JP7481817B2 - Stretch sheet for absorbent article, absorbent article having same, and method for manufacturing stretch sheet for absorbent article - Google Patents

Description

The present invention relates to a stretch sheet for absorbent articles, an absorbent article having the same, and a method for manufacturing the stretch sheet for absorbent articles.

In order to make absorbent articles such as diapers fit the body, stretchable sheet members made by bonding an elastic member such as rubber thread between two sheets are used as components of absorbent articles. For example, Patent Document 1 describes an elastic laminate having an elastic member with a first surface and a second surface, a first nonwoven fabric layer bonded to the elastic member, and a second nonwoven fabric layer disposed on the elastic member side of the laminate, the laminate having been subjected to a mechanical stretching operation.

The applicant has also previously proposed a stretch sheet in which multiple elastic filaments made of a specific resin composition are arranged so that they extend in one direction without crossing each other and are bonded to at least one side of a stretchable nonwoven fabric (Patent Document 2).

JP 2002-540977 A JP 2009-030182 A

The sheets described in Patent Documents 1 and 2 are stretchable along the extension direction of the elastic member or elastic filament. However, as a result of the inventor's investigation, it was found that there is room for improvement in the stretch characteristics of the sheets described in these patent documents.

The object of the present invention is therefore to provide a stretch sheet for absorbent articles having excellent stretch properties, an absorbent article having the same, and a method for producing the stretch sheet for absorbent articles.

The present invention relates to a nonwoven fabric having extensibility, and a plurality of elastic filaments in an unstretched state, which are arranged on one surface of the nonwoven fabric so as to extend in one direction without crossing each other, are bonded to the nonwoven fabric by fusion bonding;
The present invention provides a stretch sheet for absorbent articles, in which the elastic filaments are exposed on the one surface side.

The present invention also provides an absorbent article that has the stretch sheet for absorbent articles as a component.

The present invention also provides a method for producing a stretch sheet for absorbent articles, which includes a step of contacting a plurality of elastic filaments in a molten or softened state spun from a plurality of spinning nozzles with one side of an original sheet before the elastic filaments solidify to obtain a composite sheet in which the elastic filaments are fused to the original sheet, and imparting stretchability to the composite sheet.

According to the present invention, it is possible to provide a stretch sheet for absorbent articles having excellent stretch characteristics, and an absorbent article having the same. Furthermore, according to the manufacturing method of the stretch sheet for absorbent articles of the present invention, the stretch sheet for absorbent articles can be efficiently manufactured.

FIG. 1 is a perspective view showing one embodiment of a stretch sheet for absorbent articles according to the present invention. FIG. 2 is a cross-sectional view of the sheet shown in FIG. 1 taken along line II-II. FIG. 3 is a view corresponding to FIG. 2 and showing another embodiment of the stretch sheet for absorbent articles of the present invention. FIG. 4 is an enlarged cross-sectional view showing a schematic diagram of the necked filament having one neck shown in FIG. FIG. 5 is a diagram showing still another embodiment of the stretch sheet for absorbent articles of the present invention, and is a cross-sectional view taken along the extending direction of the elastic members. FIG. 6 is a diagram showing yet another embodiment of the stretch sheet for absorbent articles of the present invention, and is a cross-sectional view taken along the extension direction of the elastic filaments. FIG. 7 is a perspective view showing a fusion step in the manufacturing method of the stretch sheet for absorbent articles shown in FIG. FIG. 8 is a perspective view showing a schematic view of the lower end surface (nozzle installation surface) of the spinning head in the spinning apparatus shown in FIG. 7, with the lower end surface (nozzle installation surface) being drawn on the upper side. FIG. 9 is a plan view showing the arrangement of the spinning nozzles shown in FIG. 10(a) and (b) are diagrams showing a pair of rolls in a fusion step, and are cross-sectional views taken along the radial direction of the rolls. FIG. 11 is a diagram showing the winding angle of the nonwoven fabric around the first roll in the fusion step, and is a cross-sectional view taken along the radial direction of the first roll. 12(a) and (b) are diagrams showing one embodiment of a roll of composite sheets obtained in the fusion step, and are cross-sectional views of adjacent composite sheets in the roll. FIG. 13 is a perspective view showing a stretchability imparting step in the method for producing the stretch sheet for absorbent articles shown in FIG.

The stretch sheet of the present invention will be described below based on a preferred embodiment with reference to the drawings. Figures 1 to 3 show a stretch sheet 1a for absorbent articles according to a preferred embodiment of the present invention. Hereinafter, the stretch sheet for absorbent articles will also be referred to simply as a stretch sheet.

As shown in Figures 1 and 2, the stretch sheet 1a comprises a single layer of nonwoven fabric 2 and a number of elastic filaments 4 bonded to one side of the nonwoven fabric 2. In the stretch sheet 1a, the elastic filaments 4 are arranged so as to extend in one direction without crossing each other. In this embodiment, the elastic filaments 4 are continuous over the entire length of the stretch sheet 1a and extend in a straight line. The elastic filaments 4 may extend in one direction in a meandering manner, as long as they do not cross each other.

The stretch sheet 1a of this embodiment has a longitudinal direction X and a width direction Y perpendicular to the longitudinal direction X. The longitudinal direction X coincides with the extension direction of the elastic filaments 4.

Each of the multiple elastic filaments 4 is joined to the nonwoven fabric 2 by fusion. That is, the elastic filaments 4 and the nonwoven fabric 2 are not joined via other components such as an adhesive, but are joined by melting at least one of the resin constituting the elastic filaments 4 and the resin constituting the nonwoven fabric 2. From the viewpoint of the joining strength between the elastic filaments 4 and the nonwoven fabric 2, it is preferable that the elastic filaments 4 are joined to the nonwoven fabric 2 by continuous fusion over their entire length.
The elastic filaments 4 are bonded to the nonwoven fabric 2 in an unstretched state. The "unstretched state" means a state in which the elastic filaments 4 do not shrink any further when an external force is removed.

In this embodiment, the nonwoven fabric 2 has a low basis weight portion 21 and a high basis weight portion 23 in which the nonwoven fabric 2 is made of more material than the low basis weight portion 21. The low basis weight portion 21 and the high basis weight portion 22 extend along a direction (width direction Y) perpendicular to the extension direction of the elastic filament 4, and are alternately arranged along the extension direction (longitudinal direction X) of the elastic filament 4. The low basis weight portion 21 and the high basis weight portion 22 are formed in the nonwoven fabric 2 by an elasticity imparting process described below. The elasticity imparting process gives the nonwoven fabric 2 extensibility that allows it to stretch along the extension direction (longitudinal direction X) of the elastic filament 4. "Having extensibility" includes (a) the case where the constituent fibers of the nonwoven fabric 2 themselves are stretched, and (b) the case where the constituent fibers themselves are not stretched, but the fibers bonded at the intersections are separated, the three-dimensional structure formed by multiple fibers is structurally changed due to bonding between fibers, the constituent fibers are torn, or the slack of the fibers is stretched, so that the nonwoven fabric as a whole is stretched. The nonwoven fabric 2 in this embodiment has the configuration of (b) above. However, it is not prevented that the nonwoven fabric 2 also has the configuration of (a) above. "Having extensibility" means that the elongation rate (change in length) measured by the following measurement method, for example, is 30% or more. From the viewpoint of further improving the stretch properties of the stretch sheet described later, it is preferable that the elongation rate of the nonwoven fabric 2 is 100% or more and 300% or less.

[Method of measuring elongation rate]
From the stretch sheet 1a with two marks 1 cm apart in the longitudinal direction and extending in the width direction, the elastic filaments 4 are removed, and the nonwoven fabric 2 is cut out to include the two marks and have a longitudinal dimension of 2 cm x width of 1 cm, which is used as a test piece. The elastic filaments 4 can be removed by dissolving only the elastic filaments 4 using an organic solvent in which the nonwoven fabric 2 is insoluble and only the elastic filaments 4 are soluble, and then the nonwoven fabric 2 is naturally dried. For example, when the elastic filaments 4 are made of a styrene-based block copolymer of a thermoplastic elastomer and the nonwoven fabric 2 is made of polypropylene, toluene can be used as the organic solvent. Next, the longitudinal direction of the test piece is aligned with the tensile direction, and the two marks on the test piece are attached to the chucks of a tensile tester (Tensilon tensile tester RTM100 manufactured by Orientec Co., Ltd.). At this time, the distance between the chucks is 1 cm. Next, the test piece is pulled to a load of 50 g at a tensile speed of 100 mm/min, and the length of the test piece is measured. Then, the elongation rate is calculated by the following formula.
Elongation rate (%) = [length of test piece after pulling (mm) - length of test piece before pulling (mm)] / length of test piece before pulling (mm) x 100

When measuring a stretch sheet incorporated in an absorbent article such as a commercially available diaper, the adhesive used to bond the stretch sheet to other components in the absorbent article is dissolved in an organic solvent, and the stretch sheet is removed. The organic solvent used is one that does not dissolve the elastic filaments. The removed stretch sheet is dried to remove the organic solvent, and then subjected to the measurement method described above or other measurement methods described in this specification.

