CN109640909B

CN109640909B - Spunbonded nonwoven fabric, sheet, and absorbent article

Info

Publication number: CN109640909B
Application number: CN201780051057.6A
Authority: CN
Inventors: 神野文夫; 徐晓师
Original assignee: Oji Holdings Corp
Current assignee: Oji Holdings Corp
Priority date: 2016-08-23
Filing date: 2017-08-21
Publication date: 2022-05-24
Anticipated expiration: 2037-08-21
Also published as: JP6406478B2; TWI687564B; CN109640909A; RU2719524C1; TW201812131A; JP2019049089A; JP6820890B2; JPWO2018038053A1; WO2018038053A1; JP2020022759A

Abstract

The spunbonded nonwoven fabric uses fibers of thermoplastic resin, wherein the nonwoven fabric has the following specified water resistance: when the water pressure resistance is repeatedly measured according to ISO811, the decrease of the second water pressure resistance measured for the second time or later relative to the first water pressure resistance measured for the first time is less than or equal to a predetermined pressure, and the first water pressure resistance is 160mmH₂O or more, and a predetermined pressure of 30mmH₂O or less.

Description

Spunbonded nonwoven fabric, sheet, and absorbent article

Technical Field

The present application relates to an absorbent article such as a disposable diaper, a sanitary napkin and the like, a suitable sheet material used therein, and a suitable spunbond nonwoven fabric used therein.

Background

Conventionally, an absorbent article is provided with a water-resistant sheet that can withstand a predetermined water pressure in addition to an absorbent pad that can absorb liquid such as urine and menstrual blood excreted by a wearer. The sheet is provided in the three-dimensional gathers, the outer edge portion thereof, or the like, and thereby liquid leakage of the absorbent article can be suppressed.

As one of the water-resistant sheets, a meltblown nonwoven fabric is used. Meltblown nonwoven fabrics have small meshes and are not easily penetrated by moisture, but have low strength. On the other hand, a spunbonded nonwoven fabric, which is one of the other types of nonwoven fabrics, has a higher strength, though moisture is easily transmitted, because the mesh is larger than the meltblown nonwoven fabric.

Water-resistant sheets have been developed in which meltblown nonwoven fabrics are reinforced with spunbond nonwoven fabrics. For example, it has been studied to use an SMS nonwoven fabric 40 as a water-resistant sheet, in which the SMS nonwoven fabric 40 is reinforced with a meltblown nonwoven fabric 42 by sandwiching the meltblown nonwoven fabric 42 between two layers of spunbonded

nonwoven fabrics

41,41 as shown in fig. 3A, and the meltblown nonwoven fabric 42 is reinforced with the spunbonded

nonwoven fabrics

41,41 as shown in fig. 3B (see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-66308

Disclosure of Invention

Problems to be solved by the invention

However, in the SMS nonwoven fabric, when the meltblown nonwoven fabric layer is broken, the water pressure resistance of the sheet is significantly reduced to a water pressure resistance corresponding to the mesh of the spunbond nonwoven fabric layer. Therefore, if high water pressure is repeatedly applied to a water-resistant sheet using an SMS nonwoven fabric in an absorbent article, leakage may not be suppressed. Therefore, there is room for improvement in ensuring comfort for the wearer.

The absorbent article, the sheet suitable for use therein, and the spunbonded nonwoven fabric suitable for use therein according to the present application are inventions made in view of the above-described problems, and one of the objects is to ensure comfort for the wearer.

It should be noted that the present invention is not limited to the object described herein, and other objects of the present invention are also directed to the effects and effects derived from the respective configurations described in the following "detailed description of the invention", that is, the effects and effects that cannot be obtained by the conventional techniques.

Means for solving the problems

As a result of intensive studies to solve the above-described problems, the inventors of the present application have found that an absorbent article can ensure comfort for a wearer from a new viewpoint of imparting a predetermined water resistance to a spunbond nonwoven fabric used for a sheet, rather than a conventional viewpoint of imparting water resistance to a meltblown nonwoven fabric used for a sheet.

(1) Use of the spunbonded nonwovens disclosed hereinFibers of thermoplastic resins. The spunbonded nonwoven fabric has the following specified water resistance: when the water pressure resistance is repeatedly measured in accordance with ISO811, the amount of decrease in the second and subsequent measurements of the second water pressure resistance relative to the first water pressure resistance measured at the first time is equal to or less than a predetermined pressure. In addition, the first water-resistant pressure is 160mmH₂O or more, and the above predetermined pressure is 30mmH₂O or less. The predetermined water resistance means a property of continuously satisfying the water pressure resistance required for the sheet.

(2) Preferably, the average fineness of the fibers is 0.1 to 1.0 denier, and the weight per unit area of the spunbonded nonwoven fabric is 8 to 20g/m²。

(3) The thermoplastic resin is preferably a polyolefin resin containing polypropylene.

(4) The polyolefin resin preferably satisfies the following < characteristics a > to < characteristics h >.

< characteristic a > the meso pentad fraction is 30 to 80 mol%.

If the meso pentad fraction is "A" and the racemic pentad fraction is "B", the inequality I "B/(1-A) ≦ 0.1" is satisfied.

< property c > rac-meso-rac-meso pentad fraction is more than 2.5 mol%.

<Characteristic d>When the meso triad fraction is "C", the racemic triad fraction is "D" and the triad fraction is "E", the inequality II "C × D/E" is satisfied²≦2.0”。

< Property e > the weight-average molecular weight is 10000-200000.

< characteristic f > when the weight-average molecular weight is "Mw" and the number-average molecular weight is "Mn", inequality III "Mw/Mn ≦ 4" is satisfied.

< property g > the amount of the extract extracted with boiling diethyl ether is 0 to 10 mass%.

< property h > the low crystalline polyolefin resin satisfying the above < properties a > to < property g > is 5 to 50 mass% based on the total solid content.

(5) The sheet disclosed herein preferably comprises the spunbond nonwoven described above but does not comprise a meltblown nonwoven. That is, the sheet is preferably composed of only the above spunbonded nonwoven fabric.

(6) In the sheet, the area ratio of the embossed portion where the fibers are fused to each other is preferably 5 to 25%.

(7) The sheet is preferably formed by overlapping two or more sheets.

(8) In the absorbent article disclosed herein, the sheet is preferably disposed on the skin surface side.

(9) In the absorbent article of the present invention, the sheet is preferably used for a three-dimensional gather standing on the skin surface side.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the absorbent article of the present application, the spunbonded nonwoven fabric used for the sheet has a predetermined water resistance, and thus, the liquid excreted by the wearer can be prevented from passing through the sheet, and leakage can be prevented. This ensures comfort for the wearer.

Drawings

Fig. 1 is a partial sectional view of a diaper (absorbent article) broken in a crotch portion.

Fig. 2 is a perspective view schematically showing a sheet of spunbond nonwoven fabric.

In fig. 3, fig. 3A and 3B are perspective views schematically showing a sheet of the SMS nonwoven fabric, fig. 3A shows a state in which nonwoven fabric layers are separated from each other, and fig. 3B shows a state in which nonwoven fabric layers are laminated.

