JP2023068337A - Elastic sheet and its manufacturing method - Google Patents

Abstract

To provide: a stretchable sheet which exhibits a good appearance and satisfies both of high stretchability and high air permeability; and a production method thereof.SOLUTION: Provided is a production method of a stretchable sheet for absorbent article, comprising: a step of contacting elastic filaments in a fusible state with a nonwoven cloth to form a laminate formed by fusion of the elastic filaments to the nonwoven cloth; and stretching the laminate to provide the same with a treatment for stretchability manifestation. As the nonwoven fabric, there is used one having maximum strength of 40 N/50 mm or less under a condition of a strain rate of 3.3 s-1. In the treatment step for stretchability manifestation, the laminate is stretched at a strain rate of 30 s-1 to 200 s-1.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a stretch sheet and a manufacturing method thereof.

As a conventional technique related to stretch sheets made by combining elastic fibers and nonwoven fabrics, the present applicant previously disclosed that a large number of elastic filaments arranged so as to extend in one direction without proposed a stretch sheet bonded to a stretchable nonwoven fabric over the entire length thereof (see Patent Document 1). This stretch sheet is produced by stretching a composite in which elastic filaments are fused to a nonwoven fabric to impart stretchability to the composite.

JP 2015-113547 A

The stretch sheet produced by the method described in Patent Literature 1 has excellent stretchability and sufficient strength for practical use while maintaining air permeability.
By the way, this kind of stretch sheet is required to have higher air permeability. Attempting to increase the elastic filament tends to break. The occurrence of breakage in the elastic filaments contributes to a reduction in stretchability of the stretch sheet and a reduction in appearance.
Accordingly, an object of the present invention is to provide a stretch sheet and a method for producing the stretch sheet that can overcome the drawbacks of the prior art described above.

The present invention comprises a step of contacting elastic filaments in a fusible state with a nonwoven fabric to form a laminate in which the elastic filaments are fused to the nonwoven fabric;
A method for producing a stretchable sheet for absorbent articles, comprising a step of stretching the laminate and subjecting it to elasticity development treatment,
The nonwoven fabric used has a maximum strength of 40 N/50 mm or less under conditions of a strain rate of 3.3 s ^-1 ,
The present invention provides a method for producing a stretch sheet for absorbent articles, wherein the laminate is stretched at a strain rate of 30 s ^-1 or more and 200 s ^-1 or less in the elasticity development treatment step.

The present invention also includes a step of contacting elastic filaments in a fusible state with a nonwoven fabric to form a laminate in which the elastic filaments are fused to the nonwoven fabric;
A method for producing a stretchable sheet for absorbent articles, comprising a step of stretching the laminate and subjecting it to elasticity development treatment,
Using a nonwoven fabric having a strength of less than 12 N/50 mm at 5% elongation,
The present invention provides a method for producing a stretch sheet for absorbent articles, wherein the laminate is stretched at a strain rate of 30 s ^-1 or more and 200 s ^-1 or less in the elasticity development treatment step.

Further, the present invention provides a stretchable absorbent article in which a plurality of elastic filaments arranged so as to extend in one direction without intersecting each other are joined to an extensible nonwoven fabric over their entire lengths in a substantially unstretched state. a sheet,
The stretchable sheet has an elongation rate of 120% or more at a load of 3N/50mm,
In the stretch sheet, the number of cut points of the elastic filaments is 2.0 points/cm ² or less in a non-stretched state of the stretch sheet,
High-stretch regions and low-stretch regions extending in a direction orthogonal to the stretch direction of the stretch sheet are alternately arranged along the stretch direction, and the stretch direction along the stretch direction when stretched 2.2 times. Provided is a stretch sheet for absorbent articles, wherein the ratio W _H /W _L of the width W _H of the high elongation region along the stretch direction to the width W _L of the low elongation region is 10 or less.

INDUSTRIAL APPLICABILITY According to the present invention, a stretch sheet exhibiting a good appearance and having both high stretchability and high breathability and a method for producing the same are provided.

FIG. 1 is a partially broken perspective view showing one embodiment of the stretch sheet of the present invention. 2(a) and 2(b) are vertical cross-sectional views of the elastic sheet shown in FIG. 1 in a natural state and a stretched state, respectively, along the direction in which the elastic filaments extend. FIG. 3 is a schematic diagram showing an apparatus suitably used for manufacturing the stretch sheet of the present invention. FIG. 4 is an explanatory diagram showing a method of calculating a strain rate in manufacturing the stretch sheet of the present invention.

The present invention will be described below based on its preferred embodiments.
The present invention relates to stretch sheets for absorbent articles. As used herein, the absorbent article broadly includes articles used to absorb and retain bodily fluids excreted from the human body. Examples include diapers and incontinence pads used to absorb and retain urine and feces, sanitary napkins used to absorb and retain menstrual blood, and breast pads used to absorb and retain breast milk. However, it is not limited to these.