The stretch sheet 1a stretches along the direction in which the elastic filaments 4 extend. The stretchability of the stretch sheet 1a is manifested by the elasticity of the elastic filaments 4. "Elastic" means the property of being able to be stretched and contracting when the stretching force is released. When the stretch sheet 1a is stretched along the direction in which the elastic filaments 4 extend, the elastic filaments 4 and the nonwoven fabric 2 extend. When the stretch sheet 1a is released from the stretching, the elastic filaments 4 contract, and the nonwoven fabric 2 returns to its pre-stretch state. In the stretch sheet 1a, the elastic filaments 4 do not cross each other, so when the stretch sheet 1a is stretched along the direction in which the elastic filaments 4 extend, the stretch sheet 1a can be stretched with almost no shrinkage in the direction perpendicular to the stretching direction, i.e., with almost no width shrinkage.

In the stretch sheet 1a, as shown in FIG. 1, the elastic filament 4 is exposed on one side of the nonwoven fabric 2. In contrast, in conventional stretch sheets, such as the stretch sheet described in Patent Document 2, an elastic filament is arranged between two nonwoven fabrics, and the stretch of the elastic filament is restrained by the two nonwoven fabrics. The stretch sheet of this embodiment, which is made of one nonwoven fabric and an elastic filament arranged on one side of the nonwoven fabric, is less restrained by the nonwoven fabric in stretching than conventional stretch sheets, so the original stretch characteristics of the elastic filament 4 are less likely to be impaired and excellent stretch characteristics are exhibited. In other words, since the elastic filament 4 has a portion that is not joined to other components such as the nonwoven fabric 2, a portion that does not restrain the movement of the elastic filament 4 due to the extension and contraction is secured, making it easier to express the original stretch characteristics. Furthermore, the stretch sheet 1a can be stretched to the stretchable length of the nonwoven fabric 2 or to the maximum elongation of the elastic filament 4. Since the stretch sheet 1a of this embodiment has such excellent stretch characteristics, it can be suitably used as a component of an absorbent article. For example, the stretch sheet 1a can be used as an exterior body that forms the outer surface of a diaper. When such a diaper is worn, the elastic filaments 4 contract well, so that the diaper fits well to the wearer's body. It is also preferable that the stretch sheet 1a used as the exterior body is incorporated into the diaper so that its longitudinal direction X is aligned with the waist circumference direction of the diaper. When such a diaper is put on by a wearer, the exterior body stretches well in the waist circumference direction, so that it can be easily unfolded with little force, which makes it easy to put on.

In order to ensure that the stretch sheet 1a exhibits sufficient stretch characteristics when incorporated into an absorbent article, the ratio of the 50% return load G2 to the 50% forward load G1 (G2/G1) is preferably 45% or more, more preferably 50% or more, and preferably 100% or less. The 50% forward load G1 is the load when the stretch sheet 1a is stretched to 1.5 times (50%) its original length along the extension direction of the elastic filaments 4. The 50% return load G2 is the load when the stretch sheet 1a is stretched to 2.0 times (100%) its original length along the extension direction of the elastic filaments 4 and then returned to 1.5 times (50%) its original length from that state. The method for measuring these loads will be described later.

From the same viewpoint as above, the 50% return load G2 of the stretch sheet 1a is preferably 30 cN/50 mm or more, more preferably 50 cN/50 mm or more, and is preferably 150 cN/50 mm or less, more preferably 135 cN/50 mm or less.
From the same viewpoint as above, the 50% going load G1 of the stretch sheet 1a is preferably 300cN/50mm or less, more preferably 150cN/50mm or less, and even more preferably 70cN/50mm or less. The 50% going load G1 can be used as an index of the ease of stretching the stretch sheet. The smaller the 50% going load G1, the easier the stretch sheet is to stretch, so the lower limit of the 50% going load G1 is not particularly limited. In order to develop the stretch characteristics, the 50% return load G2 does not exceed the 50% going load G1, so the lower limit of the 50% going load G1 is equal to or greater than the 50% return load G2.

[Method of measuring 50% forward load G1 and 50% return load G2]
A 100% extension cycle test of the stretch sheet is performed using a tensile tester (AG-IS manufactured by Shimadzu Corporation). Specifically, first, a sample of the stretch sheet to be used for the 100% extension cycle test (20 cm long x 5 cm wide) is prepared, and the extension direction of the elastic filament is aligned with the tensile direction, and the sample is attached to the tensile tester. The chuck distance at this time is 150 mm. After the sample is extended by 150 mm at a speed of 300 mm/min (the total distance between the chucks is 300 mm), it is immediately returned to its initial length at a speed of 300 mm/min. In such a 100% extension cycle test, the state in which the sample is extended to twice its initial length is defined as 100% elongation. In the process of extending to this 100% elongation, the tensile force at the point when the elongation reaches 50%, i.e., when the sample reaches 1.5 times its initial length, is defined as the "50% load G1". In addition, the tensile force at the point where the elongation reaches 50% in the process of returning to the initial length after elongation to 100% is defined as the "50% return load G2". If a sample cannot be taken in the above size, a sample is prepared with a longitudinal dimension of 5 cm x width of 2 cm, and measurements are performed under the same conditions as above, except that the chuck distance is 30 mm. The value obtained by converting the measured value to a 5 cm width is defined as the "50% forward load G1" or "50% forward load G1".

From the viewpoint of making the stretch sheet easier to stretch, the 200% load G3 of the stretch sheet 1a is 0 cN/50 mm or more, and preferably 500 cN/50 mm or less, more preferably 300 cN/50 mm or less. The 200% load G3 is the tensile force measured when the sample is stretched to 3.0 times its initial length, and can be measured in the same manner as the measurement method for the 50% load G1 described above, except for the stretched length. The stretch ratio at the 200% load G3, i.e., the stretch ratio of 3.0 times, corresponds to the stretch ratio of the outer body that is expanded when the diaper is put on a wearer. In other words, the lower the 200% load G3, the easier it is to stretch the stretch sheet, so the lower limit is not particularly limited.

In order to ensure good stretch properties, the residual strain (%) of the stretch sheet 1a is 0% or more, and preferably 20% or less, and more preferably 15% or less. The residual strain (%) is the ratio (%) of the sample length at the point when the tensile force becomes 0 to the initial length in the process of returning the sample to its initial length (elongation degree 0%) after it has been stretched to twice its initial length. The residual strain (%) can be measured in the same manner as the above-mentioned measurement method for the 50% return load G2, except that the sample is returned to its initial length until the tensile force becomes 0. The lower the residual strain (%), the better the stretch properties, so there is no particular lower limit.

From the viewpoint of further improving the above-mentioned stretch properties, the basis weight of the stretch sheet 1a is preferably within the following range.
The stretch sheet 1a has an overall basis weight of preferably 10 g/ ^m2 or more, more preferably 20 g/ ^m2 or more, and preferably 70 g/ ^m2 or less, more preferably 50 g/ ^m2 or less.
The nonwoven fabric 2 constituting the stretch sheet 1a preferably has a basis weight of 5 g/ ^m2 or more, more preferably 10 g/ ^m2 or more, and preferably 50 g/ ^m2 or less, more preferably 30 g/ ^m2 or less.
The basis weight of the low basis weight portion 21 of the nonwoven fabric 2 is preferably 3 g/ ^m2 or more, more preferably 7 g/ ^m2 or more, and is preferably 20 g/ ^m2 or less, more preferably 15 g/ ^m2 or less.
The basis weight of the high basis weight portion 23 of the nonwoven fabric 2 is preferably 5 g/ ^m2 or more, more preferably 10 g/ ^m2 or more, and is preferably 50 g/ ^m2 or less, more preferably 30 g/ ^m2 or less.

