JP2014070317A - Nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonwoven fabric having an improved flexibility and an enough thickness and specific volume.SOLUTION: A nonwoven fabric comprises heat fusible composite fibers F1 and F2 overlapped crossing each other and a constricted heat fused portion B1 heat fusing the heat fusible composite fibers F1 and F2 at a crossing region R1. The constricted heat fused portion B1 has a concave surface directing through a center P1 of the crossing region R1 to a center line A1 extending to a crossing direction Z1 of the heat fusible composite fiber. A distance between the heat fusible composite fibers F1 and F2 is larger than a summation of fiber radius of each heat fusible composite fiber. The thickness under a load of 3.0 gf/cmis 0.5 to 3.0 mm. The specific volume is 6 to 300 cm/g.

Description

  The present invention relates to a nonwoven fabric.

  In absorbent articles such as disposable diapers and sanitary napkins, a nonwoven fabric used as a constituent member such as a top sheet is usually formed in a belt shape, wound and stored in a roll shape, and unwound from the roll when used. .

  When the nonwoven fabric is wound in the form of a roll, the nonwoven fabric is compressed in the thickness direction to reduce the bulk (thickness) of the nonwoven fabric. May decrease.

  As a method for recovering the bulk of a nonwoven fabric having a reduced volume, a method is known in which hot air is blown onto the nonwoven fabric in an air-through manner to recover the bulk of the nonwoven fabric (Patent Document 1). In this method, hot air is blown in the thickness direction of the nonwoven fabric (perpendicular to the nonwoven fabric).

  On the other hand, as a method for producing a nonwoven fabric, a method is known in which a water vapor stream is sprayed onto a fiber assembly to make the fiber assembly into a nonwoven fabric (Patent Document 2). In this method, a water vapor flow is applied in the thickness direction of the fiber assembly (perpendicular to the fiber assembly). As a result, the fibers are separated and a bridging structure (FIG. 4 of Patent Document 2) is formed between the fibers. It is formed. And the improvement of the softness | flexibility of a nonwoven fabric is achieved by the bridging structure formed between fibers.

JP 2004-137655 A JP 2009-62650 A

  However, in the methods described in Patent Documents 1 and 2, pressure is applied in the thickness direction of the nonwoven fabric or fiber assembly by hot air or steam flow (that is, in the direction opposite to the direction in which the thickness increases), and thus improved flexibility. And it was difficult to manufacture the nonwoven fabric which has sufficient thickness and specific volume.

  Then, an object of this invention is to provide the nonwoven fabric which has the improved softness | flexibility and sufficient thickness and specific volume.

In order to solve the above-described problems, the present invention provides a heat-fusible conjugate fiber that intersects and overlaps with each other, and a constricted shape that heat-fuses the heat-fusible conjugate fiber in an intersecting region of the heat-fusible conjugate fiber. A non-woven fabric having a heat fusion part, wherein the constricted heat fusion part is centered on a virtual line extending in the overlapping direction of the heat-fusible conjugate fiber through the center of the intersecting region, The distance between the heat-fusible conjugate fibers having a concave surface toward the center line and heat-sealed by the constricted heat-sealing part is determined by the sum of the fiber radii of the heat-fusible conjugate fibers. The nonwoven fabric has a thickness of 0.5 to 3.0 mm under a load of 3.0 gf / cm ² and a specific volume of 6 to 300 cm ³ / g.

  According to the present invention, a nonwoven fabric having both improved flexibility and sufficient thickness and specific volume is provided.

FIG. 1 (a) is a plan view when viewed from above with one of the heat-fusible conjugate fibers intersecting and overlapping each other positioned on the upper side and the other on the lower side, and FIG. It is the II sectional view taken on the line of Fig.1 (a). FIG. 2 (a) is a plan view when viewed from above with one of the heat-fusible conjugate fibers intersecting and overlapping each other positioned on the upper side and the other on the lower side, and FIG. It is the II-II sectional view taken on the line of Fig.2 (a). FIG. 3 is an overall view of a bulk recovery device according to an embodiment. FIG. 4 is an enlarged cross-sectional view of the heating chamber. FIG. 5 is an end view of the heating chamber. FIG. 6 is a diagram showing another embodiment of the bulk recovery device. FIG. 7 is a view showing still another embodiment of the bulk recovery device. FIG. 8 is an overall view of a bulk recovery device of a comparative example. FIGS. 9A to 9C are electron micrographs of the nonwoven fabric before bulk recovery (before carrying in the bulk recovery device). 10A to 10C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 1. FIG. FIGS. 11A to 11C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 2. FIG. 12A to 12C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 1. FIG. FIGS. 13A to 13C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 2. FIG. 14A to 14C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 3. FIG.

Hereinafter, the nonwoven fabric of the present invention will be described in detail.
The nonwoven fabric of the present invention has a heat-fusible conjugate fiber that intersects and overlaps with each other, and a constricted heat-sealed portion that heat-fuses the heat-fusible conjugate fiber in the intersecting region of the heat-fusible conjugate fiber.

The nonwoven fabric of the present invention has improved flexibility since the heat-fusible conjugate fiber is heat-sealed by the constricted heat-sealing part. The flexibility of the nonwoven fabric can be evaluated based on, for example, the compression characteristics of the nonwoven fabric. Examples of the compression characteristics of the nonwoven fabric include a compression energy WC (N · m / m ² ) per 1 cm ^{2 of} the nonwoven fabric and a compression resilience RC (%) measured by the KES compression test. The WC value indicates compressive deformability, and the greater the WC value, the higher the compressive deformability. Moreover, RC value shows compression recovery property, and compression recovery property is so high that RC value is near 100%. For the KES compression test, for example, an automated compression tester KES-FB3 manufactured by Kato Tech Co., Ltd. can be used. The WC value is preferably 0.5 N · m / m ² or more, more preferably 1.0 N · m / m ² or more. The RC value is preferably 30% or more, more preferably 40% or more.

  The nonwoven fabric of the present invention includes a large number of intersecting regions of heat-fusible conjugate fibers, but it is not necessary that the heat-fusible conjugate fibers are heat-sealed in all the intersecting regions. It is sufficient that the heat-fusible conjugate fiber is heat-sealed.

  In the non-woven fabric of the present invention, the heat-fusible conjugate fiber intersects with the heat-fusible conjugate fiber when one of the heat-sealable conjugate fibers that overlap and overlap each other is positioned on the upper side and the other on the lower side. This is a region where the adhesive composite fibers overlap (see FIG. 1A), and is a region that spreads in the overlapping direction (vertical direction) of the heat-fusible composite fibers in a cross-sectional view (see FIG. 1). 1 (b)).

  The nonwoven fabric of the present invention includes a large number of heat-sealing portions that heat-fuse the heat-fusible conjugate fibers that intersect and overlap each other in the intersecting region. The heat-sealed portion includes a portion existing inside the intersecting region of the heat-fusible conjugate fiber, but the entire portion does not need to exist inside the intersecting region of the heat-fusible conjugate fiber, and heat-fusible A portion extending to the outside of the intersecting region of the composite fiber may be included.

  A part or all of the large number of heat fusion parts contained in the nonwoven fabric of the present invention is a constricted heat fusion part. The ratio of the number of constricted heat fusion parts in the total number of heat fusion parts contained in a certain region of the nonwoven fabric of the present invention is not particularly limited, but is preferably 1/10 to 9/10, more preferably 2 / 8 to 8/10. The ratio of the number of constricted heat fusion portions to the total number of heat fusion portions is, for example, that the nonwoven fabric is observed with a microscope such as a scanning electron microscope, and the total number of heat fusion portions in the microscope field of view and the constricted heat fusion portion are observed. It can be calculated by counting the number of landing parts. The magnification of the microscope during observation is usually 100 to 500 times, preferably 200 to 400 times.

  The constricted heat-sealed part has a concave surface toward the center line when a virtual line extending in the overlapping direction of the heat-fusible conjugate fiber through the center of the intersecting region of the heat-fusible conjugate fiber is used as the center line. Have

  Hereinafter, an embodiment of a constricted heat fusion part will be described by taking a heat-fusible conjugate fiber that intersects perpendicularly as an example. For convenience of explanation, in this embodiment, the crossing angle of the heat-fusible conjugate fiber is vertical, but the crossing angle of the heat-fusible conjugate fiber is not limited to vertical.

  FIG. 1A is a plan view of the heat-sealable conjugate fibers F1 and F2 that intersect and overlap each other with the heat-sealable conjugate fiber F1 on the upper side and the heat-sealable conjugate fiber F2 on the lower side. It is a top view when it sees. FIG.1 (b) is the II sectional view taken on the line of Fig.1 (a). In addition, the direction of the II line | wire of Fig.1 (a) corresponds with the direction of the axis line L2 of the heat-fusible conjugate fiber F2.

