FUNCTIONAL NONWOVEN FABRIC AND MANUFACTURING METHOD THEREFOR

Abstract

The problem addressed by the present invention is to suppress a decrease in air permeability of a nonwoven fabric while suppressing falling off of functional particles. The means for solving the problem of the present invention is that a functional nonwoven fabric 1 is formed to contain long fibers made of synthetic resin and integrated with functional particles 4, 4 having a predetermined function. A diameter of the long fiber changes in a longitudinal direction of the fibers so that a plurality of large diameter portions 2, 2 and a plurality of small diameter portions 3, 3 are alternately arranged. The small diameter portions 3, 3 are monofilaments formed of the synthetic resin. At least a part of the large diameter portions 2, 2 contain the functional particle 4. A fiber diameter of the small diameter portions 3, 3 is equal to or smaller than a diameter of the functional particles 4, 4 contained in the large diameter portions 2, 2.

Claims

1. A functional nonwoven fabric comprising long fibers made of synthetic resin and integrated with a functional particle having a predetermined function, wherein the functional particle is a particle having thermal expansion properties, a diameter of the long fiber changes in a longitudinal direction of the long fiber so that a plurality of large diameter portions and a plurality of small diameter portions are alternately arranged, the small diameter portion is a monofilament formed of the synthetic resin, at least a part of the large diameter portion contains the functional particle, and a fiber diameter of the small diameter portion is equal to or smaller than a diameter of the functional particle contained in the large diameter portion.

2. The functional nonwoven fabric according to claim 1, wherein at least a part of the large diameter portion is formed by solidifying a plurality of the functional particles into a string-like or dumpling-like shape with the synthetic resin.

3. The functional nonwoven fabric according to claim 2, wherein the fiber diameter of the small diameter portion is 1/100 or more of the diameter of the functional particle.

4. The functional nonwoven fabric according to claim 3, wherein the fiber diameter of the small diameter portion is 100 nanometers or more and 10 micrometers or less, and the diameter of the functional particle is 300 nanometers or more and 200 micrometers or less.

5. (canceled)

6. The functional nonwoven fabric according to claim 1, wherein the functional particle is an aluminum phosphite particle.

7. (canceled)

8. The functional nonwoven fabric according to claim 1, wherein the functional nonwoven fabric is a functional nonwoven fabric having thermal expansion properties, and the long fiber is configured so that the plurality of large diameter portions and the plurality of small diameter portions are alternately arranged in the form of a string of beads.

9. The functional nonwoven fabric according to claim 8, wherein the functional particle is an aluminum hydrogen phosphite particle.

10. The functional nonwoven fabric according to claim 8, wherein the large diameter portion is string-like or dumpling-like, and the functional particle is integrated with the large diameter portion by being wrapped in the synthetic resin in a film, net, or fiber bundle form, or by being bonded with the synthetic resin.

11. The functional nonwoven fabric according to claim 8, wherein the fiber diameter of the small diameter portion is 1/100 or more of the diameter of the functional particle.

12. The functional nonwoven fabric according to claim 11, wherein the fiber diameter of the small diameter portion is 100 nanometers or more and 10 micrometers or less, and the diameter of the functional particle is 300 nanometers or more and 200 micrometers or less.

13. A method for manufacturing the functional nonwoven fabric according to claim 1, the method comprising: a first step of dispersing functional particles in a synthetic resin liquefied by heat melting or by dissolving in a solvent, and a second step of, following the first step, forming the nonwoven fabric while spinning long fibers from the liquefied synthetic resin containing the dispersed functional particles by a melt-blowing method or an electrospinning method.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a schematic diagram illustrating a structure of a functional nonwoven fabric of a first embodiment;

[0029] FIG. 2 is a schematic diagram illustrating a structure of a large diameter portion and a small diameter portion;

[0030] FIG. 3 is a micrograph illustrating a structure of Example of the functional nonwoven fabric of the first embodiment;

[0031] FIG. 4 is a micrograph illustrating a structure of Example 2 of the functional nonwoven fabric;

[0032] FIG. 5 is a micrograph illustrating a structure of Example 3 of the functional nonwoven fabric;

[0033] FIG. 6 is a schematic diagram illustrating a structure of the first embodiment of a thermally expandable nonwoven fabric 5; and

[0034] FIG. 7 is a schematic sectional view illustrating an example of a usage form of the first embodiment of the thermally expandable nonwoven fabric 5.

DESCRIPTION OF EMBODIMENTS

[0035] An embodiment of the invention in a case of using particles having thermal expansion properties as functional particles will be described as an example below with reference to the drawings. The invention is not limited to individual embodiments described below. The embodiments can also be modified and implemented.

[0036] A functional nonwoven fabric 1 of a first embodiment is a functional nonwoven fabric containing long fibers made of synthetic resin and integrated with functional particles 4, 4 having a predetermined function. Here, the long fibers refer to long fibers in contrast to short fibers in fibers constituting the nonwoven fabric. The long fibers are also called filament yarns. The short fibers are called staple fibers or the like. The short fibers have a length of approximately several mm to several tens of cm. In contrast, the long fibers are fibers that are not cut short. The long fibers are typically spun by a melt-blowing method, an electrospinning method, or a spunbonding method. The spun long fibers are directly stacked to form the nonwoven fabric. Note that the functional nonwoven fabric 1 does not need to be composed only of the long fibers. The functional nonwoven fabric 1 may contain the short fibers. The long fibers and the short fibers may be mixed and spun so that they are entangled.

[0037] Although not essential, a blending amount of the functional particles 4, 4 to the functional nonwoven fabric 1 is preferably about 10 to 500 g/m.sup.2.

[0038] Further, the functional nonwoven fabric may be a single layer. Alternatively, the functional nonwoven fabric may be a laminated nonwoven fabric including a plurality of nonwoven fabric layers, and film, sheet, woven fabric, or the like, that are stacked together. Further, the functional nonwoven fabric may be a composite nonwoven fabric including a layer of nonwoven long fibers that is stacked on a woven fabric or mesh material. The long fibers made of synthetic resin and integrated with the functional particles may be included only in one of the nonwoven fabric layers.

[0039] Further, all of the long fibers contained in the functional nonwoven fabric 1 may be the long fibers made of synthetic resin and integrated with the functional particles. Alternatively, the functional nonwoven fabric 1 may contain other long fibers, for example, long fibers that are not integrated with the functional particles. Although not essential, the functional nonwoven fabric 1 of the present embodiment is a single-layer functional nonwoven fabric. This functional nonwoven fabric is obtained by forming a nonwoven fabric from the long fibers made of synthetic resin, integrated with the functional particles, and spun by the electrospinning method.

[0040] FIG. 1 illustrates a schematic diagram of the functional nonwoven fabric 1 of the first embodiment. In addition, FIG. 3 is a micrograph of Example of the functional nonwoven fabric of the first embodiment. Note that in FIG. 1, small diameter portions 3, 3 are each represented by a single solid line. A diameter of the long fibers contained in the functional nonwoven fabric 1 varies in a longitudinal direction of the fibers so that a plurality of large diameter portions 2, 2 and a plurality of small diameter portions 3, 3 are alternately arranged. In other words, the long fibers are fibers that are configured so that the large diameter portions 2, 2 and the small diameter portions 3, 3 are in the form of a string of beads.

[0041] The small diameter portions 3, 3 of the long fibers are monofilaments formed of the synthetic resin. There are no particular limitations on the synthetic resin as long as it is a resin that can be made into fibers. The synthetic resin is preferably a resin that is suitable for manufacturing the long fibers by the melt-blowing method or the electrospinning method. Further, the synthetic resin is preferably a resin that adheres to the functional particles described below. As the synthetic resin that is a raw material for the long fibers, for example, a polyurethane resin or a polyvinyl chloride resin can be preferably used.