From the viewpoint of realizing a good feel on the skin, the thickness T1 (see FIG. 2) of the stretch sheet 1a is preferably 0.2 mm or more, more preferably 0.25 mm or more, even more preferably 0.3 mm or more, and is preferably 0.5 mm or less, more preferably 0.4 mm or less. The thickness of the stretch sheet 1a is measured by sandwiching the sheet to be measured between flat plates at a load of 0.5 cN/ ^cm2 and measuring the distance between the flat plates. The measurement is performed at any three points of the stretch sheet, and the average of these is taken as the thickness of the stretch sheet.

From the same viewpoint as above, the thickness of the nonwoven fabric 2 is preferably 0.05 mm or more, more preferably 0.1 mm or more, even more preferably 0.15 mm or more, and is preferably 5 mm or less, more preferably 1 mm or less, even more preferably 0.5 mm or less. The thickness of the nonwoven fabric 2 is measured by the following method. A razor is applied to the stretch sheet to be measured, and the stretch sheet is cut by hitting the upper part of the razor with a hammer or the like. The cut stretch sheet is sandwiched between flat plates at a load of 0.5 cN/ ^cm2 , and the cross section of the stretch sheet is observed under a microscope at a magnification of 50 to 200 times. The thickness of the nonwoven fabric is then measured in the observation field. Measurements are performed at any three points on the cross section, and the average of these measurements is taken as the thickness of the nonwoven fabric.

As described above, the nonwoven fabric 2 has the low basis weight portion 21 and the high basis weight portion 23, and is thereby capable of stretching in the longitudinal direction X. From the viewpoint of further improving the stretchability of the nonwoven fabric 2, the length L11 (see FIG. 1 ) in the longitudinal direction X of the low basis weight portion 21 is preferably 50% or more, more preferably 100% or more, and is preferably 300% or less, more preferably 200% or less, of the length L13 (see FIG. 1 ) of the high basis weight portion 23 in the same direction X.
From the same viewpoint as above, the length L11 (see FIG. 1) of the low basis weight portion 21 in the longitudinal direction X is preferably 0.2 mm or more, more preferably 0.5 mm or more, and is preferably 1.5 mm or less, more preferably 1 mm or less.
From the same viewpoint as above, the length L13 (see FIG. 1) of the high basis weight portion 23 in the longitudinal direction X is preferably 0.1 mm or more, more preferably 0.3 mm or more, and is preferably 1 mm or less, more preferably 0.7 mm or less.

From the viewpoint of achieving a good feel on the skin, the end-to-end distance L14 (see FIG. 2) between adjacent elastic filaments 4 in the width direction Y is preferably 0.4 mm or more, more preferably 0.6 mm or more, and also preferably 2 mm or less, more preferably 1 mm or less, and even more preferably 1 mm or less. The end-to-end distance L14 may be constant between all elastic filaments, or may be different between one elastic filament and another elastic filament. When the end-to-end distance L14 is not constant, it is preferable that the average end-to-end distance between the elastic filaments is within the above-mentioned preferred range, and it is more preferable that the end-to-end distance between all elastic filaments is within the above-mentioned preferred range.

The distance L14 between the ends of adjacent elastic filaments 4 is measured by magnifying a cut surface of a sample of stretch sheet 1a cut in the width direction Y with a microscope. Measurements are taken at 100 random locations, and the average value is taken as the average end-to-end distance. In addition, multiple cut surfaces at different positions in the longitudinal direction X are cut out, and the distance between the ends of adjacent elastic filaments 4 on the multiple cut surfaces is measured.

In the cross section perpendicular to the extension direction (hereinafter also referred to as the width direction cross section), the elastic filament 4 includes a constricted filament 41 having a constriction and a single filament 4 having no constriction. The elastic filament 4 in the stretch sheet 1a may be composed of only a single filament 4 as shown in FIG. 2, may be composed of both a constricted filament 41 and a single filament 4 as shown in FIG. 3, or may be composed of only a constricted filament 41. The constricted filament 41 is a filament having one or more constrictions 42 in the width direction cross section. The constrictions 42 in the constricted filament 41 are a pair of portions recessed from the circumferential surface of the filament toward the inside of the width direction cross section as shown in FIG. 4. The constricted filament 41 shown in FIG. 3 has one constriction 42. The constricted filament may have two or more constrictions 42.

The monofilament 4 is obtained by stretching the molten resin discharged from the spinning nozzle on the spinning line. The diameter D of the monofilament 4 is not particularly limited. From the viewpoint of the balance between the texture of the stretch sheet 1a and the productivity of the elastic filament 4, the diameter of the monofilament 4 is preferably 40 μm or more, more preferably 80 μm or more, and also preferably 200 μm or less, more preferably 180 μm or less. The diameter of the monofilament 4 is measured by magnifying the cut surface of a sample of the stretch sheet 1a cut in the width direction Y with a microscope. The measurement is performed on the cut surface at any 20 points, and the average of these measured values is the diameter of the monofilament 4.

The neck filament 41 is obtained, for example, by bonding two or more filaments discharged from two or more adjacent spinning nozzles together during drawing. Hereinafter, the filaments that constitute the neck filament 41 are also referred to as constituent filaments. The neck filament 41 has a cross-sectional shape in the width direction in which multiple circles are connected in the width direction Y with some overlapping, as shown in FIG. 4. For example, the cross-sectional shape of a neck filament 41 having one neck 42 has a cross-sectional shape in the width direction in which two circles c1 and c2 that form the outline of the constituent filament are connected in the width direction Y with some overlapping, as shown in FIG. 4. In FIG. 4, the part where the two circles partially overlap is shown by a dashed arc at the connection part between the adjacent circles. In a stretch sheet 1a having such narrow filaments 41, the length of the nonwoven fabric 2 between adjacent elastic filaments 4 that are not fused to the elastic filaments 4 is longer than in a stretch sheet having single filaments 4 corresponding to the number of filaments that make up the narrow filaments, so the thickness of the nonwoven fabric 2 is easily increased, and the feel of the stretch sheet 1a can be further improved.

From the viewpoint of further improving the feel of the stretch sheet 1a, it is preferable that the center-to-center distance P1 between adjacent circles in the widthwise cross-section of the necked filament is smaller than the sum of the radius of one circle and the radius of the other circle, and is longer than the shorter of the radius of the one circle and the radius of the other circle. For example, in a necked filament 41 having one neck 42, as shown in FIG. 4, it is preferable that the center-to-center distance P1 between adjacent circles c1 and c2 in the widthwise cross-section is smaller than the sum of the radius r1 of one circle c1 and the radius r2 of the other circle c2 (r1+r2), and is longer than the shorter of the radius r1 of one circle c1 and the radius r2 of the other circle c2 (for example, the radius r1 of one circle c1).

From the same viewpoint as above, in the cross section of a necked filament having one or more necks 42, the maximum length in the width direction Y of the necked filament is preferably 100 μm or more, more preferably 200 μm or more, and also preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and even more preferably 270 μm or less. The maximum length in the width direction Y of the necked filament is the length at which the width direction length is maximum in the cross section of the necked filament, and is measured by the following method. A sample of the stretch sheet is cut in the width direction and the cut surface is enlarged and measured with a microscope. Measurements are performed at 20 arbitrary locations at different positions in the longitudinal direction for one necked filament, and the average value is the maximum width direction length of the necked filament.

From the same viewpoint as above, it is preferable that the dimensions of the necked filament 41 having one neck 42 in the cross section in the width direction be within the following range (see FIG. 4).
The ratio of the diameter L2 of the constituent filament to the maximum length L1 in the width direction Y of the narrowed filament 41 [(L2/L1) x 100] is preferably 10% or more, more preferably 30% or more, and is preferably 60% or less, more preferably 50% or less.
The ratio of the minimum length L3 in the thickness direction Z at the constriction 42 to the diameter L2 of the constituent filaments of the constricted filament 41 [(L3/L2) x 100] is preferably 5% or more, more preferably 10% or more, and is preferably 50% or less, more preferably 30% or less.
The diameter L2 of the constituent filaments constituting the neck filament 41 is preferably 80 μm or more, more preferably 100 μm or more, and is preferably 200 μm or less, more preferably 180 μm or less.
The minimum length L3 in the thickness direction Z of the neck 42 of the neck filament 41 is preferably 5 μm or more, more preferably 10 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less.