  As shown in FIG. 1A, the heat-fusible conjugate fiber F1 extends along the axis L1, the heat-fusible conjugate fiber F2 extends along the axis L2, and heat The fusible conjugate fibers F1 and F2 intersect perpendicularly.

  In FIG. 1A, the axis line L1 and the axis line L2 are represented by straight lines, but are not limited to straight lines, and may be curved lines. However, when assuming a minute portion where the heat-fusible conjugate fibers F1 and F2 intersect, the axis line L1 and the axis line L2 can be approximated to a substantially straight line as shown in FIG.

  As shown in FIGS. 1 (a) and 1 (b), the intersecting region R1 of the heat-fusible conjugate fibers F1, F2 is a region where the heat-fusible conjugate fibers F1, F2 overlap in a plan view, and is a cross-sectional view. Is a region that spreads between the heat-fusible conjugate fibers F1 and F2 in the overlapping direction Z1 (vertical direction) of the heat-fusible conjugate fibers F1 and F2.

  As shown in FIG. 1A, the center P1 of the intersection region R1 coincides with the intersection of the axes L1 and L2 in plan view.

  As shown in FIG. 1B, the heat-fusible conjugate fibers F1 and F2 are heat-sealed by the constricted heat-sealing part B1 in the intersecting region R1. In the present embodiment, the constricted heat fusion part B1 is formed entirely inside the intersecting region R1, but may include a portion extending to the outside of the intersecting region R1.

  As shown in FIG. 1 (b), the constricted heat-sealed portion B1 passes through the center P1 of the intersecting region R1 of the heat-fusible conjugate fibers F1 and F2, and the heat-fusible conjugate fibers F1 and F2 overlap. When a virtual line extending in the direction Z1 (vertical direction) is defined as a center line A1, the surface has a concave shape toward the center line A1. The center line A1 coincides with a perpendicular drawn from the axis L1 of the heat-fusible conjugate fiber F1 to the axis L2 of the heat-fusible conjugate fiber F2 in the intersecting region R1 of the heat-fusible conjugate fibers F1 and F2. .

  A part of the outer peripheral surface of the constricted heat-sealing part B1 may be concave toward the center line A1, but it is preferable that substantially the whole is concave toward the center line A1. A cracked portion may exist on the outer peripheral surface of the constricted heat fusion part B1.

  In the nonwoven fabric of the present invention, the distance between the heat-fusible conjugate fibers that are heat-sealed by the constricted heat-sealing portion is larger than the sum of the fiber radii of the heat-fusible conjugate fibers. The greater the distance between the heat-fusible conjugate fibers that are heat-sealed by the constricted heat-sealed portion, the less the bonding strength of the heat-fusible conjugate fibers by the constricted heat-welded portion, and the flexibility of the nonwoven fabric. improves. Moreover, the thickness and specific volume (void ratio) of a nonwoven fabric increase, so that the distance between the heat-fusible composite fibers heat-sealed by the constriction-like heat-sealing part becomes large. In the above embodiment, as shown in FIG. 1B, the distance (r3) between the heat-fusible conjugate fibers F1 and F2 that are heat-sealed by the constricted heat-sealing part B1 is the heat-fusible property. It is larger than the sum (r1 + r2) of the fiber radii of the composite fibers F1 and F2.

  Examples of the heat fusion part other than the constricted heat fusion part included in the nonwoven fabric of the present invention include, for example, a virtual extending in the overlapping direction of the heat-fusible conjugate fiber through the center of the intersecting region of the heat-fusible conjugate fiber. When the line is a center line, a bulging heat fusion part having a convex surface in a direction away from the center line can be mentioned.

  Hereinafter, an embodiment of the swelled heat-sealed part will be described by taking a heat-fusible conjugate fiber that intersects vertically as an example. For convenience of explanation, in this embodiment, the crossing angle of the heat-fusible conjugate fiber is vertical, but the crossing angle of the heat-fusible conjugate fiber is not limited to vertical.

  FIG. 2A is a plan view of the heat-sealable conjugate fibers F3 and F4 that intersect and overlap each other with the heat-sealable conjugate fiber F3 on the upper side and the heat-sealable conjugate fiber F4 on the lower side. It is a top view when it sees. FIG.2 (b) is the II-II sectional view taken on the line of Fig.2 (a). In addition, the direction of the II-II line | wire of Fig.2 (a) corresponds with the direction of the axis line L4 of the heat-fusible conjugate fiber F4.

  As shown in FIG. 2A, the heat-fusible conjugate fiber F3 extends along the axis L3, and the heat-fusible conjugate fiber F4 extends along the axis L4. The fusible conjugate fibers F3 and F4 intersect perpendicularly.

  In FIG. 2A, the axis line L3 and the axis line L4 are represented by straight lines, but are not limited to straight lines, and may be curved lines. However, when a minute portion where the heat-fusible conjugate fibers F3 and F4 intersect is assumed, the axis L3 and the axis L4 can be approximated to a substantially straight line as shown in FIG.

  As shown in FIGS. 2A and 2B, the intersecting region R2 of the heat-fusible conjugate fibers F3 and F4 is a region where the heat-fusible conjugate fibers F3 and F4 overlap in a plan view, and is a cross-sectional view. Is a region that spreads between the heat-fusible conjugate fibers F3 and F4 in the overlapping direction Z2 (vertical direction) of the heat-fusible conjugate fibers F3 and F4.

  As shown in FIG. 2A, the center P2 of the intersecting region R2 coincides with the intersection of the axes L3 and L4 in plan view.

  As shown in FIG. 2B, the heat-fusible conjugate fibers F3 and F4 are heat-sealed by the bulging heat-sealing part B2 in the intersecting region R2. In the present embodiment, the swell-like heat fusion part B2 includes a portion that exists inside the intersecting region R2 and a portion that extends to the outside of the intersecting region R2, and the entirety thereof is inside the intersecting region R2. May be present.

  As shown in FIG. 2 (b), the bulging heat-sealed portion B2 passes through the center P2 of the intersecting region R2 of the heat-fusible conjugate fibers F3 and F4, and the heat-fusible conjugate fibers F3 and F4. When a virtual line extending in the overlapping direction Z2 (vertical direction) is defined as a center line A2, the surface has a convex shape toward the direction away from the center line A2. The center line A2 coincides with a perpendicular drawn from the axis L3 of the heat-fusible conjugate fiber F3 to the axis L4 of the heat-fusible conjugate fiber F4 in the intersecting region R2 of the heat-fusible conjugate fibers F3 and F4. .

  A part of the outer peripheral surface of the bulging heat fusion part B2 may be convex toward the direction away from the center line A2, but substantially the whole is directed toward the direction away from the center line A2. And is preferably convex. A cracked portion may be present on the outer peripheral surface of the bulging heat fusion part B2.

  As shown in FIG. 2B, the heat-fusible conjugate fibers F3 and F4 bite into each other, and the distance (r3) between the heat-fusible conjugate fibers F3 and F4 is the heat-fusible conjugate fiber F3. , F4 is smaller than the sum of the fiber radii (r1 + r2).

The thickness (under 3.0 gf / cm ² load) of the nonwoven fabric of the present invention is 0.5 to 3.0 mm, preferably 0.7 to 3.0 mm, and the specific volume is 6 to 300 cm ³ / g, preferably 12 -200 cm < ³ > / g. Thereby, the nonwoven fabric of this invention has sufficient thickness and specific volume. In addition, when using the nonwoven fabric of the present invention as a top sheet of an absorbent article, the liquid permeability decreases and the stickiness tends to occur when the thickness and specific volume are below the lower limit of the above range, while the upper limit of the above range is set. When it exceeds, the thickness of the whole absorbent article will increase and it will become easy to produce discomfort at the time of installation of an absorbent article.

  The thickness and specific volume of the nonwoven fabric are the ratio of the number of constricted heat fusion portions to the total number of heat fusion portions, the form of the constricted heat fusion portions, and the heat fusion bonded by the constricted heat fusion portions. It changes according to the distance etc. between the functional composite fibers. As will be described later, the nonwoven fabric of the present invention can be produced by bulk-recovering a non-bulk-recovered non-woven fabric containing heat-sealable heat-fusible conjugate fibers. By adjusting, the ratio of the number of constricted heat fusion portions to the total number of heat fusion portions, the form of the constricted heat fusion portions, and the heat-fusible conjugate fiber heat-sealed by the constricted heat fusion portions The distance between them can be adjusted, and therefore the thickness and specific volume of the nonwoven fabric can be adjusted to a desired range.