Detailed Description

An absorbent article according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications and technical applications that are not explicitly described in the embodiments below. The respective configurations of the present embodiment can be implemented by being variously modified within the scope not departing from the gist thereof. Further, they may be selected as necessary or may be appropriately combined.

The absorbent article of the present embodiment is a sanitary product to be worn by a wearer to absorb liquid such as urine or menstrual blood. Examples of the absorbent article include a tape-type or pants-type diaper (so-called "disposable diaper"), a diaper, a sanitary napkin, and a panty liner. In the following embodiments, a tape-type diaper is shown as an example of the absorbent article.

In the present embodiment, the diaper is configured such that the direction connecting the front body positioned on the abdomen and the back body positioned on the back of the wearer is the longitudinal direction, the side facing the skin of the wearer (the inner side in the worn state) is the skin surface side, and the opposite side to the skin surface side (the outer side in the worn state) is the non-skin surface side. The direction connecting the skin surface side and the non-skin surface side is defined as the thickness direction, and the direction perpendicular to both the longitudinal direction and the thickness direction is defined as the width direction.

In the present embodiment, the notation "a numerical value X to a numerical value Y" means "not less than the numerical value X and not more than the numerical value Y" unless otherwise specified.

[ I. one embodiment ]

[1. paper diaper ]

First, the basic structure of the disposable diaper will be described with reference to fig. 1. Here, the structure of the crotch portion 1 of the diaper which is positioned in the crotch of the wearer will be mainly described.

The crotch portion 1 of the diaper is located at the center in the longitudinal direction. The crotch unit 1 is provided with an absorbent body 10 on the inner side in the width direction, and a side sheet (sheet) 20 on the skin surface side on the outer side in the width direction.

The absorbent body 10 is a liquid-absorbent element composed of a plurality of sheet-like or pad-like members. In this absorbent body 10, a top sheet (also referred to as a "center sheet") 13 is disposed on the skin surface side and a back sheet 14 is disposed on the non-skin surface side with respect to an absorbent pad (also referred to as a "core") 12 wrapped (covered) with a cover sheet 11. The non-skin surface side of the absorbent body 10 (i.e., the non-skin surface side of the back sheet 14) is covered with a cover sheet 15.

In the absorbent body 10, the cover sheet 11 and the top sheet 13 have a property of transmitting liquid (liquid permeability) in order for the absorbent pad 12 to absorb liquid excreted by the wearer. On the other hand, the back sheet 14 and the cover sheet 15 have a property of not transmitting liquid (liquid-impermeable property) in order to prevent leakage of liquid absorbed by the absorbent pad 12.

In addition, in order to improve the fit of the diaper to the wearer, the diffusion of liquid discharged into the absorbent body 10, the air permeability of the diaper, and the like, the groove-like pattern 2 is provided in the absorbent body 10.

The side sheet 20 is a sheet-like member provided to prevent leakage of the diaper. Therefore, the side sheet 20 also has liquid impermeability. The side sheet 20 has a prescribed water resistance as described in detail below.

Here, each end portion in the width direction and a peripheral portion thereof (hereinafter referred to as "end edge portion") in the side sheet 20 are provided with gathers 21,22 in the longitudinal direction. In the side sheet 20, a three-dimensional gather 21 standing toward the skin surface side is formed at the end edge portion on the inner side in the width direction, and a leg gather 22 projecting toward the outer side in the width direction is formed at the end edge portion on the outer side in the width direction.

The three-dimensional gathers 21 are provided to prevent leakage of excreted liquid to the outside in the width direction.

In the three-dimensional gather 21, the

sheet portions

20a,20b located at the end edge portions on the inner side in the width direction of the side sheet 20 are folded and overlapped, and the first rubber thread (elastic member) 31 extending in the longitudinal direction is surrounded by these

sheet portions

20a,20 b. In other words, in the side sheet 20, the inner wall sheet portion 20a is disposed on the inner side in the width direction with respect to the first rubber wire 31, and the outer wall sheet portion 20b is disposed on the outer side in the width direction with respect to the first rubber wire 31. Therefore, the two

sheet portions

20a,20b overlap at a portion of the side sheet 20.

In this way, by incorporating the first rubber thread 31 in the position where the

sheet portions

20a,20b of the side sheet 20 are folded and overlapped, the three-dimensional gather 21 standing on the skin surface side and generating wrinkles is formed.

The leg gathers 22 are provided to improve the conformability to the legs of the wearer and to improve the comfort.

In the leg gathers 22, the outer sheet portion 20c located at the widthwise outer end edge of the side sheet 20 overlaps the outer sheet portion 15c located at the widthwise outer end edge of the cover sheet 15, and the second rubber threads (elastic members) 32 extending in the longitudinal direction are surrounded by these

outer sheet portions

20c,15 c.

In this way, by incorporating the second rubber thread 32 in the position where the side sheet 20 and the

outer sheet portions

20c,15c of the cover sheet 15 overlap, the leg gathers 22 that protrude outward in the width direction and are wrinkled are formed.

[2. side sheet ]

Next, the detailed structure of the side sheet 20 will be described.

The side sheet 20 is formed of a spunbond nonwoven fabric using only fibers of a thermoplastic resin. Therefore, the side sheet 20 does not include: a nonwoven fabric including a meltblown layer (meltblown nonwoven fabric) such as an SMS nonwoven fabric or SMMS nonwoven fabric, or a meltblown nonwoven fabric including only a meltblown layer.

The spunbonded nonwoven fabric refers to a sheet-like member obtained by dissolving a thermoplastic resin as continuous fibers and collecting the obtained spun yarn. In the spun-bonded nonwoven fabric, the collected filaments are each formed into long fibers. Here, the spunbond nonwoven fabric is subjected to embossing processing for fusing the fibers to each other by either or both of heating and pressing.

Specific production methods of the spunbonded nonwoven fabric are as exemplified below.

First, a long fiber group composed of spun fibers discharged in a molten state of a thermoplastic resin is introduced into an air suction pipe, stretched and opened, and gathered on a conveyor belt to obtain a fiber web. Next, the long fiber groups forming the web are joined to each other by embossing. For example, an uneven pattern regularly arranged in the flow direction of the conveyor belt and in the direction orthogonal thereto is imparted to the web by an emboss roller having an uneven pattern formed on the outer periphery thereof corresponding to the uneven pattern. The embossed web was thus produced as a spunbond nonwoven fabric.

The meltblown nonwoven fabric is a sheet-like member obtained by spraying a molten thermoplastic resin in a spray form and collecting short fibers produced. The meltblown nonwoven fabric has a lower strength than the spunbond nonwoven fabric, and tends to have a smaller mesh.

The side sheet 20 will be described in detail below in the order of structural configuration and chemical configuration.