[0042] The monofilaments as the small diameter portions 3, 3 may be composed only of the synthetic resin described above. Alternatively, the monofilament may contain other compounding materials, for example, particles having a diameter smaller than the diameter of the small diameter portion, such as reinforcing materials or bulking materials, or chemicals that improve properties of the synthetic resin. Further, the monofilaments as the small diameter portions 3, 3 may be monofilaments that do not substantially contain the functional particles described below.

[0043] Although not essential, a fiber diameter of the small diameter portions 3, 3 is preferably 100 nanometers or more and 10 micrometers or less. The fiber diameter of the small diameter portions 3, 3 is particularly preferably 500 nanometers or more and 3 micrometers or less. Here, the fiber diameter refers to a diameter of the fiber measured in a direction perpendicular to an extension direction of the fiber. For example, the fiber diameter of the small diameter portions is determined by measurement on a photographed micrograph of the functional nonwoven fabric 1. The fiber diameter of the small diameter portions is preferably measured at 10 to 20 locations. An average of these measured values is used as the fiber diameter of the small diameter portions.

[0044] At least a part of the large diameter portions 2, 2 is formed by a plurality of functional particles 4, 4 that are solidified into a string-like or dumpling-like shape by the synthetic resin. Here, string-like means that, with respect to a shape of the large diameter portion, a length in the extension direction of the fiber is longer than a length in the direction perpendicular to the extension direction of the fiber, and preferably is at least three times the length in the direction perpendicular to the extension direction of the fiber. In addition, dumpling-like means that, with respect to the shape of the large diameter portion, the length in the extension direction of the fiber is approximately the same as the length in the direction perpendicular to the extension direction of the fiber, and preferably is at least half and at most twice the length in the direction perpendicular to the extension direction of the fiber. Note that the long fiber may have a large diameter portion that does not contain any functional particles, or a large diameter portion that contains only one functional particle.

[0045] A diameter of the large diameter portions 2, 2 is larger than the fiber diameter of the small diameter portions 3, 3. The diameter of the large diameter portions is a diameter measured in the direction perpendicular to the extension direction of the fiber. The diameter of the large diameter portions is preferably measured at 10 to 20 locations. An average of these measured values is used as the diameter of the large diameter portions. Although not essential, the diameter of the large diameter portions 2, 2 is preferably 150 nanometers or more and 300 micrometers or less. The diameter of the large diameter portions 2, 2 is particularly preferably 1 micrometer or more and 50 micrometers or less. Further, the diameter of the large diameter portions 2, 2 is preferably 3 to 20 times the fiber diameter of the small diameter portions 3, 3, and particularly preferably 4 to 10 times.

[0046] FIG. 2 schematically illustrates a structure of the large diameter portions 2, 2 and the small diameter portions 3, 3. Although not essential, in an embodiment illustrated in FIG. 2, the large diameter portion 2 contains the plurality of functional particles 4, 4. The functional particles 4, 4 are preferably wrapped or bonded by the same synthetic resin as the synthetic resin constituting the small diameter portion. In this way, the functional particles 4, 4 are solidified into a string-like or dumpling-like shape. In the large diameter portions 2, 2, the functional particles 4, 4 may be bonded to each other by the synthetic resin. Alternatively, one or more functional particles 4, 4 may be wrapped by a synthetic resin formed in a film-like or net-like shape. In the large diameter portions 2, 2, only one functional particle may be present in a radial direction of the fiber. Alternatively, the plurality of functional particles may be present in the radial direction of the fiber. At end portions of the large diameter portions 2, 2, the large diameter portion 2 and the small diameter portion 3 are continuous with each other so that the synthetic resin contained in the large diameter portion directly forms the monofilaments of the small diameter portions 3, 3.

[0047] The functional particles contained in the large diameter portions 2, 2 have a predetermined function. Although not essential, in the functional nonwoven fabric 1 of the present embodiment, the particles having the thermal expansion properties are used as the functional particles. Examples of the particles having the thermal expansion properties include thermally expandable microcapsules, thermally expandable graphite, and aluminum phosphite. Examples of aluminum phosphite particles having the thermal expansion properties include APA-100 from Taihei Chemical Industrial Co., Ltd. Among the aluminum phosphite particles, aluminum hydrogen phosphite (such as NSF from Taihei Chemical Industrial Co., Ltd.) can be particularly preferably used. These particles have a property of expanding when heated to a predetermined temperature. When the large diameter portions 2, 2 contain the particles having the thermal expansion properties and the functional nonwoven fabric is heated, the large diameter portions 2, 2 expand and change so that vacant spaces in the nonwoven fabric become smaller or narrower. In this way, a change occurs in which air permeability of the nonwoven fabric decreases.

[0048] A fiber diameter Ds of the small diameter portions 3, 3 is equal to or smaller than a diameter Dp of the functional particles 4, 4 contained in the large diameter portions 2, 2. The fiber diameter Ds of the small diameter portions 3, 3 and the diameter Dp of the functional particles 4, 4 may be substantially the same. Note that the diameter Dp of the functional particles 4, 4 in the present invention refers to a volume average diameter. The diameter Dp of the functional particles 4, 4 contained in the large diameter portion is typically 300 nanometers or more and 200 micrometers or less. In addition, although not essential, the fiber diameter Ds of the small diameter portions 3, 3 is preferably 1/100 or more of the diameter Dp of the functional particles 4, 4.

[0049] A method for manufacturing the functional nonwoven fabric 1 of the first embodiment will be described. The functional nonwoven fabric 1 can be manufactured by applying the melt-blowing method or the electrospinning method.

[0050] First, in a first step, liquefied synthetic resin and the functional particles are mixed together. The synthetic resin is melted by heating. The synthetic resin is liquefied by heating, or by dissolving in a solvent. The functional particles are mixed and dispersed in the liquefied synthetic resin. A liquid synthetic resin containing dispersed functional particles may be obtained by heating and melting the synthetic resin into which the functional particles have been kneaded in advance. Alternatively, the synthetic resin may be dissolved and liquefied by the solvent or the like, and then the functional particles may be mixed and dispersed therein.

[0051] In the present embodiment, the polyurethane resin is dissolved and liquefied by the solvent. Aluminum phosphite powder (NSF manufactured by Taihei Chemical Industrial Co., Ltd., volume average diameter 5 micrometers) as the functional particles 4, 4 is mixed into the liquefied polyurethane resin, and dispersed by stirring.

[0052] Subsequently, as a second step, following the first step, the nonwoven fabric is formed by depositing long fibers while spinning the long fibers from the liquid synthetic resin containing the dispersed functional particles 4, 4 by the melt-blowing method or the electrospinning method.

[0053] The liquid synthetic resin discharged from a spinning nozzle is stretched by centrifugal force, gravity, electrostatic force, or the like, to be thin fibers. The thin fibers form the small diameter portions 3, 3 of the long fibers. At this time, the functional particles 4, 4 are discharged from the nozzle together with the liquid synthetic resin. Then, a portion where the functional particles 4, 4 gather together solidifies into a string-like or dumpling-like shape to form the large diameter portions 2, 2. At the same time, excess synthetic resin is stretched to form the small diameter portions 3, 3. In this way, the long fibers in which the large diameter portions 2, 2 and the small diameter portions 3, 3 are alternately arranged in the form of a string of beads are continuously formed. The long fibers thus formed are solidified as the solvent evaporates or the temperature drops. At the same time, the long fibers are deposited on a base of a spinning apparatus (nonwoven fabric manufacturing apparatus). In this way, the functional nonwoven fabric 1 is manufactured.

[0054] In Example, aluminum hydrogen phosphite NSF (average particle diameter: 5 micrometers) was used as the functional particles. The diameter of the large diameter portions 2, 2 of the obtained functional nonwoven fabric 1 was approximately 2 to 10 micrometers (average diameter: 6 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.5 to 1.5 micrometers (average diameter: 0.9 micrometers). The micrograph of the functional nonwoven fabric 1 is illustrated in FIG. 3.