Although the basic weight of the nonwoven fabric of this invention is not specifically limited, Preferably it is 10-80 g / m < ² >, More preferably, it is 15-60 g / m < ² >.

  The heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention is not particularly limited as long as it can exhibit heat-fusibility. Examples of the heat-fusible conjugate fiber include a first component (hereinafter referred to as “high melting point component”) and a second component having a melting point lower than that of the first component (hereinafter referred to as “low melting point component”). And a second component (low-melting point component) that is continuously present in the length direction on at least a part of the fiber surface. The component that exhibits heat-fusibility is mainly a low melting point component. The heat-fusible conjugate fiber may be a conjugate fiber containing three or more types of components having different melting points or softening points. Examples of the form of the heat-fusible conjugate fiber include a core-sheath type (concentric circle type, eccentric type, etc.), a sea-island type, a split type, a side-by-side type, and the like. May be used. In the case of the core-sheath type composite fiber, the sheath component and the core component can be composed of a low melting point component and a high melting point component, respectively. The heat-fusible conjugate fiber is preferably subjected to a stretching treatment at the raw material stage (before being used for the production of the nonwoven fabric).

  The kind of the high melting point component and the low melting point component is not particularly limited as long as it has fiber forming ability. The high melting point component and the low melting point component are usually synthetic resins. Examples of the high melting point component include polypropylene (PP), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Examples include polyethylene such as high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE), ethylene propylene copolymer, polystyrene, polypropylene (PP), and copolyester. It is done. For example, in the case of a core-sheath type composite fiber, as the sheath component (low melting point component) when the core component (high melting point component) is PP, for example, polyethylene such as HDPE, LDPE, LLDPE, ethylene propylene copolymer, Examples of the sheath component (low melting point component) when the core component (high melting point component) is PET, PBT, etc. include PP and copolyester.

  The heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention preferably contains more low melting point components than high melting point components, and the mass ratio of the low melting point component to the high melting point component (low melting point component / high melting point component). The component is preferably 4/6 to 8/2, more preferably 5/5 to 7/3. Thereby, heat fusion by an air through method occurs reliably, and fluffing on the surface of the air through nonwoven fabric after the bulk recovery treatment can be effectively prevented. The mass ratio of the low melting point component / the high melting point component is, for example, the cross-sectional area of the high melting point component and the low melting point component and the density of the high melting point component and the low melting point component measured by cross-sectional observation of the heat-fusible composite fiber Can be calculated based on this.

  The difference in melting point between the high melting point component and the low melting point component is preferably 20 ° C. or higher, more preferably 25 ° C. or higher. Thereby, the difference of the orientation of each component, crystallinity, etc. becomes large, and the formability of a nonwoven fabric improves. The melting point is measured, for example, as a melting peak temperature when a finely cut fiber sample is thermally analyzed at a heating rate of 10 ° C./min using a differential scanning calorimeter (eg, DSC6200 manufactured by Seiko Instruments Inc.). can do. If the melting point cannot be measured clearly, the softening point may be used instead of the melting point.

  Although the fiber diameter of the heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention is not particularly limited, it is preferably 10 to 30 μm, more preferably 15 to 25 μm, from the viewpoint of reducing the surface roughness. The fiber diameter of the heat-fusible conjugate fiber can be measured, for example, by observing the nonwoven fabric with a microscope such as a scanning electron microscope.

  Although the fineness of the heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention is not particularly limited, for example, when the nonwoven fabric of the present invention is used for a top sheet of an absorbent article, it is preferably 1 to 6 dtex. In addition, when the fineness is less than 1 dtex, the thickness of the nonwoven fabric tends to be thin due to the decrease in the strength of the composite fiber, and the breathability and liquid permeability of the nonwoven fabric tend to be reduced. On the other hand, when the fineness exceeds 6 dtex, The strength of the fiber itself tends to increase, and the tactile feel of the nonwoven fabric tends to decrease.

  The amount of the heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention is preferably 20 to 100% by mass, more preferably 30 to 100% by mass, based on the total fibers constituting the nonwoven fabric.

  The nonwoven fabric of the present invention may contain other fibers (for example, a single fiber) in addition to the heat-fusible conjugate fiber. Examples of other fibers include natural fibers (wool, cotton, etc.), regenerated fibers (rayon, acetate, etc.), inorganic fibers (glass fibers, carbon fibers, etc.), synthetic fibers (polyethylene fibers, polypropylene fibers, polyester fibers, acrylics). Fiber etc.). By incorporating other fibers, the functions of the fibers (for example, hygroscopicity in the case of cotton, breathability in the case of synthetic fibers) can be imparted to the nonwoven fabric. In addition, the nonwoven fabric of the present invention includes hollow fibers, flat fibers such as flat, Y-shaped, and C-shaped fibers; three-dimensional crimped fibers such as latent crimped fibers and actual crimped fibers; physical properties such as water flow, heat, and embossing. Divided fibers and the like that are divided by the mechanical load may be mixed.

  When the nonwoven fabric of the present invention contains fibers other than the heat-fusible conjugate fiber, the content of fibers other than the heat-fusible conjugate fiber is preferably 80% by mass or less, more preferably the entire fibers constituting the nonwoven fabric. Is 70% by mass or less.

  A three-dimensional crimped shape may be imparted to the heat-fusible conjugate fiber contained in the nonwoven fabric of the present invention. Examples of the three-dimensional crimped shape include a zigzag shape, an Ω shape, and a spiral shape. Examples of the method for imparting the three-dimensional crimped shape include mechanical crimping and thermal shrinkage. Mechanical crimping can be controlled by the difference in peripheral speed of the line speed, heat, pressurization, etc. for continuous linear fibers after spinning, and the greater the number of crimps per unit length, the greater the resistance to external pressure. Buckling strength is increased. The number of crimps is usually 5 to 35 pieces / inch, preferably 15 to 30 pieces / inch. In heat shrinkage, three-dimensional crimping is possible using the difference in heat shrinkage caused by the difference in melting point.

  When the nonwoven fabric of the present invention contains latently crimped fibers and / or actual crimped fibers, the fiber orientation is mainly directed in the plane direction, but partially in the thickness direction. Thereby, since the buckling strength of the fiber in the thickness direction of the nonwoven fabric is increased, even if an external pressure is applied to the nonwoven fabric, the bulk of the nonwoven fabric is hardly reduced. Further, when a spiral shape is imparted to the heat-fusible conjugate fiber, the bulk is easily recovered when the external pressure on the nonwoven fabric is released. The latent crimped fiber and / or the actual crimped fiber contained in the nonwoven fabric of the present invention may be a heat-fusible conjugate fiber having a three-dimensional crimped shape, May be another fiber.

  The nonwoven fabric of the present invention may be hydrophilized. Since the nonwoven fabric provided with hydrophilicity is easy to permeate into the absorbent article without contacting the excrement on the surface of the nonwoven fabric when it comes into contact with hydrophilic excrement (urine, sweat, feces, etc.) It can be suitably used as a liquid-permeable top sheet for absorbent articles. Examples of the hydrophilic treatment of the nonwoven fabric include treatment with a hydrophilic agent, kneading of the hydrophilic agent into the constituent fibers of the nonwoven fabric, and application of a surfactant to the nonwoven fabric.

  The fibers constituting the nonwoven fabric of the present invention may contain an inorganic filler such as titanium oxide, barium sulfate, calcium carbonate or the like in order to enhance whitening properties. In the case of the core-sheath type composite fiber, the core component may contain an inorganic filler, or the sheath component may contain an inorganic filler.

  The surface of the nonwoven fabric of the present invention may have an uneven structure. Presence / absence of the concavo-convex structure can be confirmed, for example, in a cross-sectional shape cut in a direction (CD direction) perpendicular to the transport direction (MD direction) during manufacture of the nonwoven fabric. On the surface of the nonwoven fabric of the present invention, for example, a plurality of convex portions whose inside is composed of heat-fusible conjugate fibers relatively oriented in the thickness direction of the nonwoven fabric, and heat-fusible properties oriented in the plane direction of the nonwoven fabric A plurality of recesses made of composite fibers can be formed. In the concavo-convex structure, the thickness of the concave portion is smaller than the thickness of the convex portion. When the surface of the nonwoven fabric of the present invention is unevenly shaped, the contact area with the skin can be reduced, which is suitable as a top sheet for absorbent articles.