The stretch sheet of the present invention is applied to various parts of absorbent articles that require stretchability. For example, the outer body constituting the outer surface of the absorbent article, the leakage-preventing cuffs arranged on both sides of the absorbent article, the waist gathers constituting the waist opening area of the absorbent article, and the leg opening area of the absorbent article. The stretch sheet of the present invention can be applied to leg gathers and the like. An absorbent article in which the stretch sheet of the present invention is applied to these parts has a good fit to the wearer's body due to the stretchability of the stretch sheet, and the breathability of the stretch sheet. As a result, it becomes difficult for stuffiness to occur in the wearing state.

The stretch sheet of the present invention comprises elastic filaments and nonwoven fabric. In this specification, elasticity and stretchability are stretchable and when the force is released from a state of being stretched 100% with respect to the original length (becomes 200% of the original length) In addition, it is the property of returning to a length of 125% or less of the original length.

The stretch sheet of the present invention can have, for example, one nonwoven fabric and a plurality of elastic filaments arranged on one surface of the nonwoven fabric. Alternatively, the stretch sheet of the present invention can have two nonwoven fabrics and a plurality of elastic filaments disposed between the two nonwoven fabrics. Each elastic filament is bonded with a nonwoven. If the elastic filaments are arranged between two nonwovens, each elastic filament is bonded to at least one nonwoven, or to both nonwovens. Also, when the elastic filaments are arranged between two nonwoven fabrics, the two nonwoven fabrics may be of the same type or of different types. In this specification, nonwoven fabrics of the same kind mean nonwoven fabrics having the same manufacturing process, the same type of constituent fibers of the nonwoven fabric, the fiber diameter and length of the constituent fibers, the thickness and basis weight of the nonwoven fabric, and the like. If at least one of these is different, it is said to be a heterogeneous nonwoven fabric.

It is preferable to employ fusion bonding as a mode of joining the elastic filaments and the nonwoven fabric. By joining the two by fusion bonding, the stretch sheet can be made flexible and highly stretchable. If, for example, an adhesive is used to join the two, the stretch sheet tends to feel hard due to the solidification of the adhesive. In addition, the adhesive tends to inhibit the expansion and contraction of the elastic filaments.

The stretchable sheet is stretchable in the same direction as the direction in which the elastic filaments extend. The stretchability of the stretch sheet is developed due to the elasticity of the elastic filaments. When the stretchable sheet is stretched in the same direction as the direction in which the elastic filaments extend, the elastic filaments and the nonwoven fabric are stretched. When the stretching of the stretchable sheet is released, the elastic filaments contract, and the nonwoven fabric returns to its original state before being stretched along with the shrinkage.

An elastic filament has a filamentous form with thickness and length. The length of the elastic filaments is very large relative to the thickness, for example the length of the elastic filaments can be 500 times or more, in particular 1000 times or more, the thickness.

Each elastic filament preferably exists substantially continuously over the entire length of the stretch sheet. The elastic filaments contain elastic resin. Each elastic filament is arranged so as to extend in one direction. Each elastic filament may extend linearly or meanderingly. Each elastic filament is preferably arranged so as to extend in one direction without intersecting each other. However, crossing of the elastic filaments is not prevented. For example, unintentional crossing of elastic filaments due to unavoidable variations in stretch sheet manufacturing conditions is acceptable.

The direction in which the elastic filaments extend may coincide with the machine direction during manufacture of the nonwoven fabric, or may be perpendicular to the machine direction during manufacture of the nonwoven fabric. When the stretch sheet is manufactured according to the preferred manufacturing method described below, the direction in which the elastic filaments extend coincides with the machine direction during manufacture of the nonwoven fabric.

The basis weight of the elastic filaments is preferably 4 g/m ² or more and 30 g/m ² or less, particularly 6 g/m ² or more and 15 g/m ^{2 or} less, from the viewpoint of stretchability, texture, thickness, and cost. The thickness of the elastic filaments, the number of arranged filaments, the arrangement intervals, etc. may be appropriately set according to the basis weight of the elastic filaments. For example, the diameter of the elastic filament can be set to 30 μm or more and 200 μm or less, particularly 50 μm or more and 130 μm or less. As shown in FIG. 1, which will be described later, when the elastic filaments are aligned in one direction, the pitch of adjacent elastic filaments (the distance between the centers of adjacent elastic filaments) is 0.5. It can be set to 1 mm or more and 5 mm or less, particularly 0.3 mm or more and 1.8 mm or less.

Preferably, the elastic filaments are bonded to the nonwoven in a substantially non-stretched state. When the elastic filaments are joined to the nonwoven fabric in an unstretched state, there is an advantage that relaxation (creep) due to stretching does not occur and stretchability is less likely to decrease. Furthermore, for example, when an elastic filament is stretched twice and bonded to a non-woven fabric, if it shrinks to 1.3 times the initial size, it can only be stretched to 1.54 times from this state, but in the non-stretched state. When the elastic filament and the nonwoven fabric are joined by , the initial origin when the elastic sheet is stretched is different, so it is possible to stretch it to the stretchable length of the nonwoven fabric or the maximum elongation of the elastic filament. There are advantages.