[2-1. Structure constitution ]

As shown in fig. 2, the side sheet 20 of the present embodiment can suppress a decrease in strength and can provide a predetermined water resistance by using a spunbond nonwoven fabric having a small mesh which is manufactured using a high density of small diameter fibers having a diameter smaller than that of fibers used in a conventional spunbond nonwoven fabric (see reference numeral 41 in fig. 3). That is, the water resistance of the side sheet 20 is secured by the spunbond nonwoven fabric constituting the side sheet 20. Therefore, the spunbonded nonwoven fabric has a predetermined water resistance.

The predetermined water resistance as used herein means a physical property that continuously satisfies the water pressure resistance required for the side sheet 20 when water pressure is repeatedly applied.

Since the spunbonded nonwoven fabric used in the side sheet 20 can secure strength, the reduction or variation of the water pressure resistance can be suppressed even when the water pressure is repeatedly applied, and thus the water pressure resistance is improved. In other words, the side sheet 20 made of the spunbonded nonwoven fabric has a strength more secured than, for example, a nonwoven fabric including a meltblown layer, is less likely to be broken by the applied water pressure, and is likely to maintain a water pressure resistance corresponding to the "mesh". Therefore, even if the water pressure is repeatedly applied, the water pressure resistance is not easily lowered.

The predetermined water resistance described above corresponds to the "water pressure resistance" of the spunbonded nonwoven fabric, and also corresponds to the "mesh" and the "area ratio of the embossed portion (hereinafter, simply referred to as" embossed area ratio ") of the spunbonded nonwoven fabric.

Here, the spunbonded nonwoven fabric used in the side sheet 20 will be described with respect to "water pressure resistance", "mesh", and "embossed area ratio".

< Water pressure resistance >

"Water pressure resistance" refers to the upper limit of water pressure that can be tolerated. Specifically, the upper limit value of the water surface height of the spunbond nonwoven fabric, which is not penetrated by water fed into the bottomless cylinder provided in the spunbond nonwoven fabric, is "water pressure resistance".

Specifically, a spunbond nonwoven fabric satisfying the following conditions is used for the side sheet 20: when the water pressure resistance is repeatedly measured in accordance with ISO811, a second water pressure resistance P measured for the second time or later is measured₂Relative to the first water pressure resistance measured at the first timeP₁The reduction amount of (2) is a predetermined pressure P_PThe following.

First water pressure resistance P₁And the first water resisting pressure P₁Minus a predetermined pressure P_PAnd a second prescribed pressure P is obtained₂More than the water pressure required for preventing leakage of the discharged liquid. The water pressure may be 130mmH₂O。

First water resistance pressure P here₁Is set to 160mmH₂O or more. The first water pressure resistance P is set to prevent leakage reliably₁Preferably 170mmH₂O or more, more preferably 180mmH₂O or more.

In addition, a predetermined pressure P_PIs set to 30mmH₂O or less. The predetermined pressure P is set to maintain the leakage prevention performance_PPreferably 20mmH₂O or less, more preferably 10mmH₂O or less.

Thus, the second water pressure resistance P₂Is set to at least 130(═ 160-30) mmH₂O or more, preferably 140(═ 170-30 ═ 160-20) mmH₂O or more, and more preferably 150(═ 180-30 ═ 170-20 ═ 160-10) mmH₂O or more. Further, the second water pressure resistance P₂Still more preferably 160(═ 180-20 ═ 170-10) mmH₂O or more, and even more preferably 170(═ 180-10) mmH₂O or more.

< mesh >

"mesh" is a parameter indicating the size of pores (fine pores) in the spunbonded nonwoven fabric. Therefore, if the "mesh" is small, the liquid is not easily penetrated, whereas if the "mesh" is large, the liquid is easily penetrated. Further, the smaller the "mesh" is, the higher the "water pressure resistance" is.

However, since the spunbond nonwoven fabric is stretched and the "mesh" is increased as the water pressure applied to the side sheet 20 is increased, the size of the "mesh" strictly speaking corresponds to the height of the "water pressure resistance" and is not linear (linear). In addition, the size of the pores of the spunbond nonwoven fabric is not uniform and is discrete. Therefore, it is difficult to directly use "mesh" as a parameter corresponding to "water pressure resistance".

Therefore, in the parameters corresponding to the "mesh", the "fineness" and the "weight per unit area" which do not vary regardless of whether the water pressure applied to the side sheet 20 is high or low are used.

"fineness" is a parameter corresponding to the fiber diameter (thickness) and cross-sectional area of the fiber, and is expressed by weight per predetermined length. Here, for one fiber, grams per 9000m [ denier ] is used as "fineness". Therefore, the smaller the "fineness" of the spunbonded nonwoven fabric, the smaller the fiber diameter.

Since the spunbond nonwoven fabric has a variation in fiber diameter, the average value of the "fineness" of the fibers is used as a parameter. Therefore, the average value of the "fineness" of the fibers is simply referred to as "fineness".

The "weight per unit area" is a parameter corresponding to the thickness or the degree of lamination of the nonwoven fabric, and is expressed as a weight per unit area. Here, the number of grams per square meter is taken as "weight per unit area".

The smaller the "fineness" is, the smaller the fiber diameter is and the more the number of fibers (the number of fibers) is increased, and thus the smaller the "mesh" is, in the same "basis weight". In addition, the larger the "weight per unit area" is, the larger the number of fibers increases, and thus the smaller the "mesh" is, with the same "fineness".

The side sheet 20 of the present embodiment has a "fineness" of 0.1 to 1.0 denier and a "weight per unit area" of 8 to 20g/m²A spunbonded nonwoven fabric.

When the "fineness" is less than 0.1 denier, the strength of the fiber decreases and the fiber diameter decreases, thereby decreasing the spinnability of the fiber. On the other hand, if the "fineness" is larger than 1.0 denier, the fiber diameter increases, and thus the "mesh" easily increases. The "fineness" is preferably 0.2 to 0.8 denier, more preferably 0.4 to 0.6 denier, from the viewpoint of ensuring spinnability of the fiber and suppressing "mesh".

The weight per unit area is less than 8g/m²In this case, the thickness and strength may be reduced, and the formation of the spunbond nonwoven fabric may be reduced. On the other hand, the "weight per unit area" is greater than 20g/m²Thickness, strengthThe degree increases, and the touch (skin touch) of the spunbonded nonwoven fabric may decrease. The "weight per unit area" is preferably 10 to 18g/m from the viewpoint of compatibility between the formation property and the touch of the spunbonded nonwoven fabric²More preferably 12 to 16g/m²。

By setting the "fineness" and the "basis weight" within the above-described predetermined ranges, the strength of the side sheet 20 of the spunbonded nonwoven fabric is suppressed from being reduced, and the "mesh" can be reduced by providing fibers finer than those of conventional spunbonded nonwoven fabrics at a high density. This enables the spunbonded nonwoven fabric used in the side sheet 20 to secure a predetermined water resistance.

< embossed area Rate >

The "embossed area ratio" is the ratio of the total planar area of the embossed portion of the spunbond nonwoven relative to the overall planar area. Here, when the total planar area of the spunbond nonwoven fabric is "S1" and the total planar area of the embossed portions is "S2", the percentage of "S1" to "S2" (which is ═ S1/S2> × 100) is defined as "embossed area ratio".

