JP7298064B2 - Sheet for absorbent articles - Google Patents

Description

The present invention relates to a sheet for absorbent articles.

Nonwoven fabrics having a two-layer structure have been proposed as topsheets for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads and panty liners. For example, Patent Document 1 is composed of a laminated nonwoven fabric having an upper layer arranged on the user's skin side and a lower layer arranged on the absorbent body side, and the hydrophilicity of the lower layer is higher than that of the upper layer before liquid permeation. is substantially equal, and the hydrophilicity of the upper layer is higher than that of the lower layer after liquid permeation.
According to Patent Document 1, since the surface sheet of the absorbent article has such characteristics, the liquid permeability is stably maintained during use of the absorbent article, and liquid surface flow and wetback are prevented during use for a long time. It can be prevented.

Japanese Patent Application Laid-Open No. 2005-324010

In Patent Document 1, the contact angle, liquid passage time, repeated contact angle, and Klemm water absorbency of each of the upper and lower layers forming the two-layer structure are measured. The amount of backing has not been confirmed. Furthermore, the two-layered nonwoven fabric sheet has not been considered to be incorporated into an absorbent article. Therefore, the use of the nonwoven fabric sheet having the two-layer structure of Patent Document 1 in actual absorbent articles is not necessarily clear.

By the way, in an absorbent article that absorbs a large amount of liquid per one time and in the whole, a problem such as wet back easily occurs when the load applied to the absorbent article is large. Therefore, conventional sheets for absorbent articles may not have sufficient liquid absorption performance.

As a result of intensive studies, the present inventors surprisingly found that a nonwoven fabric having at least a two-layer structure of a first fiber layer and a second fiber layer, in which the fiber treatment applied to the fibers forming the first fiber layer If there is a specific relationship between the hydrophilicity and water resistance of the agent and the hydrophilicity and water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer, the nonwoven fabric having the two-layer structure is By arranging the absorbent article so that water passes from the first fiber layer to the second fiber layer, the amount of wet back can be reduced without significantly increasing the liquid absorption time. The inventors have found that a sheet useful for articles can be obtained, and have completed the present invention.

That is, in one gist of the present invention,
A sheet for absorbent articles comprising a nonwoven fabric having a first fiber layer and a second fiber layer adjacent to the first fiber layer,
The hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer,
The water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer,
The first fiber layer is arranged on the skin side and the second fiber layer is arranged on the absorbent body side,
A sheet for absorbent articles is provided.

INDUSTRIAL APPLICABILITY The present invention has the characteristics described above, so it is possible to provide a sheet that is useful for absorbent articles that can reduce the amount of wet back without significantly increasing the liquid absorption time. Furthermore, the sheet can be preferably used for absorbent articles having a large amount of liquid absorption.

The present invention provides a sheet for absorbent articles.
Absorbent articles generally include a liquid-retaining absorbent body, a liquid-impermeable backsheet, and a liquid-permeable topsheet, with the backsheet disposed between the absorbent body and the topsheet. The absorbent article sheet according to the aspect of the present invention is preferably arranged as a top sheet that contacts the wearer's skin, or as an intermediate sheet that is positioned between the top sheet and the absorbent body. It is particularly preferred to be arranged as a topsheet. As the backsheet and absorbent, those commonly used in absorbent articles can be used.
For example, a thermoplastic resin film having or not having moisture permeability can be used as the back sheet. For example, as an absorbent, an absorbent in which pulp fibers, superabsorbent polymer particles, or a mixture thereof is wrapped or sandwiched between paper such as tissue paper can be used.

The sheet for absorbent articles according to the aspect of the present invention is
A sheet for absorbent articles comprising a nonwoven fabric having a first fiber layer and a second fiber layer adjacent to the first fiber layer,
The hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer,
The water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer,
The first fibrous layer is arranged on the skin side, and the second fibrous layer is arranged on the absorbent body side.
The nonwoven fabric is positioned so that the first fibrous layer faces the person's skin, ie faces the outside of the absorbent article.

Furthermore, the fineness of the fibers forming the second fiber layer is preferably larger than the fineness of the fibers forming the first fiber layer.
In the present invention, fibers with a smaller fineness are used for the first fiber layer facing the human skin, and fibers with a larger fineness than the first fiber layer are used for the second fiber layer facing the absorbent body. is preferred.
If the fineness of the fibers of the first fiber layer facing the human skin is smaller than the fineness of the fibers of the second fiber layer, the texture of the nonwoven fabric can be improved and the liquid absorption time can be shortened, which is preferable. In particular, in the present invention, the water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer. It is preferable to provide such a difference in fineness between the layer and the second fiber layer because the amount of wet back can be reduced and the repeated liquid absorption time can be shortened.

The fineness of the fibers forming the first fiber layer is preferably 1.0 to 3.0 dtex, more preferably 1.5 to 2.8 dtex, and more preferably 1.6 to 2.6 dtex. Especially preferred.
The fineness of the fibers forming the second fiber layer is preferably 1.7 to 5.6 dtex, more preferably 2.0 to 5.0 dtex, and more preferably 2.6 to 4.0 dtex. Especially preferred.

