester fibers with a polymer layer 6 in which wet heat adhesive fibers are melted, and having fine communication holes 7 therebetween. ing.
[0026]
Hereinafter, the manufacturing method of the fiber composite body which has a fiber fusion | melting dense layer of this invention is demonstrated in detail.
The precursor containing wet heat adhesive fibers is impregnated with water, and the precursor containing water is heated. A suitable heating method is, for example, heating by microwaves at 2450 MHz. By performing wet heat treatment in a state where bubbles are generated in the fiber layer, a large number of amorphous cell-shaped voids can be formed in the fiber layer and on the surface thereof. The treatment requires the presence of a sufficient amount of water to generate bubbles under heating. Cellular voids are formed in the fiber layer by the bubbles. By the way, even if bubbles are generated in the fiber layer and the constituent fibers move, the cellular void portion is not formed unless the structure is fixed in the fiber layer. In order to form cellular voids in the fiber layer, wet heat adhesive fibers are required. That is, the fiber layer containing the wet heat adhesive fibers in a state containing bubbles is heat-fused to form and fix the cellular void. Using this basic configuration, fiber composites of various shapes such as a sheet shape and a cylindrical shape can be produced.
[0027]
The heating required to generate bubbles in the fiber layer depends on the atmospheric pressure of the heating atmosphere, and is usually about 100 ° C. at 1 atm. If heating is performed under reduced pressure or increased pressure, the boiling temperature varies depending on the atmospheric pressure. In order to form cellular voids, it is important that the precursor is heated in the presence of sufficient bubbles. The precursor containing water can be heated by steam blowing, high frequency electromagnetic waves or a reduced pressure heating machine (vacuum setting machine). According to the high frequency electromagnetic wave heating, bubbles are easily generated in the fiber layer.
[0028]
The heating temperature is also related to the fusing temperature of the wet heat adhesive fiber. It is preferable that the heating temperature becomes a temperature equal to or higher than the fusing temperature of the wet heat adhesive fiber and less than 10 ° C. The wet heat treatment time can be adjusted by the fiber amount of the precursor, the degree of fiber fusion, and the like.
[0029]
After the wet heat adhesive fibers are fused, the fiber molded body is cooled by a known method to fix the structure of the porous fiber molded body. Since the fiber molded body after the wet heat treatment contains hot water, it is preferably immersed in cold water or cooled by a cold water shower, and cooling by cold air is low in efficiency. If the fiber molded body is compressed before it is sufficiently cooled, there is a risk of deformation of the cellular void. On the other hand, it is also possible to adjust the cellular gap by using a compression process. It is one of the advantages of the present invention that the porous structure of the fiber molded body can be adjusted by such a simple method.
[0030]
The method for forming a fiber fusion dense layer on the surface of the fiber layer is to thermocompression-bond the fiber layer surface after the above-mentioned wet heat treatment by an ordinary method, whereby the wet heat adhesive fiber of the surface layer is melted and re-solidified. Thus, a dense layer having a smooth surface is formed. As a continuous thermocompression bonding method, a method of contact heating with a 180 ° C. heat roller is preferable.
The present invention has the advantage that no organic solvent or foamable resin is required to form the cellular void. In addition, even in the formation of a dense layer on the surface, the load and burden on the environment and the operator are extremely small because no resin or solvent is used, and the manufacturing cost can be reduced. This advantage is a great effect in practical use.
[0031]
The product of the present invention can be applied in various ways by a composite structure composed of a fiber fusion dense layer and a fiber layer having a cellular void, for example, a soundproofing material, a heat insulating material, a heat insulating clothing, a wire covering material, a rug, It can be used for various purposes such as bedding mats, water absorbing materials for civil engineering, various liquid absorbing materials such as ink, leather-like sheets, liquid spreading sheets, paint roller base fabrics, medical liquid absorbing materials, and support materials.
[0032]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In the examples, all the examples using 100% wet heat-adhesive fibers are described. Of course, different materials may be mixed, but the wet heat-adhesive fibers are denier, crimped, and cross-sectional shapes. Of course, they may be mixed in different ways.