From the viewpoint of further improving the feel of the stretch sheet 1a, it is preferable that the narrow filament 41 has one narrowing 42 in the cross section in the width direction. From the same viewpoint as above, in the stretch sheet 1a, the ratio (%) of the number of narrow filaments 41 having one narrowing 42 to the number of elastic filaments 4 is preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, and also preferably 100% or less, more preferably 50% or less. The ratio is obtained by cutting the stretch sheet at any 20 points along the width direction Y, enlarging the cut surface with a microscope, and counting the number of elastic filaments and the number of narrow filaments having one narrowing 42. The number of elastic filaments 4 is the sum of the single filaments 4 and the narrowing filaments 41. The constricted filament 41 is formed by bonding together filaments that were multiple in length immediately after spinning, but in terms of the "number of elastic filaments," the filament that was incorporated into the stretch sheet 1a in the state immediately after spinning, the filament with one constriction, and the filament with two constrictions are all counted as "one."

When the stretch sheet 1a includes, as the elastic filaments 4, constricted filaments 42 having multiple constrictions and constricted filaments 41 having one constriction 42, from the same viewpoint as above, the ratio of the number of filaments 41 having one constriction to the total number of constricted filaments 41 is preferably 50% or more, more preferably 60% or more, even more preferably 90% or more, and preferably 100% or less.

The material for forming the stretch sheet 1a will now be described. As the nonwoven fabric 2, for example, an air-through nonwoven fabric, a heat-rolled nonwoven fabric, a spunlace nonwoven fabric, a spunbonded nonwoven fabric, a meltblown nonwoven fabric, or the like can be used. These nonwoven fabrics can be continuous filament or staple fiber nonwoven fabrics.

The constituent fibers of the nonwoven fabric 2 can be, for example, inelastic fibers made of a substantially inelastic resin. In this case, the nonwoven fabric 2 can be a stretchable fiber layer mainly made of the inelastic fibers. Examples of such inelastic fibers include fibers made of polyesters such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and polyamides. The constituent fibers of the nonwoven fabric 2 can be short or long fibers, and can be hydrophilic or water-repellent. In addition, core-sheath or side-by-side composite fibers, split fibers, modified cross-section fibers, crimped fibers, heat-shrinkable fibers, etc. can also be used. These fibers can be used alone or in combination of two or more types.

A preferred example of the constituent fibers of the nonwoven fabric 2 is a composite fiber consisting of two or more components, a low melting point component and a high melting point component. In this case, the constituent fibers are joined at the fiber intersections by thermal fusion of at least the low melting point component. As a core-sheath type composite fiber consisting of two or more components, a low melting point component and a high melting point component, it is preferable that the core is made of high melting point PET or PP and the sheath is made of low melting point PET, PP, or PE. The use of these composite fibers is particularly preferable because they are strongly fused to the elastic filament 4, making it less likely for peeling to occur between the two.

The elastic filaments 4 are made from elastic resins such as thermoplastic elastomers and rubber. In particular, when a thermoplastic elastomer is used as the raw material, it can be melt spun using an extruder in the same way as ordinary thermoplastic resins, and the elastic filaments obtained in this way are easy to heat fuse, making it suitable for the stretch sheet 1a. Examples of thermoplastic elastomers include styrene-based elastomers such as SBS (styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), SEBS (styrene-ethylene-butadiene-styrene), and SEPS (styrene-ethylene-propylene-styrene), olefin-based elastomers (ethylene-based α-olefin elastomers, propylene-based elastomers copolymerized with ethylene, butene, octene, etc.), polyester-based elastomers, and polyurethane-based elastomers, and these can be used alone or in combination of two or more.

Figures 5 and 6 show another embodiment of the stretch sheet of the present invention. For the embodiment shown in Figures 5 and 6, components that differ from the embodiment shown in Figures 1 to 4 described above will be mainly described, and similar components will be given the same reference numerals and will not be described. For components that are not particularly described, the description of the embodiment shown in Figures 1 to 4 described above will be applied as appropriate. For the configuration of the first nonwoven fabric 2 described below, the description of the nonwoven fabric 2 in the embodiment shown in Figures 1 and 2 described above will be applied as appropriate.

The stretch sheet 1b of the embodiment shown in FIG. 5 has a nonwoven fabric 2 and elastic filaments 4 having the same configuration as the embodiment shown in FIG. 1 to FIG. 4 described above, and a nonwoven fabric 5 is laminated as a separate sheet on one side (elastic filament 4 side) of the nonwoven fabric 2. That is, the stretch sheet 1b of this embodiment has two nonwoven fabrics 2, 5 and an elastic filament 4 arranged between these nonwoven fabrics 2, 5. From the viewpoint of distinguishing between the two nonwoven fabrics 2, 5 and making the explanation easier, hereinafter, of the two nonwoven fabrics 2, 5, the nonwoven fabric 2 that is joined to the elastic filaments 4 by fusion is referred to as the first nonwoven fabric 2, and the nonwoven fabric 5 arranged on the opposite side of the first nonwoven fabric is referred to as the second nonwoven fabric 5.

In the stretch sheet 1b of this embodiment, a plurality of elastic filaments 4 in an unstretched state are arranged on one side of the first nonwoven fabric 2 so as to extend in one direction without intersecting with each other, and are joined to the first nonwoven fabric 2 by fusion. From the viewpoint of the bonding strength between the elastic filaments 4 and the nonwoven fabric 2, it is preferable that the elastic filaments 4 are joined to the first nonwoven fabric 2 by continuous fusion over their entire length.

The second nonwoven fabric 5 is typically non-stretchable and non-elastic. "Non-stretchable" means that the above-mentioned elongation rate (change in length) is less than 30%. "Non-elastic" means that the elongation recovery rate (%) measured by the following [Method for measuring elongation recovery rate] is 20% or less, or that the fabric breaks before elongating 100%. It is preferable that the non-elastic nonwoven fabric has a maximum elongation of 90% or less.
[Method for measuring elongation recovery rate]
A sample piece of nonwoven fabric 50 mm long and 25 mm wide is prepared, and using a tensile tester (Orientec Co., Ltd.'s "Tensilon" RTC-1210A), the sample piece is fixed at a chuck distance K0 and stretched at a speed of 300 mm/min to a length at 100% elongation K2 (K2 = K0 x 2), and then the sample piece begins to return at the same speed as the tensile speed, and the length of the sample piece when the stress becomes 0 is defined as the length after elongation recovery K1. The elongation recovery rate at 100% elongation is calculated from the following formula.
Elongation recovery rate (%) at 100% elongation = [(K2-K1)/(K2-K0)] x 100

In the stretch sheet 1b, the second nonwoven fabric 5 is intermittently bonded to the elastic filaments 4 in a non-stretched state. In this embodiment, as shown in FIG. 5, the first nonwoven fabric 2, the elastic filaments 4, and the second nonwoven fabric 5 are bonded via joints 6 formed intermittently in the longitudinal direction X. Such joints 6 are formed by fusion using embossing or the like.

The stretch sheet 1b of this embodiment is obtained by stretching a laminate of a first nonwoven fabric 2 and elastic filaments 4 in the longitudinal direction X, laminating a second nonwoven fabric 5 in an unstretched state on the elastic filament 4 side of the laminate, and forming the joints 6. Between the joints 6 in the longitudinal direction X, the second nonwoven fabric 5 is not joined to the elastic filaments 4. Therefore, when the stretch of the laminate is released after the joints 6 are formed, the laminate shrinks in the longitudinal direction X. Due to such shrinkage, in the unstretched stretch sheet 1b, the second nonwoven fabric 5 between the joints 6 is separated from the first nonwoven fabric 2 and the elastic filaments 4. As a result, the second nonwoven fabric 5 between the joints 6 protrudes from the elastic filaments 4, so that a convex portion 51 made of the second nonwoven fabric 5 is formed between the joints 6, and a concave portion 52 is formed at the joints 6. In this way, the second nonwoven fabric 5 in the stretch sheet 1b is separated from the first nonwoven fabric 2 between the joints 6 to form a convex portion 51.

In the stretch sheet 1b of this embodiment, the second nonwoven fabric 5 covering the elastic filaments 4 suppresses stickiness caused by the elastic filaments 4, making it pleasant to the touch, and the convex portions 51 formed by the second nonwoven fabric 5 give it a good texture. In addition, the stretch sheet 1b of this embodiment has the second nonwoven fabric 5 and the elastic filaments joined by the intermittently formed joints 6, so it can be stretched with a lower stress than the stretch sheet of Patent Document 2, and has the advantage of improved breathability. Therefore, it can be used for the exterior body of an absorbent article, preferably the waist portion of the exterior body that is placed around the waist of the wearer.