  The nonwoven fabric of the present invention can be applied to various fields that take advantage of bulkiness, compression deformability, compression recovery, and the like. The nonwoven fabric of the present invention is, for example, in the field of disposable hygiene articles such as disposable diapers and sanitary napkins, top sheets of absorbent articles, second sheets (sheets disposed between the top sheet and the absorber), back sheets It can be suitably used as a leak-proof sheet. Moreover, the nonwoven fabric of this invention can be used conveniently also with the wiping sheet for people, the sheet | seat for skin care, the wiper for objectives, etc.

  The non-woven fabric of the present invention can be produced by subjecting a non-bulk-recovered non-woven fabric containing a heat-sealable heat-fusible conjugate fiber to a bulk recovery treatment.

  A preferred bulk recovery process is to prepare a heating chamber having an inlet and an outlet, and after entering the heating chamber through the inlet, proceeding through the heating chamber, and then transporting the unwoven fabric before bulk recovery to exit the heating chamber through the outlet. However, the heated fluid is allowed to enter the heating chamber through one of the inlet and the outlet, proceed through the heating chamber while being in contact with the nonwoven fabric before bulk recovery, and then exit the heating chamber through the other of the inlet and the outlet. And a step of supplying at a higher speed than the conveying speed of the nonwoven fabric before bulk recovery.

  The nonwoven fabric before bulk recovery is preferably an air-through nonwoven fabric in which a web containing a heat-fusible conjugate fiber is subjected to an air-through treatment and the heat-fusible conjugate fiber is thermally fused, and is heated in the bulk restoration treatment. The fluid preferably enters the heating chamber via the inlet and exits the heating chamber via the outlet. The nonwoven fabric before bulk recovery is preferably transported without being supported in the heating chamber. It is preferable that the non-woven fabric before bulk recovery is conveyed in the heating chamber so that both sides of the non-woven fabric before bulk recovery continue to face each other. Two or more preferred embodiments may be combined.

Hereinafter, an embodiment of a method for producing a nonwoven fabric of the present invention will be described based on the drawings.
In this embodiment, the bulk recovery apparatus 1 for recovering the bulk of the nonwoven fabric F shown in FIG. 3 is used.

  The non-woven fabric F is a non-woven fabric containing heat-fusible conjugate fibers that are heat-sealed. Examples of the non-woven fabric include an air-through non-woven fabric, a point bond non-woven fabric, and a spun bond non-woven fabric, and an air-through non-woven fabric is preferable.

  The air-through nonwoven fabric is a nonwoven fabric obtained by passing hot air through a web containing a heat-fusible conjugate fiber and thermally fusing the intersection of the heat-fusible conjugate fibers. The web containing the heat-fusible conjugate fiber can be formed by a known web forming method using a card machine or the like. Examples of the web forming method include a method (air array method) in which short fibers are conveyed in an air stream and deposited on a net. In addition, the web formed in this way is a fiber aggregate before making into a nonwoven fabric, and has not been subjected to a treatment applied in the nonwoven fabric production process (for example, heat-sealing treatment in an air-through method, a calendar method, etc.) Is very loosely entangled. The air-through treatment for the web containing the heat-fusible conjugate fiber can be performed by, for example, a hot air spraying device. In the air-through treatment, hot air heated to a predetermined temperature (for example, 120 to 160 ° C.) is blown against the web, and the hot air passes through the web, so that the intersection of the heat-fusible conjugate fibers in the web is heat-sealed. The As a nonwoven fabric manufactured by such an air-through process, for example, a sheath component is a high-density polyethylene and a core component is polyethylene terephthalate, and the fiber length is 20 to 100 mm, preferably 35 to 65 mm. And a nonwoven fabric mainly composed of a core-sheath type composite fiber having a fineness of 1.1 to 8.8 dtex, preferably 2.2 to 5.6 dtex.

  The blowing of hot air is an example of a heat treatment for heat-sealing the intersections of the heat-fusible conjugate fibers in the web. The heat treatment is not particularly limited as long as it can be heated to the melting point or higher of the heat-fusible conjugate fiber (low melting point component). The heat treatment can be performed using a heat medium such as microwaves, steam, infrared rays, etc. in addition to hot air.

  The nonwoven fabric F may have irregularities on its surface. The unevenness can be imparted to the surface of the nonwoven fabric F by, for example, spraying hot air against the web, whereby the inside is composed of heat-fusible conjugate fibers oriented relatively in the thickness direction of the nonwoven fabric F on the surface of the nonwoven fabric F. It is possible to form a plurality of convex portions and a plurality of concave portions made of heat-fusible conjugate fibers oriented in the plane direction of the nonwoven fabric.

  As FIG. 3 shows, the nonwoven fabric F exists in the state wound by the roll R, and the bulkiness of the nonwoven fabric F is reducing resulting from this. Therefore, in order to recover the bulk of the nonwoven fabric F, the bulk recovery device 1 is used.

  The nonwoven fabric F includes a large number of heat-sealing portions that heat-fuse the heat-fusible conjugate fibers that intersect and overlap each other in the intersecting region. A large number of heat-sealing parts included in the nonwoven fabric F are mainly swelled heat-sealing parts shown in FIG. On the other hand, at the time of the bulk recovery process by the bulk recovery device 1, a part or all of the bulged heat fusion part shown in FIG. 2 is changed to the constriction heat fusion part shown in FIG. That is, during the bulk recovery process by the bulk recovery device 1, the swelled heat fusion part is softened or melted, and the heat-fusible conjugate fiber thermally fused by the swelled heat fusion part is slightly separated. Along with this, the swell-like heat-sealed portion slightly expands and changes to a constricted heat-sealed portion. In particular, in the bulk recovery process performed by the bulk recovery device 1, as will be described later, hot air flows in parallel to the nonwoven fabric F before bulk recovery and the hot air speed is higher than the nonwoven fabric speed. Occurs and heat is easily transmitted. Further, since force is not applied to the constituent fibers of the nonwoven fabric F in one direction but force is applied to the constituent fibers along the flow of air, the swell-like heat fusion part slightly expands and the constricted heat fusion occurs. It is easy to change to the wearing part.

  When the heat-sealed portion changes from a bulging shape to a constricted shape, the bonding strength of the heat-fusible conjugate fiber by the heat-welding portion decreases. Therefore, when the heat-sealed portion changes from a bulging shape to a constricted shape, the degree of freedom of the fiber with respect to compressive deformation increases, and the fiber becomes easy to move. For this reason, the nonwoven fabric F subjected to bulk recovery treatment exhibits excellent compressive deformability. Moreover, since heat is easily transmitted to the heat-fusible conjugate fiber during the bulk recovery treatment, the resin constituting the heat-fusible conjugate fiber is oriented by heat, and the crystallinity is enhanced. Therefore, in the nonwoven fabric F subjected to the bulk recovery treatment, the initial strength of the fiber is increased, the fiber is difficult to sag against the initial deformation, and the shape maintaining property is improved. For this reason, the nonwoven fabric F subjected to bulk recovery treatment exhibits excellent compression recovery properties.

The basis weight of the nonwoven fabric F is substantially constant before and after the bulk recovery process. The basis weight of the nonwoven fabric F is, for example, 10 to 80 g / m ² (particularly 15 to 60 g / m ² ). The thickness of the nonwoven fabric F increases by the bulk recovery process. The thickness of the nonwoven fabric F (under 3.0 gf / cm ² load) is, for example, from 0.2 to 0.6 mm (particularly from 0.3 to 0.5 mm) (before bulk recovery treatment), from 0.5 to 3.0 mm. (Especially 0.7 to 3.0 mm). The specific volume of the nonwoven fabric F is increased by the bulk recovery process. The specific volume of the nonwoven fabric F is, for example, increases from 2.5~50cm ³ / g (especially 5~33cm ³ / g) in 6~300cm ³ / g (especially 12~200cm ³ / g).

  As shown in FIG. 3, the bulk recovery device 1 includes a transporter 2 that unwinds and transports the belt-shaped nonwoven fabric F from the roll R. The transporter 2 includes two roller pairs 2a and 2b. Each roller pair 2a, 2b includes rollers that rotate in opposite directions, and when these rollers are rotated, the nonwoven fabric F is conveyed. In the present embodiment, the nonwoven fabric F is transported in a transport direction MD that substantially coincides with the horizontal direction so that one surface and the other surface thereof are generally directed upward and downward.

  As shown in FIG. 3, the bulk recovery device 1 also includes a heater 3 for heating the conveyed nonwoven fabric F with a fluid. The heater 3 includes a fluid source 3a, a supply pipe 3b connected to the outlet of the fluid source 3a, a nozzle 3c connected to the outlet of the supply pipe 3b, a flow meter 3ba arranged in the supply pipe 3b, A regulator 3d disposed in the supply pipe 3b downstream of the flow meter 3ba, an electric heater 3e disposed in the supply pipe 3b downstream of the regulator 3d, and a housing 3f are provided. The nozzle 3c has, for example, an elongated rectangular outlet.