The side sheet 20 of the present embodiment uses a spunbonded nonwoven fabric having an "embossed area ratio" of 5 to 25%.

When the "embossed area ratio" is less than 5%, the spunbond nonwoven fabric is likely to be fluffed, and the shape-fixing property of the side sheet 20 may be lowered. On the other hand, if the "embossed area ratio" is larger than 25%, the strength or rigidity of the side sheet 20 may be increased, and the tactile sensation may be lowered. The "embossed area percentage" is preferably 6 to 20% in terms of compatibility between the shape-fixing property and the touch of the side sheet 20. The greater the "embossed area ratio", the higher the water pressure resistance of the spunbonded nonwoven fabric tends to be.

< others >

As the side sheet 20 of the present embodiment, a spunbond nonwoven fabric in which fibers are oriented in a specific direction may be used, or a spunbond nonwoven fabric in which fibers are irregularly oriented may be used.

When the former spunbonded nonwoven fabric is used, the degree of freedom in designing the absorbent article can be improved because the strength and rigidity (anisotropy) in a specific direction can be ensured. In the case of using the latter spunbonded nonwoven fabric, variations in strength and rigidity (isotropy) can be suppressed, and therefore, the side sheet 20 can be disposed without taking the orientation into consideration, contributing to improvement in the manufacturing workability of the absorbent article.

[2-2. chemical constitution ]

Next, the chemical structure of the side sheet 20 of the spunbonded nonwoven fabric will be described. The chemical constitution described hereinafter is a preliminary example for suppressing the diameter of the fibers used in the spunbond nonwoven fabric constituting the side sheet 20 while ensuring the spinnability of the fibers.

The spunbond nonwoven fabric constituting the side sheet 20 uses a polyolefin resin as fibers. The polyolefin resin contains polypropylene (PP). The polyolefin resin referred to herein may contain Polyethylene (PE).

The polypropylene is roughly classified into low-crystalline polypropylene (low-crystalline polyolefin resin) having a melting point of less than 100 ℃ and high-crystalline polypropylene (high-crystalline polyolefin resin) having a melting point of 100 ℃ or higher. Examples of the highly crystalline polypropylene include propylene homopolymers, propylene random copolymers, propylene block copolymers, and the like. The low-crystalline polypropylene is described in detail in the following item [2-2-2 ].

[2-2-1. polyolefin resin ]

The melt flow rate (also referred to simply as "MFR") of the polyolefin resin is preferably 20 to 100g/10 min. The melt flow rate is one of the criteria indicating the fluidity of a resin in a solution state, and the higher the value of the melt flow rate is, the higher the fluidity and the moldability are, but the tensile strength tends to decrease.

When the melt flow rate is less than 20g/10 min, the spinnability into the fiber from the polyolefin resin may be reduced. On the other hand, when the melt flow rate is more than 100g/10 min, the touch of the side sheet 20 made of the spunbonded nonwoven fabric molded from the polyolefin resin may be reduced. Therefore, the melt flow rate of the polyolefin resin is more preferably 20 to 90g/10 min, particularly preferably 20 to 80g/10 min, from the viewpoint of ensuring the spinnability and the touch.

Further, other thermoplastic resins or additives may be mixed in the polyolefin resin used.

The other thermoplastic resin contains an olefin polymer. Examples of the olefin-based polymer include a propylene-ethylene copolymer, a propylene-ethylene-diene copolymer, an ethylene/α -olefin copolymer, an ethylene-vinyl acetate copolymer, and a hydrogenated styrene-based elastomer. These may be used alone or in combination of two or more.

Examples of the additives include conventionally known additives such as a lubricant, a foaming agent, a crystal nucleating agent, a weather resistant stabilizer, an ultraviolet absorber, a light stabilizer, a heat resistant stabilizer, an antistatic agent, a spun-bond adhesive, a flame retardant, a synthetic oil, a wax, an electrical property improving agent, an anti-slip agent, an anti-blocking agent, a viscosity modifier, an anti-coloring agent, an anti-fogging agent, a pigment, a dye, a plasticizer, a softener, an anti-aging agent, a hydrochloric acid absorbent, a chlorine trapping agent, an antioxidant, and a spun-bonding agent.

[2-2-2. Low-crystallinity Polypropylene ]

The chemical structure of the low-crystalline polypropylene used will be described in detail below.

First, the basic stereoregularity (sequence) of the low-crystalline polypropylene to be used will be described. Here, the steric regulation of a diad in which two side chain methyl groups are arranged in the same direction is referred to as "meso" < m ", and the steric regulation of a diad in which two side chain methyl groups are arranged in different directions is referred to as" rac "< r". In addition, the stereoregularity in which two dyads are aligned is referred to as a triad sequence, and the stereoregularity in which three dyads are aligned is referred to as a pentad sequence.

Examples of the triad sequence include meso triad < mm >, racemic triad < rr >, and triad < mr >. The meso triad is the stereorule that two meso triads are side-by-side, the racemic triad is the stereorule that two racemic triads are side-by-side, and the triads are the stereorule that meso and racemic sequences are arranged.

Examples of the pentad sequence include meso pentad < mmmm >, racemic pentad < rrrr >, racemic-meso-racemic-meso pentad < rmrm >. The meso pentad is a three meso side-by-side steric rule, the racemic pentad is a three racemic side-by-side steric rule, and the rac-meso-rac-meso pentad is a steric rule in which the rac, meso, rac, and meso are arranged in this order.

The proportions (percentages herein) of the various stereoregularity in the low-crystalline polypropylene used are defined by the names "+" fraction "(% by mole)" of the "stereoregularity" names. For example, in the low-crystalline polypropylene used, the proportion of meso pentads is the meso pentads, and the proportion of rac-meso-rac-meso pentads is the rac-meso-rac-meso pentads.

Examples of the low-crystalline polypropylene to be used include crystalline polypropylene having slightly disturbed stereoregularity. Specifically, low-crystalline polypropylene satisfying the following < characteristics a > to < characteristics h > is preferably used.

< Property a > meso five-unit fraction

The meso pentad fraction is preferably 30 to 80 mol%.

If the meso pentad fraction is less than 30 mol%, the low-crystalline polypropylene may be slowly solidified after melting, and the moldability of the fiber may be lowered. On the other hand, if the meso pentad fraction is more than 80 mol%, the crystallinity of the low-crystalline polypropylene becomes too high, and therefore the fibers are likely to be broken, and the moldability of the fibers may be lowered. Therefore, the meso pentad fraction is preferably 40 to 70 mol%, more preferably 50 to 60 mol%, from the viewpoint of ensuring the moldability of the fiber.

< Property b > ratio of meso pentad fraction to racemic pentad fraction

When the meso pentad fraction is "a" and the racemic pentad fraction is "B", inequality I "B/(1-a) ≦ 0.1" is preferably satisfied.