In the first fiber layer and the second fiber layer, it is preferable that all the fibers forming them have a fineness within the above range. may be included.

The fiber diameter of the fibers forming the first fiber layer is preferably 10 to 20 μm, more preferably 12 to 19 μm, even more preferably 14 to 18 μm.
The fiber diameter of the fibers forming the second fiber layer is preferably 13-28 μm, more preferably 15-26 μm, even more preferably 17-24 μm, and even more preferably 17-21 μm.

The fibers (raw material or material) of the first fiber layer are not particularly limited as long as the intended nonwoven fabric of the present invention can be obtained.
The fibers of the first fibrous layer can include, for example, the following fibers: natural fibers such as cotton, silk and wool; viscose rayon, cupra, and solvent spun cellulose fibers (e.g. Regenerated fibers such as Tencel (registered trademark); polyolefin fibers, polyester fibers, polyamide fibers, (poly)acrylic fibers made of acrylonitrile, polycarbonate fibers, polyacetal fibers, polystyrene fibers, and cyclic polyolefins Synthetic fibers such as fibres.
The fibers of the first fiber layer are not only fibers made of a single type of resin, but also composite fibers made of two or more types of resin (e.g., concentric or eccentric core-sheath type composite fibers, sea-island type composite fibers). , side-by-side type composite fiber) can also be used.
When natural fibers are included, the fineness or fiber diameter can be calculated according to the method according to JIS L 1019 7.4.1 micronaya.

As the fibers of the first fiber layer, synthetic fibers are preferred, and polyester fibers, polyolefin fibers and combinations thereof are more preferred. The fibers of the first fiber layer can contain regenerated fibers and/or natural fibers in addition to synthetic fibers, as long as the intended nonwoven fabric of the present invention can be obtained.
The fibers of the first fiber layer are, for example, polyester fibers such as polyethylene terephthalate; and polyethylene (high-density polyethylene, low-density polyethylene, linear low-density polyethylene), polypropylene, ethylene-propylene copolymer, ethylene-butene -polyolefin-based fibers such as 1-propylene terpolymers; and fibers that are combinations thereof.

It is more preferable that the polyethylene is a high-density polyethylene because it can easily be crimped. In the present invention, a fiber treatment agent may be used to render the fibers hydrophilic, as described below. If crimps can be easily imparted to the fibers, the fiber treatment agent can reduce the need to contain additional components, for example to impart water repellency, and can reduce unwanted effects on liquid absorption properties.
These fibers can be used alone or in combination.

When two types of fibers are combined, there are no particular restrictions on the form of combination, such as fibers in which the respective fibers are simply mixed, concentric or eccentric core-sheath type composite fibers, etc., as long as the desired nonwoven fabric can be obtained. do not have.
A concentric or eccentric core-sheath type conjugate fiber is preferable, and a concentric core-sheath type conjugate fiber is more preferable because the thickness of the first fiber layer can be reduced.
The thinner the nonwoven fabric, the shorter the distance to the absorber, the better the mobility of the liquid, and the more improved the liquid absorption time and the amount of wet back. is preferred.
A concentric or eccentric core-sheath type conjugate fiber composed of a polyester resin and a polyolefin resin is even more preferable. Particularly preferred is a core-sheath type conjugate fiber in which the core component is a polyester-based resin and the sheath component is a polyolefin-based resin.

The fibers of the first fiber layer preferably contain 50% by mass or more of concentric sheath-core composite fibers, more preferably 70% by mass or more, and all the fibers forming the first fiber layer are concentric sheath-core composite fibers. Fibers are particularly preferred. When the fibers of the first fiber layer contain 50% by mass or more of the concentric core-sheath type conjugate fibers, the increase in the thickness of the nonwoven fabric can be further suppressed.
The fibers of the first fiber layer can contain additives such as titanium oxide in order to improve texture and touch. Such an additive is preferably contained in an amount of 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on 100% by mass of the total fiber including additives. Moreover, when the fibers of the first fiber layer are core-sheath type conjugate fibers, the additive is preferably contained in a larger amount in the core component, and preferably contained in only the core component. If the additive is included in the sheath component, it may damage equipment for manufacturing nonwoven fabrics and the like.

In the case of core-sheath type composite fibers, the weight ratio of the core component to the sheath component is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and 60: More preferably 40 to 40:60.

The fibers (raw material or material) of the second fiber layer are not particularly limited as long as the intended nonwoven fabric of the present invention can be obtained.
The fibers of the second fibrous layer can include, for example, the following fibers: natural fibers such as cotton, silk and wool; viscose rayon, cupra, and solvent spun cellulose fibers (e.g. Regenerated fibers such as Tencel (registered trademark); polyolefin fibers, polyester fibers, polyamide fibers, (poly)acrylic fibers made of acrylonitrile, polycarbonate fibers, polyacetal fibers, polystyrene fibers, and cyclic polyolefins Synthetic fibers such as fibres.
The fibers of the second fiber layer are not only fibers made of a single type of resin, but also composite fibers made of two or more types of resin (e.g., concentric or eccentric core-sheath type composite fibers, sea-island type composite fibers). , side-by-side type composite fiber) can also be used.
When natural fibers are included, the fineness or fiber diameter can be calculated according to the method according to JIS L 1019 7.4.1 micronaya.

