JP2001140153A - Nonwoven fabric heat-insulating material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonwoven fabric heat-insulating material which uses fiber raw materials and can realize a high heat-insulating effect without enhancing the cost. SOLUTION: This nonwoven fabric heat-insulating material produced by laminating plural card webs, is characterized by containing matrix fibers and thermally fusible fibers in each card web, containing a thin film formed by fusing the thermally fusible fibers on the surface of each card web, fusing the thermally fusible fibers in each card web, and integrally fusing the thermally fusible fibers among the plural card webs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material, and more particularly to a heat insulating material using a fiber material such as polyester.

[0002]

2. Description of the Related Art As a heat insulating material using a fiber material, there is a heat insulating material disclosed in International Publication WO99 / 43903. The heat insulating material disclosed in this publication is a heat insulating material in which a plurality of card webs are laminated, and the card web is a polyester fiber and a core-sheath type composite fiber using a low-melting point component having a lower melting point than the core in the sheath. And a fused portion in which the fibers are mutually fused by melting the sheath portion of the core-sheath composite fiber.

According to the invention disclosed in the above-mentioned publication, compared to heat insulating materials such as glass wool and rock wool, the fibers are fused to each other by the melting of the sheath portion, so that the shape and the heat insulating ratio with the passage of time are reduced. It is possible to provide a heat insulating material for a house which has little change and can be easily cut in the laminating direction of the card web, so that the workability at the site is good.

Further, in order to prevent the recent global warming phenomenon, in order to reduce the carbon dioxide emitted by improving the heating and cooling efficiency in the house, a higher heat insulating property in conformity with the next-generation energy saving standard is adopted. There is a need for a heat insulating material for homes having the following.

[0005]

However, the heat insulating material disclosed in the above-mentioned publication satisfies the heat insulation rate of the next-generation energy-saving standard (a good heat insulation means a low heat conductivity). I can't let it. Therefore, the heat insulation standard is realized by increasing the thickness of the heat insulating material or increasing the fiber density of the nonwoven fabric constituting the heat insulating material.

When the thickness of the heat insulating material is increased, heat insulation satisfying the above-mentioned criteria can be realized, but the cost increases. In addition, when the fiber density of the nonwoven fabric constituting the heat insulating material is increased, heat insulation satisfying the above-mentioned criteria can be realized, but the cost increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a heat insulating material using a fiber material, which can realize desired heat insulation without increasing the cost. It is.

[0008]

The non-woven fabric heat insulating material according to the first aspect of the present invention is a non-woven fabric heat insulating material containing a matrix fiber and a heat-sealing fiber. It includes a thin film formed by fusion of fibers.

According to the first aspect of the present invention, the matrix fibers and the heat-fusible fibers are entangled with each other to form minute voids inside the non-woven fabric heat insulating material and to maintain the overall shape of the non-woven fabric heat insulating material. . By heating the surface of the nonwoven fabric, the heat-fused fibers on the surface of the nonwoven fabric fuse with each other to form a thin film on the surface of the nonwoven fabric heat insulating material. Thereby, air is held in the voids formed inside the nonwoven fabric, and a heat insulating effect is exhibited. Further, the thin film formed on the surface hinders the release of air held in the heat insulating material, and enhances the heat insulating effect.
As a result, it is possible to provide a heat insulating material using a fiber material capable of realizing desired heat insulation without increasing the cost.

A nonwoven fabric heat insulating material according to a second aspect of the present invention is a nonwoven fabric heat insulating material in which a plurality of card webs are laminated, wherein each card web includes a matrix fiber and a heat fusion fiber, The web surface includes a thin film formed by fusing the heat-fusible fibers, and each card web has the heat-fusible fibers fused inside the card web, and the plurality of card webs are heat-sealed between the card webs. It is a nonwoven fabric heat insulating material in which fused fibers are fused and integrated.

According to the second aspect of the present invention, the heat-fused fibers on the surface of the card web form a thin film on the surface of the plurality of card webs laminated. Also, the heat-sealing fibers inside the card web integrate the card web. further,
The heat fusible fibers between the card webs integrate the card webs. Thus, the thin film formed on the surface of the nonwoven fabric hinders the convection of air existing inside the plurality of nonwoven fabrics, and enhances the heat insulating effect. The integrated plurality of card webs enhances shape retention. As a result, it is possible to provide a heat insulating material using a fiber material capable of realizing desired heat insulation without increasing the cost.