The left side of the inequality I can be used as an index indicating the uniformity of the regularity distribution of the low crystalline polypropylene, and if this value is increased, it becomes a cause of stickiness. Therefore, from the viewpoint of reliably suppressing the stickiness, it is more preferable to satisfy the inequality I ' ″ B/(1-a) ≦ 0.05 ', and it is particularly preferable to satisfy the inequality I ″ ' B/(1-a) ≦ 0.04 ".

< Property c > rac-meso-rac-meso pentad fraction

The rac-meso-rac-meso pentad fraction is preferably more than 2.5 mol%.

When the number of the rac-meso-rac-meso pentad is 2.5 mol% or less, the randomness of the low-crystalline polypropylene is reduced, and the crystallinity is increased by crystallization of the isotactic polypropylene block chain. Thus, the fibers are easily broken, and the formability of the fibers may be reduced. Therefore, from the viewpoint of ensuring the moldability of the fiber, the rac-meso-rac-meso pentad fraction is preferably more than 2.6 mol%, more preferably more than 2.7 mol%.

The upper limit of the number of the rac-meso-rac-meso pentad is usually about 10 mol%. Therefore, the number of the rac-meso-rac-meso pentad is preferably 10 mol% or less.

< Property d > ratio of meso triad fraction, racemic triad fraction and triad fraction

When the meso triad fraction is "C", the racemic triad fraction is "D", and the triad fraction is "E", the inequality II "CxD/E" is preferably satisfied²≦2.0”。

The left side of inequality II can be used as an index for expressing the randomness of the polymer, and the smaller the value, the more the randomness tends to increase. Further, since the higher the randomness of the polymer, the less the fibers are broken and the more the stickiness is suppressed, it is more preferable to satisfy the inequality II' ″ 0.2 ≦ C × D/E from the viewpoint of suppressing the randomness to be too high, securing the formability of the fibers, and suppressing the stickiness at the same time²2.0 ≦ C × D/E, and particularly preferably satisfies inequality II "" 0.25 ≦ C × D/E²≦1.8”。

< Property e > weight average molecular weight

The low-crystalline polypropylene used preferably has a weight-average molecular weight of 10000 to 200000.

When the weight average molecular weight is less than 10000, the viscosity of the low-crystalline polypropylene is excessively lowered, and the fibers are likely to be broken, and the fiber formability may be lowered. On the other hand, if the weight average molecular weight is more than 200000, the viscosity of the low-crystalline polypropylene is too high, and the spinnability of the fiber may be deteriorated. Therefore, the weight average molecular weight is more preferably 30000 to 100000, and particularly preferably 40000 to 80000, from the viewpoint of satisfying both the moldability and spinnability of the fiber.

< characteristic f > molecular weight distribution (ratio of weight average molecular weight to number average molecular weight)

The low-crystalline polypropylene used preferably satisfies inequality III "Mw/Mn ≦ 4" when the weight average molecular weight is "Mw" and the number average molecular weight is "Mn".

The left side of inequality III can be used as an index indicating the stickiness of the fiber, and if it is more than 4, the fiber is liable to be sticky. Therefore, from the viewpoint of suppressing stickiness, it is more preferable to satisfy inequality III' ″ "Mw/Mn ≦ 3", and it is further preferable to satisfy inequality III "" Mw/Mn ≦ 2 ".

< Property g > amount of boiling diethyl ether extract

The amount of the boiling diethyl ether extract is preferably 0 to 10% by mass with respect to the low-crystalline polypropylene used.

The amount of boiling diethyl ether extract can be used as an index of fiber stickiness, and the larger the value, the more easily the stickiness is. Therefore, the amount of the boiling diethyl ether extract is more preferably 0 to 5% by mass in order to suppress stickiness of the fibers.

< Property h > Mass ratio of Low-crystalline Polypropylene

The mass ratio of the low-crystalline polypropylene to be used is preferably 5 to 50 mass% based on the total solid content. The "total solid content" as used herein refers to the total content of the low-crystalline polypropylene and the high-crystalline polypropylene.

When the above-mentioned mass ratio is less than 5% by mass, the disadvantage of the highly crystalline polypropylene cannot be compensated, and it is difficult to reduce the fiber diameter without increasing the number of weft yarns. On the other hand, when the mass ratio is in the above-mentioned mass% range, the low-crystalline polypropylene can be reliably contained, the fibers are not easily broken, and the spinnability is improved, whereby the fibers having a small diameter can be stably produced. From such a viewpoint, the mass ratio of the low-crystalline polypropylene is more preferably 10 to 50 mass%, and particularly preferably 20 to 50 mass%.

< other > preparation method

As a method for producing a low-crystalline polypropylene satisfying the above-mentioned < characteristics a > to < characteristics h >, a method using a metallocene catalyst or a method described in Japanese patent No. 4242498 can be used.

[3. action and Effect ]

Since the diaper is configured as described above, the following operation and effect can be obtained.

(1) According to the diaper of the present embodiment, since the spunbond nonwoven fabric constituting the side sheet 20 has a predetermined water resistance, it is possible to suppress the liquid discharged from the diaper from penetrating the side sheet 20 and to suppress liquid leakage. This ensures comfort for the wearer.

In the conventional disposable diapers, a technical idea of imparting water resistance to the spunbonded nonwoven fabric has not been originally developed.

The reason for this is that it is difficult to achieve both water resistance and touch. For example, if the weight per unit area of the spunbond nonwoven fabric is increased, the feel is likely to be reduced although the water resistance can be secured. On the other hand, if the weight per unit area of the spunbond nonwoven fabric is suppressed in order to secure the touch, it is difficult to secure the water resistance.

Therefore, in sanitary products and absorbent articles such as disposable diapers which are intended to secure a tactile sensation, there is a background that it is not easy to obtain an assumption that the spunbonded nonwoven fabric has water resistance.

In contrast, the disposable diaper of the present embodiment is invented based on the novel idea that the spunbonded nonwoven fabric has a predetermined water resistance. In other words, by providing the spunbonded nonwoven fabric used in the side sheet 20 with a predetermined water resistance, leakage can be suppressed, and a diaper which can ensure comfort for the wearer can be provided.

(2) In the conventional disposable diaper, in the side sheet using the SMS nonwoven fabric, the spunbond nonwoven fabric layer is not broken but the meltblown nonwoven fabric layer may be broken when water pressure is applied. In the SMS nonwoven fabric having a breakage like this, the water pressure resistance is significantly reduced from the water pressure resistance corresponding to the meshes of the meltblown nonwoven fabric layer to the water pressure resistance corresponding to the meshes of the spunbond nonwoven fabric layer, as compared to the SMS nonwoven fabric before breakage, and therefore, the water pressure resistance is easily reduced when water pressure is repeatedly applied to the side sheet using the conventional SMS nonwoven fabric, and the water pressure resistance after reduction may not satisfy the required water pressure resistance.

In contrast, the side sheet 20 of the present embodiment uses a spunbond nonwoven fabric that can suppress a decrease or variation in water pressure resistance even when water pressure is repeatedly applied. Therefore, even in the case where the wearer intermittently discharges liquid, that is, in the case where the water pressure is repeatedly applied to the side sheet 20, leakage can be continuously suppressed.