As the fibers of the second fiber layer, synthetic fibers are preferred, and polyester fibers, polyolefin fibers and combinations thereof are more preferred. The fibers of the second fiber layer can contain regenerated fibers and/or natural fibers in addition to synthetic fibers, as long as the intended nonwoven fabric of the present invention can be obtained.
The fibers of the second fiber layer are, for example, polyester fibers such as polyethylene terephthalate; and polyethylene (high-density polyethylene, low-density polyethylene, linear low-density polyethylene), polypropylene, ethylene-propylene copolymer, ethylene-butene -polyolefin-based fibers such as 1-propylene terpolymers; and fibers that are combinations thereof.

It is more preferable that the polyethylene is a high-density polyethylene because it can easily be crimped. In the present invention, a fiber treatment agent may be used to render the fibers hydrophilic, as described below. If crimps can be easily imparted to the fibers, the fiber treatment agent can reduce the need to contain additional components, for example to impart water repellency, and can reduce unwanted effects on liquid absorption properties.
These fibers can be used alone or in combination.

When two types of fibers are combined, there are no particular restrictions on the form of combination, such as fibers in which the respective fibers are simply mixed, concentric or eccentric core-sheath type composite fibers, etc., as long as the desired nonwoven fabric can be obtained. do not have.
A concentric or eccentric core-sheath type conjugate fiber is preferable, and a concentric core-sheath type conjugate fiber is more preferable because the thickness of the second fiber layer can be reduced.
The thinner the nonwoven fabric, the shorter the distance to the absorber, the better the mobility of the liquid, and the more improved the liquid absorption time and the amount of wet back. is preferred.
A concentric or eccentric core-sheath type conjugate fiber composed of a polyester resin and a polyolefin resin is even more preferable. Particularly preferred is a core-sheath type conjugate fiber in which the core component is a polyester-based resin and the sheath component is a polyolefin-based resin.

The fibers of the second fiber layer preferably contain 50% by mass or more of concentric sheath-core composite fibers, more preferably 70% by mass or more, and all the fibers forming the second fiber layer are concentric sheath-core composite fibers. Fibers are particularly preferred. When the fibers of the second fiber layer contain 50% by mass or more of the concentric core-sheath type conjugate fibers, the increase in the thickness of the nonwoven fabric can be further suppressed. The fibers of the second fiber layer may contain additives such as titanium oxide in order to improve texture and touch. Such an additive is preferably contained in an amount of 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on 100% by mass of the entire fiber including the additive of the second fiber layer. Moreover, when the fibers of the second fiber layer are core-sheath type conjugate fibers, the additive is preferably contained in a larger amount in the core component, and preferably contained in only the core component. If the additive is included in the sheath component, it may damage equipment for manufacturing nonwoven fabrics and the like.

In the case of core-sheath type composite fibers, the weight ratio of the core component to the sheath component is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and 60: More preferably 40 to 40:60.

The thickness of the nonwoven fabric is preferably 0.3 to 3.0 mm, more preferably 0.4 to 2.5 mm, still more preferably 0.5 to 2.0 mm. In the case of disposable diapers, the thickness of the nonwoven fabric should be as low as possible in terms of cost, and in that case the thickness is preferably 0.3 to 3.0 mm, more preferably 0.4 to 2.5 mm. more preferred.

The basis weight of the first fiber layer is preferably 3 to 30 g/m ² , more preferably 5 to 15 g/m ² , still more preferably 6 to 13 g/m ² , and 7 to 11 g/m 2 . ² is particularly preferred.
The basis weight of the second fiber layer is preferably 3 to 30 g/m ² , more preferably 5 to 15 g/m ² , even more preferably 6 to 13 g/m ² , further preferably 7 to 11 g/m 2 . ² is particularly preferred.

The ratio of the basis weight of the second fiber layer to the basis weight of the first fiber layer (the basis weight of the second fiber layer/the basis weight of the first fiber layer) is preferably 0.8 to 3.0, and 1.0 to 2 0.5 is more preferred, and 1.3 to 2.0 is even more preferred. Especially when the basis weight of the first fiber layer having a smaller fiber diameter is smaller than the basis weight of the second fiber layer, that is, the ratio of the basis weight of the second fiber layer to the basis weight of the first fiber layer (the basis weight of the second fiber layer/ It is more preferable that the weight per unit area of the first fiber layer) is greater than 1, since better liquid absorption properties can be obtained while maintaining texture and feel.

Furthermore, the basis weight of the entire nonwoven fabric is preferably 6 to 60 g/m ² , more preferably 12 to 50 g/m ² , still more preferably 15 to 40 g/m ² , particularly preferably 15 to 20 g/m 2 . ^m2 .
In the case of disposable diapers, the basis weight of the entire ^nonwoven fabric should be as low as possible from the viewpoint of cost ^.

The hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer,
The water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer.