Examples of elastic resins constituting the elastic filaments include synthetic rubbers such as natural rubber, EVA rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber and neoprene rubber, polyurethanes and thermoplastic elastomers. These elastic resins can be used singly or in combination of two or more.

In particular, it is preferable to use a thermoplastic elastomer as the elastic resin because it is easy to develop desired elasticity. Thermoplastic elastomers can be melt-spun using an extruder in the same manner as ordinary thermoplastic resins, and the elastic filaments thus obtained are easy to fuse, making them suitable for the manufacturing method described below. be.

Examples of thermoplastic elastomers include SBS (styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), SEBS (styrene-ethylene-butadiene-styrene), and SEPS (styrene-ethylene-propylene-styrene). Olefin-based elastomers such as styrene-based elastomers, ethylene-based α-olefin elastomers, and propylene-based elastomers obtained by copolymerizing ethylene/butene/octene, etc., polyester-based elastomers, and polyurethane-based elastomers can be mentioned.

The nonwoven fabric to which the elastic filaments are joined is extensible. Specifically, the nonwoven fabric can be stretched in the same direction as the direction in which the elastic filaments extend. Extensible means (a) when the constituent fibers of the nonwoven fabric themselves are elongated, and (b) even if the constituent fibers themselves are not elongated, the fibers bonded at the intersection point are separated or the fibers are bonded together. It includes the case where the three-dimensional structure formed by a plurality of fibers is structurally changed, the constituent fibers are torn, or the slackness of the fibers is stretched, so that the nonwoven fabric as a whole is elongated.

The nonwoven fabric may already be extensible in the raw state before being joined with the elastic filaments. Alternatively, the nonwoven fabric is not extensible in the original state before being joined to the elastic filaments, but is made extensible by being processed so as to be extensible after being joined to the elastic filaments. good too. Specific methods for making the nonwoven fabric stretchable include heat treatment, stretching between rolls, bite stretching by tooth grooves or gears, tensile stretching by a tenter, and the like. Considering the suitable manufacturing method of the elastic sheet described later, it is preferable that the nonwoven fabric is not stretchable in its raw state, in order to improve the transportability of the nonwoven fabric when the elastic filaments are fused to the nonwoven fabric.

In addition to being extensible as described above, the nonwoven is preferably substantially inelastic. For this purpose, the nonwoven preferably comprises non-elastic fibers and no elastic fibres. Inelastic, as used herein, refers to properties that do not meet the definition of elasticity set forth above.

Examples of non-elastic fibers constituting the non-woven fabric include fibers made of polyethylene (PE), polypropylene (PP), polyester (PET or PBT), polyamide, and the like. The fibers constituting the nonwoven fabric may be short fibers or long fibers, and may be hydrophilic or water-repellent. In addition, core-sheath or side-by-side conjugate fibers, split fibers, modified cross-section fibers, crimped fibers, heat-shrinkable fibers, and the like can also be used. These fibers can be used singly or in combination of two or more. The nonwoven can be a continuous filament or staple fiber nonwoven.
The basis weight of the nonwoven fabric is preferably 3 g/m ² or more and 100 g/m ² or less, more preferably 5 g/m ² or more and 30 g/m ^{2 or} less, from the viewpoint of texture, thickness, design properties, and the like.

One embodiment of the elastic sheet is shown in FIG. 2(a) and 2(b) show cross-sectional views in the thickness direction of the stretch sheet shown in FIG. 2(a) and 2(b) are cross-sectional views along the direction in which the elastic filaments extend in the stretch sheet.
The stretch sheet 10 of the embodiment shown in FIG. 1 is composed of a total of two nonwoven fabrics, a first nonwoven fabric 11 and a second nonwoven fabric 12, and a plurality of elastic filaments 13 sandwiched between the two nonwoven fabrics. Each elastic filament 13 is arranged so as to extend in one direction without intersecting each other.

FIG. 2(a) is a cross-sectional view of the stretch sheet 10 in a natural state (relaxed state), and FIG. 2(b) is a cross-sectional view of the stretch sheet 10 in a stretched state. In the natural state, the elastic sheet 10 has a wavy shape in which crests 14' and troughs 14'' are alternately arranged. . When the stretch sheet 10 is viewed from above, the peaks 14 ′, the ridges 15 ′, and the valleys 14 ″ extend in a direction orthogonal to the stretch direction of the stretch sheet 10 .

On the other hand, in the stretched state, the elastic sheet 10 has low-density regions 14 and high-density regions 15 alternately arranged along the direction in which the elastic filaments 13 extend. Each of the regions 14 and 15 extends in a strip shape in the direction in which the elastic filaments 13 extend, that is, in the direction orthogonal to the stretching direction of the stretchable sheet 10 . The low-density regions 14 and the high-density regions 15 are alternately arranged at regular intervals. As for the low-density regions 14, those protruding above the stretch sheet 10 and those protruding below the stretch sheet 10 are alternately arranged. The low-density region 14 protruding upward from the stretch sheet 10 originates from the apex 14' of the stretch sheet 10 in its natural state shown in FIG. 2(a). On the other hand, the low-density regions 14 projecting downward from the stretch sheet 10 are derived from the valleys 14'' in the stretch sheet 10 in the natural state shown in FIG. It is derived from the ridge line portion 15' in the stretch sheet 10 in the natural state shown in 2(a).