Specifically, the first water pressure resistance P is set₁Is 160mmH₂O or more, as the first water pressure P₁To a second water-resistant pressure P₂Predetermined pressure P of reduction amount of_PIs 30mmH₂O or less. That is, the second water pressure resistance P is set₂Is at least 130(═ 160-30) mmH₂O or more. Thus, the water pressure P is resisted₁,P₂Higher than the water pressure necessary to prevent leakage of the drained liquid. Therefore, the leakage can be reliably and continuously suppressed. In other words, the predetermined pressure P can be suppressed_PThereby suppressing the lowering of the liquid leakage preventing function.

(3) In addition, in the conventional disposable diaper, in the side sheet using the SMS nonwoven fabric, water resistance and touch are secured by the meltblown nonwoven fabric, and strength is secured by the spunbond nonwoven fabric. Therefore, the water resistance and the touch feeling are secured not by the spunbond nonwoven fabric but by the meltblown nonwoven fabric.

In contrast, in the side sheet 20, small-diameter fibers having a diameter smaller than that of the fibers used in the conventional spunbond nonwoven fabric are used at a high density. Specifically, the side sheet 20 has a "fineness" of 0.1 to 1.0 denier and a "weight per unit area" of 8 to 20g/m²A spunbonded nonwoven fabric. Therefore, the side sheet 20 not only has a predetermined water resistance but also can secure a tactile sensation.

(4) Further, the two

sheet portions

20a,20b overlap at a portion of the side sheet 20. Therefore, the water pressure resistance of the side sheet 20 can be improved at the position where the two

sheet portions

20a and 20b overlap.

Further, the two

sheet portions

20a,20b are merely bent and overlapped, and are not integrated in the overlapping direction. Therefore, a decrease in the tactile sensation due to an increase in rigidity can be suppressed as compared with a side sheet having twice the "basis weight". In general, the

sheet portions

20a and 20b can be prevented from becoming hard (a hard feeling).

(5) As described above, the side sheet 20 has a predetermined water resistance and also ensures a tactile sensation. Therefore, the side sheet 20 can be disposed on the skin surface side of the diaper where the tactile sensation is required. Conversely, in the diaper in which the side sheet 20 of the spunbonded nonwoven fabric is disposed on the skin surface side, leakage of liquid can be suppressed, and the feeling can be ensured.

(6) Similarly, since the side sheet 20 can secure a tactile sensation in addition to the predetermined water resistance, the side sheet 20 can be used for the three-dimensional gather 21, which is particularly required to have a tactile sensation, in the diaper. Conversely, in the diaper using the side sheet 20 for the three-dimensional gather 21, leakage in the width direction can be suppressed, and the feeling can be ensured. Thus, the comfort of the wearer can be ensured.

[ II. examples ]

Examples of the present application are described below.

The materials, amounts, ratios, processing contents, processing procedures, and the like shown in the following examples may be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present application should not be construed as being limited to the specific examples shown below.

[1. method for producing nonwoven Fabric ]

First, the resin used for the material of the nonwoven fabric will be described with reference to table 1.

As the resin a, a polypropylene-based polyolefin resin (high crystalline polypropylene) is used. The melting point of the resin A was 162 ℃ and the melt flow rate was 30g/10 min.

Further, as the resin B, a polypropylene-based polyolefin resin (low crystalline polypropylene) satisfying the above < characteristics a > to < characteristics h > is used. The melting point of the resin B was 52 ℃ and the melt flow rate was 45g/10 min.

These resin A and resin B were mixed in the proportions shown in Table 1 to prepare a mixture. That is, polypropylene fibers are spun to produce a nonwoven fabric.

The following describes a method for producing spunbonded nonwoven fabrics (examples 1 to 6 and comparative examples 4 to 6).

First, resin a and resin B were melted by an extruder to obtain a melt. Subsequently, the melt was discharged from the spinneret, and polypropylene fibers were spun. Then, the spun polypropylene fibers were cooled with cooling air, and then subjected to tension by stretching air to obtain a predetermined fineness (fineness shown in table 1), and the fibers were collected directly on a conveyor belt and accumulated so as to have a predetermined basis weight (basis weight shown in table 1). Then, heat and pressure were applied to the stacked polypropylene fibers by an emboss roller, and a part of the fibers was melted at a predetermined emboss area ratio (emboss area ratio shown in table 1) to wind the fibers. Thus, nonwoven fabrics of examples 1 to 6 and comparative examples 4 to 6 were obtained.

Next, a method for producing an SMS nonwoven fabric (comparative examples 1 to 3) will be described.

In this method, a meltblown nonwoven fabric is deposited on a deposit of polypropylene fibers forming a spunbond nonwoven fabric, and then the polypropylene fibers forming the spunbond nonwoven fabric are deposited. The formation and stacking of the polypropylene fibers forming the spunbonded nonwoven fabric are the same as in the above-described production method.

Specifically, a meltblown nonwoven fabric having a predetermined basis weight (basis weight shown in table 1) was formed by meltblowing on a web in which polypropylene fibers forming a spunbond nonwoven fabric were deposited. And then stacking the polypropylene fibers to form a spunbond nonwoven fabric. Then, heat and pressure were applied by an embossing roll in the same manner as in the production of the spunbonded nonwoven fabric, and a part of the fibers was melted at a predetermined embossing area ratio (embossing area ratio shown in table 1) to be entangled. Thus, nonwoven fabrics of comparative examples 1 to 3 were obtained.

[2. measuring method and evaluating method ]

The measurement method or the evaluation method for deriving the results shown in table 1 is shown in < method i > to < method vi > below. Methods for evaluating chemical compositions are also shown in < method vii > to < method x >.

< method i > melt flow Rate

The melt flow rate was determined as follows: according to JIS-K7210 "test methods for Melt Flow Rate (MFR) and melt volume flow Rate (MVR) of Plastic-thermoplastic" Table 1, measurements were made using a melt flow rate apparatus (manufactured by Toyo Seiki Seiko Co., Ltd.: melt extension S-101) with a hole diameter of 2.095mm, a hole length of 0.8mm, and a load of 2160 g. The measurement temperature was measured at 230 ℃ and the amount (g) of the molten polymer discharged per 10 minutes was calculated from the time required to discharge a certain volume amount, to determine the melt flow rate.

< method ii > fineness

Regarding the fineness, 10cm of both ends of the nonwoven fabric to be manufactured was removed, and roughly five equal parts in the width direction were sampled, and a 1cm square test piece was sampled, and the diameters of the fibers at 20 points were measured with a microscope, respectively, and the fineness was calculated from the average value thereof.

< method iii > weight per unit area

The weight per unit area was determined by removing 10cm from both ends of the nonwoven fabric to be produced, randomly collecting 5 test pieces 20cm long by 20cm wide, measuring the weight, and converting the average value thereof into the weight per unit area.