"The hydrophilicity of the fiber treatment agent applied (applied) to the fibers forming the first fiber layer is higher than the hydrophilicity of the fiber treatment agent applied (applied) to the fibers forming the second fiber layer. "High or equivalent" means that the degree of hydrophilicity (hydrophilicity) of the fiber treatment agent applied to the fibers forming the first fiber layer when it comes into contact with water for the first time is It means that the degree of hydrophilicity is higher than or equal to the degree of hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer when wet.

The degree of hydrophilicity (hydrophilicity) of the fiber treatment agent applied to the fibers forming the first fiber layer or the second fiber layer when it comes into contact with water for the first time can be obtained by the following run-off measurement. , can be evaluated by the first numerical value. It is considered that the smaller the value of the first run-off (initial degree of hydrophilization), the higher the degree of hydrophilization. As for the hydrophilicity of the fiber treatment agent, if the difference in the run-off value is within 0.2 cm, the hydrophilicity is considered to be the same.
2. The degree of hydrophilization of the fiber treatment agent applied to the fibers forming the first fiber layer is preferably 5.0 cm or less, more preferably 4.0 cm or less. 5 cm or less is particularly preferred. The degree of hydrophilization of the fiber treatment agent applied to the fibers forming the second fiber layer is preferably 5.0 cm or less, more preferably 4.0 cm or less, in the initial degree of hydrophilization. 5 cm or less is particularly preferred.

The degree of hydrophilicity of the fiber treatment agent applied (applied) to the fibers forming the first fiber layer is such that the initial degree of hydrophilicity is 5.0 cm or less, and the degree of hydrophilicity applied to the fibers forming the second fiber layer is The degree of hydrophilization of the (applied) fiber treatment agent is more preferably 5.0 cm or less because the liquid absorption time can be shortened.

The degree of hydrophilicity of the fiber treatment agent was evaluated by measuring the run-off as follows.

[Runoff]
A concentric core-sheath type composite fiber (fineness: 2.2 dtex, fiber length: 38 mm) having a core made of polyethylene terephthalate, a sheath made of high-density polyethylene, and a composite ratio (core/sheath, mass ratio) of 50/50. (For example, NBF (SH) (trade name) manufactured by Daiwabo Polytech Co., Ltd.) is provided with 0.40% by mass of a fiber treatment agent, and a parallel card method and an air-through method (heating temperature: 140 ° C., treatment time: 10 seconds, wind speed) A nonwoven fabric sample (weight: 18.0 g/m ² , dimensions: length 18.0 cm x width 7.0 cm, thickness: 1.40 mm) was prepared by using a nonwoven fabric sample (weight: 1.0 m/s).

A triangular prism having a substantially right-angled isosceles triangular bottom surface was laid down to prepare a support base having an inclined surface at an angle of 45 degrees with the horizontal plane. Two pieces of filter paper (trade name: Lister Paper (Grade 989, Grade 989, 27.5 cm x 14 cm) manufactured by MEZGER inc.) were laid on the slope, and a nonwoven fabric sample was placed and fixed thereon.

0.90% physiological saline (colored with blue dye) was applied to a position 1 cm below the top of the nonwoven fabric from a microtube pump or burette at a rate of 1.0 g/30 sec for a total of 1.0 g over 30 sec. , dripped. The position of the saline tip was measured when all of the saline was absorbed by the nonwoven and the drops of saline disappeared from the surface of the nonwoven. The distance between this position and the position where the saline solution was dropped on the surface of the nonwoven fabric, that is, the longest distance that the drops of saline solution flowed on the surface of the nonwoven fabric was determined.

For the second run-off, the same non-woven fabric sample used for the first run-off was used. Physiological saline was dropped on the surface of the nonwoven fabric, and the distance over which the physiological saline flowed on the surface of the nonwoven fabric was determined. The third and subsequent runoffs were similarly repeated using the previous nonwoven sample.

"The water resistance of the fiber treatment agent applied (applied) to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied (applied) to the fibers forming the second fiber layer. "High" means that the degree of hydrophilicity (hydrophilization) of the fiber treatment agent applied to the fibers forming the first fiber layer when in contact with water is reduced when in contact with water. It means that the degree of hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer is less than the degree of decrease.

The fiber treatment agent applied to the first fiber layer preferably has water resistance. Moreover, it is preferable that the fiber treatment agent applied to the second fiber layer also has water resistance. Having water resistance means that even if it comes into contact with water, all of the fiber treatment agent will not be lost at one time. That is, it means that the fibers forming the first fiber layer or the second fiber layer still have the hydrophilicity imparted by the fiber treatment agent even after being in contact with water once. When both the fiber treatment agents applied to the first fiber layer and the second fiber layer have water resistance, the liquid absorption time can be shortened even after repeated liquid absorption, which is more preferable.