[0055] By adjusting the blending amount of the functional particles, viscosity and discharge speed of the liquid synthetic resin, nozzle diameter, applied voltage of static electricity, distance from the nozzle to the base, atmospheric temperature, and the like, the sizes, lengths, and diameters of the large diameter portions 2, 2 and the small diameter portions 3, 3, a ratio of the both, and the like can be adjusted.

[0056] The functional nonwoven fabric 1 is manufactured by using the melt-blowing method or the electrospinning method. In this case, the synthetic resin is sucked out from what will be the large diameter portion to what will be the small diameter portion during spinning. Therefore, an amount of the synthetic resin remaining in the large diameter portion is reduced. Thus, a synthetic resin coating covering the functional resin becomes thin or net-like in the large diameter portion. When the functional particles perform substance exchange, adsorption, reaction, or the like on a particle surface, the synthetic resin coating becomes thin or net-like, so that functions of the functional particles are preferably exhibited more effectively.

[0057] Actions and effects of the functional nonwoven fabric 1 of the above embodiment will be described. In conventional functional nonwoven fabrics such as those in Patent Literature 1, the functional particles are adhered ex post facto to the fibers that have been made into the nonwoven fabric. In this way, the functional nonwoven fabric is manufactured. In conventional technology, a binder or the like is used in combination to surely adhere the functional particles. However, when the binder is used, it is possible to suppress falling off of the functional particles, but the binder component is likely to clog the vacant spaces in the nonwoven fabric. Therefore, the air permeability is likely to decrease. In particular, when an attempt is made to increase the blending amount of the functional particles, the binder and the functional particles stick to each other in a plate-like or film-like shape between the fibers. In this way, the vacant spaces in the nonwoven fabric are clogged. Therefore, a decrease in the air permeability is likely to be more noticeable. Further, in the conventional technology, the functional particles are filtered out by the nonwoven fabric and adhered to the nonwoven fabric. Therefore, when the attempt is made to increase the blending amount of the functional particles, the functional particles are likely to concentrate on a surface of the nonwoven fabric. As a result, a problem also occurs that the air permeability is easily decreased.

[0058] In the functional nonwoven fabric 1 of the above embodiment, at least a part of the large diameter portions 2, 2 contains the functional particles 4, 4. Then, the long fibers are formed that include the large diameter portions 2, 2 and the small diameter portions 3, 3 alternately arranged. The functional nonwoven fabric 1 is configured to contain such long fibers. Therefore, the functional particles 4, 4 are firmly integrated with the long fibers. Therefore, the falling off of the functional particles 4, 4 from the functional nonwoven fabric 1 is suppressed. In particular, the functional particles 4, 4 are solidified into a string-like or dumpling-like shape by the synthetic resin to form the large diameter portions 2, 2. In this case, the falling off of the functional particles 4, 4 from the functional nonwoven fabric 1 is more reliably suppressed.

[0059] In addition, the diameter of the long fibers contained in the functional nonwoven fabric 1 changes in the longitudinal direction of the fibers so that the plurality of large diameter portions 2, 2 and the plurality of small diameter portions 3, 3 are alternately arranged. Therefore, when the fibers overlap each other, there arise portions where the large diameter portions 2, 2 come into contact with each other, and portions where the large diameter portion 2 and the small diameter portion 3 come into contact with each other. If there arise such portions, a gap will occur in the thickness direction when the long fibers are stacked to form the nonwoven fabric. Therefore, in the functional nonwoven fabric 1, even when the fiber diameter of the small diameter portion 3 is small, it is suppressed that stack of the long fibers is crushed into a flat shape and thus the nonwoven fabric has become a thin plate shape, resulting in deteriorated air permeability. That is, the diameter of the long fibers contained in the functional nonwoven fabric 1 changes in the longitudinal direction of the fibers so that the plurality of large diameter portions and the plurality of small diameter portions are alternately arranged. Thus, the stack of the long fibers has a three-dimensional structure with a three-dimensional thickness. Therefore, the decrease in the air permeability can be suppressed. Then, in the functional nonwoven fabric 1, the fiber diameter of the small diameter portions 3, 3 is equal to or smaller than the diameter of the functional particles 4, 4 contained in the large diameter portion. Therefore, it is suppressed that the fibers in the small diameter portions reduce a gap between the fibers of the nonwoven fabric. This can suppress the decrease in the air permeability.

[0060] Further, as in the functional nonwoven fabric 1 of the above embodiment, the functional particles 4, 4 are solidified into a string-like or dumpling-like shape by the synthetic resin and are integrated with the long fibers as the large diameter portions 2, 2. In this case, even when the blending amount of the functional particles is increased, the decrease in the air permeability of the nonwoven fabric can be suppressed. When the blending amount of the functional particles is increased, a proportion of the large diameter portions 2, 2 in a space inside the functional nonwoven fabric 1 is increased. However, the large diameter portions 2, 2 are string-like or dumpling-like. Therefore, even when the large diameter portions come into contact with each other, the space is left around them. As a result, functional particles and binder do not block the gap between the fibers in the plate-like or film-like form, as in the conventional technology. Therefore, in the functional nonwoven fabric 1, even when the blending amount of the functional particles is increased, the decrease in the air permeability of the nonwoven fabric can be suppressed. When a ratio of the fiber diameter of the large diameter portion to the fiber diameter of the small diameter portion increases, such an effect is more likely to increase.

[0061] Further, in the functional nonwoven fabric 1 of the above embodiment, the functional particles 4, 4 are contained in the large diameter portions 2, 2 of the long fibers. Therefore, the functional particles 4, 4 can be dispersed almost uniformly by simply stacking the long fibers. That is, the nonwoven fabric can contain the functional particles 4, 4 that are uniformly dispersed throughout the entire thickness direction of the nonwoven fabric. Therefore, unlike the conventional technology, when an attempt is made to increase the blending amount of the functional particles, a problem of the functional particles concentrating on the surface of the nonwoven fabric does not occur.

[0062] In addition, although not essential, when the fiber diameter of the small diameter portions 3, 3 is set to 1/100 or more of the diameter of the functional particles, as in the functional nonwoven fabric 1 of the above embodiment, a bulking effect can be obtained by the large diameter portions 2, 2, while the small diameter portions 3, 3 can firmly connect the large diameter portions 2, 2. Therefore, the falling off of the large diameter portions 2, 2 or the functional particles 4, 4 can be more effectively suppressed.

[0063] In addition, although not essential, the above effect is more effectively exhibited when the fiber diameter of the small diameter portions 3, 3 is further set to be 100 nanometers or more and 10 micrometers or less, and the diameter of the functional particles 4, 4 is set to be 300 nanometers or more and 200 micrometers or less, as in the functional nonwoven fabric 1 of the above embodiment. Therefore, even when the blending amount of the functional particles is increased, the decrease in the air permeability of the nonwoven fabric can be particularly effectively suppressed.

[0064] In addition, although not essential, when the functional particles 4, 4 are the particles having the thermal expansion properties, as in the functional nonwoven fabric 1 of the above embodiment, the air permeability of the nonwoven fabric can be changed by applying heat during use so that the air permeability of the functional nonwoven fabric is decreased. In particular, in the above functional nonwoven fabric 1, the nonwoven fabric has the air permeability. Then, the thermally expandable functional particles are arranged so as to be dispersed throughout the nonwoven fabric. Therefore, the functional particles are quickly expanded by heating the functional particles by means of an airflow, so that the air permeability can be quickly changed. Such a functional nonwoven fabric can be used for applications such as ventilation passages in an air flow system. This functional nonwoven fabric is used in a ventilation state under normal circumstances (when an air temperature is low) utilizing the air permeability of the functional nonwoven fabric 1. On the other hand, when high-temperature air flows into the ventilation passage in the event of a fire or the like, the flow of the high-temperature air can be suppressed by reducing the air permeability of the functional nonwoven fabric 1.

