JP2016188456A - Absorbent sheet and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorbent sheet which has such absorption performance as to rapidly absorb and keep an object to be absorbed therein even though the object has high viscosity, and also has superior biodegradability, and to provide a method for manufacturing the same.SOLUTION: The absorbent sheet is provided with an absorbing layer 3 formed of a nonwoven fabric which is obtained by heat-treating an air-laid web formed by stacking a first web formed of a first raw material fiber and a second web formed of a second raw material fiber. The first raw material fiber contains 2.5% to 50% of a thermally adhesive fiber that is selected from a thermally adhesive fiber (x1) made of resin (A) selected from polybutylene succinate and the like, and a thermally adhesive fiber (x2) made of resin (B) selected from polylactic acid and the like and the resin (A), 0.15% to 95% of a specific average fiber that is made of the resin (B) and has a hollow part, 50% or more of polyvinyl alcohol resin with respect to the content of the thermally adhesive fiber, and 0% or more and less than 5% of a cellulose fiber. The second raw material fiber contains 2.5% to 50% of the thermally adhesive fiber and 2.5% to 95% of a cellulose fiber.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an absorbent sheet and a method for producing the same.

Absorbers that absorb and hold liquids are used in various applications. For example, many absorbent articles such as volatilizers for body fluids, excrement, food drip, oil absorption, osboli, waste ink, cosmetics, liquid fragrances, repellents, etc. Is provided with a sheet-like absorber. As the absorber, for example, a nonwoven fabric made of pulp fiber or hydrophilic resin fiber, a hydrophilic resin sheet, or the like is used.
The absorbent body is required to have a liquid retaining property for retaining the absorbed liquid, particularly moisture. However, an absorbent body having a high liquid retaining property has a property of retaining itself without allowing liquid to permeate, and therefore, the liquid absorption rate tends to be slow, and the amount of liquid remaining on the surface of the absorbent body is usually high. If the liquid remains on the surface of the absorbent body, the object to be absorbed leaks out of the absorbent article, or the part in contact with the absorbent article becomes dirty. Therefore, in an absorbent article, a top sheet having higher permeability than the absorber is disposed on the absorber. The liquid in contact with the top sheet of such an absorbent article quickly passes through the top sheet and moves below the surface, and is then absorbed by the absorber. This method is effective when the object to be absorbed is a low viscosity liquid such as urine. However, excretions such as those containing a high-viscosity liquid or solid content, such as candy-like foods, creamy cosmetics, loose stools, and mud stools, tend to remain on the top sheet.

  Various studies have been made to further improve the absorbability of the absorbent body and absorbent articles. For example, Patent Document 1 discloses at least a base layer composed of a dry nonwoven web or mat mainly composed of natural cellulose fibers as an ink absorber that can smoothly penetrate and diffuse even with high viscosity and concentration inks. It describes what laminated a bulky synthetic fiber sheet layer having a specific density and thickness on one side. Patent Document 2 describes an absorbent product including a distribution unit that distributes liquid discharged from a wearer of the absorbent product to the surface of the absorbent body. In Patent Document 3, as an absorbent article that can keep soft stool away from the skin promptly, and securely house and hold the soft stool at a position far from the skin, a surface sheet that transmits excrement, a transmission sheet that transmits excrement, and The thing provided in order with the absorption element containing the cotton-like pulp which hold | maintains excrement is described. Patent Document 4 discloses a liquid-permeable top sheet and a liquid-impermeable back sheet as an absorbent article that is excellent in diffusivity in the surface direction of urine and the like and can quickly absorb urine and the like. In the above description, a structure having an absorptive laminate having a specific structure is provided.

In recent years, biodegradability has been required for absorbent articles such as disposable diapers and sanitary napkins. In particular, those having water decomposability that decomposes when in contact with a large amount of water have been studied in various ways because they have the advantage that they can be directly discarded in a flush toilet.
For example, Patent Document 5 discloses a liquid-permeable surface sheet that appears on the skin-side surface and a water-decomposable back surface that appears on the clothing-side surface as an absorbent article having good water-disintegrating properties and excellent liquid-absorbing and leak-proofing properties. And a sheet using a specific water-decomposable nonwoven fabric as the top sheet.

JP 2000-135797 A JP 2002-238946 A JP 2007-097643 A JP 2012-24206 A JP 2004-344443 A

When the object to be absorbed has a high viscosity, for example, when it contains a high-viscosity liquid or solid content, for improving the absorption performance, the permeability can be quickly transmitted through the object having a high viscosity and absorbed under the surface. In addition, it is necessary to improve both the liquid retention properties that can sufficiently retain the liquid contained in the absorbed object to be absorbed. In addition, in order to suppress the reversal of the absorption target as much as possible, the absorption target is quickly taken into the absorber, and the absorption target viewed from the absorption surface side is kept so that the absorption target does not remain on the surface of the absorber. It is also required to reduce the diffusion area.
However, it cannot be said that conventional absorbent bodies and absorbent articles sufficiently satisfy these characteristics. In particular, in the case of biodegradable absorbers and absorbent articles, especially water-degradable absorbers and absorbent articles, the raw materials that can be used are limited, and the techniques that can be applied to improve water absorption performance are also limited. The
Therefore, even if it is a high-viscosity absorption target, it absorbs quickly and the diffusion area of the absorption target viewed from the absorption surface side can be reduced and retained, and the water-degradable absorber and absorption There is a need for a technique that can achieve both excellent biodegradability that can be used as a functional article.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an absorbent sheet having extremely excellent absorption performance and biodegradability and a method for producing the same.

The present invention for solving the above problems has the following aspects.
[1] An absorbent layer comprising a nonwoven fabric obtained by heat-treating an airlaid web in which a first web composed of first raw fibers and a second web composed of second raw fibers are laminated,
The first raw fiber is 0.25% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fiber (x1) and the following fiber (x2), and the following resin (B ) And containing 0.15% by mass to 95% by mass of a latent crimpable composite fiber having a hollow portion and an average fineness of 5 to 50 dtex, and containing 0% by mass to less than 5% by mass of cellulose fiber,
The second raw fiber is 2.5% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fibers (x1) and the following fibers (x2), and 2 cellulose fibers. An absorbent sheet containing 5% by mass or more and 95% by mass or less.
Fiber (x1): polybutylene succinate, polylactic acid, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate) Nate / carbonate), poly (butylene adipate / terephthalate), and heat-fusible fiber comprising at least one resin (A) selected from polyethylene succinate.
Fiber (x2): a heat-fusible fiber comprising at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid, and cellulose acetate and the resin (A).

[2] The absorbent sheet according to [1], wherein the latent crimpable conjugate fiber is a side-by-side type polylactic acid resin having a different molecular weight.
[3] The absorbent sheet according to [1] or [2], wherein the first raw material fiber further contains a high melting point fiber (Y) made of the resin (B).
[4] The absorbent sheet according to any one of [1] to [3], wherein the first raw fiber further includes a polyvinyl alcohol resin fiber.
[5] The content of the heat-fusible fiber (X) in the first raw fiber is 2% to 10% by mass according to any one of [1] to [4]. Absorption sheet.
[6] The absorbent sheet according to any one of [1] to [5], wherein the fineness of the heat-fusible fiber (X) in the first raw fiber is 10 dtex or more.
[7] The content of the heat-fusible fiber (X) in the first raw fiber is 10% by mass or more and 50% by mass or less, and the content of the polyvinyl alcohol resin fiber is the heat-fusible property. The absorbent sheet according to any one of [1] to [6], which is 50% by mass or more based on the content of the fiber (X).
[8] The second raw material fiber further contains the heat-fusible fiber (X),
The content of the cellulose fiber in the second raw fiber is 5% by mass or more and 95% by mass or less, and the content of the heat-fusible fiber (X) is 5% by mass or more and 15% by mass or less. The absorbent sheet according to any one of [1] to [7].
[9] The absorbent sheet according to any one of [1] to [8], wherein the basis weight of the first web is 100 g / m ² or more and 500 g / m ² or less.

[10] A gas-permeable carrier sheet is disposed on the mesh-shaped endless belt, and the second raw fiber is deposited on the gas-permeable carrier sheet while being mixed in the air by an airlaid web forming apparatus. Forming an airlaid web by forming a second web and subsequently depositing the first raw fibers while mixing in air to form the first web;
Bonding the fibers contained in the airlaid web by heating the airlaid web obtained,
The first raw fiber is 0.25% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fiber (x1) and the following fiber (x2), and the following resin (B ) And containing 0.15% by mass to 95% by mass of a latent crimpable composite fiber having a hollow portion and an average fineness of 5 to 50 dtex, and containing 0% by mass to less than 5% by mass of cellulose fiber,
The second raw fiber is 2.5% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fibers (x1) and the following fibers (x2), and 2 cellulose fibers. The manufacturing method of the absorption sheet characterized by containing 5 mass% or more and 95 mass% or less.
Fiber (x1): polybutylene succinate, polylactic acid, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate) Acid / carbonate), poly (butylene adipate / terephthalate), and heat-fusible fiber comprising at least one resin (A) selected from polyethylene succinate.
Fiber (x2): a heat-fusible fiber comprising at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate, and the resin (A).