The hydrophilic water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer or the second fiber layer when in contact with water is the fifth run-off value obtained by the above run-off measurement ( cm) minus the value (cm) for the first time (difference). It is considered that the smaller the numerical value of the hydrophilic water resistance (water resistance index) of the fiber treatment agent obtained by this method, the higher the water resistance.
The water resistance index of the fiber treatment agent applied to the fibers forming the first fiber layer is preferably 5.0 cm or less, more preferably 4.0 cm or less, and 3.0 cm or less. is more preferable, and 1.5 cm or less is particularly preferable. The water resistance index of the fiber treatment agent applied to the fibers forming the second fiber layer is preferably 5.0 cm or less, more preferably 4.0 cm or less, and 3.0 cm or less. is particularly preferred. The water resistance index of the fiber treatment agent applied to the fibers forming the second fiber layer is preferably 0.5 cm or more, more preferably 0.9 cm or more. 2 cm or more is particularly preferred.

The water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer has a water resistance index of 5.0 cm or less, and the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer. is more preferable when the water resistance index is 5.0 cm or less, because high hydrophilicity can be maintained even after repeated liquid absorption and the liquid absorption time can be shortened.

The water resistance index (water resistance index A) of the fiber treatment agent applied to the fibers forming the first fiber layer, and the water resistance index (water resistance index) of the fiber treatment agent applied to the fibers forming the second fiber layer B) (water resistance index B - water resistance index A) is preferably 0.1 cm or more and 5.0 cm or less, more preferably 0.3 cm or more and 3.0 cm or less, and 0.5 cm or more. 2.0 cm or less is particularly preferable. When the difference in water resistance index is within this range, it is possible to reduce the amount of wetback without significantly increasing the liquid absorption time, which is preferable.

Further, when the value (difference) obtained by subtracting the first run-off value (cm) from the third run-off value (cm) obtained by the above run-off measurement is 5.0 cm or less, the fiber treatment agent is water resistant. can be considered to have

Since the hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer, the liquid absorption time is shortened. I can do it.
Since the water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer, the liquid absorption time should not be excessively increased. Therefore, the amount of wet back can be reduced.

As the fiber treatment agent attached to the fibers forming the first fiber layer or the second fiber layer, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants are appropriately used. be able to. Examples of components for imparting hydrophilic water resistance to the fiber treatment agent include polyglycerin fatty acid esters, polyether-polyester block copolymers, polyether-modified silicones, fatty acid esters of ethylene oxide-added polyhydric alcohols, and the like. be able to.
Such a fiber treatment agent can be applied to the surface of the fiber, for example, to impart hydrophilicity to the first fiber layer or the second fiber layer. degree of water resistance can be imparted.
Treatment of fibers with a fiber treatment agent may be performed either before or after the fibers form a fiber layer.

The fibers of the first fiber layer and the fibers of the second fiber layer are coated with 0.1 to 1.5% by mass of the above-described fiber treatment agent, based on 100% by mass of the entire fiber including the fiber treatment agent. more preferably 0.2 to 1.0% by mass, and even more preferably 0.25 to 0.8% by mass. A predetermined amount of the fiber treatment agent adhering to the fibers is more preferable because desired liquid absorption properties, particularly wetback properties, are improved.

The first fibrous layer and the second fibrous layer used in the present invention can be produced using various fibrous web production methods. The manufacturing method is not particularly limited as long as the intended sheet for absorbent articles of the present invention can be obtained. Examples of such manufacturing methods include card methods such as parallel web, cross web, criss-cross web, semi-random web and random web, and air lay methods.

The sheet for absorbent articles according to the embodiment of the present invention can be produced by stacking and integrating the first fiber web and the second fiber web. The manufacturing method is not particularly limited as long as the intended sheet for absorbent articles of the present invention can be obtained. Examples of such a manufacturing method include an air through method (hot air penetration type heat treatment method), a hot air blowing heat treatment method, a heat roll method, an infrared heat treatment method, a needle punch method, and the like.
The fibers of the first fibrous layer and the fibers of the second fibrous layer of the integrated sheet may be bonded.
The sheet for absorbent articles in the form of the present invention can further have additional layers that the sheet normally has, if desired.

The sheet for absorbent articles according to the embodiment of the present invention may optionally be subjected to additional processing such as embossing, and may have such additional forms and shapes.

The absorbent article sheet of the present invention can be used for various absorbent articles such as disposable diapers, sanitary napkins, incontinence pads and panty liners.
Furthermore, the present invention can provide various absorbent articles including such a sheet for absorbent articles.

The absorbent article sheet of the present invention can be preferably used for absorbent articles having a large amount of liquid absorption. The "absorbent article having a large liquid absorption amount" includes an absorbent article having a liquid absorption amount of 100 to 200 ml per time and being repeatedly absorbed 2 to 6 times.
Examples of "absorbent articles with high liquid absorption" include adult diapers, pads, nursing care sheets, animal diapers and animal sheets, and the like.

EXAMPLES The present invention will be described below using examples and comparative examples, but these examples are for the purpose of explaining the present invention and do not limit the present invention in any way.