A nonwoven fabric heat insulating material according to a third aspect of the present invention is a nonwoven fabric heat insulating material in which the laminating direction of each card web and the heat insulating direction are parallel to the configuration of the second aspect of the present invention. .

According to the third aspect of the present invention, the heat-fused fibers form a thin film on the surface of the plurality of nonwoven fabrics laminated. Thereby, since the laminating direction and the heat insulating direction of the plurality of nonwoven fabrics are parallel, the thin film formed on the surface of the nonwoven fabric is
Suppresses the convection of the air existing inside the plurality of nonwoven fabrics in the heat insulating direction, and enhances the heat insulating effect. As a result, it is possible to provide a heat insulating material using a fiber material capable of realizing desired heat insulation without increasing the cost. Note that the heat insulation direction is a direction in which heat is not transmitted. For example, in the case of a residential heat insulating material, it refers to the direction from indoor to outdoor or from outdoor to indoor.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a non-woven fabric heat insulating material, the method comprising the steps of: mixing a matrix fiber and a heat fusion fiber;
A carding step of converting the mixed fibers into a card web; and a heat treatment step of heating the surface of the card web to fuse the thermally fused fibers on the card web surface.

According to the fourth aspect of the present invention, in the mixing step, the matrix fibers and the heat-fusible fibers are mixed.
In the carding step, the mixed fibers are turned into a card web, and voids are formed therein. In the heat treatment step, the surface of the card web is heated to fuse the heat-fused fibers on the surface of the card web to form a thin film on the surface of the nonwoven fabric. Thereby, air is held in the voids formed inside the nonwoven fabric, and a heat insulating effect is exhibited. Further, the thin film formed on the surface hinders the release of air held in the heat insulating material, and enhances the heat insulating effect. As a result, it is possible to provide a manufacturing method capable of manufacturing a heat insulating material using a fiber material capable of realizing desired heat insulation without increasing the cost.

According to a fifth aspect of the present invention, there is provided a method for producing a non-woven fabric heat insulating material in which a plurality of card webs are laminated, wherein a matrix fiber and a heat fusion fiber are mixed. A carding step of converting the mixed fibers into a card web; and heating the surface of the card web to fuse the heat-fused fibers on the card web surface to form a thin film on the card web surface. A heat treatment step, a lamination step of laminating a plurality of card webs that have been heat-treated in the first heat treatment step,
A second heat treatment step of fusing the heat-fused fibers inside the plurality of stacked card webs and fusing the heat-fused fibers between the card webs to integrate them.

According to the fifth aspect of the invention, in the mixing step, the matrix fibers and the heat-fusible fibers are mixed.
In the carding step, the mixed fibers are turned into a card web, and voids are formed therein. In a first heat treatment step, the surface of the card web is heated to fuse the heat-fused fibers on the surface of the card web to form a thin film on the surface of the nonwoven fabric. In the laminating step, the card web is laminated. In a second heat treatment step, the laminated card web is heated to fuse the heat-fused fibers in the card web and the heat-fused fibers between the card webs, thereby integrating the laminated card webs. . Thus, the thin film formed on the surface of the nonwoven fabric hinders the convection of air existing inside the plurality of nonwoven fabrics, and enhances the heat insulating effect. The integrated plurality of card webs enhances shape retention. As a result, it is possible to provide a manufacturing method capable of manufacturing a heat insulating material using a fiber material capable of realizing desired heat insulation without increasing the cost.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, repetition of detailed description thereof will be appropriately omitted. <Embodiment 1: Non-woven fabric heat insulating material> [Constituent fibers] The fibers constituting the non-woven fabric heat insulating material according to Embodiment 1 of the present invention will be described.

When a synthetic fiber is used as the matrix fiber constituting the nonwoven fabric heat insulating material, the polymer is not particularly limited. For example, polyethylene terephthalate, aromatic polyesters such as polybutylene terephthalate, aliphatic polyesters such as polylactic acid and polycaprolactan,
Polyolefins such as polypropylene and polyethylene, polyamides such as nylon 6 and nylon 66, and copolymers thereof, and the like can be used. Also, a mixture of these two or more fibers may be used.