[0065] In addition, although not essential, further, when the functional particles 4, 4 are aluminum phosphite particles, as in the functional nonwoven fabric 1 of the above embodiment, the air permeability of the functional nonwoven fabric can be efficiently changed to be decreased by applying heat during use.

[0066] In addition, according to the method for manufacturing the functional nonwoven fabric 1 using the melt-blowing method or the electrospinning method as described above, it is possible to stably and efficiently manufacture the functional nonwoven fabric 1 having the large diameter portion and the small diameter portion as described above. In addition, when the functional nonwoven fabric 1 is manufactured using the melt-blowing method or the electrospinning method, the small diameter portions 3, 3 are formed so that the synthetic resin is sucked out from what will be the large diameter portions 2, 2 during spinning. Therefore, the amount of the synthetic resin remaining in the large diameter portions 2, 2 is reduced. As a result, a synthetic resin film covering the functional particles 4, 4 becomes thin or net-like in the large diameter portions 2, 2. Thus, the functions of the functional particles 4, 4 are more easily exhibited. For example, when the functional particles 4, 4 are particles having the thermal expansion properties and if the synthetic resin film covering the functional particles 4, 4 is made thinner, the functional particles will expand more quickly when they come into contact with a high-temperature airflow.

[0067] Further, according to the method for manufacturing the functional nonwoven fabric 1 using the electrospinning method as described above, it is also possible to prevent the temperature from being high during spinning. This case is preferable when integrating heat-sensitive functional particles into the functional nonwoven fabric. Examples of the heat-sensitive functional particles are aromatic functional particles containing a fragrance.

[0068] The invention is not limited to the above embodiment. Various modifications can be made. Other embodiments of the invention are described below. In the following description, differences from the above embodiment will be mainly described. Details of similar parts are omitted. Further, these embodiments can be implemented by combining parts of them with each other. Alternatively, these embodiments can be implemented by replacing parts of them. For example, in description of the above embodiment, it has been described that the long fibers contained in the functional nonwoven fabric 1 are simply in contact with each other in a portion where they are entangled. However, in an entangled portion, the long fibers may be bonded to each other. For example, the large diameter portions 2, 2 may be adhered to each other in the portion where the long fibers are entangled. Alternatively, three or more (preferably four or more) small diameter portions 3, 3 may be connected to one large diameter portion in appearance. In such a structure, the small diameter portions 3, 3 connect the large diameter portions 2, 2 in a network shape. In this way, a three-dimensional structure of the functional nonwoven fabric 1 is easily maintained. Therefore, the air permeability is also good.

[0069] Other examples of the functional nonwoven fabric 1 manufactured by changing manufacturing conditions and the like are described below. FIG. 4 is a micrograph illustrating the structure of the functional nonwoven fabric of Example 2, manufactured by changing the manufacturing conditions and the like. The manufacturing conditions were adjusted such that the long fibers were entirely thickened compared to the above-mentioned example. Example 2 is the same as the above-mentioned example in that the synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are aluminum hydrogen phosphite (average particle diameter: 5 micrometers), and the long fibers are manufactured by the electrospinning method.

[0070] In the functional nonwoven fabric of Example 2, the diameter of the large diameter portions 2, 2 was approximately 2 to 15 micrometers (average diameter: 8 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.5 to 1.8 micrometers (average diameter: 1.0 micrometer). Further, the nonwoven fabric of Example 2 was found to have a portion where three or more small diameter portions extended to branch from the large diameter portion.

[0071] FIG. 5 is a micrograph illustrating the structure of the functional nonwoven fabric of Example 3, manufactured by changing the manufacturing conditions and the like. The manufacturing conditions were adjusted such that the blending amount of the functional particles was reduced compared to the above-mentioned example. Example 3 is the same as the above-mentioned example in that the synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are NSF (average particle diameter: 5 micrometers), and the long fibers are manufactured by the electrospinning method.

[0072] In the functional nonwoven fabric of Example 3, the diameter of the large diameter portions 2, 2 was approximately 3 to 8 micrometers (average diameter: 5 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.3 to 1.0 micrometers (average diameter: 0.6 micrometers). Further, the nonwoven fabric of Example 3 was also found to have the portion where three or more small diameter portions extended to branch from the large diameter portion.

[0073] The functional nonwoven fabrics of Example, Example 2, and Example 3 all have appropriate air permeability. In addition, when these functional nonwoven fabrics were exposed to hot air, the functional particles expanded, thereby decreasing the air permeability.

[0074] In the above embodiment, the functional particles are described as the particles having the thermal expansion properties. However, the functions of the functional particles are not limited to the thermal expansion properties. For example, the functional particles may be particles having water retention or water absorption properties. In this case, a cooling effect can also be obtained by increasing the water absorption properties of the nonwoven fabric or evaporating absorbed moisture.

[0075] Further, the functional particles may also be particles having a deodorizing or odor eliminating function, such as particles containing an aldehyde adsorbent or activated carbon particles. The functional nonwoven fabrics containing such functional particles can be used for deodorizing or odor eliminating purposes. Further, when particles containing a fragrance are used as the functional particles, the functional nonwoven fabric can have an aromatic function.

[0076] Further, the functional particles may also be particles having heat generating or heat absorbing properties. Further, the functional particles may also be particles having heat conducting or conductive properties. Further, the functional particles may also be particles having a function to react with chemical substances present in an environment in which the functional nonwoven fabric is used, or a catalytic function to promote the reaction. Furthermore, the functional particles may also be particles having optical functions such as light absorption, low reflectance, fluorescence, reflectivity, or refraction.

[0077] Further, the functional nonwoven fabric can also be applied to technical fields other than those exemplified in the above embodiment. For example, a functional nonwoven fabric integrated with functional particles having deodorizing properties can be used for deodorizing purposes or the like in a living room.

[0078] Hereinafter, an embodiment (a second embodiment) in which the functional nonwoven fabric has particularly thermal expansion properties, that is, in which the functional nonwoven fabric is the thermally expandable nonwoven fabric will be described. An embodiment of the invention of a thermally expandable functional nonwoven fabric having the thermal expansion properties (hereinafter also simply referred to as thermally expandable nonwoven fabric) and including long fibers integrated with the functional particles having the thermal expansion properties will be described below with reference to the drawings. The invention is not limited to the individual embodiments described below. Modification of the embodiments can also be implemented.

[0079] A thermally expandable nonwoven fabric 5 of a second embodiment is a functional nonwoven fabric containing long fibers made of synthetic resin and integrated with functional particles 4, 4 having a predetermined function. Here, the long fibers refer to long fibers in contrast to short fibers in fibers constituting the nonwoven fabric. The long fibers are also called filament yarns. The short fibers are called staple fibers or the like. The short fibers have a length of approximately several mm to several tens of cm. In contrast, the long fibers are fibers that are not cut short. The long fibers are typically spun by a melt-blowing method, an electrospinning method, or a spunbonding method. The spun long fibers are directly stacked to form the nonwoven fabric. Note that the thermally expandable nonwoven fabric 5 does not need to be composed only of the long fibers. The thermally expandable nonwoven fabric 5 may contain the short fibers. The long fibers and the short fibers may be mixed and spun so that they are entangled.

[0080] Although not essential, the blending amount of the functional particles 4, 4 to the thermally expandable nonwoven fabric 5 is preferably about 10 to 500 g/m.sup.2.

[0081] Further, the thermally expandable nonwoven fabric may be a single layer. Alternatively, the thermally expandable nonwoven fabric may be a laminated nonwoven fabric including a plurality of nonwoven fabric layers, and film, sheet, woven fabric, or the like, that are stacked together. Further, the thermally expandable nonwoven fabric may be a composite nonwoven fabric including a layer of nonwoven long fibers that is stacked on a woven fabric or mesh material. The long fibers made of synthetic resin and integrated with the functional particles may be included only in one of the nonwoven fabric layers.