The [fibers] used to produce the sheets containing the nonwoven fabrics of Examples and Comparative Examples are shown below.
Fiber 1: Polyethylene terephthalate is the core, high-density polyethylene is the sheath, the composite ratio (core/sheath, mass ratio) is 50/50, fineness 2.2 dtex (fiber diameter 16 μm), fiber length 38 mm concentric. Core-sheath type composite fiber (trade name NBF (SH) manufactured by Daiwabo Polytech Co., Ltd.)
Fiber 2: Polyethylene terephthalate is the core, high-density polyethylene is the sheath, the composite ratio (core/sheath, mass ratio) is 50/50, fineness 3.3 dtex (fiber diameter 19 μm), fiber length 51 mm concentric Core-sheath type composite fiber (trade name NBF (SH) manufactured by Daiwabo Polytech Co., Ltd.)
Fiber 3: Polyethylene terephthalate is the core, high-density polyethylene is the sheath, the composite ratio (core/sheath, mass ratio) is 50/50, fineness 2.0 dtex (fiber diameter 15 μm), fiber length 45 mm concentric Core-sheath type composite fiber (trade name NBF (SH) manufactured by Daiwabo Polytech Co., Ltd.)
Fiber 4: Polyethylene terephthalate is the core, high-density polyethylene is the sheath, the composite ratio (core/sheath, mass ratio) is 60/40, fineness 3.3 dtex (fiber diameter 19 μm), fiber length 51 mm, eccentricity Eccentric core-sheath type composite fiber with a rate of 25% (trade name NBF (SH) V manufactured by Daiwabo Polytech Co., Ltd.)

The [fiber treatment agent (hydrophilic agent)] used to produce the sheets containing the nonwoven fabrics of Examples and Comparative Examples is shown below. The hydrophilicity and durability of the fiber treatment agent were evaluated as follows. About 0.40% by mass of the fiber treatment agent is added to the entire fiber including the fiber treatment agent, etc., assuming that the mass of the entire fiber is 100%.
Fiber treatment agent A: Water resistant hydrophilic fiber treatment agent containing C12 alkyl phosphate potassium salt and having water resistance Fiber treatment agent B: Fiber treatment agent containing C12 alkyl phosphate potassium salt and having water resistance Water-resistant hydrophilic fiber treatment agent having water resistance (water resistance index) lower than that of A Fiber treatment agent C: Contains C12 alkyl phosphate potassium salt, has water resistance, and has water resistance equivalent to that of fiber treatment agent A ( Water-resistant hydrophilic fiber treatment agent with water resistance index)

[The degree of hydrophilicity of the fiber treatment agent when it comes into contact with water for the first time (initial degree of hydrophilicity), and the hydrophilic water resistance of the fiber treatment agent (water resistance index)]
The initial degree of hydrophilicity of the fiber treatment agents A to C is defined by the numerical value of the first run-off performed as follows, and the smaller the numerical value, the higher the hydrophilicity. As for the hydrophilicity of the fiber treatment agent, if the difference in the run-off value is within 0.2 cm, the hydrophilicity is considered to be the same.

In addition, the hydrophilic water resistance (water resistance index) of the fiber treatment agents A to C is defined by the value (difference) obtained by subtracting the value of the first run-off from the value of the fifth run-off. is high.

[Runoff]
A concentric core-sheath type composite fiber (fineness: 2.2 dtex, fiber length: 38 mm) having a core made of polyethylene terephthalate, a sheath made of high-density polyethylene, and a composite ratio (core/sheath, mass ratio) of 50/50. (NBF (SH) (trade name) manufactured by Daiwabo Polytech Co., Ltd. was provided with 0.40% by mass of a fiber treatment agent, and the parallel card method and air-through method (heating temperature: 140 ° C., treatment time: 10 seconds, wind speed: 1. 0 m/s) was used to prepare a nonwoven fabric sample (basis weight: 18.0 g/m ² , dimensions: length 18.0 cm x width 7.0 cm, thickness: 1.40 mm).

A triangular prism having a substantially right-angled isosceles triangular bottom surface was laid down to prepare a support base having an inclined surface at an angle of 45 degrees with the horizontal plane. Two pieces of filter paper (trade name: Lister Paper (Grade 989, Grade 989, 27.5 cm x 14 cm) manufactured by MEZGER inc.) were laid on the slope, and a nonwoven fabric sample was placed and fixed thereon.

0.90% physiological saline (colored with blue dye) was applied to a position 1 cm below the top of the nonwoven fabric from a microtube pump or burette at a rate of 1.0 g/30 sec for a total of 1.0 g over 30 sec. , dripped. The position of the saline tip was measured when all of the saline was absorbed by the nonwoven and the drops of saline disappeared from the surface of the nonwoven. The distance between this position and the position where the saline solution was dropped on the surface of the nonwoven fabric, that is, the longest distance that the drops of saline solution flowed on the surface of the nonwoven fabric was determined.

For the second run-off, the same non-woven fabric sample used for the first run-off was used. Physiological saline was dropped on the surface of the nonwoven fabric, and the distance over which the physiological saline flowed on the surface of the nonwoven fabric was determined. The third and subsequent runoffs were similarly repeated using the previous nonwoven sample.
Table 1 shows the results.
The level of hydrophilicity (initial degree of hydrophilicity) at the time of first contact with water was the highest for the fiber treatment agent C, and the fiber treatment agents A and B were equivalent. Moreover, the hydrophilic water resistance (water resistance index) of the fiber treatment agents A and C was higher than that of the fiber treatment agent B.