  According to the present invention, absorption having a small diffusion area of an absorption object viewed from the absorption surface side so that the absorption object has excellent absorption performance and biodegradability and does not remain on the surface of the absorber. A sheet and a manufacturing method thereof can be provided.

It is a schematic longitudinal cross-sectional view explaining the structure of the absorbent sheet 10 which concerns on 1st embodiment of this invention. It is a schematic longitudinal cross-sectional view explaining the structure of the absorption sheet 20 which concerns on 2nd embodiment of this invention.

  Hereinafter, the present invention will be described with reference to the accompanying drawings.

<First embodiment>
FIG. 1 is a schematic longitudinal sectional view illustrating the configuration of the absorbent sheet 10 according to the first embodiment of the present invention.
The absorbent sheet 10 includes an absorbent layer 3 composed of a first region 1 and a second region 2. The absorbent layer 3 is made of a non-woven fabric obtained by heat-treating an air laid web in which a first web and a second web are laminated, and the first region 1 and the second region 2 are respectively the first web of the air laid web, Derived from the second web.
As will be described later, the air laid web sequentially deposits the first raw fiber constituting the first web and the second raw fiber constituting the second web in this order or in the reverse order. In the nonwoven fabric obtained by heat-treating this, there is no clear interface between the first region 1 and the second region 2.
The absorbent sheet 10 is used such that the object to be absorbed first contacts the surface of the absorbent layer 3 on the first region 1 side.

As a manufacturing method of a nonwoven fabric, the method of passing through the web formation process which forms a sheet-like web from raw material fiber, and the fiber joint process which couple | bonds the raw material fiber in the obtained web is common.
The “non-woven fabric obtained by heat-treating the air-laid web” is formed by forming a web (air-laid web) by the air-laid method in the web forming step and bonding the raw fibers by the thermal bond method in the fiber bonding step. The airlaid method is a method of forming a web by randomly laminating raw material fibers three-dimensionally using an air flow. The thermal bond method is a method in which a heat treatment is performed on a web to melt a heat-fusible component (resin (A) in the present embodiment) in the web to form a bond between raw fibers. By combining the airlaid method and the thermal bond method, it is possible to obtain a non-woven fabric excellent in absorption performance as compared with other methods.
For example, as a web forming method, there is a carding method in which a fiber card is mechanically wound using a roller card machine (carding machine), and a sheet-like web is formed from raw fibers having a long fiber length. The carding method is the same dry method as the airlaid method, but even if the resulting nonwoven fabric has the same density and thickness, the nonwoven fabric formed from the airlaid web has better absorption performance and a high viscosity absorbent object Even so, it can be quickly absorbed and retained.
This is thought to be due to the following reasons. That is, the air laid method is a method of forming a web in which raw fiber having a short fiber length is laminated using an air flow, and therefore the raw fiber is randomly oriented three-dimensionally in the obtained air laid web. By applying the thermal bond method to such a web, it is considered that a large number of voids suitable for absorbing and holding a high-viscosity absorbent object are formed in the obtained airlaid web. On the other hand, for example, when the web is formed by a carding method, the fibers are oriented almost two-dimensionally in the obtained card web.

Furthermore, in the present embodiment, the airlaid web is formed by laminating the first web composed of the first raw fiber and the second web composed of the second raw fiber, Two regions 1 and 2 having different functions are provided in one nonwoven fabric (absorbing layer 3).
In the absorption layer 3, an absorption target object first contacts the surface on the first region 1 side.
1st area | region 1 corresponding to a 1st web has the outstanding permeability | transmittance which can permeate | transmit quickly even if it is a high-viscosity absorption object with a large space | gap between raw material fibers, and can be absorbed under the surface. In order to suppress the reversal of the absorption object as much as possible, it functions as a transmission layer that can reduce the diffusion area of the absorption object viewed from the absorption surface side so that the absorption object does not remain on the surface of the absorber. . In addition, the first region 1 is excellent in shape retention, and is not easily deformed such as a decrease in thickness due to its own weight. Therefore, it is difficult for the transmission / absorption capacity of the object to be absorbed to decrease due to a decrease in thickness.
The second region 2 corresponding to the second web has excellent liquid absorption and liquid retention, and absorbs and holds liquid (moisture, etc.) contained in the object to be absorbed that has passed through the first region 1. Acts as a layer. When the object to be absorbed contains a solid content, the solid content can be retained as long as the solid content is fine enough to pass through the gaps between the raw material fibers in the second region 2. Moreover, the 2nd area | region 2 is excellent in shape retention property. Therefore, even when the liquid absorption amount in the second region 2 is saturated, the thickness decrease due to the weight of the liquid is small, and when the external force is applied to the second region 2, the amount of liquid that can be held is reduced. Less connected thickness is less likely to occur.
Furthermore, both the first region 1 and the second region 2 have water decomposability. The first raw fiber and the second raw fiber constituting the first region 1 and the second region 2 are biodegradable materials (resin (A), resin (B), polyvinyl alcohol, cellulose, respectively). Etc.) are contained in a certain amount or more. Therefore, both the first region 1 and the second region 2 are excellent in biodegradability. Therefore, the absorbent sheet 10 made of the absorbent layer 3 can be discarded after use by a simple method such as flowing into a flush toilet or burying in soil. In addition, it decomposes in a short period even if it is buried in the soil and discarded.

{First region 1}
The first region 1 is derived from the first web composed of the first raw fiber.
In the first raw fiber, the content of at least one heat-fusible fiber (X) selected from the following fiber (x1) and the following fiber (x2) in the first raw fiber is 0.25 mass. % To 50% by mass of a latent crimpable composite fiber comprising the following resin (B) and having a hollow portion and an average fineness of 5 to 50 dtex of 0.15% by mass to 95% by mass, Content is 0 mass% or more and less than 5 mass%. In addition, each content is a ratio with respect to the total amount (100 mass%) of a 1st raw material fiber.
Fiber (x1): polybutylene succinate, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate / carbonate) ), Poly (butylene adipate / terephthalate) and polyethylene succinate, a heat-fusible fiber comprising at least one resin (A).
Fiber (x2): a heat-fusible fiber comprising at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate, and the resin (A).

Resin (A) is a resin having a relatively low melting point, and functions as a heat-fusible component in a fiber bonding step by a thermal bond method. Therefore, the heat-fusible fiber (X) containing the resin (A) contributes to improving the shape retention of the first region 1.
The first web is bulky because it is formed by the airlaid method as described above. When the heat-fusible fiber (X) is contained in the first raw material fiber in an amount of 0.25% by mass or more, there are sufficient binding points between the raw material fibers in the first region 1 to be formed, and the shape retention Improves. The first raw fiber is composed of at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate, and has an average fineness of 5 to 50 dtex having hollow portions. Some latent crimped conjugate fibers are also included. Since this composite fiber has a hollow portion, the basis weight of the first web can be reduced, cushioning properties can be imparted, and as a result, the rigidity of the absorbent sheet of the present invention can be reduced. The latent crimpable conjugate fiber is effectively crimped (crimped, curled, spiraled) by heat applied at the time of sheet formation due to, for example, a resin with different heat shrinkability being arranged in a side-by-side type. A cushioning property can be imparted to the seat. In the present invention, a latent crimpable conjugate fiber having a polylactic acid resin having a different molecular weight arranged in a side-by-side manner and having a hollow portion and an average fineness of 5 to 50 dtex is preferably used. Moreover, even if it does not contain a cellulose fiber, even if it contains, the moisture content (water retention) in the 1st area | region 1 becomes low because the content is less than 5 mass%. Therefore, the formed 1st area | region 1 becomes bulky, a low density, and a thing which does not lose shape easily, and exhibits the outstanding permeability | transmittance also with respect to a high viscosity absorption target object.

If only the heat-fusible fiber (X) is used as the first raw fiber, water decomposability cannot be obtained. If the content of the heat-fusible fiber (X) in the first raw fiber is 50% by mass or less, water decomposability is obtained.
From the viewpoint of water decomposability, the first raw fiber preferably contains a high melting point fiber (Y) made of the resin (B) in addition to the heat-fusible fiber (X). Thereby, since the ratio of heat-fusible fiber (X) becomes comparatively low and the binding point of the raw material fibers in the 1st area | region 1 decreases, the water disintegration of the 1st area | region 1 improves.
From the viewpoint of water decomposability, the first raw fiber is added to the heat-fusible fiber (X), or in addition to the heat-fusible fiber (X) and the high-melting fiber (Y), and further, a polyvinyl alcohol resin. It is preferable to contain fibers (hereinafter referred to as PVA fibers). By combining PVA fibers, which are water-soluble fibers, the PVA fibers dissolve when contacted with a large amount of water, so that the binding points between the raw material fibers in the first region 1 are reduced. Decomposes (hydrolysis). In addition, biodegradability is improved because it is easy to decompose when processing such as burying in soil.