As is clear from the comparison between FIG. 2(a) and FIG. 2(b), the portions that are mainly stretched when the stretchable sheet 10 is stretched are the top portions 14′ and the valley portions 14″ in FIG. 2(a). , is the low-density region 14 in Fig. 2(b) In other words, the ridgeline portion 15' in Fig. 2(a) (that is, the high-density region 15 in Fig. 2(b)) stretches the stretch sheet 10 In this manner, the stretch sheet 10 has high-stretch regions and low-stretch regions extending in a direction perpendicular to the stretch direction, which are alternately arranged along the stretch direction. High elongation areas are peaks 14' and valleys 14'' in FIG. 2(a) and low density areas 14 in FIG. 2(b). The low elongation region is the ridge 15' in FIG. 2(a) and the high density region 15 in FIG. 2(b). In order to form the high stretch region and the low stretch region in the stretch sheet 10, the stretch sheet 10 may be manufactured, for example, by the method described later.

As described above, the high elongation region in the stretch sheet 10 is the low density region 14 and the low elongation region is the high density region 15 . Therefore, in the stretched state of the stretch sheet 10 , the air permeability of the high-stretched regions, which are the low-density regions 14 , is higher than that of the low-stretched regions, which are the high-density regions 15 . It is also effective to increase the drawing speed as a method of increasing air permeability. When the stretching speed is high, the nonwoven fabric is locally stretched to a large extent, resulting in high air permeability. Conversely, if the stretching speed is low, the nonwoven fabric will be stretched as a whole, and the amount of local stretching will be small. That is, the ratio of the width _WH of the high elongation region to the width _WL of the low elongation region decreases as the drawing speed increases. From this point of view, _WH / _WL , which is the ratio of the width _WH of the high stretch region along the stretch direction to the width WL of _the low stretch region along the stretch direction when the stretch sheet 10 is stretched 2.2 times. A value of 10 or less is preferable from the viewpoint of achieving both breathability and stretchability of the stretchable sheet 10 . From the viewpoint of making this advantage even more remarkable, the value of W _H /W _L is more preferably 6.5 or less, and even more preferably 6.3 or less. From the viewpoint of imparting sufficient stretchability to the stretch sheet 10, the value of W _H /W _L is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. .
A method for measuring the width _WL of the low-stretch region and the width _WH of the high-stretch region will be described later in Examples.

As used herein, the term "low elongation region" refers to a region in which the rate of strain change before and after elongation is less than 10% when the stretch sheet is stretched by 50% along its stretch direction. The high elongation region is a region where the rate of change in strain is 10% or more.

By appropriately selecting the width W _L of the low elongation region and the width W _H of the high elongation region, the stretch sheet 10 becomes highly breathable. Specifically, the air permeability measured according to JIS P8117 is preferably 900 cc/(cm ² ·sec) or more, more preferably 1000 cc/(cm ² ·sec) or more, and 1100 cc. /(cm ² ·sec) or more is more preferable.

Next, a preferred method for manufacturing the stretch sheet of the present invention will be described with reference to FIG. 3, taking as an example the method for manufacturing the stretch sheet 10 shown in FIGS.
In this manufacturing method, as shown in FIG. 3, a plurality of fusible elastic filaments 13 spun from a spinning nozzle 16 are drawn at a predetermined speed and stretched, and before solidification of the elastic filaments 13, The elastic filaments 13 are brought into contact with the original nonwoven fabrics 11' and 12' so that the elastic filaments 13 are arranged in one direction without intersecting each other, and the elastic filaments 13 contact the original nonwoven fabrics 11' and 12'. A laminated body 19 is formed by fusion bonding. Next, the layered body 19 is subjected to an elasticity development treatment for stretching along the direction in which the elastic filaments 13 extend, thereby imparting stretchability to the layered body 19 .

A spinning nozzle 16 is provided on a spinning head 17 . A spinning head 17 is connected to the extruder. The elastic resin melted and kneaded by the extruder is supplied to the spinning head 17 . A large number of spinning nozzles 16 are arranged in a straight line in the spinning head 17 . The spinning nozzles 16 are arranged along the width direction of the first and second raw nonwoven fabrics 11' and 12'. The distance between adjacent spinning nozzles 16 corresponds to the distance between elastic filaments 13 in the target stretchable sheet 10 . The spinning nozzle 16 is generally circular and its diameter affects the diameter of the elastic filament 13 and the draw ratio. From this point of view, the diameter of the spinning nozzle 16 is preferably 0.1 mm or more and 2 mm or less, particularly 0.2 mm or more and 0.6 mm or less. The elastic filaments 13 are formed in a composite form (side-by-side, core-sheath, sea-island structure).