Considering the recyclability of the heat insulating material. The polymer is preferably a polyester-based polymer. As the polyester fiber, any of ordinary polyethylene terephthalate, polyhexamethylene terephthalate, polytetramethylene terephthalate, poly-1,4-dimethylcyclohexane terephthalate, polyhydrolactone, or a copolymer fiber thereof or a composite fiber obtained by conjugate spinning is used. it can. Side-by-side conjugate fibers composed of two polymers having different heat shrinkage rates are preferable because they exhibit a spiral crimp and have a three-dimensional structure, and are particularly preferably hollow fibers having a hollow ratio of 5 to 30%.

It is preferable to use a matrix fiber having a fineness of 1 to 30 dtex and a cut length of 25 to 150 mm.

Synthetic fibers are used as the heat-fusible fibers constituting the nonwoven fabric heat insulating material. In this case, the polymer is not particularly limited. For example, aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate; aliphatic polyesters such as polylactic acid and polycaprolactane; polyolefins such as polypropylene and polyethylene; polyamides such as nylon 6 and nylon 66; and copolymers thereof. Etc. can be used. Also,
A mixture of two or more of these fibers may be used.

The heat-fusible fiber may be a single component composed of the above-mentioned polymer, but a normal polyester fiber component is used for the core, and a low-melting polyester, polyolefin, polyamide, or the like is used for the sheath, and the core component is used as the core. Any of the composite fibers produced in combination so that the difference in the melting points of the sheath components is 30 ° C. or more can be used. When such a sheath-core conjugate fiber is used, a heat-sealing function can be exhibited while maintaining the shape-retaining function of the core component, and thus it is suitable for use as a heat insulating material used for a long time.

It is preferable to use heat-fused fibers having a fineness of 2 to 20 dtex and a cut length of 25 to 76 mm.

In the card web used for the heat insulating material according to the embodiment of the present invention, it is preferable to mix the matrix fibers and the heat-fusible fibers in a weight ratio of 95 to 40: 5 to 60. [Manufacturing method] The nonwoven fabric heat insulating material according to the present embodiment is, for example, a card web in which a matrix fiber and a core-sheath type composite fiber using a low-melting point component having a lower melting point than the core are used for a sheath. In which a first heat treatment is performed to form a thin film on the surface of the card web.
Details of this manufacturing method will be described below. [Mixing Step to Carding Step] Referring to FIG. 1, a hopper 10 for opening and mixing the matrix fibers and the heat fusion fibers, and a belt conveyor 14 for transporting the mixed fiber mixture 12. And belt conveyor 1
A feed roller 16 for introducing the fiber mixture 12 conveyed in 4 into a carding machine, a cylinder roller 18 for carding the fiber mixture 12 into a web, and a card carded by the cylinder roller 18 Web 2
And a doffer 20 for unloading 2
The card web 22 is manufactured. The fiber mixture 12
Is processed into the card web 22 while traveling in the direction of arrow A. [First Heat Treatment Step] Referring to FIG. 1, a conveyor 26 for conveying the card web 22 including the matrix fibers and the heat-bonded fibers to the first heat treatment step, and the conveyor 26 is opposed to the conveyor 26. A heater 24 for heating the surface of the card web 22;
And a cooling roller 28 for cooling the card web 22 and compressing the card web 22 to a predetermined thickness.
0 is produced. The card web 22 is processed into the nonwoven fabric heat insulating material 30 while traveling in the direction of arrow B.

The heater 24 is only required to be able to heat the surface of the card web 22, and is not limited to a specific one. It is preferable that a non-uniform heat treatment is performed on the surface of the card web 22 in the thickness direction of the card web to fuse the heat-fused fibers existing on the surface, thereby forming a thin film on the surface of the card web 22. For this reason, an infrared heater is used as the heater 24, and indirect heating is performed from at least one side by the radiant heat. In this case, the degree of fusion gradually decreases at the central portion and the back side in the thickness direction of the card web 22 where the radiant heat is not directly radiated. Therefore, a thin film is formed only on the surface.