[Thickness of non-woven fabric]
The thickness of the nonwoven fabric was measured with a thickness measuring machine (trade name: THICKNESS GAUGE Model CR-60A manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.) under a load of 300 Pa applied to the nonwoven fabric.

[Example 1]
Using Fiber 1 to which 0.40% by mass of fiber treatment agent A was applied, a parallel carding machine was used to produce a first fiber web serving as a first fiber layer. The basis weight of the first fibrous web was about 9 g/m ² .
Using the fiber 2 to which 0.4% by mass of the fiber treatment agent B was applied, a parallel carding machine was used to produce a second fiber web serving as the second fiber layer. The basis weight of the second fibrous web was about 9 g/m ² .
The first fibrous web and the second fibrous web were superimposed and heat-treated at 135° C. using a hot-air penetration type heat treatment machine to integrate them to obtain the nonwoven fabric of Example 1. The nonwoven fabric of Example 1 had a basis weight of 18.5 g/m ² and a thickness of 0.45 mm.

[Example 2 to Reference Example 3 ] and [Comparative Example 2]
For Examples 2 to 3 and Comparative Example 2, using the fibers and fiber treatment agents listed in Table 2, using the same method as the production method of Example 1 above, Example 2 to Reference Example 3 and Comparative Example 2 were obtained.

[Comparative Example 1]
For Comparative Example 1, a method similar to that of Example 1 above was used, except that the fibers and fiber treatment listed in Table 2 were used to prepare and not laminate a second fibrous web. A nonwoven fabric of Comparative Example 1 was obtained.

Using the nonwoven fabrics (sheets for absorbent articles) of Examples and Comparative Examples thus obtained, absorbent articles for evaluation were produced and their absorbency was evaluated.
[Manufacture of absorbent article for evaluation]
An absorbent article having a topsheet/absorbent two-layer structure was taken out from a commercially available diaper (trade name Relief Leakage Safety Pad manufactured by Kao Corporation). The topsheet was peeled off and removed from the absorbent article, and instead of the topsheet, the nonwoven fabrics of the above Examples and Comparative Examples were laminated to obtain absorbent articles for evaluation. In addition, the first fiber layer was arranged so as to face outward during lamination. Using this absorbent article for evaluation, the liquid absorbency (wet back and liquid absorption time) of the nonwoven fabrics of Examples and Comparative Examples was evaluated.

[Wet back amount]
The amount of wetback of the nonwoven fabrics of Examples and Comparative Examples was evaluated by the following method.
(1) The following items were prepared to measure the amount of wet back.
Absorbent articles for evaluation of the above examples and comparative examples Acrylic plate with injection cylinder (dimensions of acrylic plate are length 200 mm × width 100 mm × thickness 8 mm, cylinder height from acrylic plate top surface is 50 mm, cylinder The inner diameter of the cylinder is 22 mm in the large diameter part from the upper end of the cylinder to 40 mm, the inner diameter gradually decreases in the range from the large diameter part to 5 mm downward, and the small diameter part (height 5 mm) to the lower end of the cylinder is 10 mm The acrylic plate also had a coaxial hole with an inner diameter of 10 mm. Each was linear.)
0.90% saline (colored with blue dye)
Filter paper (ADVANTEC (registered trademark) No. 2 manufactured by Toyo Roshi Kaisha, Ltd.) 10 cm × 10 cm
Weight (5kg) 10cm x 10cm

(2) Method Wet back amount was measured according to the following procedure.
(i) The absorbent article for evaluation was placed so that the nonwoven fabric (length 42 cm x width 21 cm) faced upward, and a plate with an injection tube was placed thereon. Then, a weight was placed on the acrylic plate so that a load of 10 g/cm ² was applied to the absorbent article for evaluation.
(ii) 150 ml of physiological saline warmed to about 37° C. was injected from the cylinder. The nonwoven fabric was left to stand until the physiological saline disappeared from the surface of the nonwoven fabric (the physiological saline was no longer confirmed as a liquid).
(iii) The acrylic plate with the injection cylinder was removed and allowed to stand for 10 minutes.
(iv) Filter paper (30 sheets) weighed in advance was placed on the nonwoven fabric, and a weight of 5 kg was placed thereon for 20 seconds. After that, the mass of the filter paper was measured. The difference between the mass of the filter paper before being placed on the nonwoven fabric and the mass of the filter paper after being placed on the nonwoven fabric and further with the weight corresponds to the amount of wet back.
(vi) Returning to the above (i), (i) to (iv) were repeated to perform the measurement twice. The amount of wetback was evaluated a total of three times.

Three samples were prepared for one sample (nonwoven fabric). The average value of the amount of wet back measured for each of the three samples was taken as the amount of wet back for that sample.
Table 2 shows the results. The smaller the amount of moisture exuding from the nonwoven fabric, the less stuffy the human skin becomes, so the smaller the value of the wet back amount, the better.