[Heat-bondable fiber (X)]
Commercially available fibers (x1) and fibers (x2) can be used as the heat-fusible fibers (X). Moreover, you may use what was manufactured by the well-known manufacturing method.
Here, the “heat-sealable fiber” refers to a material fiber that can be heat-sealable by heat treatment because at least a part of the material fiber constituting the fiber group is a heat-sealable component.
Both the fiber (x1) and the fiber (x2) have the resin (A) as a heat-fusible component.
The fiber (x1) is made of the resin (A), part or all of which is melted by heat treatment, and the melted part acts as a binder for fusing the surfaces of the raw fiber.
The fiber (x2) is composed of the resin (A) and the resin (B), and a part or all of the portion (for example, the sheath portion of the core-sheath structure) composed of the resin (A) is melted by heat treatment. The melted part acts as a binder.

Resin (A) is polybutylene succinate, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate / Carbonate), poly (butylene adipate / terephthalate) and at least one selected from polyethylene succinate. Resin (A) is excellent in biodegradability and has a melting point of 60 to 165 ° C. suitable for fusing in a fiber bonding step by a thermal bond method. It is preferable that melting | fusing point of resin (A) is 100-165 degreeC.
The resin (B) is at least one selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid, and cellulose acetate. Resin (B) is excellent in biodegradability and has a melting point of 170 ° C. or higher suitable for maintaining the fiber form without melting in the fiber bonding step by the thermal bond method. The melting point of the resin (B) is preferably 170 to 250 ° C.
In the present specification, the melting point of the resin is a value measured by a micro melting point measuring method DSC (scanning calorimeter) or the like.

As fiber (x1), if it consists of resin (A), it will not specifically limit, A commercially available thing can be used. Moreover, you may use what was manufactured by the well-known manufacturing method.
The resin (A) constituting the fiber (x1) may be one type or two or more types.
When the resin (A) constituting the fiber (x1) is two or more kinds, the fiber (x1) may be composed of a mixture of two or more kinds of resins (A), or two or more kinds of resins ( A composite synthetic fiber obtained by combining A) may be used. Examples of the composite synthetic fiber include a synthetic fiber having a side-by-side structure obtained by combining two different types of resins (A), a synthetic fiber having a core-sheath structure, and the like. The core-sheath structure may be a concentric core-sheath structure or an eccentric core-sheath structure.

The fiber (x2) is not particularly limited as long as it is made of the resin (A) and the resin (B) and at least a part of the fiber surface is made of the resin (A), and a commercially available product can be used. Moreover, you may use what was manufactured by the well-known manufacturing method.
The resin (A) and the resin (B) constituting the fiber (x2) may each be one type or two or more types.
Examples of the fiber (x2) include a synthetic fiber having a side-by-side structure obtained by combining the resin (A) and the resin (B), a synthetic fiber having a core-sheath structure, and the like. In the case of the core-sheath structure, the resin (A) constitutes the sheath part, and the resin (B) constitutes the core part. The core-sheath structure may be a concentric core-sheath structure or an eccentric core-sheath structure.
The mass ratio of the resin (A) to the resin (B) in the fiber (x2) (for example, the core-sheath composite ratio in the core-sheath structure) is resin (A) / resin (B) = 2/8 to 8/2. 4/6 to 6/4 is more preferable.

The fibers (x2) may be latent crimped synthetic fibers.
Latent crimped synthetic fiber is a synthetic fiber in which crimps (crimp, curl, spiral) are manifested by heat. When crimping becomes apparent when the air-laid web is heat-treated, the air-laid web becomes more bulky.
Examples of latent crimped synthetic fibers used as the fibers (x2) include, for example, synthetic fibers having a side-by-side structure obtained by combining the resin (A) and the resin (B), and synthetic fibers having an eccentric core-sheath structure. Is mentioned.
The latent crimped synthetic fiber may have mild crimps in advance or may not have.

  In the first raw fiber, the fiber length of the heat-fusible fiber (X) (fiber (x1), fiber (x2)) is preferably 2 to 20 mm, more preferably 2 to 10 mm, and further preferably 2 to 6 mm. . With such a fiber length, when forming an air laid web, these fibers are three-dimensionally laminated at random, and as a result, the first region 1 is bulky and has a high viscosity for an object to be absorbed. However, it tends to exhibit excellent permeability. Moreover, it becomes difficult to lose shape. On the other hand, if the fiber length is less than the lower limit of this range, the fibers become dense in the first region 1 and the permeability may be lowered. In addition, when touching the skin in the first region 1, there is a concern that the touch becomes hard and an irritating feeling occurs.

  The fiber diameter of the heat-fusible fiber (X) is preferably 0.5 to 74 dtex, more preferably 0.8 to 35 dtex, and still more preferably 1.0 to 20 dtex. With such a fiber diameter, the first region 1 tends to exhibit excellent permeability even for a bulky, high viscosity object to be absorbed. Moreover, it is excellent also in the touch. On the other hand, when the fiber diameter is less than the lower limit of this range, the touch is good, but the gap size is small, the resistance when absorbing a high viscosity object is increased, and the permeability is poor. Tend. If the fiber diameter exceeds the upper limit of this range, the fiber itself becomes stiff and the tingling sensation increases and the touch tends to deteriorate.

In this specification, the fiber length of the raw fiber is an average value of lengths measured by observation with an electron microscope using 50 or more arbitrarily selected fibers as samples.
The fiber diameter of the raw fiber is represented by the unit “dtex (decitex)”. 1 dtex is the thickness of a thread having a length of 10,000 m and a weight of 1 g.

  As the heat-fusible fiber (X), one type may be used alone, or two or more types may be used in combination. For example, the fiber (x1) and the fiber (x2) may be used in combination, two or more types may be used in combination as the fiber (x1), and two or more types may be used in combination as the fiber (x2).

Among the above, the heat-fusible fiber (X) preferably contains the fiber (x2). The resin (B) is a resin having a higher melting point than the resin (A), and does not melt at a normal heat treatment temperature in the thermal bond method. The higher the ratio of the fiber (x2) containing the resin (B) in the heat-fusible fiber (X), the higher the volume of the first region 1 obtained, and the better the permeability of the high-viscosity absorption object. It is in.
It is preferable to use latent crimped synthetic fibers as the fibers (x2) because they tend to be more bulky and excellent in the absorbability of an object to be absorbed having a high viscosity.

The ratio of the heat-fusible fiber (X) in the first raw fiber is 2% by mass or more and 50% by mass or less. When the proportion of the heat-fusible fiber (X) is 2% by mass or more, the shape retention is sufficiently improved and excellent permeability is exhibited. Water decomposability and biodegradability are improved when the content is 50% by mass or less.
The content of the heat-fusible fiber (X) in the first raw fiber is preferably 5% by mass or more from the viewpoint of shape retention and permeability, and 30% by mass from the viewpoint of water decomposability and biodegradability. The following is preferable, and 20% by mass or less is more preferable.
However, in the case where the content of the heat-fusible fiber (X) in the first raw material fiber is 10% by mass or more, in order to obtain sufficient water decomposability, the PVA fiber is further added to the first raw material fiber. It is preferable to contain.
In consideration of these, when the first raw fiber does not contain PVA fiber, the content of the heat-fusible fiber (X) in the first raw fiber is more preferably 2% by mass or more and 20% by mass or less. 5 mass% or more and 15 mass% or less are especially preferable.
When the first raw fiber includes PVA fiber, the content of the heat-fusible fiber (X) in the first raw fiber is not particularly limited as long as it is in the range of 2% by mass to 50% by mass. However, 10 mass% or more and 50 mass% or less are preferable, 10 mass% or more and 30 mass% or less are more preferable, and 10 mass% or more and 20 mass% or less are especially preferable.
When the content of the heat-fusible fiber (X) in the first raw material fiber is 10% by mass or more and 50% by mass or less, the content of the PVA fiber in the first raw material fiber is the heat-fusible fiber. It is preferable that it is 50 mass% or more with respect to content of (X), and it is more preferable that it is 100-200 mass%.