As the heater 24, a hot plate or a heating roller can be brought into contact with the card web 22 to form a thin film on the surface of the card web 22.

The heating temperature (surface temperature of the card web 22) by the heater 24 is preferably in the range of 110 to 220 ° C. When the temperature is within this range, it is sufficient to melt the polymer of the heat-fusible fibers present on the surface to form a thin film, and has little effect on the matrix fibers. For this reason, a change in physical properties or the like caused by polymer deterioration or the like due to the heat history received by the matrix fibers is also suppressed.

In the first heat treatment, the amount of heat received by the card web 22 is changed, so that the degree of fusion of the heat-fused fibers can be changed. The degree of melting can be changed by changing the heating time by changing the feed speed of the card web in the direction of arrow B. [Non-woven fabric heat insulating material] The non-woven fabric heat insulating material manufactured by the above-mentioned manufacturing method may be used alone as the non-woven fabric heat insulating material 30, or may be used as a heat insulating material by stacking a plurality of non-woven fabric heat insulating materials 30. Absent. Due to the thin film formed on the surface of the nonwoven fabric heat insulating material 30, convection of air contained in the nonwoven fabric heat insulating material 30 can be inhibited.

As described above, the nonwoven fabric heat insulating material according to the present embodiment can form a thin film on the surface of the nonwoven fabric by the first heat treatment. With this thin film, convection of air contained in the heat insulating material can be inhibited. Thereby, it is possible to provide a heat insulating material using a fiber material, which can realize desired heat insulation without increasing the cost. <Second Embodiment: Laminated Heat Insulating Material> A laminated heat insulating material according to a second embodiment of the present invention will be described below. The fibers constituting the laminated heat insulating material according to the present embodiment are the same as the fibers constituting the nonwoven fabric heat insulating material according to the first embodiment, and therefore, detailed description thereof will not be repeated here.

The laminated heat insulating material according to the present embodiment is different from the method for manufacturing the nonwoven fabric heat insulating material 30 produced by performing the first heat treatment described in the first embodiment in the laminating step and the second heat treating step. It is manufactured by a manufacturing method in which
That is, a laminate is formed by laminating a plurality of nonwoven fabric heat insulating materials 30 that have been subjected to the first heat treatment, and a second laminate is formed on the laminate.
And heat-fused fibers inside the non-woven fabric heat insulating material 30 and heat-fused fibers between the plurality of non-woven fabric heat insulating materials 30 are fused. Details of this manufacturing method will be described below. [Lamination Step] A predetermined number (10 to 20) of the nonwoven fabric heat insulating materials 30 having a predetermined basis weight, density, and shape manufactured through the first heat treatment step are laminated to form a laminate. At this time, the front and back directions of the nonwoven fabric heat insulating material 30 are not particularly limited. [Second heat treatment step] The laminate is compressed and held between plates such as a metal plate having good thermal conductivity, and the laminate is erected (the thickness direction of the laminated layer of the card web becomes vertical). In such a state), heat treatment is performed in a steam pot. Next, the laminate is rotated by 90 degrees while being compressed and held, and heat-treated so that the load does not affect the thickness direction of the laminate.

In the second heat treatment, sufficient heat reaches the inside of the laminate, so that the heat-fused fibers inside the laminate are fused to each other, and the heat-fused fibers are interposed between the non-woven fabric heat insulating materials 30. The heat treatment conditions are determined so as to fuse. The heat treatment conditions are determined so that the thin film formed on the surface of the nonwoven fabric heat insulating material 30 by the first heat treatment is maintained.

Further, by performing the second heat treatment, the downward movement of the fiber due to its own weight is suppressed by the repulsive force of the fiber acting in the horizontal direction. In this second heat treatment, the pressure inside the steam pot was reduced to 100 kPa or more,
It is preferable to carry out by introducing steam of kPa or more,
The plate for compressing and holding the laminate is preferably a perforated plate.