[0033]
Example 1
Polyethylene terephthalate containing 3% by weight of silica [phenol / tetrachloroethane, etc. in a mixed solvent such as intrinsic viscosity = 0.68 measured at 30 ° C.] as the core component and the sheath component as the ethylene content A core-sheath composite fiber was obtained using an ethylene vinyl alcohol copolymer of 40 mol% and MI = 10. (Core / sheath ratio = 50/50, 150 denier / 48 filament)
This fiber is used to perform false twisting at a false twist number of 2350 T / M, a one-stage heater temperature of 120 ° C., a two-stage heater temperature of 135 ° C., and a false twisting rate of 17%. I got a thread.
[0034]
A circular knitted bore was knitted using a cut pile yarn of two denier yarns of 150 denier wet heat adhesive fibers and a denier yarn of 300 denier and regular polyester 150 denier false twist yarn.
The circular knitted bore knitted fabric was cut into a 30 cm square, immersed in water in an expanded state, and irradiated with microwaves of 2450 MHz and 1 KW. Bubbles are observed from inside the pile surface of the knitted fabric by microwave irradiation. Irradiation was continued for about 1 minute after the generation of bubbles, then taken out, cooled in water, centrifuged and dehydrated, and dried to obtain a fiber structure having cellular voids on the surface and inside.
Next, the fiber structure was subjected to thermocompression bonding using a calender roll having a pressure bonding temperature of 180 ° C. and a roll linear pressure of 5 kg / cm. The obtained fiber composite is provided with a dense layer having a smooth surface, and a fiber layer having a cell-like void is formed on the lower surface thereof.
[0035]
Example 2
Using the same composite fiber as used in Example 1, the core-sheath composite staple fiber having a crimp extension of 7% with 3 denier and a cut length of 64 mm is obtained through spinning, drawing and crimping steps. It was.
The obtained core / sheath composite staple fiber was carded to prepare a needle punched nonwoven fabric having a punch density of 90 / cm ² , a thickness of 10 mm, and a basis weight of 300 g / m ³ .
The needle punched nonwoven fabric was sufficiently impregnated with water at room temperature, and irradiated with microwaves of 2450 MHz 1 kw while being suppressed by a net so that the nonwoven fabric did not float. After confirming the generation of bubbles from the nonwoven fabric, the irradiation was continued for 2 minutes. After the treatment, the nonwoven fabric was taken out and immersed in cooling water at room temperature to be cooled and fixed. Next, this was centrifuged and dehydrated and dried at a dry heat of 110 ° C.
[0036]
In the cross section of the obtained nonwoven fabric, fiber bundles penetrating in the thickness direction were distributed almost uniformly as needle marks, and a large number of large cellular voids of 1 mm to 5 mm were confirmed between the fiber bundles. On the other hand, when the surface of the nonwoven fabric was sliced and the internal state was observed, amorphous cellular voids existed, and independent voids or partially linked cellular voids could be confirmed.
Next, both sides of the nonwoven fabric were guided to a calender roll, and both sides were thermocompression bonded at 180 ° C. A smooth dense layer was formed on both surfaces, and a fiber composite was obtained in which the inner layer adjacent to the surface formed the above-described fiber layer having the cellular voids.
[0037]
Example 3
Using the circular knitted bore of Example 1, a fiber fusion dense layer was formed prior to microwave irradiation. That is, the surface of the circular knitted bore was thermocompression bonded using a calender roll having a pressure bonding temperature of 180 ° C. and a roll linear pressure of 5 kg / cm.
The obtained fiber structure has a dense layer with a smooth surface. The fiber structure was immersed in water and irradiated with 2450 MHz and 1 KW microwaves. Bubbles are observed from inside the pile surface of the knitted fabric by microwave irradiation. Irradiation is continued for about 1 minute after the generation of bubbles, and then taken out, cooled in water, centrifuged and dehydrated, and dried to form a fiber layer having cellular voids between the fiber fusion dense layer and the support layer. It was confirmed.