In the stretch sheet 1b shown in FIG. 5, the joint 6 joins the first nonwoven fabric 2, the elastic filament 4, and the second nonwoven fabric 5, but the joint 6 may join the elastic filament 4 and the second nonwoven fabric 5. Such a stretch sheet 1b also has the advantages described above.

From the viewpoint of further improving the effects of the above-mentioned advantages, the thickness T2 (see FIG. 5) of the stretch sheet 1b of this embodiment is preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and is preferably 5 mm or less, more preferably 4 mm or less. The thickness includes the height of the protrusions 51.

From the same viewpoint as above, the length L16 between the joints 6 in the longitudinal direction X (see FIG. 5) is preferably 0.3 mm or more, more preferably 0.5 mm or more, even more preferably 0.7 mm or more, and is preferably 5 mm or less, more preferably 4 mm or less.

The second nonwoven fabric 5 can be made of the same material as the nonwoven fabric 2 described above. In the stretch sheet 1b of this embodiment, the first nonwoven fabric 2 and the second nonwoven fabric can be made of the same or different sheet materials. "The same type of sheet material" refers to sheet materials that are all the same in terms of the manufacturing process of the sheet material, the type of constituent fibers of the sheet material, the fiber diameter and length of the constituent fibers, the thickness and basis weight of the sheet material, etc. When at least one of these is different, it is called "different type of sheet material."

The stretch sheet 1b in this embodiment includes a laminate of elastic filaments 4 and nonwoven fabric 2 bonded to the elastic filaments 4, and a second nonwoven fabric 5 as a separate sheet, but the separate sheet is not limited to nonwoven fabric and may be a film, a laminate sheet of nonwoven fabric and film, or other sheet.

Stretch sheet 1c of the embodiment shown in FIG. 6 is different from the embodiment shown in FIG. 5 in the bonding of second nonwoven fabric 5, elastic filament 4, and first nonwoven fabric 2. Specifically, second nonwoven fabric 5 is bonded to first nonwoven fabric 2 and elastic filament 4 via adhesive 66 applied to the entire surface of the surface facing elastic filament 4 in an unstretched state. As a result, when such stretch sheet 1c is viewed in cross section along the longitudinal direction X in an unstretched state, the entire sheet 1c forms a convex portion 51 protruding toward the second nonwoven fabric 5 side due to contraction of elastic filament 4 (see FIG. 6). Stretch sheet 1c of this embodiment has the same configuration as the embodiment shown in FIG. 5, except for the bonding by adhesive 66 and the fact that the entire sheet 1c forms a convex portion 51. Like the embodiment shown in FIG. 5, the stretch sheet 1c of this embodiment also includes a laminate of elastic filaments 4 and nonwoven fabric 2 bonded to the elastic filaments 4, and a second nonwoven fabric 5 as a separate sheet, but the separate sheet is not limited to nonwoven fabric and may be a film, a laminate sheet of nonwoven fabric and film, or other sheet.

The stretch sheet 1c in this embodiment has the following advantages and can be used for the exterior body of an absorbent article, preferably for the side portion of the exterior body. The side portion of the exterior body is the portion disposed on and near the wearer's flank. The stretch sheet 1c in this embodiment has higher sheet strength because the second nonwoven fabric 5 is bonded to the entire surface of the laminate. Such a stretch sheet 1c is preferable in that it is less likely to tear or have fingers penetrated even when a tensile load is applied in one direction, such as when the absorbent article is worn and pulled up toward the waist. The "finger penetration" refers to the user's fingers penetrating the stretch sheet when handling an absorbent article that includes the stretch sheet as a component.

From the viewpoint of further improving the effects of the above-mentioned advantages, the thickness T3 (see FIG. 6) of the stretch sheet 1c of this embodiment is preferably 0.5 mm or more, more preferably 1 mm or more, even more preferably 1.5 mm or more, and is preferably 3 mm or less, more preferably 2.5 mm or less. The thickness is the length from the top of the convex portion 51 to the other surface of the first nonwoven fabric 2 at the bottom of the concave portion 52 (the surface opposite the elastic filament 4).

Next, the manufacturing method of the stretch sheet of the present invention will be described with reference to Figs. 7 to 12, taking as an example the manufacturing method of the stretch sheet 1a of the embodiment shown in Fig. 1 described above. This manufacturing method includes a fusion process in which a plurality of elastic filaments 4 in a molten or softened state spun from a plurality of spinning nozzles are brought into contact with one side of an original sheet 2a before the elastic filaments 4 solidify, to obtain a composite sheet 1' in which the elastic filaments 4 are fused to the original sheet 2a, and a stretchability imparting process in which stretchability is imparted to the composite sheet 1'. In this manufacturing method, the conveying direction of the original sheet 2a, the elastic filaments 4, and the composite sheet 1' is represented by the symbol X1. The direction perpendicular to the conveying direction X1 is represented by the symbol Y1.

Figure 7 shows a spinning device 10 used in the fusion process. The spinning device 10 includes a spinning head 11 that spins molten resin from a spinning nozzle to produce elastic filaments 4 in a molten or softened state, a pair of rolls 15a, 15b that take up the elastic filaments 4 discharged from the spinning head 11 together with the raw sheet 2a, and an anti-blocking agent coating section 14 arranged downstream of the pair of rolls 15a, 15b in the conveying direction X1. The pair of rolls 15a, 15b typically have smooth surfaces. The basic configuration of the spinning process section in the spinning device 10 is the same as that of a known melt-blowing type spinning device.

The pair of rolls 15a, 15b includes a first roll 15a around which the raw sheet 2a is wound, and a second roll 15b that is arranged opposite the first roll 15a and brings the raw sheet 2a into contact with the elastic filament 4. Both rolls 15a, 15b have smooth surfaces. The spinning device 10 is a device that spins filaments by a so-called melt spinning method, and is equipped with a melt extruder (not shown) that melts elastic resin chips and sends them to the spinning head 11 in addition to the spinning head 11. The spinning head 11 and the pair of rolls 15a, 15b are electrically connected to a control unit (not shown), and the control unit can adjust the resin discharge speed by the spinning head 11 and the take-up speed by the pair of rolls 15a, 15b.
The anti-blocking agent coating section 14 coats an anti-blocking agent on the surface (other surface) of the composite sheet 1' opposite to the surface on which the elastic filaments 4 are arranged.

As shown in FIG. 8, the spinning head 11 includes a bottom wall portion 11L having a rectangular shape in a plan view that forms the lower end surface 11a of the head 11, and a side wall portion 11S connected to the periphery of the bottom wall portion 11L. The internal space of the spinning head 11 defined by these walls 11L and 11S is a storage portion 13 for the molten resin supplied from the melt extruder. The lower end surface 11a of the spinning head 11 has a longitudinal direction (hereinafter also referred to as the first direction X2) and a direction perpendicular thereto (hereinafter also referred to as the second direction Y2). The lower end surface 11a is provided with a plurality of spinning nozzles 12, and the storage portion 13 of the spinning head 11 is connected to the outside through each spinning nozzle 12. The material of the spinning head 11 can be set in the same manner as known materials, and is usually metal.

8, as an example of an embodiment, the lower end surface 11a, which is the nozzle installation surface of the spinning head 11, is provided with a staggered arrangement section 12A in which multiple spinning nozzles 12 are arranged in a staggered manner. In the staggered arrangement section 12A, multiple nozzle rows 12L (parts surrounded by dotted lines in FIG. 9) in which multiple spinning nozzles 12 are arranged at intervals in the first direction X2 of the lower end surface 11a are formed in multiple rows (two rows in this embodiment) in the second direction Y2 perpendicular to the first direction X2, i.e., in the width direction of the lower end surface 11a, and the positions of the spinning nozzles 12 are shifted by half a pitch between adjacent nozzle rows 12L, 12L in the first direction X2. In this specification, "staggered arrangement" includes not only a state in which multiple spinning nozzles 12 are perfectly arranged as described above, but also a state in which there is a slight unintended misalignment, such as a misalignment unavoidable during manufacturing. When the spinning nozzles 12 are arranged in a staggered pattern in this manner, adjacent elastic filaments tend to flow independently from each other upstream, i.e., immediately after being discharged from the spinning nozzle, and thus a constricted filament 41 and a single filament 4 having a single constriction 42 are easily formed. These filaments are easy to cool from the molten state, so excessive fusion between the filaments and the nonwoven fabric 2 is more effectively suppressed. This prevents hardening due to fusion, softens the raw sheet 2a, and more effectively prevents holes from being generated in the fused portions when the raw sheet 2a is stretched.