< method iv > embossing area Rate

The embossing area ratio was calculated by removing 10cm from both ends of the manufactured nonwoven fabric, roughly dividing the nonwoven fabric into five equal parts in the width direction, sampling a 1cm square test piece, taking a magnified image of the nonwoven fabric with a microscope, measuring the area ratio of the depressions of the nonwoven fabric corresponding to the embossing at 20 points for each test piece using an image processing program, and calculating the average value.

< method v > Water pressure resistance

The water pressure resistance was measured in accordance with ISO811 or JIS L1092.

The measurement of the water pressure resistance is described in detail below.

For measuring the water pressure resistance, the nonwoven fabric thus produced was cut into eight pieces of 20cm each, and the cut nonwoven fabric was placed on a sample holder for a water pressure resistance tester FX-3000 produced by TEX TEST. The nonwoven fabric was set in one or two sheets so that no wrinkles were generated and the measurement area was 100cm²。

Thereafter, in the pressure test mode, the water pressure was set to 600mmH₂The O/min rate was increased and the water pressure resistance was measured. In this measurement, the water pressure is determined as the pressure resistance at three or more positions where water leaks.

When the water pressure resistance is repeatedly measured, the sample after the water pressure resistance measurement is taken out from the tester, and water is removed from both sides (front and back sides) of the nonwoven fabric sheet with a paper towel or the like in a state of being held in the sample holder, and the nonwoven fabric is set in the tester again, and the water pressure resistance is measured by the same procedure.

< method vi > touch feeling

With respect to the touch, five test pieces 20cm long by 20cm wide were arbitrarily collected as measurement samples except for 10cm at both ends of the nonwoven fabric produced, and evaluated as hand feeling (hand touch feeling) when the test piece was touched with a hand. The evaluation was rated on three scales of ". smallcircle" (good), "Δ" (normal), "x" (poor).

< method vii > molecular weight distribution

The following are the relevant apparatuses and conditions for the measurement of the molecular weight distribution.

GPC measurement device

Column: TOSO GMHHR-H (S) HT

A detector: RI detector WATERS150C for liquid chromatography

Measurement conditions

Solvent: 1,2, 4-trichlorobenzene

Measuring temperature: 145 deg.C

Flow rate: 1.0ml/min

Sample concentration: 2.2mg/ml

Injection amount: 160 μ l

And (3) correcting a curve: general correction (Universal Calibration)

And (3) analysis program: HT-GPC (Ver.1.0)

< method viii > amount of boiling diethyl ether extracted

The following are the apparatus and conditions for measuring the amount of boiling diethyl ether extracted.

Soxhlet extractor

Measurement conditions

And (3) sample extraction: 5 to 6g

Sample shape: powder (for granular material, it is used by pulverizing it into powder)

Extracting a solvent: diethyl ether

Extraction time: 10 hours

The extraction times are as follows: more than 180 times

The method for calculating the extraction amount comprises the following steps: calculated by the following equation.

[ amount (g) extracted into diethyl ether/weight (g) of powder charged) ] X100

< method ix > meso pentad fraction, racemic pentad fraction and rac-meso-rac-meso pentad fraction

The proportion of each stereoregular polypropylene used in the spunbonded nonwoven fabric was determined by measuring the 13C-NMR spectrum. The assay was performed according to the assignment of peaks proposed by A.Zambelli et al in Macromolecules,8,687(1975) ".

The following are the devices and conditions for the present measurement.

The device comprises the following steps: JNM-EX400 type 13C-NMR apparatus manufactured by Japan electronic Co., Ltd

The method comprises the following steps: perhydro decoupling process

Concentration: 220mg/ml

Solvent: 1. 90:10 mixed solvent of 2, 4-trichlorobenzene and benzene-d 6

Temperature: 130 deg.C

Pulse width: 45 degree

Pulse repetition time: 4 seconds

Integration: 10000 times

< equation >

M＝m/S×100

R＝γ/S×100

S＝Pββ+Pαβ+Pαγ

S: signal intensity of side chain methyl carbon atom of all propylene units

Pββ：19.8～22.5ppm

Pαβ：18.0～17.5ppm

Pαγ：17.5～17.1ppm

γ: racemic pentad chain: 20.7 to 20.3ppm

m: meso pentad chain: 21.7 to 22.5ppm

< method x > melting Point and crystallization temperature

Melting points and crystallization temperatures were obtained using the apparatus and method described below.

A sample (10 mg) was previously melted at 230 ℃ for 3 minutes in a nitrogen atmosphere using a differential scanning calorimeter (manufactured by Perkin Elmer Co., Ltd., DSC-7), and then cooled to 0 ℃ at 10 ℃ per minute. The crystallization temperature was determined as the peak top of the maximum peak of the crystallization exothermic curve obtained at this time. After further holding at 0 ℃ for 3 minutes, the melting point was determined as the peak top of the maximum peak of the melting endothermic curve obtained by raising the temperature at 10 ℃ per minute.

[3. results and discussion ]

Next, the nonwoven fabrics of examples 1 to 6 and comparative examples 1 to 6 were examined.

< example >

First, the spunbonded nonwoven fabrics of examples 1 to 6 were examined.

In the spunbonded nonwoven fabrics of examples 1 to 6, the water pressure resistance (first water pressure resistance P) measured for the first time₁) And the water pressure resistance (second water pressure resistance P) measured for the second time₂) Is 130mmH₂O or more, higher than the water pressure required to prevent leakage of the discharged liquid. Further, the water pressure resistance measured from the first time to the second time (second water pressure resistance P)₂) Decrease amount of (predetermined pressure P)_P) Is suppressed to 30mmH₂O or less.

The reason why the above-described liquid leakage prevention function and the function reduction suppression function were reliably achieved is considered to be that, in examples 1 to 5, the strength reduction was suppressed in the spunbond nonwoven fabric and the spunbond nonwoven fabric was provided with a predetermined water resistance by using the small-diameter fibers at a high density by the above-described "fineness" and "basis weight".

The water pressure resistance measured in the first and second times was observed in detail and was 160 to 170mmH in examples 3 and 4₂O, 170 to 180mmH in examples 1,2 and 6₂O above, 200mmH in example 5₂O or more.

The water pressure resistance measured in example 5 was higher than that measured in examples 1 to 4 and 6, and it is considered that one piece of spun-bonded nonwoven fabric was used in examples 1 to 4 and 6, while two pieces of spun-bonded nonwoven fabric were used in example 5 in a stacked manner.

In addition, attention is paid to the amount of decrease (predetermined pressure P) from the first measured water resistance pressure to the second measured water resistance pressure_P) Examples 1 to 6 all had 10mmH₂O below, in particular 0mmH in examples 1 and 6₂O。

The reason why the water pressure resistance was maintained in examples 1 and 6 in this way is considered to be that the embossed area ratio was higher in examples 1 and 6 than in other examples 2 to 5. In example 6, it is considered that the weight per unit area is larger than those of the other examples 1 to 5.

In addition, the spunbonded nonwoven fabrics of examples 1 to 5 were evaluated for the feel as "o".

The favorable evaluation of the feel was considered to be due to the use of small-diameter fibers in a spunbond nonwoven fabric at a high density as described above.