In this embodiment, the fluid is air and the fluid source 3a is a compressor. When the compressor 3a is operated, air flows through the supply pipe 3b. The flow meter 3ba detects the flow rate of air flowing through the supply pipe 3b, and outputs the air flow rate in the form of an amount in a standard state (0 ° C., 1 atm). The air pressure in the supply pipe 3b is reduced from, for example, 0.6 MPaG to 3 MPaG to 0.01 MPaG by the regulator 3d. The air is then heated by the electric heater 3e. The heated air then flows out from the nozzle 3c. The amount of air flowing out from the nozzle 3c is set to 2380 L / min (2.38 m ³ / min, standard state), for example. The air is heated to, for example, 100 to 200 ° C. by the electric heater 3e so that the temperature of the air flowing out from the nozzle 3c becomes, for example, 70 to 160 ° C. Note that the temperature of the air flowing out from the nozzle 3c can be detected by a temperature sensor disposed in the vicinity of the outlet of the nozzle 3c.

  As shown in FIGS. 4 and 5, the housing 3f includes a top wall 3fu and a bottom wall 3fb extending in a horizontal direction at intervals, and a pair of side walls 3fs, which are disposed between the top wall 3fu and the bottom wall 3fb. An internal space 3s having a rectangular cross section is defined by the top wall 3fu, the bottom wall 3fb, and the side walls 3fs, 3fs. The internal space 3s includes a pair of openings 3si and 3so facing each other.

  A heating chamber 3g having inlets 3gi and 3go is defined in the internal space 3s downstream of the outlet of the nozzle 3c. In the present embodiment, the outlet of the nozzle 3c is disposed in the opening 3si of the internal space 3s. Therefore, the heating chamber 3g coincides with the internal space 3s. The inlet 3gi of the heating chamber 3g matches the opening 3si of the internal space 3s, and the outlet 3go of the heating chamber 3g matches the opening 3so of the internal space 3s.

  The nonwoven fabric F enters the heating chamber 3g through the inlet 3gi by the transporter 2, travels through the heating chamber 3g, and is then transported out of the heating chamber 3g through the outlet 3go. In this case, no roller or belt for conveying the nonwoven fabric F is disposed in the heating chamber 3g. In other words, the nonwoven fabric F is conveyed without being supported in the heating chamber 3g. Moreover, the nonwoven fabric F is conveyed in the heating chamber 3g so that both surfaces Fs of the nonwoven fabric F continue to face the top wall 3fu and the bottom wall 3fb, which are partition walls defining the heating chamber 3g, respectively.

  On the other hand, the air that has flowed out of the nozzle 3c enters the heating chamber 3g through the inlet 3gi, travels through the heating chamber 3g while being in contact with the nonwoven fabric F being conveyed, and then exits the heating chamber 3g through the outlet 3go. In this case, in the heating chamber 3g, air is supplied so that the linear velocity of air is higher than the conveyance speed of the nonwoven fabric F.

  In the present embodiment, the top wall 3fu and the bottom wall 3fb are formed of a stainless plate having a thickness of 3 mm, for example. The length L3 in the transport direction MD of the housing 3f or the heating chamber 3g is 1675 mm. The width W3f of the housing 3f is 240 mm, and the width W3g of the heating chamber 3g is 200 mm. The height H3f of the housing 3f is 11 mm, and the height H3g of the heating chamber 3g is 5 mm.

  In the present embodiment, the top wall 3fu and the bottom wall 3fb extend in a horizontal plane. The angle θ (see FIG. 4) formed by the directional line of the nozzle 3c and the horizontal plane H is preferably 0 to 30 degrees, more preferably 0 to 10 degrees, and most preferably 0 degrees.

  As shown in FIG. 3, the bulk recovery device 1 also includes a cooler 4 for cooling the conveyed nonwoven fabric F with a fluid downstream of the heater 3. The cooler 4 includes a fluid source 4a, a supply pipe 4b connected to the outlet of the fluid source 4a, a nozzle 4c connected to the outlet of the supply pipe 4b, a regulator 4d arranged in the supply pipe 4b, and a cooling device. 4e and a housing 4f.

  In this embodiment, the fluid is air and the fluid source 4a is a compressor. When the compressor 4a is activated, air flows through the supply pipe 4b. The air pressure in the supply pipe 4b is reduced by the regulator 4d. The air is then cooled by the cooling device 4e. The cooled air then flows out from the nozzle 4c.

  Like the housing 3f of the heater 3, the housing 4f of the cooler 4 includes a top wall and a bottom wall that are spaced apart from each other, and a pair of side walls disposed between the top wall and the bottom wall. The bottom wall and the side wall define a cooling chamber 4g having a rectangular cross section. The cooling chamber 4g includes an inlet 4gi and an outlet 4go facing each other.

  The nonwoven fabric F carried out from the heater 3 enters the cooling chamber 4g via the inlet 4gi by the carrier 2, and is conveyed so as to exit the cooling chamber 4g via the outlet 4go after traveling through the cooling chamber 4g. . In this case, no roller or belt for conveying the nonwoven fabric F is disposed in the cooling chamber 4g. In other words, the nonwoven fabric F is conveyed without being supported in the cooling chamber 4g. Moreover, the nonwoven fabric F is conveyed in the cooling chamber 4g so that both surfaces Fs of the nonwoven fabric F continue to face the top wall and the bottom wall, which are partition walls defining the cooling chamber 4g, respectively.

  In the present embodiment, the nozzle 4c of the cooler 4 is disposed at the inlet 4gi. Accordingly, the air flowing out from the nozzle 4c enters the cooling chamber 4g through the inlet 4gi, travels through the cooling chamber 4g while being in contact with the nonwoven fabric F being conveyed, and then exits the cooling chamber 4g through the outlet 4go. In this case, in the cooling chamber 4g, air is supplied so that the linear velocity of air is higher than the conveyance speed of the nonwoven fabric F.

  Now, the nonwoven fabric F rewound from the roll R is first conveyed so as to pass through the heating chamber 3g of the heater 3. At the same time, air heated from the nozzle 3c of the heater 3 is supplied into the heating chamber 3g. As a result, the nonwoven fabric F is heated in contact with the heated air, and the bulk of the nonwoven fabric F is increased. That is, the bulk of the nonwoven fabric F is recovered.

  In this case, air mainly travels along the surface Fs of the nonwoven fabric F. As a result, the air flow does not prevent the bulk of the nonwoven fabric F from being restored. That is, the bulk of the nonwoven fabric F is recovered satisfactorily.

  Furthermore, in this embodiment, the linear velocity of air is higher than the conveyance speed of the nonwoven fabric F in the heating chamber 3g. As a result, the air flow adjacent to the surface Fs of the nonwoven fabric F is disturbed. For this reason, various molecules contained in the air collide with the surface Fs of the nonwoven fabric F at random angles. Therefore, the fibers of the nonwoven fabric F are loosened, and the recovery of the bulk is promoted. In addition, the nonwoven fabric F flutters in the heating chamber 3g due to the turbulence of the air flow. As a result, the heated air easily penetrates into the nonwoven fabric F, and the nonwoven fabric F can be efficiently heated. For this reason, the length L3f (FIG. 4) of the heating chamber 3g or the housing 3f can be shortened.

  Further, the housing 3f does not require equipment for supplying air and equipment for sucking air. Therefore, the size of the housing 3f can be further reduced.

  Furthermore, the nonwoven fabric F is conveyed within the heating chamber 3g without being supported by a roll or the like. As a result, the bulk recovery of the nonwoven fabric F is not hindered by the roll or the like.

  The nonwoven fabric F carried out from the heating chamber 3g is then conveyed so as to pass through the cooling chamber 4g of the cooler 4. At the same time, the air cooled from the nozzle 4c of the cooler 4 is supplied into the cooling chamber 4g. As a result, the nonwoven fabric F is cooled in contact with the cooled air.

  In this case, air mainly travels along the surface Fs of the nonwoven fabric F. As a result, the air flow prevents the nonwoven fabric F from being reduced in volume.

  Moreover, the linear velocity of air is higher than the conveyance speed of the nonwoven fabric F in the cooling chamber 4g. As a result, the whole nonwoven fabric F located in the cooling chamber 4g can be cooled. That is, the nonwoven fabric F can be efficiently cooled. For this reason, the size of the cooling chamber 4g or the housing 4f can be reduced.