The spun elastic filaments 13 in a molten state join the first raw nonwoven fabric 11' and the second raw nonwoven fabric 12' which are fed out from the raw fabric at the same speed, respectively, and join both raw nonwoven fabrics 11'. , 12' and taken up at a predetermined speed. The take-up speed of the elastic filaments 13 coincides with the delivery speed of both original nonwoven fabrics 11' and 12'. The first raw nonwoven fabric 11 ′ and the second raw nonwoven fabric 12 ′ are stretched by the elasticity development processing device 22 described later, and the first nonwoven fabric 11 and the second nonwoven fabric 12 in the target stretchable sheet 10 Become. The conveying direction of the first original nonwoven fabric 11' and the second original nonwoven fabric 12' coincides with the machine direction during the manufacture of these two original nonwoven fabrics 11' and 12'.

The elastic filaments 13 join the first and second raw nonwoven fabrics 11', 12' before solidification, that is, in a fusible state. As a result, the elastic filaments 13 are fused to the first and second original nonwoven fabrics 11' and 12' while being sandwiched between them. That is, while the elastic filaments 13 before being solidified are fused to the two raw nonwoven fabrics 11' and 12' that are conveyed, the elastic filaments 13 are drawn and stretched. When the elastic filaments 13 are fused, the first and second raw nonwoven fabrics 11' and 12' are not externally heated. That is, the elastic filaments 13 and the two original nonwoven fabrics 11' and 12' are fused only by the heat of fusion caused by the elastic filaments 13 that are fused. As a result, among the constituent fibers of both original nonwoven fabrics 11' and 12', only the fibers existing around the elastic filaments 13 are fused to the elastic filaments, and the fibers existing further apart are fused. do not. As a result, the heat applied to the two original nonwoven fabrics 11' and 12' is kept to a minimum, so that the original good texture of the nonwoven fabrics themselves is maintained. Thereby, the stretch sheet 10 to be obtained has a good texture.

When the elastic filaments 13 and the original nonwoven fabrics 11' and 12' are joined, the elastic filaments 13 are substantially in a non-stretched state (a state in which they do not shrink when the external force is removed). In the bonded state of the two, the fibers forming the original nonwoven fabrics 11' and 12' and the elastic filaments 13 are at least partially fused. In this state, it is preferable that the two original nonwoven fabrics 11' and 12' are fused together while holding the elastic filaments 13 therebetween.

Thus, a laminate 19 is obtained in which the elastic filaments 13 are sandwiched between the two original nonwoven fabrics 11' and 12'. When the nonwoven fabrics 11' and 12' are originally stretchable, this laminate 19 becomes the elastic sheet 10 itself. On the other hand, when the raw nonwoven fabrics 11 ′ and 12 ′ are originally non-extensible, the laminate 19 including the raw nonwoven fabrics 11 ′ and 12 ′ is stretched so that the elastic filaments 13 are stretched. An operation is performed to impart stretchability to the laminate 19 by subjecting it to elasticity development treatment along the direction. In this manufacturing method, this operation is performed by using an elasticity development processing device 22 equipped with a pair of tooth groove rolls 20 and 21 each having teeth and tooth bottoms alternately formed in the circumferential direction, and the laminate 19 is transported in the conveying direction. That is, the elastic filament 13 is subjected to elastic development treatment along the extending direction.

The elasticity developing device 22 has a known elevating mechanism (not shown) for vertically displacing the pivots of one or both of the tooth gap rolls 20, 21, and the gap between the tooth gap rolls 20, 21 can be adjusted. It has become. In this manufacturing method, the teeth of one tooth space roll 20 are loosely inserted between the teeth of the other tooth space roll 21, and the teeth of the other tooth space roll 21 are inserted into the teeth of one tooth space roll. The grooved rolls 20 are combined so as to be loosely inserted between the teeth of the grooved rolls 20, and the laminate 19 is inserted between the tooth grooved rolls 20 and 21 in that state and subjected to elastic development treatment.

The target stretchable sheet 10 is obtained by subjecting the laminate 19 to elastic development treatment by a pair of tooth groove rolls 20 and 21 . After passing through the tooth groove rolls 20 and 21, the obtained stretchable sheet 10 is quickly released from the stretched state in the conveying direction by its own shrinkage restoring force. As a result, the stretchable sheet 10 restores its length in the conveying direction. As a result, in the stretched state, the high stretch regions and the low stretch regions are alternately arranged in the direction in which the elastic filaments 13 extend.