[0082] Further, all of the long fibers contained in the thermally expandable nonwoven fabric 5 may be the long fibers made of synthetic resin and integrated with the functional particles. Alternatively, the thermally expandable nonwoven fabric 5 may contain other long fibers, for example, long fibers that are not integrated with the functional particles. Although not essential, the thermally expandable nonwoven fabric 5 of the present embodiment is a single-layer functional nonwoven fabric. This functional nonwoven fabric is obtained by forming a nonwoven fabric from the long fibers made of synthetic resin, integrated with the functional particles, and spun by the electrospinning method.

[0083] FIG. 6 illustrates a schematic diagram of the thermally expandable nonwoven fabric 5 of the second embodiment. In addition, FIG. 3 is a micrograph of Example of the thermally expandable nonwoven fabric of the present embodiment. Note that in FIG. 6, small diameter portions 3, 3 are each represented by a single solid line. A diameter of the long fibers contained in the thermally expandable nonwoven fabric 5 varies in a longitudinal direction of the fibers so that a plurality of large diameter portions 2, 2 and a plurality of small diameter portions 3, 3 are alternately arranged. In other words, the long fibers are fibers that are configured so that the large diameter portions 2, 2 and the small diameter portions 3, 3 are in the form of a string of beads.

[0084] The small diameter portions 3, 3 of the long fibers are monofilaments formed of the synthetic resin. There are no particular limitations on the synthetic resin as long as it is a resin that can be made into fibers. The synthetic resin is preferably a resin that is suitable for manufacturing the long fibers by the melt-blowing method or the electrospinning method. Further, the synthetic resin is preferably a resin that adheres to the functional particles described below. As the synthetic resin that is a raw material for the long fibers, for example, a polyurethane resin or a polyvinyl chloride resin can be preferably used.

[0085] The monofilaments as the small diameter portions 3, 3 may be composed only of the synthetic resin described above. Alternatively, the monofilaments may contain other compounding materials, for example, particles having a diameter smaller than the diameter of the small diameter portion, such as reinforcing materials or bulking materials, or chemicals that improve properties of the synthetic resin. Further, the monofilaments as the small diameter portions 3, 3 may be monofilaments that do not substantially contain the thermally expandable functional particles.

[0086] Although not essential, a fiber diameter of the small diameter portions 3, 3 is preferably 100 nanometers or more and 10 micrometers or less. The fiber diameter of the small diameter portions 3, 3 is particularly preferably 500 nanometers or more and 3 micrometers or less. Here, the fiber diameter refers to a diameter of the fiber measured in a direction perpendicular to an extension direction of the fiber. The fiber diameter of the small diameter portions is determined by measurement on a photographed micrograph of the thermally expandable nonwoven fabric 5. The fiber diameter of the small diameter portions is preferably measured at 10 to 20 locations. An average of these measured values is used as the fiber diameter of the small diameter portions.

[0087] The large diameter portions 2, 2 contain the thermally expandable functional particles 4, 4. At least a part of the large diameter portions 2, 2 is formed by a plurality of functional particles 4, 4 that are solidified into a string-like or dumpling-like shape by the synthetic resin. Here, string-like means that, with respect to a shape of the large diameter portion, a length in the extension direction of the fiber is longer than a length in the direction perpendicular to the extension direction of the fiber, and preferably is at least three times the length in the direction perpendicular to the extension direction of the fiber. In addition, dumpling-like means that, with respect to the shape of the large diameter portion, the length in the extension direction of the fiber is approximately the same as the length in the direction perpendicular to the extension direction of the fiber, and preferably is at least half and at most twice the length in the direction perpendicular to the extension direction of the fiber. Note that the long fiber may have a large diameter portion that does not contain any functional particles, or a large diameter portion that contains only one functional particle.

[0088] A diameter of the large diameter portions 2, 2 is larger than the fiber diameter of the small diameter portions 3, 3. The diameter of the large diameter portions is a diameter measured in the direction perpendicular to the extension direction of the fiber. The diameter of the large diameter portions is preferably measured at 10 to 20 locations. An average of these measured values is used as the diameter of the large diameter portions. Although not essential, the diameter of the large diameter portions 2, 2 is preferably 150 nanometers or more and 300 micrometers or less. The diameter of the large diameter portions 2, 2 is particularly preferably 1 micrometer or more and 50 micrometers or less. Further, the diameter of the large diameter portions 2, 2 is preferably 3 to 20 times the fiber diameter of the small diameter portions 3, 3, and particularly preferably 4 to 10 times.

[0089] FIG. 2 schematically illustrates the structure of the large diameter portions 2, 2 and the small diameter portions 3, 3. In the example of the embodiment illustrated in FIG. 2, the large diameter portion 2 contains a plurality of thermally expandable functional particles 4, 4. The thermally expandable functional particles contained in the large diameter portion 2 may be one. Further, there may be present a large diameter portion containing no functional particles while present a large diameter portion containing, in a part thereof, the thermally expandable functional particles. Although not essential, in the illustrated form, the functional particles 4, 4 are wrapped or bonded by the same synthetic resin as the synthetic resin constituting the small diameter portion. In this way, the functional particles 4, 4 are solidified into a string-like or dumpling-like shape. In the large diameter portions 2, 2, the functional particles 4, 4 may be bonded to each other by the synthetic resin. Alternatively, one or more functional particles 4, 4 may be wrapped by a synthetic resin formed in a film-like, net-like, or fiber bundle shape. In the large diameter portions 2, 2, only one functional particle may be present in a radial direction of the fiber. Alternatively, a plurality of the functional particles may be present in the radial direction of the fiber. At end portions of the large diameter portions 2, 2, the large diameter portion 2 and the small diameter portion 3 are continuous with each other so that the synthetic resin contained in the large diameter portion directly forms the monofilaments of the small diameter portions 3, 3.

[0090] The functional particles contained in the large diameter portions 2, 2 have thermal expansion properties. That is, in the thermally expandable nonwoven fabric 5 of the present embodiment, the particles having the thermal expansion properties are used as the functional particles. Examples of the particles having the thermal expansion properties include thermally expandable microcapsules, thermally expandable graphite, and aluminum phosphite. Examples of aluminum phosphite particles having the thermal expansion properties include APA-100 from Taihei Chemical Industrial Co., Ltd. Among the aluminum phosphite particles, aluminum hydrogen phosphite (such as NSF from Taihei Chemical Industrial Co., Ltd.) can be particularly preferably used. These particles have a property of expanding when heated to a predetermined temperature. When the large diameter portions 2, 2 contain the particles having the thermal expansion properties and the functional nonwoven fabric is heated, the large diameter portions 2, 2 expand and change so that vacant spaces in the nonwoven fabric become smaller or narrower. In this way, a change occurs in which air permeability of the nonwoven fabric decreases.

[0091] A fiber diameter Ds of the small diameter portions 3, 3 is equal to or smaller than a diameter Dp of the functional particles 4, 4 contained in the large diameter portions 2, 2. The fiber diameter Ds of the small diameter portions 3, 3 and the diameter Dp of the functional particles 4, 4 may be substantially the same. Note that the diameter Dp of the functional particles 4, 4 in the present invention refers to a volume average diameter. The diameter Dp of the functional particles 4, 4 contained in the large diameter portion is typically 300 nanometers or more and 200 micrometers or less. In addition, although not essential, the fiber diameter Ds of the small diameter portions 3, 3 is preferably 1/100 or more of the diameter Dp of the functional particles 4, 4.

[0092] An example of a method for manufacturing the thermally expandable nonwoven fabric 5 of the first embodiment will be described. The thermally expandable nonwoven fabric 5 can be manufactured by applying the melt-blowing method or the electrospinning method.

[0093] First, in a first step, liquefied synthetic resin and the thermally expandable functional particles are mixed together. The synthetic resin is melted by heating. The synthetic resin is liquefied by heating, or by dissolving in a solvent. The functional particles are mixed and dispersed in the liquefied synthetic resin. A liquid synthetic resin containing dispersed functional particles may be obtained by heating and melting the synthetic resin into which the functional particles have been kneaded in advance. Alternatively, the synthetic resin may be dissolved and liquefied by the solvent or the like, and then the functional particles may be mixed and dispersed therein.