[Liquid absorption time]
(1) The following items were prepared for measuring the liquid absorption time.
Absorbent articles for evaluation of the above-mentioned examples and comparative examples Plate with injection tube (inside diameter of 2.5 cm at the bottom of the tube)
0.90% saline (colored with blue dye)
(2) Method Liquid absorption time was measured according to the following procedure.
(i) The absorbent article for evaluation was placed so that the nonwoven fabric (length 42 cm x width 21 cm) faced upward, and a plate with an injection tube was placed thereon.
(ii) 150 ml of physiological saline warmed to about 37° C. was injected from the tube. After injection of the saline, the time until the saline disappeared from the surface of the nonwoven fabric (the physiological saline was no longer confirmed as a liquid) was measured and taken as the liquid absorption time.
(iii) Returning to the above (i), (i) to (ii) were repeated to perform the measurement twice. The absorption time was evaluated three times in total.

Table 2 shows the results. The shorter the absorption time, the less stuffy the human skin becomes, so the absorption time (seconds) is preferably as short as possible.

In Examples 1 to 3 , laminated nonwoven fabrics are used, fiber treatment agent A is used in the first fiber layer, and fiber treatment agent B is used in the second fiber layer. Fiber treatment agent A has high hydrophilicity and high water resistance. Fiber treatment agent B has high hydrophilicity and weak water resistance.
Comparative Example 1 is a single layer, and the same fiber treatment agent A as in the first fiber layer of Example 1 is used.
In Comparative Example 2, a laminated nonwoven fabric is used, and the same fiber treatment agent as in the first fiber layer of Example 1 is used in the first fiber layer, but the second fiber layer has high hydrophilicity and Another textile treatment agent C is used which has high water resistance.

Comparing Example 1 with Comparative Example 1, it can be seen that lamination of single layers improves the second and third wetback amounts, that is, the repeated durability with respect to the wetback amount. In Example 1, the hydrophilicity of the fiber treatment agent in the laminated second fiber layer is lowered, so it is expected that the liquid absorption time will be longer than in Comparative Example 1, but compared to the decrease in the amount of wet back , the increase in absorption time was small.
Comparing Example 1 with Comparative Example 2, even if laminated, the fibers in the second fiber layer treated with the weakly durable fiber treatment agent were more likely to be wet-backed for the second and third times. It can be seen that the repeated durability in terms of volume, ie wetback volume, is improved.
Comparing Examples 1 and 2, it can be seen that the amount of wet back tends to improve as the basis weight increases. Conversely, in the case of a low basis weight, it is not easy to improve the amount of wet back, and it is presumed that the configuration of the present invention is more important.
Comparing Example 1 and Reference Example 3 , it can be seen that the amount of wet back tends to be improved when the fineness of the fibers forming the first fiber layer is smaller than the fineness of the fibers forming the second fiber layer. .

From the above results, the hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer, When the water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer, the laminated nonwoven fabric sheet is treated with the first fiber When arranged so that water (liquid) passes from the layer to the second fiber layer, the amount of wet back can be reduced without significantly increasing the liquid absorption time, which is useful for absorbent articles with large liquid absorption. It was found that an excellent sheet for absorbent articles can be obtained.

The present invention provides a sheet for absorbent articles. They are preferably improved in wet back amount and repeated durability without significantly increasing liquid absorption time and repeated durability, and are improved in at least one selected from cost, sheet workability, productivity, and the like. Therefore, it can be suitably used as an absorbent article sheet useful for absorbent articles having a large amount of liquid absorption.

Claims (4)

A sheet for absorbent articles comprising a nonwoven fabric having a first fiber layer and a second fiber layer adjacent to the first fiber layer,
The hydrophilicity of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than or equal to the hydrophilicity of the fiber treatment agent applied to the fibers forming the second fiber layer,
The water resistance of the fiber treatment agent applied to the fibers forming the first fiber layer is higher than the water resistance of the fiber treatment agent applied to the fibers forming the second fiber layer,
The first fiber layer is arranged on the skin side, the second fiber layer is arranged on the absorbent body side,
The fiber diameter of the fibers forming the first fiber layer is 10 to 20 μm, and the fiber diameter of the fibers forming the second fiber layer is 17 to 28 μm,
The basis weight of the first fiber layer is 5 to 15 g/m ² , the basis weight of the second fiber layer is 7 to 30 g/m ² ,
The ratio of the basis weight of the second fiber layer to the basis weight of the first fiber layer (the basis weight of the second fiber layer/the basis weight of the first fiber layer) is 1.0 to 3.0,
0.2 to 1.0% by mass of the fiber treatment agent is attached to the fibers of the first fiber layer and the fibers of the second fiber layer, based on 100% by mass of the entire fiber containing the fiber treatment agent,
The fibers of the first fiber layer contain 70% by mass or more of concentric sheath-core composite fibers,
Sheet for absorbent articles. 2. The sheet according to claim 1, wherein the fiber treatment agent applied to the first fiber layer has water resistance, and the fiber treatment agent applied to the second fiber layer also has water resistance. 3. The sheet according to claim 1, wherein the fineness of the fibers forming the second fiber layer is greater than the fineness of the fibers forming the first fiber layer. The fineness of the fibers forming the first fiber layer is 1.0 to 2.6 dtex, and the fineness of the fibers forming the second fiber layer is 2.6 to 5.6 dtex. Sheets described in any.