[Latent crimped fiber with hollow part]
The first raw fiber is composed of at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate, and has a hollow portion and an average fineness of 5 to 50 dtex. Fiber is also included. Since this composite fiber has a hollow portion, the basis weight of the first web can be reduced, cushioning properties can be imparted, and as a result, the rigidity of the absorbent sheet of the present invention can be reduced. Further, the composite fiber is a latent crimp synthetic fiber in which crimps (crimp, curl, spiral) are manifested by heat. The first web of the present invention becomes more bulky because crimps become apparent when the air laid web is heat treated. The average fineness of the composite fiber is in the range of 5 to 50 dtex. When the average fineness of the composite fiber is less than 5 dtex, the gap between the fibers constituting the first web formed is reduced, and the liquid to be absorbed is not easily transmitted through the web and absorbed on the surface of the absorbent sheet. Since the diffusion area of the absorption target viewed from the absorption surface side cannot be reduced so that the target does not remain, it is not preferable. On the other hand, if it exceeds 50 dtex, the first web on the surface of the absorbent sheet contains coarse fibers, which is not preferable because the feel is poor.
An average fineness of 5 to 5 consisting of at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate contained in the first raw fiber and having a hollow portion The amount of 50 dtex latent crimpable fiber is 0.15 mass% or more and 95 mass% or less. If it is less than 0.15% by mass, it is not preferable because sufficient effect for imparting bulkiness is not recognized, and if it exceeds 95% by mass, sufficient adhesion is obtained because there are few adhesion points between fibers in the sheet. This is not preferable because the form cannot be maintained as a sheet.
Examples of the latent crimpable fiber having a hollow portion used in the present invention include a hollow composite fiber in which resins (B) having different heat shrinkability are arranged in a side-by-side manner. In particular, a composite fiber having an average fineness of 5 to 50 dtex having a polylactic acid resin having a different molecular weight arranged in a side-by-side manner and having a hollow portion can be preferably used.

[High melting point fiber (Y)]
The high melting point fiber (Y) is a fiber made of the resin (B).
As high melting point fiber (Y), if it consists of resin (B), it will not specifically limit, A commercially available thing can be used. Moreover, you may use what was manufactured by the well-known manufacturing method.
The resin (B) constituting the high melting point fiber (Y) may be one type or two or more types.
When the resin (B) constituting the high melting point fiber (Y) is two or more kinds, the high melting point fiber (Y) may be composed of a mixture of two or more kinds of resins (B). The composite synthetic fiber which compounded the above resin (B) may be sufficient. Examples of the composite synthetic fiber include a synthetic fiber having a side-by-side structure obtained by combining two different types of resins (B), a synthetic fiber having a core-sheath structure, and the like. The core-sheath structure may be a concentric core-sheath structure or an eccentric core-sheath structure.
Like the heat-fusible fiber (X), the fiber length of the high melting point fiber (Y) is preferably 2 to 20 mm, more preferably 2 to 10 mm, and further preferably 2 to 6 mm.
The fiber diameter of the high melting point fiber (Y) is preferably 0.5 to 74 dtex, more preferably 0.8 to 35 dtex, and even more preferably 1.0 to 20 dtex, like the heat-fusible fiber (X).
As high melting point fiber (Y), 1 type may be used independently or 2 or more types may be used together.
0-93 mass% is preferable, as for the ratio of the high melting point fiber (Y) in a 1st raw material fiber, 0-90 mass% is more preferable, and 40-88 mass% is further more preferable.

[PVA fiber]
A PVA fiber will not be specifically limited if it melt | dissolves when it contacts with a lot of water, A commercially available thing can be used. Moreover, you may use what was manufactured by the well-known manufacturing method.
As a polyvinyl alcohol resin which comprises PVA fiber, what satisfy | fills JIS standard K6950 (ISO14885) of a biodegradable plastic is desirable.
Like the heat-fusible fiber (X), the fiber length of the PVA fiber is preferably 2 to 20 mm, more preferably 2 to 10 mm, and further preferably 2 to 6 mm.
The fiber diameter of the PVA fiber is preferably 0.5 to 74 dtex, more preferably 0.8 to 35 dtex, and even more preferably 1.0 to 20 dtex, like the heat-fusible fiber (X).

  The content of the PVA fiber in the first raw fiber is preferably 2% by mass or more and 95% by mass or less, more preferably 5 to 50% by mass, and further preferably 7 to 30% by mass. When the proportion of the PVA fiber is 2% by mass or more, water decomposability and biodegradability are improved. When the content is 95% by mass or less, the transparency is improved.

  When the content of the heat-fusible fiber (X) in the first raw material fiber is 10% by mass or more and 50% by mass or less, the content of the PVA fiber in the first raw material fiber is as described above. Furthermore, it is preferable that it is 50 mass% or more with respect to content of heat-fusible fiber (X), and it is more preferable that it is 100-200 mass%.

[Any raw fiber]
The first raw fiber may contain fibers other than the heat-fusible fiber (X), the high-melting fiber (Y), and the PVA resin fiber.
As this other fiber, what is necessary is just a thing which does not impair the biodegradability of the 1st area | region 1, For example, a cellulose fiber (a pulp, rayon, cupra, cotton, etc.), a natural fiber, etc. are mentioned.
As a cellulose fiber, the thing similar to what is mentioned by description of the 2nd area | region 2 mentioned later can be used.
However, if the cellulose fiber content is too high, the permeability of the first region 1 may be impaired. Therefore, the ratio of the cellulose fiber in the first raw fiber is less than 5% by mass, preferably 3% by mass or less, and more preferably 2% by mass or less.

As the first raw material fiber, the heat-fusible fiber (X) is 0.25% by mass to 50% by mass, made of the resin (B), and has a hollow portion with an average fineness of 5 to 50 dtex. Although what is necessary is just to contain a crimpable conjugate fiber 0.15 mass% or more and 95 mass% or less, what contains any one or both of a high melting point fiber (Y) and PVA fiber is further preferable.
Especially, it is preferable that it is the following raw material fiber (I-1) or (I-2) at the point from which the absorbent sheet excellent in water disintegration is obtained.
Raw material fiber (I-1): The total amount of the high melting point fiber (Y) and the PVA fiber is 80% by mass or more (preferably 90% by mass or more), and the content of the heat-fusible fiber (X) is 2 Raw material fibers that are not less than 20% by mass and not more than 20% by mass (more preferably not less than 2% by mass and not more than 10% by mass).
Raw material fiber (I-2): The content of the heat-fusible fiber (X) is 10% by mass or more and 50% by mass or less, and the content of the PVA fiber is the content of the heat-fusible fiber (X). The raw fiber which is 50 mass% or more (preferably 100 mass% or more).
It is particularly preferable that the raw fibers (I-1) and (I-2) each have a total amount of 100% by mass of the high melting point fiber (Y), the PVA fiber, and the heat-fusible fiber (X). .

The first region 1 may be composed only of the first raw fiber, and if necessary, other components other than the first raw fiber may be added as long as the effects of the present invention are not impaired. You may contain.
As the other components, known additives can be used without particular limitation as additives in the absorbent sheet, and examples thereof include functional powders, functional fibers, and functional liquids.
As the functional powder and functional fiber, those having at least one of a deodorizing function, an antibacterial function, an antiviral function, an antiallergen function, an antifungal function, an aroma function, a functional liquid and the like are preferable. For example, zeolite, activated carbon, chitin, chitosan, scallop shell, titanium oxide, titanium dioxide, magnesium oxide, plant extract, mushroom extract, catechin, flavonol, cyclodextrin, collagen fiber, iron oxide, citric acid, zinc pyrithione, hinokitiol, Examples include eucalyptus extract.

The first region 1 is preferably a basis weight of 30~1000g / ^{m 2,} more preferably from 60~800g / ^{m 2,} further preferably 100 to 500 g / ^{m 2.} When the basis weight of the first region 1 is equal to or greater than the lower limit of the above range, the ability to hold the absorption object is excellent. When the basic weight of the first region 1 is not more than the upper limit of the above range, the wearing feeling and handleability of the absorbent sheet 10 and the productivity of the absorbent layer 3 are good. Moreover, the 1st area | region 1 consists of 0.25 mass% or more and 50 mass% or less of heat-fusible fiber (X), resin (B), and the latent fineness which has a hollow part is 5-50 dtex It may be a layer in which two or more layers of webs made of fiber materials containing 0.15% by mass to 95% by mass of crimped conjugate fiber are laminated.

The first region 1 is preferably a density of 0.005~0.1g / cm ^3, more preferably 0.005~0.06g / cm ^3, 0.01~0.05g / cm ³ is more preferable. When the density exceeds the upper limit of the above range, there are few voids or the void size is too small, and the permeability of the object to be absorbed may be insufficient. In addition, the feeling of use becomes worse. If the density is less than the lower limit of the above range, there are too many voids in the first region 1 or the void size is too large, and the object to be absorbed is a highly viscous liquid or semi-solid. In this case, the first region 1 may be crushed by its own weight, and the absorbency may be significantly reduced. Even if the object to be absorbed is temporarily absorbed, it is difficult to hold the object, and there is a possibility that reversal occurs.

{Second area 2}
The second region 2 is derived from the second web composed of the second raw fiber.
In the second raw fiber, the content of cellulose fiber in the second raw fiber is 5% by mass or more and 98% by mass or less. In addition, this content is a ratio with respect to the total amount (100 mass%) of a 2nd raw material fiber.