[0094] In the present embodiment, the polyurethane resin is dissolved and liquefied by the solvent. Aluminum phosphite powder (NSF manufactured by Taihei Chemical Industrial Co., Ltd., volume average diameter 5 micrometers) as the functional particles 4, 4 is mixed into the liquefied polyurethane resin, and dispersed by stirring.

[0095] Subsequently, as a second step, following the first step, the nonwoven fabric is formed by depositing long fibers while spinning the long fibers from the liquid synthetic resin containing the dispersed functional particles 4, 4 by the melt-blowing method or the electrospinning method.

[0096] The liquid synthetic resin discharged from a spinning nozzle is stretched by centrifugal force, gravity, electrostatic force, or the like, to be thin fibers. The thin fibers form the small diameter portions 3, 3 of the long fibers. At this time, the functional particles 4, 4 are discharged from the nozzle together with the liquid synthetic resin. Then, a portion where the functional particles 4, 4 gather together solidifies into a string-like or dumpling-like shape to form the large diameter portions 2, 2. At the same time, excess synthetic resin is stretched to form the small diameter portions 3, 3. In this way, the long fibers in which the large diameter portions 2, 2 and the small diameter portions 3, 3 are alternately arranged in the form of a string of beads are continuously formed. The long fibers thus formed are solidified as the solvent evaporates or the temperature drops. At the same time, the long fibers are deposited on a base of a spinning apparatus (nonwoven fabric manufacturing apparatus). In this way, the thermally expandable nonwoven fabric 5 is manufactured.

[0097] In Example, aluminum hydrogen phosphite NSF (average particle diameter: 5 micrometers) was used as the functional particles. The diameter of the large diameter portions 2, 2 of the obtained thermally expandable nonwoven fabric 5 was approximately 2 to 10 micrometers (average diameter: 6 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.5 to 1.5 micrometers (average diameter: 0.9 micrometers). The blending amount of the functional particles 4, 4 to the obtained thermally expandable nonwoven fabric 5 was approximately 100 g/m.sub.2. By stacking a large amount of long fibers, it is also possible to increase the blending amount of the functional particles 4, 4 per unit area in the thermally expandable nonwoven fabric 5. Further, FIG. 3 illustrates a micrograph of the thermally expandable nonwoven fabric of Example. In FIG. 3, only a small portion of the layers in the thickness direction of the nonwoven fabric is photographed so that morphology of the fibers can be clearly seen. The same is true for FIGS. 4 and 5.

[0098] By adjusting the blending amount of the functional particles, viscosity and discharge speed of the liquid synthetic resin, nozzle diameter, applied voltage of static electricity, distance from the nozzle to the base, atmospheric temperature, and the like, the sizes, lengths, and diameters of the large diameter portions 2, 2 and the small diameter portions 3, 3, a ratio of the both, and the like can be adjusted.

[0099] The thermally expandable nonwoven fabric 5 is manufactured by using the melt-blowing method or the electrospinning method. In this case, the synthetic resin is sucked out from what will be the large diameter portion to what will be the small diameter portion during spinning. Therefore, an amount of the synthetic resin remaining in the large diameter portion is reduced. Thus, a synthetic resin coating covering the functional resin becomes thin or net-like in the large diameter portion. When the functional particles can perform substance exchange, adsorption, reaction, or the like on a particle surface, by the synthetic resin coating being thin or net-like, the thermal expansion properties and other functions of the functional particles become preferably exhibited more effectively.

[0100] FIG. 7 illustrates a schematic sectional view of an example of a usage form of the thermally expandable nonwoven fabric 5 of the second embodiment. The thermally expandable nonwoven fabric 5 of the second embodiment is attached to a cylindrical ventilation passage 9. Left and right ends of the ventilation passage 9 are open. As illustrated by a white arrow, the ventilation passage 9 is configured so that air flowing in from the left end passes through the ventilation passage 9 and flows out from the right end.

[0101] The thermally expandable nonwoven fabric 5 is provided to divide an internal space of the ventilation passage 9 into a left end side and a right end side. As in the present embodiment, the thermally expandable nonwoven fabric 5 is preferably provided diagonally to a flow direction of the airflow. An area of the thermally expandable nonwoven fabric 5 is set larger than a sectional area of the passage. The air flowing in from the left end of the ventilation passage 9 passes through the thermally expandable nonwoven fabric 5 having the air permeability and flows out from the right end of the ventilation passage 9. Although not essential, a support member such as a metal mesh may preferably be provided downstream of the thermally expandable nonwoven fabric 5.

[0102] In this usage form, the air permeability of the thermally expandable nonwoven fabric 5 is maintained under normal circumstances. The ventilation passage 9 functions as a ventilation passage for passing the airflow. On the other hand, when the high-temperature air that is hotter than the expansion start temperature of the thermally expandable particles flows into the ventilation passage 9 due to a fire or the like that occurs upstream of the airflow, the high-temperature airflow expands the thermally expandable functional particles contained in the thermally expandable nonwoven fabric 5. As a result, the air permeability of the thermally expandable nonwoven fabric 5 is limited. This makes it difficult for the airflow to flow through the ventilation passage 9. In this way, the high-temperature airflow flowing out downstream is suppressed or prevented.

[0103] The actions and effects of the thermally expandable nonwoven fabric 5 of the above embodiment will be described. In conventional thermally expandable members such as those in Patent Literature 2, a material itself of the member does not have the air permeability. When the air permeability is required, it is necessary to form a ventilation hole by molding or the like. On the other hand, according to the thermally expandable nonwoven fabric 5 of the above embodiment, the thermally expandable nonwoven fabric containing the long fibers having the large diameter portion and the small diameter portion is formed. This nonwoven fabric has the air permeability. Therefore, as in the usage form illustrated in FIG. 7 above, the thermally expandable nonwoven fabric of the present invention can be used in an arrangement or configuration in which airflow passes through the inside of the nonwoven fabric.

[0104] Further, in the conventional thermally expandable members such as those in Patent Literature 2, the thermally expandable material is kneaded so as to be embedded in the resin. Further, the conventional thermally expandable members are each heated from a surface of the member and expand. Therefore, it is difficult to expand the entire member uniformly. It takes time for heat to be transferred from the surface of the conventional thermally expandable member to its inside. Therefore, the expansion is slow. In particular, when only the surface of the member expands, an expanded part acts as a kind of a heat-insulating layer. As a result, expansion of deeper parts of the member is easily hindered.

[0105] In the thermally expandable nonwoven fabric 5 of the above embodiment, the large diameter portions 2, 2 and the small diameter portions 3, 3 are alternately arranged in the form of a string of beads to form the long fibers. The thermally expandable functional particles 4, 4 are contained in the large diameter portions 2, 2 of the long fibers. The thermally expandable nonwoven fabric 5 is configured to contain such long fibers. In addition, the diameter of the long fibers contained in the functional nonwoven fabric 5 changes in the longitudinal direction of the fibers so that the plurality of large diameter portions 2, 2 and the plurality of small diameter portions 3, 3 are alternately arranged. Therefore, when the fibers overlap each other, there arise portions where the large diameter portions 2, 2 come into contact with each other, and portions where the large diameter portion 2 and the small diameter portion 3 come into contact with each other. If there arise such portions, a gap will occur in the thickness direction when the long fibers are stacked to form the nonwoven fabric. Therefore, in the thermally expandable nonwoven fabric 5, even when the fiber diameter of the small diameter portion 3 is small, it is suppressed that stack of the long fibers is crushed into a flat shape and thus the nonwoven fabric has become a thin plate shape, resulting in deteriorated air permeability. That is, the diameter of the long fibers contained in the thermally expandable nonwoven fabric 5 changes in the longitudinal direction of the fibers so that the plurality of large diameter portions and the plurality of small diameter portions are alternately arranged in a string of beads. Thus, the stack of the long fibers has a three-dimensional structure with a three-dimensional thickness. Therefore, the decrease in the air permeability can be suppressed. Then, in the thermally expandable nonwoven fabric 5, the fiber diameter of the small diameter portions 3, 3 is equal to or smaller than the diameter of the functional particles 4, 4 contained in the large diameter portion. Therefore, it is suppressed that the fibers in the small diameter portions reduce a gap between the fibers of the nonwoven fabric. This can suppress the decrease in the air permeability of the nonwoven fabric.