As a result of various studies on the elasticity development treatment, the inventors of the present invention have found that depending on the conditions of the elasticity development treatment, the elastic filaments 13 may be unintentionally cut while the laminate 19 is being stretched. . Cutting of the elastic filaments 13 is an event that should be avoided as much as possible because it is a cause of impairing the stretchability and appearance of the intended stretchable sheet 10 . As a result of studies conducted by the present inventors to avoid this inconvenience, the strain rate of the laminate 19 in the elastic development treatment step should be controlled in order to successfully stretch the laminate 19 without unintentionally breaking the elastic filament 13. was found to be effective. The strain rate is the value obtained by dividing the amount of deformation per unit time by the original length, and its unit is s ⁻¹ . As a result of studies by the present inventors, it is preferable to set the strain rate of the laminate 19 to 200 s ⁻¹ or less in the elasticity development treatment step, in order to effectively suppress unintended breakage of the elastic filaments 13 . From this point of view, it is more preferable to set the strain rate of the laminate 19 to 180 s ^-1 or less, and more preferably to 150 s ^-1 or less. The lower the strain rate, the more desirable it is from the viewpoint of preventing breakage of the elastic filaments 13. On the other hand, in order to further increase air permeability, it is necessary to increase the strain rate and locally stretch the nonwoven fabric to a large extent. be. In order to locally apply a large amount of stretching to the nonwoven fabric, it is necessary to set the strain rate to 30 s ⁻¹ or more. From this point of view, the strain rate of the laminate 19 in the elasticity development treatment step is preferably 30 s ^-1 or more and 200 s ^-1 or less, more preferably 50 s ^-1 or more and 180 s ^-1 or less, and 80 s ^-1 or more and 150 s ^-1 or less is more preferable.

Calculation of the strain rate in the elasticity development treatment using the pair of tooth groove rolls 20 and 21 is performed by the method described in paragraph [0051] and FIG. 3 of JP-A-2016-151076. That is, let L be the length of the arc from the point where the nonwoven fabric and roll projections begin to contact to the point where the imaginary straight line connecting the centers of the rolls intersects the nonwoven fabric. The deformation time T is obtained by dividing the arc length L by the peripheral velocity Vc of the roll. Next, in a state where the tooth groove roll 20 and the tooth groove roll 21 are meshed, as shown in FIG. Let the partial draw ratio of a nonwoven fabric be the maximum draw ratio. Assuming that the nonwoven fabric does not slip, and that the convex portion 21A is positioned at the center L _C of the concave portion 20B, the maximum draw ratio is determined by It is obtained by dividing the distance between the edges 21D by the length of the original nonwoven fabric. The strain rate is determined as deformation rate/T=Vc/Vi·maximum draw ratio (times)/T. Vi is the feeding speed of the nonwoven fabric. In FIG. 4, each of the end sides 20D, 20E, 21D, and 21E is a side in the face width direction, and is indicated by a black circle for easy understanding of the position.

When the inventors of the present invention investigated in more detail the phenomenon in which the elastic filaments 13 are cut when the laminate 19 is subjected to the elasticity development treatment, the stress applied to both the original nonwoven fabrics 11' and 12' when the laminate 19 is stretched was found to be , is transmitted to the elastic filaments 13 through the fusion points between the elastic filaments 13 and the two original nonwoven fabrics 11' and 12'. Therefore, by reducing the stress applied to both original nonwoven fabrics 11' and 12' when the laminate 19 is stretched, the stress transmitted to the elastic filaments 13 can be reduced. From this point of view, it is advantageous to use the raw nonwoven fabrics 11' and 12' having a low maximum strength until breakage. From this point of view, it is preferable to use those having a maximum strength of 40 N/50 mm or less, more preferably 35 N/50 mm or less, and 30 N/50 mm or less. It is more preferable to use one. The lower the maximum strength value, the more effective it is in preventing the elastic filament 13 from breaking. From this point of view, it is preferable to use those having a maximum strength of 5 N/50 mm or more and 40 N/50 mm or less, and 10 N/50 mm or more and 35 N/50 mm or less as both raw nonwoven fabrics 11 ′ and 12 ′. More preferably, it is more preferable to use 15 N/50 mm or more and 30 N/50 mm or less.
The maximum strength mentioned above was measured under conditions of a strain rate of 3.3 s ⁻¹ . The reason why the maximum strength is measured at this strain rate is that the present inventor found that the elastic filament 13 is more likely to break when the strain rate increases. The maximum strength is measured with a rectangular test piece having a length of 50 mm along the stretch direction of the stretch sheet 10 and a length of 50 mm perpendicular to the stretch direction. The distance between the chucks of the tensile tester is set to 5 mm, and the strain rate is set to 3.3 s ⁻¹ for measurement.

In order to effectively prevent the elastic filaments 13 from being cut when the laminate 19 is subjected to the elasticity development treatment, as described above, both the original nonwoven fabrics 11' and 12' must have a maximum It is advantageous to use those with low strength. In other words, it is advantageous to use nonwoven fabrics with high extensibility as the original nonwoven fabrics 11' and 12'. From this point of view, it is preferable to use those having a maximum elongation in the machine direction of 100% or more, more preferably 120% or more, and 130% or more as both raw nonwoven fabrics 11 ′ and 12 ′. is more preferably used. The higher the maximum elongation value, the more effective it is in preventing the non-woven fabric from being cut. From this point of view, it is preferable to use those having a maximum elongation of 100% or more and 250% or less, more preferably 120% or more and 250% or less, as both raw nonwoven fabrics 11' and 12'. It is more preferable to use one having a content of 130% or more and 250% or less.
The maximum elongation mentioned above was measured under the condition of a strain rate of 0.03 s ^-1 . The maximum elongation is measured with a rectangular test piece having a length of 200 mm along the stretch direction of the stretch sheet 10 and a length of 50 mm perpendicular to the stretch direction. The distance between the chucks of the tensile tester is set to 150 mm, and the strain rate is set to 0.03 s ⁻¹ for measurement.