The second web is bulky because it is formed by the airlaid method as described above. Moreover, by including a cellulose fiber, the space | gap between the raw material fibers of the 2nd area | region 2 becomes small, and a liquid absorptivity improves. Since the cellulose fiber is a hydrophilic fiber, the water absorption is particularly high.
Moreover, by including cellulose fibers, the binding points between the raw material fibers in the second region 2 do not become excessive, and the second region 2 decomposes (hydrolyzes) when it comes into contact with a large amount of water. In addition, biodegradability is improved because it is easy to decompose when processing such as burying in soil.

It is preferable that the second raw fiber further contains a heat-fusible fiber (X).
In this case, the content of the cellulose fiber in the second raw fiber is 2.5% by mass or more and 95% by mass or less, and the content of the heat-fusible fiber (X) is 2.5% by mass or more and 15% by mass. It is preferable that the content of the cellulose fiber is 50% by mass or more and 95% by mass or less, and the content of the heat-fusible fiber (X) is 5% by mass or more and 10% by mass or less. preferable.
As described above, the resin (A) in the heat-fusible fiber (X) is a resin having a relatively low melting point, and functions as a heat-fusible component in the fiber bonding step by the thermal bond method. Therefore, when 5 mass% or more of the heat-fusible fiber (X) is contained in the second raw material fiber, there are sufficient binding points between the raw material fibers in the second region 2 to be formed, and the shape retention Improves. By improving the shape retaining property, even when the liquid absorption amount in the second region 2 becomes saturated, the thickness decrease due to the weight of the liquid is small, and the thickness is increased when external force is applied to the second region 2. Difficult to decrease. Therefore, it is possible to suppress a decrease in the amount of liquid that can be absorbed due to the decrease in thickness. It is thought that liquid retention improves by these acting synergistically.
Even when the heat-fusible fiber (X) is contained, if the content is 15% by mass or less, excellent biodegradability can be maintained.

[Cellulose fiber]
As a cellulose fiber, the various cellulose fibers conventionally used for the absorber can be used. Examples of the cellulose fiber material include pulp, rayon, cotton, and cupra.
Cellulose fibers are preferably pulp fibers in terms of fiber length, foreign matter, productivity, raw material price, and the like.
Examples of the pulp fiber include wood pulp (conifers, hardwoods), rug pulp, linter pulp, linen pulp, non-wood pulp such as straw, three bases, and husk pulp, and raw pulp such as waste paper pulp. As the raw material pulp, any of mechanical pulp (GP, RGP, TMP, etc.) and chemical pulp (sulfite pulp, kraft pulp, etc.) can be used. Among these, kraft pulp is preferable from the viewpoints of supply amount, quality stability, cost, and the like.
The fiber length of the pulp fiber is preferably 4 mm or less, and more preferably 3 mm or less.
As the pulp fiber, normal wood pulp or the like can be used. However, in order to obtain a low-density non-woven fabric and ease of blending with the thermoplastic synthetic resin fiber, etc., the courseness required by the length average weight is required. 0.1 mg / m to 0.3 mg / m, preferably 0.12 mg / m to 0.25 mg / m are suitably used.

As a cellulose fiber, 1 type may be used independently or 2 or more types may be used together.
The ratio of the cellulose fiber in the second raw material fiber is 5% by mass or more and 98% by mass or less, and preferably 50% by mass or more and 95% by mass or less. When the ratio of the cellulose fiber is 5% by mass or more, the biodegradability and water decomposability are sufficiently improved. Liquid retention improves by being 98 mass% or less.

[Heat-bondable fiber (X)]
Examples of the fiber (x1) and the fiber (x2) in the heat-fusible fiber (X) are the same as those described above.
The heat-fusible fiber (X) contained in the second raw fiber and the heat-fusible fiber (X) contained in the first raw fiber may be the same or different.
In the second raw fiber, the fiber length of the heat-fusible fiber (X) (fiber (x1), fiber (x2)) is preferably 2 to 20 mm, more preferably 2 to 10 mm, and further preferably 2 to 6 mm. With such a fiber length, when forming an airlaid web, these fibers are three-dimensionally stacked randomly, and as a result, the second region 2 is bulky and exhibits excellent liquid retention. It tends to be a thing. Moreover, it becomes difficult to lose shape. On the other hand, if the fiber length is less than the lower limit of this range, the fibers become dense in the second region 2 and the absorbability may be lowered.
The fiber diameter of the heat-fusible fiber (X) is preferably 0.5 to 74 dtex, more preferably 0.8 to 35 dtex, and still more preferably 1.0 to 20 dtex. When the fiber diameter is such, the second region 2 is bulky and easily exhibits excellent liquid retention. Moreover, it becomes difficult to lose shape. On the other hand, if the fiber diameter is less than the lower limit of this range, the absorbability tends to be inferior due to an increase in resistance when absorbing the liquid. If the fiber diameter exceeds the upper limit of this range, the fiber itself becomes stiff and the tingling sensation increases and the touch tends to deteriorate.

As the heat-fusible fiber (X), one type may be used alone, or two or more types may be used in combination.
The proportion of the heat-fusible fiber (X) in the second raw fiber is preferably 2.5% by mass or more and 15% by mass or less, and more preferably 5% by mass or more and 10% by mass or less.
The total ratio of the heat-fusible fiber (X) and the cellulose fiber in the second raw fiber is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. When the total ratio is 50% by mass or more, liquid retention, water disintegration, and biodegradability are improved. The upper limit of the ratio is not particularly limited, and may be 100% by mass. It can be appropriately set in consideration of other fibers that are arbitrarily blended.

[Any raw fiber]
The second raw fiber may contain fibers other than the heat-fusible fiber (X) and the cellulose fiber.
As this other fiber, what is necessary is just the thing which does not impair the biodegradability of the 2nd area | region 2, For example, the said high melting point fiber (Y), PVA fiber, etc. are mentioned. Examples of the high melting point fiber (Y) and the PVA fiber are the same as those described above.
When the high melting point fiber (Y) is contained, the content of the high melting point fiber (Y) in the second raw material fiber is preferably 3% by mass or more and 48% by mass or less.

As a 2nd raw material fiber, what contains a cellulose fiber 5 mass% or more and 98 mass% or less should just be contained, Furthermore, the thing containing heat-fusible fiber (X) is preferable.
Among these, cellulose fiber 5% by mass or more and 95% by mass or less and heat-fusible fiber (X) 5% by mass or more and 15% by mass or less are contained in terms of excellent shape retention and water retention of the sheet after water absorption. And 5% by mass to 95% by mass of the cellulose fiber, 5% by mass to 15% by mass of the heat-fusible fiber (X), and 0% by mass to 48% by mass of the high melting point fiber (Y). More preferably, it consists of

The second region 2 may be composed of only the first raw fiber, and if necessary, other components other than the second raw fiber may be added as long as the effects of the present invention are not impaired. You may contain.
As the other components, known additives can be used without particular limitation as additives in the absorbent sheet, and examples thereof include functional powders, functional fibers, and functional liquids.
As the functional powder, those having any one or more of a deodorizing function, an antibacterial function, an antiviral function, an antiallergen function, an antifungal function, an aroma function, a functional liquid and the like are preferable. Activated carbon, chitin, chitosan, scallop shell, titanium oxide, titanium dioxide, magnesium oxide, plant extract, mushroom extract, catechin, flavonol, cyclodextrin, collagen fiber, iron oxide, citric acid, zinc pyrithione, hinokitiol, eucalyptus extract, etc. Can be mentioned.

The second region 2 is preferably a basis weight of 30~1000g / ^{m 2,} more preferably from 40~700g / ^{m 2,} further preferably 50 to 500 g / ^{m 2.} When the basis weight of the second region 2 is not less than the lower limit of the above range, the ability to hold the liquid is excellent. When the basis weight of the second region 2 is equal to or less than the upper limit of the above range, the wearing feeling and handleability of the absorbent sheet 10 and the productivity of the absorbent layer 3 are good.

The second region 2 is preferably a density of 0.01 to 0.1 g / cm ^3, more preferably 0.01~0.08g / cm ^3, 0.02~0.06g / cm ³ is more preferable. When the density exceeds the upper limit of the above range, there are few voids or the size of the voids is too small, and the absorption rate may be slow. If the density is less than the lower limit of the above range, the number of voids in the second region 2 becomes too large or the size of the voids becomes too large, and the amount of liquid absorption in the second region 2 becomes saturated. In this case, the thickness decrease due to the weight of the liquid becomes large, and the thickness tends to decrease when an external force is applied to the second region 2, so that the amount of liquid that can be absorbed may be reduced. Even if the liquid is once absorbed, it is difficult to hold it, and there is a risk of reversal.