[0106] Therefore, the thermally expandable nonwoven fabric 5 of the above embodiment expands quickly by the high-temperature air. That is, the thermally expandable nonwoven fabric has the air permeability. Therefore, when the high-temperature air reaches the nonwoven fabric, the high-temperature air easily enters the inside of the nonwoven fabric. The high-temperature air easily passes through the nonwoven fabric. Thus, the entire nonwoven fabric is easily heated by the high-temperature air. The thermally expandable functional particles contained in the large diameter portion of the long fibers are rapidly heated by the high-temperature air surrounding the fibers and expand. Thus, the thermally expandable nonwoven fabric can expand quickly by the high-temperature air.

[0107] Further, although not essential, particularly when the thermally expandable functional particles are aluminum hydrogen phosphite particles, as in the thermally expandable nonwoven fabric 5 of the above embodiment, the functional particles expand quickly. In addition, fire resistance of expanded functional particles is also good. Furthermore, even when the functional particles are exposed to flames or the like, an expanded state is maintained. Therefore, the thermally expandable nonwoven fabric 5 can also be used in applications such as blocking flames or the like in the event of a fire.

[0108] Further, although not essential, particularly as in the thermally expandable nonwoven fabric 5 of the above embodiment, the thermally expandable functional particles 4, 4 are solidified into a string-like or dumpling-like shape by the synthetic resin, and are integrated with the long fibers as the large diameter portions 2, 2. In this case, even when the blending amount of the functional particles is increased, the decrease in the air permeability of the nonwoven fabric can be suppressed. When the blending amount of the functional particles is increased, the proportion of the large diameter portions 2, 2 in the space inside the thermally expandable nonwoven fabric 5 is increased. However, when the large diameter portions 2, 2 are string-like or dumpling-like, even when the large diameter portions come into contact with each other, the space is left around them. This suppresses blocking of the gap between the fibers. In such a thermally expandable nonwoven fabric 5, even when the blending amount of functional particles is increased, the decrease in the air permeability of the nonwoven fabric can be suppressed. Therefore, the nonwoven fabric can expand quickly by the high-temperature air. Then, when the nonwoven fabric is heated so that the high-temperature air passes through the nonwoven fabric, the nonwoven fabric can expand uniformly also from the inside.

[0109] Then, as in the thermally expandable nonwoven fabric 5 of the above embodiment, the functional particles are integrated with the large diameter portion by being wrapped in the synthetic resin in a film, net, or fiber bundle form, or by being bonded with the synthetic resin. In this case, most of the functional particles are likely to be disposed near a surface of the large diameter portion of the long fibers. At the same time, the synthetic resin separating the functional particles from an outside air is very thin. Therefore, the thermally expandable functional particles are quickly heated by the high-temperature air and expand. This makes expansion of the thermally expandable nonwoven fabric 5 particularly quick.

[0110] Furthermore, in the thermally expandable nonwoven fabric 5 of the above embodiment, the thermally expandable functional particles 4, 4 are contained in the large diameter portions 2, 2 of the long fibers. Therefore, the functional particles 4, 4 can be dispersed almost uniformly simply by stacking the long fibers. That is, the nonwoven fabric can contain the functional particles 4, 4 that are uniformly dispersed throughout the entire thickness direction of the nonwoven fabric. When such a thermally expandable nonwoven fabric 5 is heated by passing the hot air therethrough, the thermally expandable nonwoven fabric can be expanded uniformly.

[0111] Further, in the thermally expandable nonwoven fabric 5, the thermally expandable functional particles expand when exposed to the high-temperature air. At this time, expansion of the large diameter portions 2, 2 reduces a space between the fibers. Due to this action, the air permeability of the nonwoven fabric can be changed to be decreased when the thermally expandable nonwoven fabric 5 is exposed to heat. For example, when the thermally expandable nonwoven fabric 5 is disposed in the ventilation hole in a ceiling panel, ventilation is performed through the ventilation hole under normal circumstances (when the air temperature is low). On the other hand, when the high-temperature air passes through the ventilation hole in the event of a fire or the like, the thermally expandable nonwoven fabric disposed in the hole expands uniformly and quickly, to block the ventilation hole in the panel. Therefore, the air permeability of the hole can be limited. That is, when the thermally expandable nonwoven fabric 5 is used in a portion of the ventilation hole or the ventilation passage, the ventilation can be performed under normal circumstances. On the other hand, when it is desired to stop the flow of the hot-temperature air in the event of a fire or the like, it is possible to limit or eliminate the air permeability, or to prevent the hot-temperature air from passing beyond the thermally expandable nonwoven fabric. The thermally expandable nonwoven fabric 5 has a similar effect even in the usage form in the ventilation passage illustrated in FIG. 7.

[0112] Furthermore, when the fiber diameter of the small diameter portions 3, 3 is 1/100 or more of the diameter of the thermally expandable functional particles 4, 4, as in the thermally expandable nonwoven fabric 5, separation of the large diameter portion and the small diameter portion are suppressed. That is, the gap is likely to occur depending on a degree of overlap of the long fibers due to presence of the large diameter portions 2, 2. This improves the air permeability of the thermally expandable nonwoven fabric. Therefore, the thermally expandable nonwoven fabric can be expanded more quickly and more uniformly by the high-temperature air.

[0113] Furthermore, when the fiber diameter of the small diameter portion is 100 nanometers or more and 10 micrometers or less, and the diameter of the functional particles is 300 nanometers or more and 200 micrometers or less, as in the thermally expandable nonwoven fabric 5, the blocking of the gap between the large diameter portions of the long fibers by the small diameter portion is suppressed. This improves the air permeability of the thermally expandable nonwoven fabric. Therefore, the thermally expandable nonwoven fabric can be expanded more quickly and more uniformly by the high-temperature air.

[0114] Further, according to a method for manufacturing the thermally expandable nonwoven fabric including the following first and second steps, the thermally expandable nonwoven fabric as described above can be efficiently manufactured. In the first step, the thermally expandable functional particles are dispersed in the synthetic resin liquefied by heat melting of the synthetic resin or by dissolution of the synthetic resin in the solvent, as described above. In the second step, following the first step, the nonwoven fabric is formed while spinning the long fibers from the liquid synthetic resin containing the dispersed functional particles by the melt-blowing method or the electrospinning method.

[0115] Further, when the thermally expandable nonwoven fabric 5 is manufactured using the melt-blowing method or the electrospinning method, the small diameter portions 3, 3 are formed so that the synthetic resin is sucked out from what will be the large diameter portions 2, 2 during spinning. Therefore, the amount of the synthetic resin remaining in the large diameter portions 2, 2 is reduced. As a result, the synthetic resin film covering the thermally expandable functional particles 4, 4 becomes thin or net-like in the large diameter portions 2, 2. This makes it easier to exhibit the thermal expansion properties more quickly. For example, when the synthetic resin film covering the thermally expandable functional particles 4, 4 is made thinner, the functional particles will expand more quickly when they come into contact with the high-temperature airflow.

[0116] Further, particularly when the synthetic resin is liquefied by dissolving in the solvent and the long fibers are spun by the electrospinning method, the fibers can be spun at a relatively low temperature. Therefore, even in the case of the thermally expandable functional particles (such as thermally expandable microcapsules) having a low expansion start temperature, the functional particles will not expand in a nonwoven fabric manufacturing process. Therefore, the functional particles can be efficiently integrated with the thermally expandable nonwoven fabric.