The spinning nozzle 12 in the spinning head 11 is circular in plan view, but in the present invention, the plan view shape of the spinning nozzle is not particularly limited and can be any shape, such as a polygonal shape. The diameter of the spinning nozzle 12, which is circular in plan view, affects the diameter and draw ratio of the elastic filament 4. From this perspective, the diameter of the spinning nozzle 12 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and is preferably 2 mm or less, more preferably 0.6 mm or less.

When the diameter of the spinning nozzle 12 is within the above range, in order to make it easier to form a necked filament 41 having one neck 42 and a single filament 4, it is preferable that the spinning nozzle be arranged as follows (see Figure 9).
In the nozzle row 12L in the staggered arrangement section 12A, the center-to-center distance (pitch P2) between adjacent spinning nozzles 12, 12 in the first direction X2 is preferably 0.5 mm or more, more preferably 0.8 mm or more, and is preferably 2 mm or less, more preferably 1.5 mm or less, from the viewpoint of stress development. In each nozzle row 12L, all spinning nozzles 12 are arranged at equal pitches.
The center-to-center distance (pitch P3) in the first direction X2 between adjacent nozzle rows 12L, 12L in the second direction Y2 is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 3 mm or less, more preferably 2 mm or less. The pitch P3 is the center-to-center distance in the first direction X2 between any one spinning nozzle 12 (hereinafter referred to as a specific nozzle 12) in one nozzle row 12L and the spinning nozzle 12 closest to the specific nozzle 12 in the other nozzle row 12L in the nozzle rows 12L, 12L adjacent to each other in the second direction Y2.

In the fusion process, a melt extruder (not shown) first melts and kneads the chips of elastic resin, which is the raw material of the elastic filaments 4, and supplies the molten elastic resin to a storage section 13 (see FIG. 8) in the spinning head 11. The molten elastic resin is discharged from a plurality of spinning nozzles 12 drilled on the lower end surface of the spinning head 11 as molten or softened elastic filaments 4 at a resin discharge speed V1. Since the plurality of spinning nozzles 12 are arranged in a staggered pattern, the plurality of elastic filaments 4 spun from each spinning nozzle 12 extend while maintaining the shape of a single elastic filament 4 without crossing each other, and some adjacent single elastic filaments 4 are bonded to each other before reaching the joining position with the original sheet 2a of the nonwoven fabric 2. This forms a narrowed filament. In this way, the plurality of elastic filaments 4 in a molten or softened state spun from the plurality of spinning nozzles 12 are supplied between a pair of rolls 15a, 15b together with the original sheet 2a.

In order to arrange the elastic filaments 4 more evenly without crossing each other, it is preferable to adjust the resin extrusion speed V1 and the take-up speed V2 of the elastic filaments 4 within the following ranges.
The ratio of the take-up speed V2 of the pair of rolls 15a, 15b to the resin extrusion speed V1 of the spinning head 11 [(V2/V1) x 100] is preferably 500% or more, more preferably 1000% or more, and is preferably 2500% or less, more preferably 2000% or less.
The resin discharge speed V1 of the spinning head 11 is preferably 5 m/min or more, more preferably 8 m/min or more, and is preferably 30 m/min or less, more preferably 25 m/min or less.
The take-up speed V2 of the pair of rolls 15a, 15b is preferably 40 m/min or more, more preferably 70 m/min or more, and is preferably 200 m/min or less, more preferably 180 m/min or less.
In particular, from the viewpoint of selectively producing the monofilament 42, the take-up speed V2 of the pair of rolls 15a, 15b is preferably 50 m/min or more, more preferably 70 m/min or more, and is preferably 200 m/min or less, more preferably 180 m/min or less.

The pair of rolls 15a, 15b take up the elastic filament 4 before solidification together with the original sheet 2a, thereby stretching the elastic filament 4 in the conveying direction X1. The elastic filament 4 before solidification is brought into contact with one side of the original sheet 2a between the pair of rolls 15a, 15b, so that the elastic filament 4 is fused to the original sheet 2a. Such fusion is caused by the melting heat of the elastic filament 4 before solidification. The melting heat melts the constituent fibers of the original sheet 2a, and the elastic filament 4 and the original sheet 2a are joined. Specifically, only the fibers present around the elastic filament 4 in the original sheet 2a are fused to the elastic filament 4, and the fibers present at a position further away are not fused. In this way, at least a part of the constituent fibers of the original sheet 2a are fused to the elastic filament 4. From the viewpoint of further improving the joining strength, it is preferable that both the elastic filament 4 and at least a part of the constituent fibers of the original sheet 2a are fused.

During the fusion process, the elastic filament 4 in a molten or softened state is stretched and the molecules are oriented in the stretching direction until it comes into contact with the raw sheet 2a. This stretching reduces the diameter. From the viewpoint of sufficiently stretching the elastic filament 4 and from the viewpoint of preventing thread breakage of the elastic filament 4, the temperature of the elastic filament 4 may be adjusted by blowing air of a predetermined temperature (hot air, cold air) onto the spun elastic filament 4. Furthermore, the stretching of the elastic filament 4 may not only be stretching in a molten state of the resin composition (elastic resin) that constitutes the elastic filament 4 (melt stretching), but also stretching in a softened state during the cooling process (softening stretching).

From the viewpoint of ensuring fiber fusion and maintaining the shape of the elastic filament 4 to further improve the stretching properties, the temperature of the elastic filament 4 when it is brought into contact with the original sheet 2a is preferably 100°C or higher, more preferably 120°C or higher, and also preferably 180°C or lower, more preferably 160°C or lower. The temperature of the elastic filament 4 when it is brought into contact with the original sheet 2a is measured by using a film having a melting point different from the melting point of the resin composition constituting the elastic filament 4 and observing the bonding state. If the elastic filament 4 and the film are fused together, it is determined that the bonding temperature is equal to or higher than the melting point of the film.

By fusing the constituent fibers of the raw sheet 2a to the elastic filaments 4, the bond strength at each bond point is increased. Reducing the density of the bond points is preferable because it reduces the inhibition of stretching caused by the raw sheet 2a and results in a stretch sheet 1a with sufficient bond strength. The density of the bond points can be reduced by weakening the clamping conditions with the smooth rolls 15a and 15b, increasing the bulk density of the raw sheet 2a, or applying an agent to the raw sheet 2a by spraying or the like that inhibits fusion with the elastic filaments 4.

Each elastic filament 4 is supplied between a pair of rolls 15a, 15b in a state where it is arranged in one direction without crossing each other, and both the elastic filament 4 and the original sheet 2a are clamped by the pair of rolls 15a, 15b. If this clamping pressure is too high, the elastic filament 4 will be easily cut into the original sheet 2a, and there is a risk that the texture will be damaged. The clamping pressure is sufficient so that the elastic filament 4 comes into contact with the original sheet 2a, and an excessively high clamping pressure is not required.

The contact between the elastic filament 4 and the original sheet 2a is achieved by winding the original sheet 2a around the first roll 15a of the pair of rolls 15a and 15b, while supplying a plurality of elastic filaments 4 between the pair of rolls 15a and 15b, and fusing the elastic filaments 4 to the original sheet 2a. At this time, the elastic filament 4 may be supplied closer to the first roll 15a than the original sheet 2a, as shown in FIG. 10(a). From the viewpoint of making it easier to form a single filament or a constricted filament having one constriction and further suppressing hardening and perforation of the original sheet 2a due to fusing, it is preferable that the elastic filament 4 is supplied farther from the first roll 15a than the original sheet 2a, as shown in FIG. 10(b). In this case, from the same viewpoint as above, the winding angle θ (see FIG. 11) around the first roll 15a is preferably greater than 0°, more preferably greater than 10°, and also preferably less than 90°, more preferably less than 60°. As shown in FIG. 11, the wrapping angle θ around the first roll 15a is the angle between two tangents a and b that are tangent to the start point F1 and the end point F2 of the wrapping of the raw sheet 2a wrapped around the roll 15a when the first roll 15a is viewed in cross section along the radial direction.