The absorption layer 3 includes the first region 1 and the second region 2.
The raw material fibers constituting the absorbent layer 3 (the total of the first raw material fibers and the second raw material fibers) include at least a heat-fusible fiber (X) and a cellulose fiber, preferably a high melting point fiber (Y). And / or PVA fibers.
In the raw material fibers constituting the absorbent layer 3, the total of the heat-fusible fiber (X), the cellulose fiber, the high melting point fiber (Y) and the PVA fiber may be 50% by mass or more from the viewpoint of biodegradability. Preferably, it is more preferably 80% by mass or more, and particularly preferably 100% by mass.

The basis weight of the absorbent layer 3 is preferably 60~1300g / ^{m 2,} more preferably from 80~900g / ^{m 2,} further preferably 100~650g / ^{m 2.}
The thickness of the absorbent layer 3 is preferably 4 to 30 mm, more preferably 6 to 25 mm, and still more preferably 8 to 20 mm.

In this specification, the thickness and density of the nonwoven fabric is used constant pressure thickness measuring device (PG-16, TECLOCK Co.), using a gauge head 5cm ^2, 8.5gf / cm ² loading conditions (the against a load 7.0gf / cm ² of the instrument is a value measured by the measurement.) adjust further by applying a load to 8.5gf / cm ^2.

{Production method of absorbent sheet 10}
The absorbent sheet 10 is, for example,
An air permeable carrier sheet is disposed on the mesh endless belt, and the second web is deposited on the air permeable carrier sheet while being mixed in the air by an air laid type web forming apparatus. And subsequently obtaining the air laid web by forming the first web by depositing the first raw fibers while mixing in air (web forming step);
By heating the obtained air laid web, it can be manufactured by a manufacturing method including a step of bonding fibers contained in the air laid web (fiber bonding step).

The air laid type web forming apparatus generally includes a nozzle that discharges an intake air flow for uniformly mixing raw fibers in air, and a suction box disposed below the mesh endless belt. The intake flow passes through the mesh endless belt and is sucked into the suction box. When the raw material fibers are supplied to the web forming apparatus, the raw material fibers are mixed by the intake air flow and fall onto the mesh endless belt, and are deposited on the air-permeable carrier sheet fed out on the mesh endless belt. It is formed.
The air permeable carrier sheet is not particularly limited as long as it can pass an intake air flow and can hold an air laid web.

As the first raw material fiber and the second raw material fiber, those mentioned above are used.
The first region 1 and the second region 2 and the absorption layer 3 that are formed by adjusting the type and blending amount of the fibers constituting each raw material fiber, the ratio of the first raw material fiber and the second raw material fiber, and the like. Can adjust the performance.
For example, as the first raw material fiber forming the first region 1, the latent crimped synthetic fiber or the high melting point fiber (Y) is highly blended, or the fiber diameter of the heat-fusible fiber (X) is increased. Since the binding points between the raw material fibers in the first region 1 to be formed are reduced and the gaps are increased, an absorbent sheet excellent in texture and touch can be obtained. Further, the same effect can be obtained by reducing the mass ratio of the resin (A) and the resin (B) in the heat-fusible fiber (x2) (for example, the core-sheath composite ratio in the core-sheath structure).
Conversely, when the object to be absorbed is a high-viscosity liquid or a semi-solid, the heat retaining fiber (X) is highly blended, or the fiber diameter is reduced, so that the shape retention of the first region 1 is achieved. Can be improved, and an absorbent sheet excellent in the ability to pass through the object to be absorbed can be obtained.

The formed air laid web can be heat-treated by a general thermal bond method, and examples thereof include a method of introducing the air laid web into a heating furnace, a method of treating the air laid web with hot air, and the like.
As the hot air treatment, a method in which the web is heat-treated by passing through a through air dryer provided with a rotating drum having air permeability on the peripheral surface (hot air circulation rotary drum method), or the web allows hot air to penetrate the web. The method (hot air circulation conveyor oven system) etc. which are heat-processed by passing through the box type dryer which can be mentioned.
In addition, the thermal bond method by a hot air process may be called an air through method or a through air method.
The heat processing temperature should just be more than melting | fusing point of resin (A) (resin (A) contained in heat-fusible fiber (X)) contained in an air-laid web. When heated to a temperature equal to or higher than the melting point of the resin (A), the resin (A) is melted and the fibers are bonded to each other through the melted resin (A). However, when the fiber (x2) or the high melting point fiber (Y) is included as the raw material fiber, the temperature is lower than the melting point of the resin (B) contained in the fiber.
When the airlaid web includes latently crimped synthetic fibers, the heat treatment in the fiber bonding step may also serve as a heat treatment for revealing the crimps of the latently crimped synthetic fibers.
In addition, before and after the fiber bonding step, a step of performing a heat treatment for revealing the crimp of the latent crimped synthetic fiber may be provided.

After the fiber bonding step, a hot press treatment may be performed for the purpose of finely adjusting the density of the formed nonwoven fabric. The press pressure in that case is, for example, a low pressure of 5 kg / cm ² or less, preferably 1 kg / cm ² or less, and is performed at a pressure smaller than that of a hot press process generally performed as a fiber bonding step for bonding fibers together.

By separating the air-permeable carrier sheet from the nonwoven fabric obtained as described above, the absorbent sheet 10 composed of the absorbent layer 3 is obtained.
The air-permeable carrier sheet may be left as it is without being peeled off. When leaving as it is without peeling, it is preferable to use a biodegradable carrier sheet as the air-permeable carrier sheet. An example of such a sheet is tissue paper.

Here, as an example of the raw material fiber, the second raw material fiber is supplied first, and then the first raw material fiber is supplied. However, conversely, the first raw material fiber is supplied first, and then the first raw material fiber is supplied. Two raw fibers may be supplied.
That is, a gas-permeable carrier sheet is arranged on a mesh-like endless belt, and the first raw fiber is deposited on the gas-permeable carrier sheet while being mixed in the air by an airlaid web forming apparatus. Forming an airlaid web by subsequently depositing the second raw fibers while mixing in air to form a second web; and
You may obtain the absorption layer 3 with the manufacturing method which has the process of couple | bonding the fiber contained in this air-laid web by heating the air-laid web obtained.
However, it is preferable to supply the second raw fiber first. Usually, the 2nd raw material fiber which gives the liquid retention property of an absorption target object has a higher basic weight, and the 1st raw material which permeate | transmits an absorption target object tends to have a lower density. Therefore, the first raw material fiber and the second raw material fiber are less likely to be mixed when the second raw material fiber is supplied first, and the functions of the first region 1 and the second region 2 are sufficiently exhibited.

<Second Embodiment>
FIG. 2 is a schematic longitudinal sectional view illustrating the configuration of the absorbent sheet 20 according to the second embodiment of the present invention. Note that, in the embodiments described below, the same reference numerals are given to the components corresponding to the first embodiment described above, and the detailed description thereof is omitted.
The absorbent sheet 20 has the same configuration as the absorbent sheet 10 except that a liquid-permeable surface layer 4 is laminated on the surface of the absorbent layer 3 on the first region 1 side.
The absorbent sheet 20 is used such that the object to be absorbed first contacts the surface of the absorbent layer 3 on the first region 1 side.
In the present embodiment, the texture, feel, biodegradability, water decomposability, and the like can be improved by selecting the surface layer 4. Moreover, the surface residue of an absorption target object can also be reduced. For example, when a non-woven fabric formed of raw material fibers having a fiber length longer than that of the raw material fibers constituting the first region 1 is provided as the surface layer 4, the tingling sensation caused by the short raw material fibers can be suppressed, and the touch is improved.

Although it will not specifically limit as the surface layer 4 if it has liquid permeability, A nonwoven fabric is preferable.
The raw material fibers constituting the nonwoven fabric constituting the surface layer 4 (hereinafter referred to as nonwoven fabric (D)) are preferably those that do not impair the biodegradability of the absorbent sheet 10, for example, the heat-fusible fibers (X) and the high melting point fibers. (Y), PVA fiber, cellulose fiber and the like.

  As the nonwoven fabric (D), any web-formed process and fiber-bonded process can be used. However, in terms of touch, those that have undergone a web-forming process other than the airlaid method are preferred. The web is formed by adopting a carding method or the like that provides a comfortable web, and then any of the resin bond method, needle punch method, spun lace method, and thermal bond method is used as a fiber bonding process for this web. Nonwoven fabrics employing these are preferred. Especially, the resin bond nonwoven fabric which employ | adopted the resin bond method for the fiber bonding process or the needle punch nonwoven fabric which employ | adopted the needle punch method is preferable, and a resin bond nonwoven fabric is especially preferable.

As the resin bond nonwoven fabric, since it is excellent in water decomposability and biodegradability, at least one selected from heat-fusible fiber (X) and high-melting fiber (Y) is kneaded with liquid PVA and bonded. Are preferred.
The needle punched nonwoven fabric is preferably one in which raw fibers including PVA fibers are mechanically entangled because of excellent water decomposability and biodegradability. The raw material fibers constituting this needle punched nonwoven fabric may be only PVA fibers or may contain other fibers. As the other fibers, various fibers exemplified above can be used.