In the spunbonded nonwoven fabric of example 6, the water pressure resistance was 130mmH, although it was measured for the first time and the second time, respectively₂O or more, but the feel was evaluated as "X".

The evaluation of the feel was low as described above, and it is considered that the spunbonded nonwoven fabric of example 6 had a larger "fineness" and a larger "weight per unit area" than those of the spunbonded nonwoven fabrics of examples 1 to 5, and therefore the nonwoven fabric had a higher rigidity and a higher stiffness due to the thick fibers being stacked.

< comparative example >

Next, the nonwoven fabrics of comparative examples 1 to 6 were examined.

In the SMS nonwoven fabrics of comparative examples 1 to 3, although the water pressure resistance measured for the first time was 160mmH₂O or more, but the water pressure resistance of the second measurement is less than 130mmH₂And O. That is, in the SMS nonwoven fabrics of comparative examples 1 to 3, the reduction amount from the water pressure resistance measured for the first time to the water pressure resistance measured for the second time was more than 30mmH₂And (O). Further, the water pressure resistance of the second measurement is lower than the water pressure required for preventing leakage of the discharged liquid.

The reason why the reduction amount of the water pressure resistance is not suppressed and the water pressure resistance measured for the second time is low is considered as follows.

The spun-bonded nonwoven fabric layers in the SMS nonwoven fabrics of comparative examples 1 to 3 had a smaller "basis weight" than the spun-bonded nonwoven fabrics of examples 1 to 6. In addition, the "fineness" of the nonwoven fabric layer in the SMS nonwoven fabrics of comparative examples 1 to 3 was larger than that of the spunbond nonwoven fabrics of examples 1 to 5, and thus the "mesh" was large. On the other hand, the SMS nonwoven fabrics of comparative examples 1 to 3 had lower strength, though the "mesh" of the meltblown nonwoven fabric layer was smaller than that of the spunbonded nonwoven fabrics of examples 1 to 6.

Therefore, it is considered that in the SMS nonwoven fabrics of comparative examples 1 to 3, the meltblown nonwoven fabric layer was broken at the first measurement of the water pressure resistance, and the water pressure resistance corresponding to the "mesh" (fineness and basis weight) of the spunbond nonwoven fabric provided around the broken portion was low at the second measurement.

Further, the SMS nonwoven fabrics of comparative examples 1 to 3 were evaluated as "Δ" in touch.

Such a poor tactile sensation evaluation is considered to be due to increased rigidity and stiffness of the SMS nonwoven fabric due to the large "fineness" of the spunbond nonwoven fabric layer.

In the spunbonded nonwoven fabrics of comparative examples 4 to 6, the water pressure resistance measured for the first time was 160mmH₂O or less, the desired water pressure resistance is not obtained. Therefore, the second water pressure resistance measurement was not performed.

It is considered that the spun-bonded nonwoven fabric of comparative example 4 has a larger "fineness" than the spun-bonded nonwoven fabrics of examples 1 to 5, and therefore has a larger "mesh" and a lower water pressure in the first measurement.

It is considered that the spunbonded nonwoven fabric of comparative example 5 has a larger "mesh" because its "basis weight" is smaller than those of the spunbonded nonwoven fabrics of examples 1 to 6, and the water pressure resistance measured for the first time is low.

It is considered that the spunbond nonwoven fabric of comparative example 6 has a large content of the resin B, and therefore the fibers used are easily broken, and the water pressure in the first measurement is low.

[ III. modification ]

Finally, another modification of the present embodiment will be described.

The side sheet 20 is not limited to being composed of a spunbond nonwoven fabric, and may include a meltblown nonwoven fabric. For example, SMS nonwoven fabric may be used for the side sheet 20. In this case, the SMS nonwoven fabric includes a spunbond nonwoven fabric layer having the above-described predetermined water resistance. When the meltblown nonwoven fabric is contained in the side sheet 20 in this manner, the first water pressure resistance P can be further improved while ensuring a predetermined water resistance₁And helps to improve the comfort of the wearer.

The spunbonded nonwoven fabric having a predetermined water resistance is not limited to the side sheet 20, and may be used for other sheet materials such as the back sheet 14 and the cover sheet 15. In short, the spunbonded nonwoven fabric and the sheet using the same are not limited to absorbent articles such as disposable diapers, but can be applied to various articles requiring predetermined water resistance. In either case, the above spunbonded nonwoven fabric can continuously satisfy the required water pressure resistance. The sheet using the spunbonded nonwoven fabric can continuously satisfy the required water pressure resistance, and other functions can be added to the sheet by components other than the spunbonded nonwoven fabric.

Description of the symbols

1 crotch part

2 pattern

10 absorbent body

12 absorbent pad

13 topsheet

14 back sheet

15 cover sheet

15c outer panel section

20 side panel (sheet material)

20a inner wall sheet part

20b outer wall sheet part

20c outer sheet part

21 three-dimensional pleat

22 leg gather

40 SMS non-woven fabric

41 spunbonded nonwoven (layer)

42 meltblown nonwoven (layer)

Claims

1. A sheet material comprising a spunbonded nonwoven fabric using fibers of a thermoplastic resin and not comprising a meltblown nonwoven fabric,

the spunbonded nonwoven fabric has the following specified water resistance: when the water pressure resistance is repeatedly measured according to ISO811, the decrease amount of the second water pressure resistance measured for the second time or later relative to the first water pressure resistance measured for the first time is equal to or less than the predetermined pressure,

the first water-resistant pressure is 160mmH₂O or more, and the above predetermined pressure is 30mmH₂O or less;

the average value of the fineness of the fibers is 0.1 to 0.6 denier;

the spun-bonded non-woven fabric has a weight per unit area of 8 to 18g/m²；

The above thermoplastic resin uses a polyolefin resin containing polypropylene,

the polyolefin resin contains 5 to 50 mass% of a low-crystalline polyolefin resin satisfying the following conditions, based on the total solid content, the conditions being:

the component number of the meso five-unit is 30 to 80 mol percent,

when the meso pentad fraction is "A" and the racemic pentad fraction is "B", the inequality I "B/(1-A) ≦ 0.1" is satisfied,

the content of the raceme-meso-raceme-meso five-unit component is more than 2.5 mol percent,

when the meso triad fraction is "C", the racemic triad fraction is "D" and the triad fraction is "E", the inequality II "CxD/E" is satisfied²≦2.0”，

The weight average molecular weight is 10000-200000,

when the weight average molecular weight is "Mw" and the number average molecular weight is "Mn", the inequality III "Mw/Mn ≦ 4" is satisfied,

the amount of the extract extracted with boiling diethyl ether is 0 to 10 mass%;

the area ratio of the embossed portion where the fibers are fused to each other is 5 to 25%.

2. The sheet according to claim 1, wherein the sheet is formed by overlapping two or more sheets.

3. An absorbent article characterized in that the sheet according to claim 1 or 2 is disposed on the skin surface side.

4. The absorbent article according to claim 3, wherein the sheet is used for the three-dimensional gathers standing on the skin surface side.