Through the above fusion process, a composite sheet 1' in which the elastic filaments 4 are fused to the original sheet 2a is obtained. Next, the composite sheet 1' can be coated with an anti-blocking agent 7 by the anti-blocking agent coating unit 14. The anti-blocking agent 7 may be coated on the surface of the composite sheet 1' on which the elastic filaments 4 are arranged, but it may also be coated on the surface opposite to the surface on which the elastic filaments 4 are arranged (the other surface). In that case, it is preferable to coat the entire surface of the opposite surface. From the viewpoint of efficient coating, it is preferable that such coating is sprayed by spraying. By coating the anti-blocking agent 7, the operability of unwinding the composite sheet 1' is improved for the composite sheet roll 1'R on which the composite sheet 1' is wound. This is because the presence of the anti-blocking agent between the adjacent elastic filaments 4 and the original sheet 2a in the roll 1'R makes it easier to peel the adjacent composite sheets 1' from each other. The composite sheet roll 1'R may be wound with the composite sheet 1' so that the original sheet 2a is located on the inside of the roll (see FIG. 12(a)), or may be wound with the composite sheet 1' so that the original sheet 2a is located on the outside of the roll (see FIG. 12(b)). In the manufacturing method of this embodiment, the anti-blocking agent 7 is applied to the composite sheet 1' in this manner, so that the finally obtained stretch sheet 1a also contains the anti-blocking agent 7 on the side opposite to the side on which the elastic filaments 4 are arranged (the other side). The content of the anti-blocking agent in the stretch sheet 1a is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, and preferably 2 parts by weight or less, more preferably 1.5 parts by weight or less, based on 100 parts by weight of the original sheet.

As a method for applying the anti-blocking agent 7 to the raw sheet 2a, the raw sheet 2a may contain fibers with the anti-blocking agent 7 kneaded into them. Such fibers are obtained by kneading the anti-blocking agent 7 into the constituent resin of the fibers. By containing fibers with the anti-blocking agent 7 kneaded into them, the anti-blocking agent 7 can be uniformly contained throughout the raw sheet 2a.

As the blocking inhibitor 7, an amide compound, silicone, modified silicone, fluorocarbon compound, a hydrocarbon compound having a side chain, mineral oil, wax, etc. can be used. Examples of the amide compound include a compound having a structure consisting of an amine and a carboxylic acid, and a polyamide compound. The amide compound may be either a compound in which the amino group and the carbonyl group end remain in the molecule, or a compound blocked in the form of an amide group. Specific examples include stearic acid amide, behenic acid amide, hexamethylene bisstearic acid amide, trimethylene bisoctyl acid amide, hexamethylene bishydroxystearic acid amide, trioctatrimellitic acid amide, distearyl urea, butylene bisstearic acid amide, xylylene bisstearic acid amide, distearyl adipic acid amide, distearyl phthalic acid amide, distearyl octadecanedioic acid amide, epsilon caprolactam, and derivatives thereof.
Examples of silicone compounds include dimethyl silicone, methylphenyl silicone, and methyl hydrogel silicone. Examples of modified silicone compounds include modified silicone compounds and silicone polymers. Among these, amino-modified silicone, diamino-modified silicone, and polyether-modified silicone are preferred. From the viewpoint of further improving the feel on the skin, amino-modified silicone or diamino-modified silicone is preferred.
Examples of fluorocarbon compounds include fluorinated polymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF).

Figure 13 shows one embodiment of the stretchability imparting process (elasticity development process). In this embodiment, the stretchability imparting process is a process in which the composite sheet 1' is stretched in the direction in which the elastic filaments 4 extend. This process imparts stretchability to the raw sheet 2a, which does not inherently have stretchability.

The stretching process can use a stretching device equipped with a pair of grooved rolls 17a, 17b in which teeth extending in the axial direction and tooth bottoms are alternately formed in the circumferential direction. The stretching device is equipped with a pair of grooved rolls 17a, 17b and a pair of nip rolls 16a, 16b, 18a, 18b arranged on the upstream side and downstream side of the grooved rolls 17a, 17b in the conveying direction X1 of the composite sheet 1'. The degree of stretching of the composite sheet 1' can be adjusted by appropriately adjusting the conveying speed of the pair of nip rolls 16a, 16b on the upstream side of the pair of grooved rolls 17a, 17b and the pair of nip rolls 18a, 18b on the downstream side.

The stretching device has a known lifting mechanism (not shown) that displaces one or both pivots of the pair of toothed rolls 17a, 17b up and down, and the distance between the toothed rolls 17a, 17b is adjustable. For example, the pair of toothed rolls 17a, 17b are combined so that the teeth of one are loosely inserted between the teeth of the other and the teeth of the other are loosely inserted between the teeth of the other. The composite sheet 1' is inserted between the toothed rolls 17a, 17b in this state to form the low basis weight portion 21 and the high basis weight portion 23, thereby performing the stretching treatment. The pair of toothed rolls 17a, 17b may both be driven by a driving source (co-rotating rolls), or only one may be driven by a driving source (co-rotating rolls). The tooth profile of the toothed rolls 17a, 17b is generally an involute tooth profile or a cycloid tooth profile, and it is particularly preferable to use these with a narrow tooth width.

In the stretchability imparting process, the composite sheet 1' is passed between a pair of grooved rolls 17a, 17b to form low basis weight portions 21 and high basis weight portions 23, thereby imparting stretchability to the composite sheet 1'. As a result, the composite sheet 1' is stretched along its conveying direction X1, i.e., the extension direction of the elastic filaments 4, to become a stretchable sheet 1a.

In this step, the constituent fibers of the raw sheet 2a, i.e., the nonwoven fabric 2, are plastically deformed and stretched, so that the fibers become thinner and the nonwoven fabric 2 becomes bulkier, improving the feel and cushioning properties. From the viewpoint of further improving such properties, the thickness of the stretch sheet 1a obtained by the stretchability imparting step is preferably 1.1 times or more, more preferably 1.3 times or more, and preferably 4 times or less, more preferably 3 times or less, the thickness of the composite sheet 1'.
For the above-mentioned stretchability imparting step, the elasticity imparting treatment described in paragraphs [0066] to [0069] of JP-A-2008-179128 can be appropriately utilized.

The stretch sheets 1b and 1c of the embodiment shown in Figures 5 and 6 are obtained by laminating a non-stretchable and non-elastic second nonwoven fabric 5 to the stretch sheet 1a obtained by the above-mentioned manufacturing method so as to cover the elastic filaments 4, and then bonding the stretch sheet 1a and the second nonwoven fabric 5 with joints 6 intermittently formed by fusion or with an adhesive 66.

The stretch sheets 1a, 1b, and 1c of the above-mentioned embodiments can be used as components of absorbent articles such as disposable diapers and sanitary napkins. Absorbent articles having these stretch sheets 1a, 1b, and 1c as components exhibit the excellent stretch characteristics described above. Absorbent articles are primarily used to absorb and retain body fluids such as urine and menstrual blood excreted from the body. Absorbent articles include, but are not limited to, disposable diapers, sanitary napkins, incontinence pads, panty liners, and the like, and broadly include articles used to absorb liquids excreted from the human body. Examples of absorbent articles include those that have an absorbent body having a top sheet, a back sheet, and a liquid-retaining absorbent interposed between the two sheets, and an exterior body located on the non-skin-facing side of the absorbent body. Examples of materials constituting absorbent articles include liquid-permeable sheets (including top sheets, sublayers, etc.) located closer to the skin than the absorbent body, sheets (outer bodies) constituting the outer surface of disposable diapers, and sheets for imparting elastic stretchability to the waist, waist, and leg areas. They can also be used as sheets forming the wings of napkins. Other components can also be used in areas where stretchability is desired. The absorbent article may further include various members according to its specific use. Such members are known to those skilled in the art. The stretch sheets 1a, 1b, and 1c according to the embodiments of the present invention have excellent stretchability properties and are therefore suitable for use as outer bodies. From the viewpoint of skin feel, it is preferable that the stretch sheet 1a shown in FIG. 1 is incorporated into the absorbent article so that the surface on the nonwoven fabric 2 side faces the skin, i.e., the surface on the elastic filament 4 side faces the non-skin facing surface. Each of the stretch sheets 1b and 1c shown in Figures 5 and 6 may be incorporated into an absorbent article so that the surface on the first nonwoven fabric 2 side faces the skin-facing side, or may be incorporated into an absorbent article so that the surface on the first nonwoven fabric 2 side faces the non-skin-facing side. The stretch sheets 1a, 1b, and 1c according to each embodiment of the present invention are joined to other constituent materials (e.g., absorbent body) in the absorbent article by a known method and incorporated into the absorbent article.