By performing such a second heat treatment, a horizontal repulsive stress can always be exerted during the second heat treatment, and a laminate having an arbitrary density can be obtained regardless of the thickness of the laminate. be able to. For example, even if the basis weight of the card web 22 is the same, it is possible to obtain a low-density product by increasing the thickness of the card web (small density), and to obtain a high-density product by reducing the thickness (high density). Products can be obtained. For example, even in the case of a thick laminate having a thickness of 1000 mm, it is possible to efficiently obtain a product that is uniformly fused to the inner layer portion, has a good overall feel, and has an excellent appearance.

Further, it is possible to easily obtain a product having a desired density and a variation range of the density within ± 5%.

By performing such a second heat treatment, the laminated heat insulating material according to the present embodiment can be manufactured. In the manufactured laminated heat insulating material, a plurality of nonwoven fabric heat insulating materials 30 are laminated, and heat-fused fibers are fused inside the laminated heat insulating material, and a thin film is formed on the surface of the nonwoven fabric heat insulating material 30 inside the laminated heat insulating material. ing.

When manufacturing the laminated heat insulating material according to the present embodiment, the second heat treatment may be performed while rotating the laminated body so that its own weight is not biased in one direction. [How to Use] Referring to FIG. 2, a wall panel 40 for a house using the laminated heat insulating material according to the present embodiment has a rectangular frame formed by a horizontal frame 42 and a vertical frame 44, and a rectangular frame. Exterior facing 46 affixed to the outside of the room, interior facing 50 affixed to the interior side of the framework, laminated heat insulating material 48 inserted into the interior space of the framework, and interior facing 50 And laminated insulation 4
8 and an exterior material 54 attached thereto.

The components of the frame are made of wood or laminated wood based on the specifications of various frame materials, and have a cross section perpendicular to the longitudinal direction of 50.8 × 101.6 mm.
Square bars having appropriate dimensions such as 50.8 × 152.4 mm are used. The thickness and the like of the heat insulating material 48 are determined according to the dimensions of the square member. The interval between the vertical frames 44 located on the panel 40 is usually every 455 mm, but may be changed depending on structural requirements. Also, the horizontal frame 42
Includes an upper frame in addition to the illustrated lower frame.

Further, as the exterior surface material 46, 7 to 12
Structural plywood having a thickness of about 9 mm can be used, and gypsum board having a thickness of about 9 to 15 mm can be used as the interior facing material 50.

The apparent thickness of the laminated heat insulating material 48 according to the present embodiment is about 90 mm that matches the width of the frame (the thickness of the horizontal frame 42 or the vertical frame 44). Laminated insulation 48
Is inserted into the frame in a state in which it is in close contact with the surface of the moisture-proof sheet 52, and is in close contact with the back surface of the exterior surface material 46, that is, the laminated heat insulating material 48 is between the walls formed by the frame material. Is inserted to completely fill the space.

Referring to FIG. 3, when the laminated heat insulating material 48 is used, it is preferable that the laminating direction of the nonwoven fabric heat insulating material 30 is along the thickness direction of the wall (the direction to be insulated). By doing so, the thin film formed on the surface of the nonwoven fabric heat insulating material 30 inhibits the flow of air convection in the heat insulating direction (the direction indicated by arrows X to Y).

As described above, in addition to the effect of the first heat treatment, the nonwoven fabric heat insulating material according to the present embodiment
By the heat treatment, the nonwoven fabric heat insulating material can be uniformly fused to the inside of the card web constituting the nonwoven fabric heat insulating material, so that the density distribution becomes uniform, the overall feeling is good, and the appearance is excellent. In addition, by the second heat treatment, the card webs constituting the nonwoven fabric heat insulating material are fused to integrate the plurality of card webs. Thereby, it is possible to provide a heat insulating material using a fiber material, which can realize desired heat insulation without increasing the cost.

[0043]

Examples of the present invention will be described below. [Laminated thermal insulation] A first heat treatment and a second heat treatment are performed on a card web having a fiber composition shown in Table 1,
Laminated insulation was produced.

[0044]

[Table 1]

[Measurement of Thermal Insulation] The thermal conductivity in the XY direction and the ZW direction of FIG. 3 was measured for the laminated thermal insulation material manufactured under the above conditions. The measurement method is described in "JIS A 1412-
1994 Method for measuring thermal conductivity and thermal resistance of thermal insulation
5.1 Direct plate method ".