  Next, the nonwoven fabric F carried out from the cooling chamber 4g is conveyed by the conveyor 2 to, for example, an absorbent article manufacturing apparatus. In the absorbent article manufacturing apparatus, the nonwoven fabric F is used as a top sheet of the absorbent article.

  In this embodiment, since the nonwoven fabric F contains the heat-fusible conjugate fiber, the temperature of the air flowing out from the nozzle 3c of the heater 3 is higher than the melting point of the heat-fusible conjugate fiber (low melting point component). Also, the temperature is preferably 50 ° C. or lower and lower than the melting point. When air temperature is lower than melting | fusing point -50 degreeC, there exists a possibility that the volume of a nonwoven fabric may not fully be recovered. If the air temperature is equal to or higher than the melting point, the fiber is melted.

  Considering efficient heating of the nonwoven fabric F, it is preferable that the cross-sectional area of the heating chamber 3g, that is, the width W3g and the height H3g are small. However, during conveyance, the nonwoven fabric F meanders in the width direction and flutters in the thickness direction. For this reason, if the width W3g or the height H3g is too small, the nonwoven fabric F may collide with the housing 3f. Moreover, when the cross-sectional area of the heating chamber 3g, that is, the air flow path area is excessively small, the pressure loss in the heating chamber 3g increases. Considering these, the width W3g is preferably 5 to 40 mm larger than the width of the nonwoven fabric F, and more preferably 10 to 20 mm larger than the width of the nonwoven fabric F. Further, the height H3g is preferably 2 to 10 mm, and more preferably 3 to 7 mm.

  In the embodiment described so far, the nozzle 3c of the heater 3 is arranged at the inlet 3gi of the heating chamber 3g. In another embodiment, the nozzle 3c is disposed at the outlet 3go of the heating chamber 3g. In this case, after entering the heating chamber 3g through the outlet 3go, proceeding through the heating chamber 3g while being in contact with the conveyed nonwoven fabric F, air is supplied so as to exit the heating chamber 3g through the inlet 3gi. .

  Then, after entering the heating chamber 3g through one of the inlet 3gi and the outlet 3go, proceeding through the heating chamber 3g while being in contact with the nonwoven fabric F, and exiting from the heating chamber 3g through the other of the inlet 3gi and the outlet 3go. Air is supplied.

  However, when the nozzle 3c is disposed at the outlet 3go, the conveyance direction MD of the nonwoven fabric F and the air flow are opposite to each other. For this reason, it is necessary to increase the force in the conveying direction MD acting on the nonwoven fabric F for conveyance, that is, the tension. When the tension is increased, the recovery of the bulk of the nonwoven fabric F may be hindered. The same problem may occur when the nonwoven fabric F is meandered alternately in the conveyance direction MD and in the opposite direction to the conveyance direction MD in the heating chamber 3g.

  On the other hand, in the embodiment shown in FIGS. 3 to 5, the nozzle 3c is disposed at the inlet 3gi, and the nonwoven fabric F is in the heating chamber so that both surfaces Fs of the nonwoven fabric F continue to face the top wall 3fu and the bottom wall 3fb, respectively. It is conveyed in 3g. Therefore, in the heating chamber 3g, the conveyance direction MD of the nonwoven fabric F and the air flow continue to be in the same direction. As a result, it is possible to recover the bulk while maintaining a small tension applied to the nonwoven fabric F for conveyance.

  Moreover, in embodiment described so far, the nozzle 3c is arrange | positioned above the nonwoven fabric F in the inlet_port | entrance 3gi. In another embodiment, the nozzle 3 c is disposed below the nonwoven fabric F. In yet another embodiment, the nozzles 3c are arranged both above and below the nonwoven fabric F.

  6A and 6B show another embodiment of the nozzle 3c. Referring to FIG. 6A, the nozzle 3c includes a main body 3ca having a rectangular parallelepiped shape, for example. The main body 3ca includes an internal space 3cb, an air inlet 3cc and an air outlet 3cd communicating with the internal space 3cb, and an air guide plate 3ce extending adjacent to the air outlet 3cd. The air inlet 3cc is connected to the supply pipe 3b.

  This nozzle 3c is integrally fixed to the housing 3f. That is, as shown in FIG. 6B, the air guide plate 3ce of the nozzle 3c is inserted into the internal space 3s via the inlet 3si of the internal space 3s of the housing 3f, and the main body 3ca is inserted into the top wall 3fu of the housing 3f. Fixed to. As a result, an air passage 5a is formed between the air guide plate 3ce and the top wall 3fu, and a nonwoven fabric passage 5b is formed between the air guide plate 3ce and the bottom wall 3fb. In this case, for example, the height H5a of the air passage 5a and the thickness t3ce of the air guide plate 3ce are each 1 mm, and the height H5b of the nonwoven fabric passage 5b is 3 mm. Note that the width of the nozzle 3c substantially matches the width of the internal space 3s.

  The air passage 5a communicates with the air outlet 3cd of the nozzle 3c on the one hand and communicates with the internal space 3s of the housing 3f on the other hand. In this case, the heating chamber 3g is defined downstream of the outlet of the air passage 5a. Accordingly, the heated air supplied from the supply pipe 3b to the main body 3ca flows into the air passage 5a through the air outlet 3cd, flows through the air passage 5a, and then flows into the heating chamber 3g through the inlet 3gi.

  The nonwoven fabric passage 5b communicates with the outside of the housing 3f on the one hand and communicates with the heating chamber 3g on the other hand. The nonwoven fabric F enters the nonwoven fabric passage 5b from the outside of the housing 3f, travels through the nonwoven fabric passage 5b, and then enters the heating chamber 3g through the inlet 3gi.

  In this case, the flow passage area at the outlet 3go of the heating chamber 3g is larger than the flow passage area of the non-woven fabric passage 5b. Therefore, the flow passage resistance at the outlet 3go is smaller than the flow passage resistance of the non-woven fabric passage 5b. Therefore, the air flowing into the heating chamber 3g through the inlet 3gi is prevented from flowing back through the nonwoven fabric passage 5b, and can be reliably circulated through the heating chamber 3g toward the outlet 3go.

  In the embodiment shown in FIG. 7, the bottom wall 3 fb of the housing 3 f is extended below the main body 3 ca of the nozzle 3 c as compared with the embodiment shown in FIG. 6. As a result, the nonwoven fabric passage 5b is also extended to the lower side of the main body 3ca of the nozzle 3c.

  The arrangement of the nozzle 4c of the cooler 4 is the same as the arrangement of the nozzle 3c of the heater 3.

  Furthermore, in the embodiment described so far, the cooler 4 is provided downstream of the heater 3. In another embodiment, the cooler 4 is omitted. That is, the nonwoven fabric F carried out from the heater 3 is conveyed to the manufacturing apparatus without being cooled by the cooler 4.

  In yet another embodiment, a heater for heating the housing 3f is provided. By this heater, the temperature of the inner surface of the housing 3f that defines the heating chamber 3g is maintained at substantially the same temperature as the temperature of the air flowing out from the nozzle 3c, for example. If it does in this way, the bulk recovery of the nonwoven fabric F can be accelerated | stimulated. As a heater for the housing 3f, a silicon rubber heater manufactured by Three High Co., Ltd. can be used. In yet another embodiment, a heater for heating the nozzle 3c is provided.

  In still another embodiment, a heat insulating material that covers the housing 3f is provided. With this heat insulating material, a temperature drop in the housing 3f or the heating chamber 3g is suppressed. In yet another embodiment, a heat insulating material covering the nozzle 3c is provided.

  The various embodiments described so far can also be combined with each other.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, these Examples and comparative examples do not limit this invention.
The measuring method of the item evaluated in the Example and the comparative example is as follows.
[Basis weight]
The basis weight is measured according to 5.2 of JIS L 1906.

[Bulk]
The bulk (thickness) is measured using a thickness meter (manufactured by Daiei Kagaku Seisaku Seisakusho, THICKNESS GAUGE UF-60) in a state where a load of 3.0 gf / cm ^{2 is} applied to the nonwoven fabric. The bulk (thickness) is measured at 10 locations of the nonwoven fabric, and the average value is defined as the bulk (thickness).

[Compression characteristics]
The compression characteristics are evaluated using an automated compression tester KES-FB3 manufactured by Kato Tech Co., Ltd.
The measurement conditions are as follows.
SENS: 2
Speed: 0.02mm / sec Stroke: 5mm / 10V
Pressurized area: 2 cm ²
Uptake interval: 0.1 seconds Upper limit load: 50 g / cm ²
Repeat count: 1 time

The compression characteristics are evaluated by the compression energy WC (N · m / m ² ) per 1 cm ² of the nonwoven fabric and the compression resilience RC (%). A total of three measurements are taken and the average value of WC and RC is calculated. In addition, WC means that it is easy to compress, so that a value is large, RC means that a recoverability is so high that a value is near 100%.