While the present invention has been described based on one preferred embodiment thereof, the present invention is not limited to this embodiment and can be modified as appropriate without departing from the spirit of the present invention.
For example, the arrangement of the spinning nozzles in the spinning head used to manufacture the stretch sheet is not limited to the above embodiment. The number of nozzle rows 12L constituting the staggered arrangement section 12A is not particularly limited, and may be three or more rows in addition to two rows as shown in Figure 9. The planar shape of the spinning nozzle 12 may be appropriately adjusted depending on the application of the stretch sheet to be manufactured, and is not particularly limited.

The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

Example 1
The stretch sheet of the embodiment shown in FIG. 1 was manufactured using an apparatus having the same configuration as the spinning apparatus shown in FIG. 7 and an apparatus having the same configuration as the stretching apparatus shown in FIG. 13. The raw sheet was made of raw resin polypropylene, fibers having a fiber diameter of 18 μm, and had a basis weight of 18 g/m ^2. Styrene-ethylene-propylene-styrene (SEPS) was used as the raw resin for the elastic filament. Using a spinning apparatus having a spinning nozzle arrangement shown in FIG. 9, the raw resin for the elastic filament was spun out in a molten state, and passed between a pair of smooth rolls together with the raw sheet to obtain a composite sheet. In this process, the elastic filament was supplied closer to the first roll than the raw sheet [see FIG. 10(a)]. Next, using the stretching apparatus shown in FIG. 13, the composite sheet was passed between a pair of grooved rolls to perform a stretching treatment. The specific manufacturing conditions are as follows.
In the nozzle row in the staggered arrangement section, the center-to-center distance (pitch P2) between adjacent spinning nozzles in the first direction X2: 1.0 mm
Center-to-center distance (pitch P3) in the first direction X2 between adjacent nozzle rows 12L, 12L in the second direction Y2: 0.5 mm
Resin discharge rate at spinning nozzle: 10 g/min
Take-off speed of a pair of smooth rolls: 150 m/min
The stretch sheet obtained under the above manufacturing conditions had a length of 0.6 mm in the low basis weight portion in the longitudinal direction and a length of 0.5 mm in the high basis weight portion in the same direction. The ratio (%) of the number of constricted filaments having one constriction to the number of elastic filaments in the stretch sheet was also calculated. The ratio (%) of the number of constricted filaments having one constriction to the total number of constricted filaments was also calculated. These ratios are shown in Table 1.

Example 2
A stretch sheet was produced in the same manner as in Example 1, except that the elastic filaments were supplied to the side farther from the first roll than the raw sheet (see FIG. 10(b)). The winding angle θ of the raw sheet around the first roll was 40°.

Example 3
A stretch sheet was produced in the same manner as in Example 2, except that an anti-blocking agent was applied to the surface of the composite sheet opposite to the surface on which the elastic filaments were arranged. Modified silicone was used as the anti-blocking agent. The amount of the anti-blocking agent applied was 0.8 parts by weight per 100 parts by weight of the original sheet.

Comparative Example 1
A stretch sheet was produced in the same manner as in Example 1, except that the two original sheets, with the elastic filament disposed between them, were passed through a pair of smooth rolls to produce a composite sheet.

[Stretchability test]
For the stretch sheets produced in each of the Examples and Comparative Examples, the 50% forward load, 50% return load, 200% forward load, and residual strain (%) were measured by the above-mentioned measuring methods. The measurement results are shown in Table 1.

[Peel strength test between stretch sheets]
The stretch sheets produced in each of the examples and comparative examples were subjected to the measurement of the peel strength between the stretch sheets. First, a laminate was prepared by laminating four stretch sheets each having a size of 25 mm x 85 mm. An acrylic plate larger than the sample size (25 mm x 85 mm) was placed on the laminate, and a weight of 20 kg was placed on the acrylic plate, so that the laminate was pressurized at 0.12 kgf/ ^cm2 . In this pressurized state, the laminate was left stationary for three months in an environment of 50°C. Next, the laminate was mounted on a tensile tester (AG-IS manufactured by Shimadzu Corporation) so that the extension direction of the elastic filament of the adjacent stretch sheets in the laminate coincided with the tensile direction. Specifically, each of the two adjacent stretch sheets was mounted on a chuck. The distance between the chucks was 30 mm. Next, the tensile strength was measured by pulling at 300 mm/min. The first maximum point that appeared in the curve of the measured tensile strength (N) was taken as the peel strength (cN/25 mm). The measurement results are shown in Table 1.

As shown in Table 1, the stretch sheets of Examples 1 to 3 had a higher 50% return load, a lower 200% forward load, and a lower residual set (%) than Comparative Example 1. That is, the stretch sheets of Examples 1 to 3 have better extensibility and shrinkability than Comparative Example 1, and therefore have high stretchability properties.
In addition, in terms of the ratio of the number of narrowed filaments, a comparison between Example 1 and Examples 2 and 3 reveals that positioning the raw sheet between a pair of smooth rolls on the side of the second roll is preferable in terms of making it easier to form a single filament or a narrowed filament having one narrowing.
Furthermore, with regard to the peel strength, a comparison of Examples 1 and 2 with Example 3 reveals that the application of an antiblocking agent is useful for peeling the stretch sheets from each other. This shows that the application of an antiblocking agent can improve the operability of the composite sheet or the roll of the stretch sheet.

1a, 1b, 1c Stretch sheet 1' Composite sheet 2 Nonwoven fabric (first nonwoven fabric)
Reference Signs List 2a Raw sheet 4 Elastic filament 5 Second nonwoven fabric 6 Bonding portion 7 Anti-blocking agent 10 Spinning device 11 Spinning head 12 Spinning nozzle 12L Nozzle row 15a, 15b Smooth rolls 17a, 17b Toothed roll

Claims (10)

The present invention comprises a nonwoven fabric having extensibility , and a plurality of elastic filaments in an unstretched state arranged on one surface of the nonwoven fabric so as to extend in one direction without intersecting with each other,
The elastic filaments are joined to the nonwoven fabric by continuous fusion over the entire length of the elastic filaments by spinning a molten resin that has been melt-kneaded and contacting the nonwoven fabric in a molten or softened state ,
The elastic filaments include a neck filament formed by bonding two or more spun constituent filaments together in a molten or softened state,
the narrow filament has a narrowed portion in a cross section perpendicular to the extension direction of the elastic filament, and is composed of the constituent filaments formed from the same molten resin,
A stretch sheet for absorbent articles, wherein the elastic filaments including the narrow filaments are exposed on the one surface side. The stretch sheet for absorbent articles according to claim 1, which contains an anti-blocking agent on the other side of the nonwoven fabric. The stretch sheet for absorbent articles according to claim 1 or 2, wherein the constricted filaments are continuous in the width direction in a width-direction cross section perpendicular to the extending direction and parallel to a surface direction of the nonwoven fabric. The stretch sheet for absorbent articles according to any one of claims 1 to 3 , wherein the ratio [(L3/L2) x 100] of the minimum length L3 in the thickness direction at the constriction to the diameter L2 of the constituent filaments is 5% or more and 50% or less. The stretch sheet for absorbent articles according to any one of claims 1 to 4, wherein the constricted filaments include constricted filaments having a plurality of the constrictions. The stretch sheet for absorbent articles according to any one of claims 1 to 5, wherein in a widthwise cross section perpendicular to the extending direction and parallel to the surface direction of the nonwoven fabric, the maximum length of the narrowed filaments in the widthwise direction is 100 µm or more and 500 µm or less. The stretch sheet for absorbent articles according to any one of claims 1 to 6, wherein the plurality of elastic filaments include the constricted filaments and monofilaments having no constriction. 8. The stretch sheet for absorbent articles according to claim 7 , wherein the diameter of the monofilament is from 40 μm to 180 μm. 9. The stretch sheet for absorbent articles according to claim 7 or 8 , wherein the ratio of the number of said narrowed filaments to the number of said elastic filaments is 5% or more and 100% or less. An absorbent article comprising the stretch sheet for absorbent articles according to any one of claims 1 to 9 as a constituent member.

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