As a result of the measurement, the thermal conductivity of Example 1 in the XY directions was 0.038 (W / m · ° C.), the thermal conductivity in the ZW direction was 0.042 (W / m · ° C.), The thermal conductivity in the XY directions for Example 2 was 0.039 (W / m ·
° C) and the thermal conductivity in the ZW direction is 0.044 (W / m ·
° C), and both Examples 1 and 2 could satisfy the C rank (0.040 to 0.035 (W / m · ° C)) of the next-generation energy saving standard.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a manufacturing process for manufacturing a nonwoven fabric heat insulating material of the present invention.

FIG. 2 is a diagram (part 1) illustrating a method of using the laminated heat insulating material according to the second embodiment of the present invention.

FIG. 3 is a diagram (part 2) for explaining a method of using the laminated heat insulating material according to the second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 hopper, 12 fiber mixture, 14, 26 belt conveyor, 16 feed roller, 18 cylinder roller, 20 doffer, 22 card web, 24 heater, 28 cooling roller, 30 non-woven fabric heat insulating material, 40
Wall material panels, 42 horizontal frames, 44 vertical frames, 46 exterior facing materials, 48 laminated heat insulating materials, 50 interior facing materials, 52 moisture-proof sheets, 54 exterior materials.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Yatsushiro 1-2-2 Umeda, Kita-ku, Osaka-shi, Osaka Kanebo Synthetic Fiber Co., Ltd. (72) Inventor Mangeo Nagata 1--2, Umeda, Kita-ku, Osaka, Osaka No. 2 Inside Kanebo Gosen Co., Ltd. (72) Inventor Noboru Nananabe 4-1 Kanebocho, Hofu City, Yamaguchi Prefecture Inside Kanebo Gosen Co., Ltd. (72) Inventor Hiroshi Onoe 1-chome Umeda, Kita-ku, Osaka City, Osaka Prefecture No. 2 No. 2 Kanebo Synthetic Fiber Co., Ltd. F term (reference) 2E001 DD01 FA03 GA24 GA28 GA42 GA46 GA47 GA63 HC01 HD11 4F100 AK41 BA02 BA03 BA06 BA10A BA10C BA13 BA22 DG01A DG01B DG01C DG15A DG15C EA061 EC03 EC02 EC02 EC03 EC02 EC02 JL12B JL12C JM02B 4L047 AA14 AA21 AA23 AA27 AA28 AB02 BA09 BB09 CA02 CA19 CB06 CB10 EA02 EA10

Claims (5)

[Claims] 1. A non-woven fabric heat insulating material comprising a matrix fiber and a heat-sealing fiber, comprising a thin film formed by fusing the heat-sealing fiber to the surface of the non-woven heat insulating material. . 2. A non-woven fabric heat insulating material in which a plurality of card webs are laminated, wherein each of the card webs includes a matrix fiber and a heat fusion fiber, and the heat fusion fiber is provided on a surface of each card web. Includes a thin film formed by fusing, wherein each of the card webs has the heat-fusible fibers fused inside the card webs, and the plurality of card webs have the heat-fusible fibers between the card webs. Is a non-woven fabric heat insulating material integrated by fusing. 3. The nonwoven fabric heat insulating material according to claim 2, wherein the laminating direction of each of the card webs and the heat insulating direction are parallel. 4. A method for producing a nonwoven fabric heat insulating material, comprising: a mixing step of mixing matrix fibers and heat-fusible fibers; a carding step of converting the mixed fibers into a card web; and heating the surface of the card web. A heat treatment step of fusing the heat-fused fibers on the card web surface. 5. A method for producing a nonwoven fabric heat insulating material in which a plurality of card webs are laminated, a mixing step of mixing matrix fibers and heat-fusible fibers, and a carding step of converting the mixed fibers into a card web. A first heat treatment step of heating the surface of the card web to fuse the heat-fusible fibers on the card web surface to form a thin film on the card web surface; Laminating a plurality of the card webs that have been heat-treated, and fusing the heat-fused fibers inside the stacked plurality of card webs, and the heat-fusible fibers between the card webs. And a second heat treatment step of fusing and integrating the nonwoven fabric.