[Liquid permeability]
The liquid permeability is evaluated using a LISTER strike-through tester manufactured by LENZING. The evaluation procedure is as follows.
(1) A sample cut to a size of 100 × 100 mm is placed on five filter papers (ADVANTEC FILTER PAPER GRADE2) cut to a size of 100 × 100 mm, and an electrically permeable liquid plate is placed thereon.
(2) Set a filter paper, a sample and a current-permeable plate on the strike-through tester body.
(3) Put 5 mL of physiological saline into the strike-through tester body.
(4) 5 mL (room temperature) of physiological saline is dropped from the strike-through tester main body into the opening portion of the conductive liquid-permeable plate.
(5) Record the energization time of the energized permeable plate.
(6) Perform a total of three measurements and calculate the average value of the liquid permeation time.
In addition, when the sample was not set, that is, the liquid permeation time in 5 filter papers was 69.13 seconds.

[Examples 1 and 2 and Comparative Examples 1 to 3]
(1) Bulk recovery treatment in Examples 1 and 2 Non-woven fabrics in the form of rolls were prepared. This non-woven fabric is an air-through non-woven fabric, and the surface subjected to the air-through treatment (the surface to which the hot air is blown) is unevenly shaped. The properties of the nonwoven fabric are shown in Table 1. In Table 1, WF indicates the width of the nonwoven fabric, tm indicates the thickness of the nonwoven fabric before being wound around the roll R, and t0 indicates the thickness of the nonwoven fabric before being unwound from the roll and carried into the bulk recovery device. ing. The thickness of the non-woven fabric was measured using a thickness measuring device FS-60DS manufactured by Daiei Kagaku Seiki Seisakusho. The pressure plate area was 20 cm ² (circular), and the measurement load was 0.3 kPa (3 gf / cm ² ).

The bulk recovery processing of the nonwoven fabric was performed using the bulk recovery device of the embodiment shown in FIGS. As the nozzle 3c, Y747-304SS manufactured by Spraying Systems Co., Ltd. was used. As the flow meter 3ba, PFD-802-40 manufactured by CKD Corporation was used. AR30-03 manufactured by SMC Corporation was used as the regulator 3d. As the electric heater 3e, a micro cable air heater (model: MCA-3P-5000, 200V, 5KW) manufactured by Sakaguchi Electric Heat was used.

  The processing conditions in Examples 1 and 2 are shown in Table 2. In Table 2, THAi is the temperature of the air at the inlet of the heating chamber, qHA is the flow rate of air discharged from the compressor (0 ° C.), SHA (= W3g · H3g) is the air flow path area in the heating chamber, and VHA ( = QHA / SHA) represents the linear velocity of air in the heating chamber, VF represents the conveyance speed of the nonwoven fabric, and τH (= L3g / VF) represents the heating time of the nonwoven fabric, that is, the time during which the nonwoven fabric stayed in the heating chamber. Yes.

(2) Bulk recovery treatment in Comparative Examples 1 to 3 The same nonwoven fabric as in Examples 1 and 2 was prepared. The bulk recovery process of the nonwoven fabric was performed using the bulk recovery apparatus shown in FIG. Referring to FIG. 8, the bulk recovery devices of Comparative Examples 1 to 3 include a breathable belt 22 driven by a pair of rollers 21 and 21, and the nonwoven fabric FF unwound from the roll is placed on the belt 22. It was conveyed in the conveyance direction MD. The bulk recovery device also sucks the air from the hot air supply device 31 that supplies hot air, the suction device 32 that sucks air from the hot air supply device 31, the cold air supply device 41 that supplies cold air, and the cold air supply device 41. And an aspirator 42. The hot air supply device 31 was composed of a fan. The hot air supply device 31 and the suction device 32 are arranged to face each other with a gap S3, and the cold air supply device 41 and the suction device 42 are arranged to face each other with a gap S4. The belt 22 passed through the gaps S3 and S4, and therefore the nonwoven fabric FF was conveyed in the gaps S3 and S4. At the same time, hot air was supplied perpendicularly to the surface of the nonwoven fabric FF from the hot air supply device 31, and this hot air passed through the nonwoven fabric FF and was then sucked into the suction device 32. Similarly, cold air was supplied perpendicularly to the surface of the nonwoven fabric FF from the cold air supply device 41, and this cold air passed through the nonwoven fabric FF and was then sucked into the suction device 42.

  The processing conditions in Comparative Examples 1 to 3 are shown in Table 3. In Table 3, THAi ′ is the temperature of the air flowing out from the hot air supplier 31, qHA ′ is the air flow rate (80 ° C.) discharged from the hot air supplier 31, and Ps ′ is the static pressure (80 C)), L3g ′ and W3g ′ are the length and width of the hot air supply device 31 and the suction device 32 where the air flow is generated, and SHA ′ (= L3g ′ · W3g ′) is the gap The air flow path area in S3, VHA ′ (= qHA ′ / SHA ′) is the linear velocity of air in the gap S3, and SF ′ (= L3g ′ · WF) is the non-woven fabric portion located in the gap S3, ie, air Represents the area of the non-woven fabric portion through which VF passes, VF ′ represents the conveyance speed of the non-woven fabric, and τH ′ represents the heating time, that is, the time during which the non-woven fabric stayed in the gap S3.

(3) Properties of bulky nonwoven fabric subjected to bulk recovery treatment Table 4 shows the properties of bulky nonwoven fabric subjected to bulk recovery treatment under the conditions of Examples 1 and 2 and Comparative Examples 1 to 3. T0 and Tm are the thicknesses of the nonwoven fabric when the pressure is constant during the compression test (T0 is 0.5 gf / cm ² , Tm is 50 gf / cm ² ). The larger the value of T0, the better the soft feeling of the nonwoven fabric. Also, the greater the Tm value, the better the thickness maintenance during compression. For example, when a nonwoven fabric is used as a top sheet of an absorbent article (for example, a diaper), the nonwoven fabric is not easily crushed even if pressure is applied to the absorbent article (for example, pressure when a wearer is sitting).

(4) Observation by electron microscope of the heat-sealed part In the nonwoven fabric before bulk recovery (before carrying in the bulk recovery device) and the bulky nonwoven fabric obtained by bulk recovery treatment under the conditions of Examples 1 and 2 and Comparative Examples 1 to 3 The heat-sealed part of the heat-fusible conjugate fiber was observed with a real surface view microscope VE-7800 manufactured by KEYENCE. At this time, the acceleration voltage was 2 kv, the magnification was 30 to 1500 times, and the stage height was 10 mm. Each bulky nonwoven fabric was cut into a predetermined size with a sharp razor or the like, and fixed to the observation stage with double-sided tape.

  First, when each nonwoven fabric was observed 300 times from the uneven surface, about 5 heat-bonded portions can be observed in the nonwoven fabric before bulk recovery, and about 10 heat-melted portions in the bulky nonwoven fabric after bulk recovery treatment. Since the welded portions were observable, the respective heat-sealed portions were magnified 1500 times, and the form of the heat-fused portions was observed.

  Electron micrographs of the heat-sealed part magnified 1500 times are shown in FIGS. FIGS. 9A to 9C are electron micrographs of the nonwoven fabric before bulk recovery (before carrying in the bulk recovery device), and FIGS. 10A to 10C are bulk recovery treatments under the conditions of Example 1. FIGS. 11 (a) to (c) are electron micrographs of the nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 2, and FIGS. 12 (a) to (c) are FIG. FIG. 13 is an electron micrograph of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 1, and FIGS. 13 (a) to (c) are electron micrographs of the nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 2; 14A to 14C are electron micrographs of a nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 3. FIG.

  As shown in FIG. 9, in the nonwoven fabric before bulk recovery, the heat-fusible conjugate fibers are biting into the heat-fusible part, and the distance between the heat-fusible conjugate fibers is as follows. It was smaller than the sum of the fiber radii. Samples for cross-sectional observation cut in a direction (CD direction) perpendicular to the conveyance direction (MD direction) during the production of the nonwoven fabric are produced, and heat is generated in the vicinity of the uneven surface, the intermediate portion of the uneven surface / flat surface, and the vicinity of the flat surface. As a result of observing the fusion-bonded portion, the heat-fusible conjugate fibers bite into almost any portion.

  As shown in FIGS. 12 to 14, in the nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Examples 1 to 3, similar to the nonwoven fabric before bulk recovery, the heat-fusible conjugate fibers dig into each other. Further, as the hot air temperature increases (80 ° C. in Comparative Example 1, 100 ° C. in Comparative Example 2, 120 ° C. in Comparative Example 3), the surface area of the heat-sealed portion increases in the surface direction of the heat-fusible conjugate fiber. A tendency to do so was observed.