The nonwoven fabric (D) preferably has an opening ratio of 30 to 80%. If it is a nonwoven fabric of such an aperture ratio, texture, touch, etc. can be improved, without disturbing the absorptivity of the absorption layer 3. FIG. The numerical aperture of the non-woven fabric (D) is preferably from 6000 to 100,000 (number / ^{m 2),} the opening area is preferably 3 to 50 (mm ² / number), 5 to 50 (mm ² / number) are more preferable.
Here, the opening ratio (%) is the number of openings formed in the nonwoven fabric (number of openings (pieces / m2)) and the opening area (mm ² / pieces). The ratio of the total area is obtained as a percentage. The numerical aperture (pieces / m ² ) means, for example, the surface of the nonwoven fabric with a digital microscope manufactured by Keyence Corporation, the number of openings formed in the predetermined area is visually counted, and the number per 1 m2 of the nonwoven fabric. It is converted to. In addition, the opening area (mm2 / piece) means, for example, the surface of the nonwoven fabric observed with a digital microscope manufactured by Keyence Corporation, and the area of each opening formed in a predetermined region is measured. Is the average value.
For example, in the fiber bonding process, when a spunlace method in which a high-pressure water stream is jetted from a nozzle to a web arranged on a net (such as a wire mesh) and the fibers are entangled with each other is adopted, It can be adjusted by changing the mesh size. When using the needle punch method (fiber bonding step in which fibers are mechanically entangled by inserting a needle with a needle into the web) or the thermal bond method, it is obtained by post-processing such as forming an opening by punching. The opening ratio of the nonwoven fabric can be adjusted.

As a density of a nonwoven fabric (D), 0.020-0.50 g / cm < ³ > is preferable. Moreover, it is preferable that thickness is 0.1-2.0 mm and basic weight (US basis) is 20-100 g / m < ² >. If it is such a range, the touch can be improved, without disturbing the absorptivity of the absorption layer which consists of a nonwoven fabric (A).

The nonwoven fabric (D) may be drilled.
A physical void is formed by the drilling process, and the permeability of the object to be absorbed including the solid content is improved by the void.

{Production method of absorbent sheet 20}
The absorbent sheet 20 is, for example,
An air permeable carrier sheet is disposed on the mesh endless belt, and the second web is deposited on the air permeable carrier sheet while being mixed in the air by an air laid type web forming apparatus. And subsequently obtaining the air laid web by forming the first web by depositing the first raw fibers while mixing in air (web forming step);
A step (lamination step) of laminating the surface layer 4 on the surface of the obtained airlaid web (absorbing layer 3) on the first web side (first region 1 side);
A step of bonding the fibers contained in the air laid web by heating the air laid web (fiber bonding step).
It can manufacture with the manufacturing method which has this.

The web forming process and the fiber bonding process can be performed in the same manner as the web forming process and the fiber bonding process described in the method for manufacturing the absorbent sheet 10.
As a method for laminating the surface layer 4, an adhesive substance (for example, resin (A) powder or the like) that exhibits an adhesive action by heat-sealing is used, and thereby the absorbent layer 3 and the surface layer 4 are bonded. There is a method (the amount of adhesive used is, for example, 3 to 15 g / m ² ). At this time, only the peripheral edge portions of the absorption layer 3 and the surface layer 4 may be bonded. Alternatively, without using an adhesive substance, the entire surface or only the peripheral portion thereof may be joined by thermal fusion using the thermal fusion property of the thermal fusion fiber (X) contained in the absorbent layer 3. Further, the surface layer 4 (for example, the nonwoven fabric (D)) is formed into a bag shape, and the absorption layer 3 is inserted into the bag, the peripheral portions of the absorption layer 3 and the surface layer 4 are folded, and the like. They may be integrated without bonding.

Further, as described above, as the method for manufacturing the absorbent sheet 20, the absorbent layer 3 can be obtained by using an adhesive substance, utilizing heat-fusibility, or adopting a method of integrating without bonding. In addition to the method of laminating the surface layer 4, for example, a method of providing the surface layer 4 on at least one surface of the absorbent layer 3 while producing the absorption layer 3 can also be mentioned.
In particular,
The surface layer 4 is disposed on the mesh endless belt, and the first raw fiber is deposited on the surface layer 4 while being mixed in the air by the airlaid web forming apparatus to form the first web. Subsequently, the second raw fiber is deposited while being mixed in the air to form an airlaid web by forming a second web (web forming step);
Heating the obtained air laid web to a temperature equal to or higher than the melting point of the resin (A) contained in the air laid web (fiber bonding step);
The absorption sheet 20 can be manufactured by the manufacturing method which has this.
This method uses the surface layer 4 as a gas-permeable carrier sheet, and in the web forming process, first the first raw fiber is supplied as the raw fiber, and then the second raw fiber is supplied. It can be performed in the same manner as described in the method for manufacturing the sheet 10.

The first embodiment to the second embodiment have been described above, but the present invention is not limited to these embodiments.
Although an example in which there is one each of the first region 1 and the second region 2 has been shown, the first web constituting the first region 1 has a plurality of different fiber types, compositions, fiber lengths, or fiber diameters. The seed raw material fibers may be sequentially deposited. Similarly, even if the second web constituting the second region 2 is formed by sequentially depositing a plurality of types of second raw material fibers having different fiber types or compositions, fiber lengths, or fiber diameters. Good.
For example, when the ratio of the heat-fusible fiber (X) in the raw fiber is lowered, the shape retention and permeability are lowered, but the texture and the touch tend to be improved. Therefore, the ratio of the heat-fusible fiber (X) in the raw fiber constituting the outer side of the first region 1 (the side that becomes the surface of the absorption layer 3) is lowered (for example, 5 to 10% by mass), and the first region When the ratio of the heat-fusible fiber (X) in the raw material fibers constituting the inner side (the second region 2 side) of 1 is increased (for example, 20 to 50% by mass), the texture and feel of the outer surface is good, and The first region 1 having good shape retention and permeability can be obtained.
The absorbent sheet may have a layer other than the absorbent layer 3 and the surface layer 4.

The absorbent sheet of the present invention is a liquid-retaining liquid that can permeate rapidly and absorb under the surface, and can sufficiently retain the liquid contained in the absorbed object even if it is a highly viscous object. Combined with sex.
In addition, the absorbent sheet of the present invention has an advantage that the absorbent layer has water decomposability and can be easily discarded. For example, it can be disposed of in a flush toilet after use. Moreover, since it has biodegradability, it can be buried in soil and discarded.
Therefore, the absorbent sheet of the present invention can be applied to various absorption objects such as water and organic solvents, inks, oils, solutions and gels in which other components are dissolved, and those mixed with solids, It is useful as various existing absorbent articles, or as a top sheet of an absorbent article (a sheet constituting a surface in contact with an absorbent object).
In the absorbent sheet of the present invention, the surface of the absorbent layer on the side composed of the first raw material fibers (first region 1 side) is the surface of the side composed of the second raw material fibers (second region 2 side) It is used so that it may come into contact with the object to be absorbed before.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these Examples.
The raw material fibers used in the following examples are as follows.
[Heat-bonding fiber]
PBS / PLA 3.3 dt: Synthetic fiber with an eccentric core-sheath structure having polybutylene succinate (PBS) as a sheath and polylactic acid (PLA) as a core (fiber diameter 3.3 dtex, fiber length 5 mm, core-sheath composite ratio = 6/4). Daiwabo Polytech NBF (KK) PLV (6/4) 3.3dt
PBS / PLA17dt: Synthetic fiber having an eccentric core-sheath structure in which PBS is a sheath and PLA is a core (fiber diameter 17 dtex, fiber length 5 mm, core / sheath composite ratio = 6/4). Daiwabo Polytech NBF (KK) PLV (6/4) 17dt
PBS / PLA17dt: Synthetic fiber with an eccentric core-sheath structure in which PBS is the sheath and PLA is the core (fiber diameter 17 dtex, fiber length 5 mm, core / sheath composite ratio = 8/2). Daiwabo Polytech NBF (KK) PLV (8/2) 17dt

[High melting point fiber]
PLA11dt: PLA fiber (fiber diameter 11 dtex, fiber length 5 mm). PL01 manufactured by Nippon Estel Co., Ltd.
[Latent crimped fiber with hollow]
PLA / PLA17dt: Synthetic fiber having a structure in which PLA / PLA is arranged in a side-by-side manner and has a hollow portion (fineness: 17 dtex, fiber length: 5 mm). Nippon Ester Co., Ltd. HP8F 17. T5mm
[PVA fiber]
PVA 2.2 dt: PVA fiber (fiber diameter 2.2 dtex, fiber length 5 mm). Kuraray WN2 × 6
[Cellulose fiber]
Pulp: Conifer kraft bleached pulp [cellulose fiber]
Pulp: Conifer craft bleached pulp.