In order to effectively prevent the elastic filaments 13 from being cut when the laminate 19 is subjected to the elasticity development treatment, the raw nonwoven fabrics 11' and 12' should have a low initial tensile strength. As a result of investigations by the present inventors, it was found that is also effective. From this point of view, as both raw nonwoven fabrics 11 ′ and 12 ′, it is preferable to use those having a strength of less than 12 N / 50 mm at 5% elongation, more preferably 11 N / 50 mm or less, and 10 N /50 mm or less is more preferable. The lower the strength value at 5% elongation, the more effective it is in preventing the elastic filament 13 from breaking. From this point of view, it is preferable to use those having a strength of 3 N/50 mm or more and less than 12 N/50 mm at 5% elongation as both raw nonwoven fabrics 11 ′ and 12 ′, and 3 N/50 mm or more and 11 N/50 mm or less. and more preferably 3 N/50 mm or more and 10 N/50 mm or less.
The strength at 5% elongation was measured under a strain rate of 0.03 s ⁻¹ . The strength at 5% elongation is measured using a rectangular test piece having a length of 200 mm along the stretch direction of the stretch sheet 10 and a length of 50 mm perpendicular to the stretch direction. The distance between the chucks of the tensile tester is set to 150 mm, and the strain rate is set to 0.03 s ⁻¹ for measurement.

As described above, in order to effectively prevent the elastic filaments 13 from being cut when the laminate 19 is subjected to the elasticity-developing treatment, the raw nonwoven fabrics 11' and 12' should be made of highly extensible fibers. It is advantageous to use the configured. As such a nonwoven fabric, for example, a nonwoven fabric composed of unstretched fibers or fibers having a low draw ratio may be used. The type of nonwoven fabric is not particularly limited, and one manufactured by a known method can be used. For example, an air-through nonwoven fabric, a spunbond nonwoven fabric, a spunlaced nonwoven fabric, a meltblown nonwoven fabric, a needle-punched nonwoven fabric, or the like can be used.

In the stretch sheet of the present invention thus obtained, cutting of the elastic filaments is suppressed during the elasticity-developing treatment, so that the elastic filaments in the stretch sheet have fewer cut points. Specifically, in a non-stretched state of the stretch sheet, that is, in a natural state where no external force is applied to the stretch sheet, the number of cut points of the elastic filaments is preferably 2.0 points/cm or ^less , more preferably 1.0 points/cm2 or less. cm ² or less, more preferably 0.8 points/cm ² or less.

The stretchable sheet of the present invention has good stretchability due to the fact that the elastic filaments are cut at fewer places as described above. Specifically, the stretch sheet of the present invention exhibits a high elongation rate of preferably 120% or more, more preferably 130% or more, and still more preferably 150% or more, and also has high return strength when returned from the stretched state. indicate a value. This elongation rate is a value at the time of 3N/50mm load. A specific measuring method is as follows. A rectangular test piece having a length of 200 mm along the stretch direction of the stretch sheet 10 and a length of 50 mm perpendicular to the stretch direction is measured. The chuck-to-chuck distance of the tensile tester is set to 150 mm, and the strain rate is set to 0.03 s ⁻¹ . The elongation when the strength of the test piece reaches 3 N/50 mm is taken as the elongation rate.

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the scope of the invention is not limited to such examples. "%" means "% by mass" unless otherwise specified.

[Example 1]
(1) Preparation of elastic filament SEPS was used as an elastic filament.

(2) Preparation of raw nonwoven fabric Two spunbond nonwoven fabrics having a basis weight of 18 g/m ² and made of polypropylene fibers were prepared. The specifications of the raw nonwoven fabric are shown in Table 1 below.

(3) Manufacture of stretch sheet The stretch sheet having the structure shown in Fig. 1 and Figs. 2(a) and 2(b) was manufactured using the apparatus shown in Fig. 3 . The elastic filament 13 had a diameter of 120 μm.
The elasticity development treatment was performed using an elasticity development treatment device 22 having a pair of tooth groove rolls 20 and 21 in which teeth and tooth bottoms were alternately formed in the axial direction. The pushing amount of the upper and lower tooth groove rolls was adjusted, and the laminate 19 was subjected to elasticity developing treatment in the direction in which the elastic filaments 13 extend at a draw ratio of 6.6 times. The strain rate at this time was as shown in Table 1. As a result, a stretchable sheet 10 that stretches in the direction in which the elastic filaments 13 extend was obtained.

[Examples 2 and 3]
The raw nonwoven fabric shown in Table 1 was used. A stretch sheet was obtained in the same manner as in Example 1 except for this.

[Comparative Example 1]
The raw nonwoven fabric shown in Table 1 was used. Also, the strain rate was set as shown in the same table. A stretch sheet was obtained in the same manner as in Example 1 except for these.