  As shown in FIGS. 10 and 11, in the nonwoven fabric subjected to the bulk recovery treatment under the conditions of Examples 1 and 2, the constricted heat fusion part shown in FIG. 1 was observed. The heat-fusible conjugate fibers were slightly separated from each other in the constricted heat-sealed portion, and the distance between the heat-fusible conjugate fibers was larger than the sum of the fiber radii of each heat-fusible conjugate fiber. . Moreover, the part which the crack has generate | occur | produced was observed. Moreover, it was confirmed that the constriction of the heat-sealed part becomes conspicuous as the temperature increases during the bulk recovery process.

  The difference in the form of the heat fusion part as shown in FIGS. 9 to 14 is considered to be based on the presence / absence of the bulk recovery process and the difference in type.

  That is, in the air-through method employed in Comparative Examples 1 to 3, since heat is not easily transmitted to the mobile conveyor surface on which the nonwoven fabric before bulk recovery is arranged, hot air is raised to a high temperature in order to achieve sufficient bulk recovery. There is a need to. Moreover, although the hot air wind speed may be relatively low, when hot air passes through the conveyor surface on which the nonwoven fabric before bulk recovery is arranged, a force acts to compress the nonwoven fabric before bulk recovery in a direction perpendicular to the conveyor surface. . Therefore, in Comparative Examples 1 to 3, the surface of the heat-fusible conjugate fiber is easily melted by the hot hot air and the melted heat-fusible conjugate fibers are compressed. It is thought that it will be in a state.

  On the other hand, in Examples 1 and 2, hot air flows in parallel to the nonwoven fabric before bulk recovery, and the hot air wind speed is larger than the nonwoven fabric speed, so turbulence occurs in the bulk recovery device and heat is transmitted. It becomes easy. In addition, since force is not applied to the constituent fibers of the nonwoven fabric in one direction and force is applied to the constituent fibers along the air flow, the swell-like heat-sealed part slightly expands and constricted heat-sealing It is easy to change to the part.

(5) Discussion As shown in Table 4, the basis weight of the bulky nonwoven fabric obtained by bulk recovery treatment under the conditions of Examples 1 and 2 is substantially the same as that of the nonwoven fabric before bulk recovery, but the bulk and specific volume are as follows. , WC value and RC value are larger than the nonwoven fabric before bulk recovery. In the case of the same basis weight, the larger the bulk, the higher the porosity (specific volume), the higher the WC value, the higher the compressive deformability, and the closer the RC value is to 100%, the higher the compression recovery. Therefore, the bulky nonwoven fabric obtained by performing the bulk recovery treatment under the conditions of Examples 1 and 2 has a higher porosity (specific volume) than the nonwoven fabric before bulk recovery, and is excellent in compression deformability and compression recovery. ing.

  Moreover, the basis weight of the bulky nonwoven fabric obtained by bulk recovery treatment under the conditions of Examples 1 and 2 is substantially the same as the bulky nonwoven fabric obtained under the conditions of Comparative Examples 1 to 3, but the bulk, specific volume, The WC value and RC value are the same as or higher than the bulky nonwoven fabric obtained under the conditions of Comparative Examples 1 to 3. In particular, when Example 1 and Comparative Example 1 (85 ° C. in Example 1 and 80 ° C. in Comparative Example 1) having the same hot-air temperature are compared, Example 1 has more compressive deformation than Comparative Example 1. The WC value shown and the RC value showing compression recovery are high. In the nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 1, the bulging heat fusion part is changed to a constricted heat fusion part, and the heat fusion part is changed from a bulging shape to a constriction. Further, the bonding strength of the heat-fusible conjugate fiber by the heat-sealing part is lowered. Therefore, it is considered that the nonwoven fabric recovered in bulk under the conditions of Example 1 has a higher degree of freedom of fiber with respect to compression deformation and the fibers can move more easily than the nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 1. . For this reason, it is considered that the nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 1 has a higher WC value indicating compressive deformation than the nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 1.

  In addition, in the nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 1, heat is easily transferred to the heat-fusible conjugate fiber during the bulk restoration treatment, so that the resin constituting the heat-fusible conjugate fiber is oriented by heat and crystallized. It is thought that the sex is improved. Therefore, the nonwoven fabric recovered in bulk under the conditions of Example 1 has an increased initial strength of the fiber and the fibers are less likely to sag against initial deformation than the nonwoven fabric subjected to bulk recovery under the conditions of Comparative Example 1. It is considered that shape maintainability is improved. For this reason, it is considered that the nonwoven fabric subjected to bulk recovery treatment under the conditions of Example 1 has a higher RC value indicating compression recovery than the nonwoven fabric subjected to bulk recovery treatment under the conditions of Comparative Example 1.

F1-F4 Heat-sealable composite fiber R1, R2 Cross-region of heat-sealable composite fiber B1 Neck-like heat-seal part B2 Swell-like heat-seal part P1, P2 Center of cross-region of heat-sealable composite fiber Z1, Z1 Overlapping direction of heat-fusible conjugate fiber A1, A2 Center line (virtual line extending in the overlapping direction of heat-fusible conjugate fiber through the center of the intersecting region of heat-fusible conjugate fiber)
r1, r2 Fiber radius of heat fusible conjugate fiber r3 Distance between heat fusible conjugate fibers

Claims (9)

A non-woven fabric having a heat-fusible conjugate fiber that intersects and overlaps with each other, and a constricted heat-fusible portion that heat-fuses the heat-fusible conjugate fiber in an intersecting region of the heat-fusible conjugate fiber,
The constricted heat-sealed part has a concave surface toward the center line when a virtual line extending in the overlapping direction of the heat-fusible conjugate fiber through the center of the intersecting region is used as a center line. ,
The distance between the heat-fusible conjugate fibers heat-sealed by the constricted heat-sealing part is larger than the sum of the fiber radii of each heat-fusible conjugate fiber,
The thickness under a load of 3.0 gf / cm ² is 0.5 to 3.0 mm,
The said nonwoven fabric whose specific volume is 6-300 cm < ³ > / g. A number of heat-fusible portions that heat-fuse the heat-fusible conjugate fibers that intersect and overlap each other in the intersecting region of the heat-fusible conjugate fibers;
The nonwoven fabric according to claim 2, wherein a ratio of the number of the constricted heat fusion portions in the total number of the heat fusion portions included in a certain region of the nonwoven fabric is 1/10 to 9/10.   The nonwoven fabric according to claim 1 or 2, wherein the heat-fusible conjugate fiber has a fiber diameter of 10 to 30 µm.   The heat-fusible conjugate fiber includes a first component and a second component having a melting point lower than that of the first component, and the mass ratio of the second component to the first component (second The non-woven fabric according to any one of claims 1 to 3, wherein (component / first component) is 4/6 to 8/2. The nonwoven fabric according to any one of claims 1 to 4, which is obtained by subjecting a nonwoven fabric before bulk recovery containing a heat-fusible conjugate fiber that has been heat-sealed to a bulk recovery treatment.
The bulk recovery process is
Providing a heating chamber having an inlet and an outlet;
After entering the heating chamber through the inlet and proceeding through the heating chamber, the nonwoven fabric before bulk recovery is conveyed so as to exit the heating chamber through the outlet, while passing through the one of the inlet and the outlet. After entering the heating chamber and proceeding through the heating chamber while in contact with the nonwoven fabric before bulk recovery, the heated fluid is allowed to exit the heating chamber through the other of the inlet and the outlet before the bulk recovery. Supplying at a speed higher than the conveying speed of the nonwoven fabric of
The said nonwoven fabric containing.   The nonwoven fabric according to claim 5, wherein the nonwoven fabric before bulk recovery is an air-through nonwoven fabric in which a web containing a heat-fusible conjugate fiber is subjected to an air-through treatment and the heat-fusible conjugate fiber is thermally fused.   The nonwoven fabric according to claim 5 or 6, wherein the heated fluid enters the heating chamber through the inlet and exits the heating chamber through the outlet.   The nonwoven fabric according to any one of claims 5 to 7, wherein the nonwoven fabric before bulk recovery is conveyed without being supported in the heating chamber.   The heating chamber is defined by two partition walls that are spaced from each other from the inlet to the outlet, and both sides of the non-woven fabric before the bulk recovery continue to face each other before the bulk recovery. The nonwoven fabric according to any one of claims 5 to 8, wherein the nonwoven fabric is conveyed in the heating chamber.