<Test Example 1>
Absorbent sheets (Comparative Examples 1 to 4 and Examples 1 to 7) having the same configuration as the absorbent sheet 10 shown in FIG. 1 were produced by the following procedure.
While feeding tissue paper onto a mesh endless belt running on a conveyor, pulp and heat-fusible fiber PBS / PLA 3.3 dt are placed in the airlaid web forming machine in the first area column of Tables 1-2. Is supplied so that the basis weight of the first region becomes the value shown in Tables 1 to 3, and is dropped together with the intake air flow onto the mesh endless belt while being uniformly mixed in the air to be deposited. As a result, a first web was formed on the tissue paper. Subsequently, the heat-fusible fibers PBS / PLA17dt, PLA / PLA17dt and PVA fibers were supplied so that the basis weight of the second region was the values shown in Tables 1-2, and meshed while being uniformly mixed in the air. An airlaid web was obtained by forming a second web on the first web by lowering and accumulating the airflow on the endless belt.
Next, this air laid web was passed through a box type dryer (hot air circulating conveyor oven) that allows hot air to penetrate the web, and was treated with hot air to obtain a nonwoven fabric (absorbing layer). The hot air treatment temperature (hot air circulation conveyor oven temperature) was 145 ° C. Thereafter, the tissue paper was peeled off from the absorbent layer to obtain an absorbent sheet comprising the absorbent layer.
The total basis weight and thickness of the obtained absorbent sheet, and the densities of the first region 1 and the second region were measured. The results are shown in Tables 1-2.

Further, the total thickness (mm) of the absorbent sheet, and the thickness (mm) of each of the first region and the second region were measured by the following procedure. The density (g / cm ³ ) of each region was calculated from the thickness and basis weight of each of the first region and the second region. The results are shown in Tables 1-2.
Further, the absorbent sheet of each example, in order to evaluate the absorption, horizontal water absorption by the following steps (g / m ^2), a liquid absorption time (seconds), and were measured the liquid spread area of (cm ^2). Moreover, the water disintegration property of each absorbent sheet was evaluated by the following procedure. The results are shown in Tables 1-2.

<Measurement of horizontal water absorption>
A 10 × 10 cm sample was immersed in 0.9% physiological saline for 10 minutes, and the water absorption was measured after netting for 1 minute.
[Horizontal water absorption (g / m ² )] = (Water absorption, sample mass after netting (g) −sample mass before water absorption (g)) × 100

<Evaluation of water disintegration>
A 3 × 3 cm sample and a 300 ml beaker containing 300 ml of water are placed on a magnetic stirrer and stirred for 3 minutes at a rotation speed of 800 rpm using a disc-shaped rotor having a diameter of 35 mm and a thickness of 12 mm. The state was confirmed (refer to JIS P 4501 Toilet paper ease test method).
Samples that collapsed and almost hydrolyzed ◎, those that almost collapsed and did not retain the original shape ○, those that have collapsed, but those that remain slightly △, some collapsed Although the prototype remains, it was evaluated as x.
<Measurement of thickness of absorbent sheet, first region and second region>
The cross section of the absorbent sheet was observed, the scale was applied, and the thickness of the first region, the second region, and the entire absorbent sheet was measured. The total thickness of each layer in the cross section is equal to the total thickness of the absorbent sheet.

<Evaluation of liquid absorption time>
10 ml of viscous liquid placed in a syringe on a 10 × 10 cm absorbent sheet was dropped at about 0.3 ml / sec, and the time until the viscous liquid disappeared and was absorbed from the surface of the absorbent sheet was measured to the second.
Viscous liquid: aqueous solution adjusted to a viscosity of 50 mPa · s with bentonite, glycerin and water <Evaluation of liquid diffusion area>
When 10 ml of viscous liquid is dropped on a 10 × 10 cm absorbent sheet at a rate of about 0.3 ml / sec, the gloss due to residual viscous liquid disappears from the surface of the absorbent sheet and is absorbed by the liquid remaining on the absorbent sheet surface when absorbed. The area of each part was measured.
Viscous liquid: Aqueous solution adjusted to a viscosity of 50 mPa · s with bentonite, glycerin and water

As shown in the above results, the absorbent sheet of the examples of the present invention was an excellent absorbent sheet having not only excellent water decomposability and a short liquid absorption time, but also a small liquid diffusion area. The absorbent sheet of Example 2 in which the basis weight of the first region was increased was slightly degraded in water disintegrability, but was disintegrated under the test conditions. On the other hand, the liquid absorption time was extremely short and the liquid diffusion area was excellent.
On the other hand, all the absorbent sheets of the comparative examples had no problem with water disintegration, but all had a long liquid absorption time and a large liquid absorption area, and there was a problem with the absorption performance.

  DESCRIPTION OF SYMBOLS 1 ... 1st area | region originating in a 1st web, 2 ... 2nd area | region originating in a 2nd web, 3 ... Absorbing layer, 4 ... Surface layer, 10 ... Absorbing sheet, 20 ... Absorbing sheet

Claims (8)

Comprising an absorbent layer made of a nonwoven fabric obtained by heat-treating an airlaid web in which a first web composed of first raw fibers and a second web composed of second raw fibers are laminated,
The first raw fiber is 0.25% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fiber (x1) and the following fiber (x2), and the following resin (B ) And having a hollow portion and an average fineness of 5 to 50 dtex, the latent crimpable conjugate fiber is 0.15% by mass to 95% by mass, and the polyvinyl alcohol resin fiber is the heat-fusible fiber (X). 50% by mass or more with respect to the content of cellulose, 0% by mass or more and less than 5% by mass of cellulose fiber,
The second raw fiber is 2.5% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fibers (x1) and the following fibers (x2), and 2 cellulose fibers. An absorbent sheet containing 5% by mass or more and 95% by mass or less.
Fiber (x1): polybutylene succinate, polylactic acid, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate) Nate / carbonate), poly (butylene adipate / terephthalate), and heat-fusible fiber comprising at least one resin (A) selected from polyethylene succinate.
Fiber (x2): a heat-fusible fiber comprising at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid, and cellulose acetate and the resin (A).   The absorbent sheet according to claim 1, wherein the latent crimpable conjugate fiber is a side-by-side type polylactic acid resin having a different molecular weight.   The absorbent sheet according to any one of claims 1 to 2, wherein the first raw fiber further contains a high-melting fiber (Y) made of the resin (B).   The absorbent sheet according to any one of claims 1 to 3, wherein a content of the heat-fusible fiber (X) in the first raw fiber is 2 mass% or more and 10 mass% or less.   The absorbent sheet according to any one of claims 1 to 4, wherein a fineness of the heat-fusible fiber (X) in the first raw fiber is 10 dtex or more.   6. The absorbent sheet according to claim 1, wherein the content of the heat-fusible fiber (X) in the first raw fiber is 10% by mass or more and 50% by mass or less. The second raw fiber further contains the heat-fusible fiber (X),
The content of the cellulose fiber in the second raw fiber is 5% by mass or more and 95% by mass or less, and the content of the heat-fusible fiber (X) is 5% by mass or more and 15% by mass or less. The absorbent sheet according to any one of claims 1 to 6. An air permeable carrier sheet is disposed on the mesh endless belt, and the second web is deposited on the air permeable carrier sheet while being mixed in the air by an air laid type web forming apparatus. And subsequently depositing the first raw fibers while mixing in air to form a first web to obtain an airlaid web;
Heating the obtained airlaid web to a temperature equal to or higher than the melting point of the resin (A) contained in the airlaid web,
The first raw fiber is 0.25% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fiber (x1) and the following fiber (x2), and the following resin (B ) And having a hollow portion and an average fineness of 5 to 50 dtex, the latent crimpable conjugate fiber is 0.15% by mass to 95% by mass, and the polyvinyl alcohol resin fiber is the heat-fusible fiber (X). 50% by mass or more with respect to the content of cellulose, 0% by mass or more and less than 5% by mass of cellulose fiber,
The second raw fiber is 2.5% by mass or more and 50% by mass or less of at least one heat-fusible fiber (X) selected from the following fibers (x1) and the following fibers (x2), and 2 cellulose fibers. The manufacturing method of the absorption sheet characterized by containing 5 mass% or more and 95 mass% or less.
Fiber (x1): polybutylene succinate, polylactic acid, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate) Acid / carbonate), poly (butylene adipate / terephthalate), and heat-fusible fiber comprising at least one resin (A) selected from polyethylene succinate.
Fiber (x2): a heat-fusible fiber comprising at least one resin (B) selected from polylactic acid, polyhydroxybutyrate, polyglycolic acid and cellulose acetate, and the resin (A).

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