[0117] The invention related to the functional nonwoven fabric having thermal expansion properties is not limited to the above embodiment. Various modifications can be made. Other embodiments of the invention are described below. In the following description, differences from the above embodiment will be mainly described. Details of similar parts are omitted. Further, these embodiments can be implemented by combining parts of them with each other. Alternatively, these embodiments can be implemented by replacing parts of them.

[0118] For example, in description of the above embodiment, it has been described that the long fibers contained in the thermally expandable nonwoven fabric 5 are simply in contact with each other in a portion where they are entangled. However, in an entangled portion, the long fibers may be bonded to each other. For example, the large diameter portions 2, 2 may be adhered to each other in the portion where the long fibers are entangled. Alternatively, three or more (preferably four or more) small diameter portions 3, 3 may be connected to one large diameter portion in appearance. In such a structure, the small diameter portions 3, 3 connect the large diameter portions 2, 2 in a network shape. In this way, a three-dimensional structure of the thermally expandable nonwoven fabric 5 is easily maintained. Therefore, the air permeability is also good.

[0119] Other examples of the thermally expandable nonwoven fabric 5 manufactured by changing manufacturing conditions and the like are described below. FIG. 4 is a micrograph illustrating the structure of the functional nonwoven fabric of Example 2, manufactured by changing the manufacturing conditions and the like. The manufacturing conditions were adjusted such that the long fibers were entirely thickened compared to the above-mentioned example. Example 2 is the same as the above-mentioned example in that the synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are NSF (average particle diameter: 5 micrometers), and the long fibers are manufactured by the electrospinning method.

[0120] In the thermally expandable nonwoven fabric of Example 2, the diameter of the large diameter portions 2, 2 was approximately 2 to 15 micrometers (average diameter: 8 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.5 to 1.8 micrometers (average diameter: 1.0 micrometer). Further, the nonwoven fabric of Example 2 was found to have a portion where three or more small diameter portions extended to branch from the large diameter portion.

[0121] FIG. 5 is a micrograph illustrating the structure of the thermally expandable nonwoven fabric of Example 3, manufactured by changing the manufacturing conditions and the like. The manufacturing conditions were adjusted such that the blending amount of the functional particles was reduced compared to the above-mentioned example. Example 3 is the same as the above-mentioned example in that the synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are NSF (average particle diameter: 5 micrometers), and the long fibers are manufactured by the electrospinning method.

[0122] In the thermally expandable nonwoven fabric of Example 3, the diameter of the large diameter portions 2, 2 was approximately 3 to 8 micrometers (average diameter: 5 micrometers). The diameter of the small diameter portions 3, 3 was approximately 0.3 to 1.0 micrometers (average diameter: 0.6 micrometers). Further, also the nonwoven fabric of Example 3 was found to have the portion where three or more small diameter portions extended to branch from the large diameter portion.

[0123] The thermally expandable nonwoven fabrics of Example, Example 2, and Example 3 all were found to have appropriate air permeability. At the same time, when these functional nonwoven fabrics were exposed to hot air (approximately 800 C.), the thermally expandable nonwoven fabrics expanded due to expansion of the functional particles. Then, a heat-insulating layer with almost no air permeability was formed.

[0124] In addition, in the description of the above embodiment, a single-layer thermally expandable nonwoven fabric containing the thermally expandable functional particles has been exemplified. However, the thermally expandable nonwoven fabric may be a multi-layer thermally expandable nonwoven fabric having a layer not containing the functional particles. For example, the thermally expandable nonwoven fabric having a two-layer structure may be formed. In the two-layer structure, a mesh material made of aramid fibers is laminated as a support layer on the above-mentioned thermally expandable nonwoven fabric.

[0125] The support layer is effective in improving mechanical properties of the thermally expandable nonwoven fabric. In particular, the support layer includes fibers made of materials, such as aramid fibers or metal fibers, having higher heat resistance than the synthetic resin that is a material of the long fibers of the thermally expandable nonwoven fabric. With this configuration, it is possible to suppress easy release of the functional particles from constraint by the long fibers, when the functional particles exposed to the high temperatures expand. When the support layer is provided, it is preferably provided downstream of an expected airflow.

[0126] In the above embodiment, the functional particles are described as the particles having the thermal expansion properties. However, the functions of the functional particles are not limited to the thermal expansion properties. For example, the functional particles may be particles having water retention or water absorption properties, besides the thermal expansion properties. In this case, a cooling effect can also be obtained by increasing the water absorption properties of the nonwoven fabric or evaporating absorbed moisture.

[0127] Further, the functional particles may also be particles having a deodorizing or odor eliminating function, besides the thermal expansion properties. The thermally expandable nonwoven fabrics containing such functional particles can also be used for deodorizing or odor eliminating purposes. Further, when particles containing a fragrance are used as the functional particles, the thermally expandable nonwoven fabric can have an aromatic function.

[0128] Further, the functional particles may also be particles having heat generating or heat absorbing properties, besides the thermal expansion properties. Further, the functional particles may also be particles having heat conducting or conductive properties, besides the thermal expansion properties. Further, the functional particles may also be particles having, besides the thermal expansion properties, a function to react with chemical substances present in an environment in which the functional nonwoven fabric is used, or a catalytic function to promote the reaction. Furthermore, the functional particles may also be particles having optical functions such as light absorption, low reflectance, fluorescence, reflectivity, or refraction, besides the thermal expansion properties.

[0129] Further, the above-mentioned thermally expandable nonwoven fabric can also be formed by using a combination of the functional particles having the thermal expansion properties and functional particles having no thermal expansion properties but other functions.

[0130] Further, as a specific use of the thermally expandable nonwoven fabric, in the above embodiment, a use has been described in which the thermally expandable nonwoven fabric disposed in the ventilation hole of the ceiling panel or the ventilation passage in a building expands in the event of a fire or the like to decrease the air permeability of the ventilation hole. However, the use is not limited to this. For example, in structural members that require fire resistance, such as doors, window sashes, or frames of the building, the thermally expandable nonwoven fabric may be disposed in a location where it is desired to prevent flame penetration or burning, damage, or the like of the member, to improve the fire resistance of the member.

[0131] Further, for example, cooling air may be sent to electrical components such as motors or inverters, wiring, cables, electronic circuits such as control circuits, integrated circuit boards, and other electrical components and elements such as power transistors, capacitors, and secondary batteries, to cool the circuits or components. When the thermally expandable nonwoven fabric as in the above embodiment is disposed in a ventilation path for the cooling air for these use, cooling can be performed by ventilation under normal circumstances. Furthermore, it is possible to suppress sending of the high-temperature air to an object to be cooled, for example, in the event of a fire in another part of a system, or to suppress sending out of the high-temperature air from the object to be cooled, for example, in the event of abnormal heat generation from the object to be cooled. This can also increase robustness of the system.

[0132] Further, the above-mentioned thermally expandable nonwoven fabric expands when exposed to the hot air. Therefore, the expanded thermally expandable nonwoven fabric can also be used as a heat-insulating material. Such a heat-insulating material is lightweight and has excellent heat insulating properties.

[0133] Further, the thermally expandable nonwoven fabric can also be applied to technical fields other than applications of the thermally expandable nonwoven fabrics as exemplified in the above embodiment. For example, the thermally expandable nonwoven fabric integrated with the functional particles having deodorizing properties can also be used for deodorizing purposes or the like in a living room.

INDUSTRIAL APPLICABILITY

[0134] The functional nonwoven fabric has high industrial utility value since it can be used for deodorizing purposes, for example.

LIST OF REFERENCE SIGNS

[0135] 1 Functional nonwoven fabric [0136] 2 Large diameter portion [0137] 3 Small diameter portion [0138] 4 Functional particle [0139] 5 Thermally expandable nonwoven fabric [0140] 9 Ventilation passage