[0038]
Comparative Example 1
After mixing and carding 6% of the core-sheath composite staple fiber used in Example 2, 3% of regular polyester staple fiber, and a cut length of 51 mm 94%, a punch density of 90 pieces / cm ² A needle punched nonwoven fabric having a basis weight of 300 g / m ³ and a thickness of 10 mm was obtained.
The above needle punched nonwoven fabric was impregnated with water and subjected to microwave irradiation at 2450 MHz and 1 kw. After confirming the generation of bubbles from inside the nonwoven fabric, irradiation was continued for 2 minutes. Subsequently, after cooling in cold water, it dried. Both sides of the nonwoven fabric were guided to a calender roll, and both sides were thermocompression bonded at 180 ° C.
The obtained non-woven fabric had weak entanglement between fibers, and a structure that could be judged as a cellular void was not found. Moreover, the state of dense layer formation was not seen on the nonwoven fabric surface, only the fiber cross section was deformed by pressure, and no fusion or solidification between the fibers was observed.
[0039]
【The invention's effect】
According to the present invention, a novel porous fiber composite having a fiber layer having a large number of cellular voids and a fiber fusion dense layer on at least one surface thereof can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of a sheet-like fiber composite of the present invention.
FIG. 2 is a schematic cross-sectional view showing another example of the sheet-like fiber composite of the present invention.
FIG. 3 is a schematic cross-sectional view showing another example of the sheet-like fiber composite of the present invention.
FIG. 4 is a partially broken schematic view showing an example of a cylindrical fiber composite of the present invention.
FIG. 5 is an enlarged partial cross-sectional view showing the structure of a dense fiber fusion layer according to the present invention.
[Explanation of symbols]
1: porous fiber layer, 2: cellular void, 3: fiber fusion dense layer, 4: fiber support layer,
5: Fiber other than wet heat adhesive fiber, 6: Molten polymer layer, 7: Micropore

Claims (7)

A fiber layer containing 10 to 100% by weight of wet heat adhesive fiber, and having a large number of cellular voids having a major axis of about 1 mm to about 30 mm formed by fusion-bonding the fiber, and at least of the fiber layer 1. A porous fiber composite comprising a breathable fiber fusion dense layer having the same fiber composition as the fiber layer on one surface. The fiber layer is composed of a fiber support layer and wet heat adhesive fibers standing on the fiber support layer, and has a breathable fiber fusion dense layer at the opposite end of the fiber support layer of the standing fiber. The sheet-like porous fiber composite according to claim 1. The sheet-like porous fiber composite according to claim 1, wherein the fiber layer is a fiber layer composed of fibers arranged substantially parallel to the plane of the fiber layer. The cylindrical porous fiber composite according to claim 1, wherein the fiber layer is a converged fiber bundle, and has a breathable fiber fusion dense layer on a circumferential surface in a length direction of the fiber bundle. The porous fiber composite according to any one of claims 1 to 4, wherein the wet heat adhesive fiber is a fiber in which an ethylene vinyl alcohol copolymer is present on at least a part of the fiber surface. At least one surface of the fiber layer is formed by immersing a fiber layer containing 10 to 100% by weight of wet heat adhesive fiber in water and forming a cellular void by heat treatment while generating bubbles in the fiber layer. A fiber layer having a large number of cellular voids, characterized in that a fiber-bonded dense layer is formed by thermocompression bonding, and air permeability comprising the same fiber composition as the fiber layer on at least one surface of the fiber layer A method for producing a porous fiber composite having a dense fiber fusion layer. After forming a fiber fusion dense layer by thermocompression bonding at least one surface of a fiber layer containing 10 to 100% by weight of wet heat adhesive fiber, the fiber layer is immersed in water to generate bubbles in the fiber layer. A fibrous layer having a large number of cellular voids, and a breathable fiber having the same fiber composition as that of the fiber layer on at least one surface of the fibrous layer. A method for producing a porous fiber composite having a fused dense layer.

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