[Comparative Example 2]
In Comparative Example 1, the strain rate was set as shown in Table 1. A stretch sheet was obtained in the same manner as in Comparative Example 1 except for this.

〔evaluation〕
With respect to the stretch sheets obtained in Examples and Comparative Examples, measurement of elastic filament cut points, and width _WH of the high elongation region and width _WL of the low elongation region were performed by the following methods. Furthermore, air permeability was measured by the method described above. Those results are shown in Table 1.

[Cut portion of elastic filament]
With the stretch sheet stretched 2.2 times, the elastic filaments were observed using a magnifying glass in the entire area of 5 cm width×15 cm length, and the number of cut points of the elastic filaments was counted. A value was calculated by dividing the total number of cut points by the measured area (5×15 cm 2 ).

[Width W _H of high elongation region and width W _L of low elongation region]
The stretchable sheet was stretched 2.2 times in the stretching direction and photographed at a magnification of 30 times. Ten high elongation regions and ten low elongation regions were arbitrarily selected, and the width along the elongation direction was measured. The arithmetic mean value of the measurement results of 10 points was used as the width _WH of the high elongation region and the width _WL of the low elongation region.

As is clear from the results shown in Table 1, the stretch sheets obtained in each example had less elastic filament breakage and had higher stretchability than the stretch sheets obtained in the comparative examples. I understand. In addition, it can be seen that the stretch sheets obtained in Examples are superior in breathability to the stretch sheets obtained in Comparative Examples.

10 elastic sheet 11 first nonwoven fabric 11' first original nonwoven fabric 12 second nonwoven fabric 12' second original nonwoven fabric 13 elastic filament 14 low density region 14' crest 14'' valley 15 high density region 15' ridge Department

Claims (11)

contacting elastic filaments in a fusible state with a nonwoven fabric to form a laminate in which the elastic filaments are fused to the nonwoven fabric;
A method for producing a stretchable sheet for absorbent articles, comprising a step of stretching the laminate and subjecting it to elasticity development treatment,
The nonwoven fabric used has a maximum strength of 40 N/50 mm or less under conditions of a strain rate of 3.3 s ^-1 ,
A method for producing a stretchable sheet for absorbent articles, wherein the laminate is stretched at a strain rate of 30 s ⁻¹ or more and 200 s ⁻¹ or less in the elasticity development treatment step. 2. The manufacturing method according to claim 1, wherein the nonwoven fabric has a maximum strength of 35 N/50 mm or less at a strain rate of 3.3 s ⁻¹ . contacting elastic filaments in a fusible state with a nonwoven fabric to form a laminate in which the elastic filaments are fused to the nonwoven fabric;
A method for producing a stretchable sheet for absorbent articles, comprising a step of stretching the laminate and subjecting it to elasticity development treatment,
Using a nonwoven fabric having a strength of less than 12 N/50 mm at 5% elongation,
A method for producing a stretchable sheet for absorbent articles, wherein the laminate is stretched at a strain rate of 30 s ⁻¹ or more and 200 s ⁻¹ or less in the elasticity development treatment step. 4. The manufacturing method according to claim 3, wherein the nonwoven fabric has a strength of 10 N/50 mm or less at 5% elongation. The manufacturing method according to any one of claims 1 to 4, wherein the nonwoven fabric has a maximum elongation of 100% or more in the machine direction. The manufacturing method according to any one of claims 1 to 5, wherein the nonwoven fabric has a maximum elongation in the machine direction of 120% or more and 250% or less. The manufacturing method according to any one of claims 1 to 6, wherein the laminate is stretched at a strain rate of 80 s ^-1 or more and 180 s ^-1 or less in the elasticity development treatment step. A stretch sheet for absorbent articles, wherein a plurality of elastic filaments arranged so as to extend in one direction without intersecting each other are joined to an extensible nonwoven fabric over their entire lengths in a substantially unstretched state,
The stretchable sheet has an elongation rate of 120% or more at a load of 3N/50mm,
In the stretch sheet, the number of cut points of the elastic filaments is 2.0 points/cm ² or less in a non-stretched state of the stretch sheet,
High-stretch regions and low-stretch regions extending in a direction orthogonal to the stretch direction of the stretch sheet are alternately arranged along the stretch direction, and the stretch direction along the stretch direction when stretched 2.2 times. A stretch sheet for absorbent articles, wherein the ratio W _H /W _L of the width W _H of the high elongation region along the stretch direction to the width W _L of the low elongation region is 10 or less. 9. The stretchable sheet for absorbent articles according to claim 8, wherein the number of cut points of the elastic filaments in the stretchable sheet is 1.0 points/cm ² or less in a non-stretched state of the stretchable sheet. A stretchable sheet for absorbent articles manufactured by the method according to any one of claims 1 to 7. A nonwoven fabric having a maximum strength of 40 N/50 mm or less under conditions of a strain rate of 3.3 s ^-1 ,
A raw nonwoven fabric that is joined with elastic filaments and used to produce stretch sheets.

Images