JPH08291495A - Absorbent paper, its production and absorbing material using the same - Google Patents

Abstract

PURPOSE: To obtain absorbent paper having a large liquid-absorbing space, high liquid absorption-permeability and high liquid diffusivity, to obtain its producing method and to obtain an absorbing material high in liquid absorbency, slight in liquid leakage and giving a comfortable wear feeling due to extra-thin thickness. CONSTITUTION: The objective absorbent paper is absorbent paper 11 containing bulky cellulosic fibers 12 and hydrophilic fine fibers 13 wherein the hydrophilic fine fibers 13 have a content in one face side in the absorbent paper 11 higher than the content in the other face side and the bulky cellulosic fibers 12 have 1.5-20mm average fiber length and intramolecular or intermolecular cross-linking or have >=0.3mg/m fiber coarseness, and the hydrophilic fine fibers 13 have 0.01-0.2mg/m fiber coarseness and 0.5-1mm average fiber length. This invention also claims a producing method of the paper and an absorbing material using the paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to absorbent paper, a method for producing the same, and absorbent articles using the same, and more specifically, absorbent paper excellent in liquid absorption permeability and liquid diffusion,
The manufacturing method and the absorbent article using the same.

[0002]

2. Description of the Related Art Regarding absorbent articles such as disposable diapers, sanitary napkins and pads for incontinence, many techniques aimed at improving the absorbability of body fluids have been proposed and improved. Has been done. And
Most of these improvements were in improving the liquid absorption rate, preventing the liquid from returning from the absorber to the surface material, preventing liquid leakage, and reducing the stickiness of the absorbent article to the body.

For example, regarding the material of the absorbent body, instead of using hydrophilic absorbent paper or pulp which absorbs and holds the liquid in the physical fine space, the liquid is subjected to a physicochemical action, that is, It has been proposed to use a super-absorbent polymer that improves the liquid absorption capacity by absorbing and holding the liquid by ionic osmotic pressure and prevents the liquid from returning after absorbing the liquid. By using a superabsorbent polymer, the liquid absorbency is improved, and at present, most absorbent articles use an absorbent body in which pulp and a superabsorbent polymer are used in combination.

However, even with such an absorbent article, liquid leakage prevention is still insufficient, as suggested by the fact that the first dissatisfaction with the absorbent article is liquid leakage.

That is, the absorption rate of a liquid is limited in a superabsorbent polymer that absorbs and retains the liquid by ionic osmotic pressure. Further, since the superabsorbent polymer cannot absorb the liquid unless it is wet with the liquid, the superabsorbent polymer has to be used in combination with pulp or absorbent paper having a high liquid absorption rate. However, pulp has a problem that when a flexible fluff absorbent layer is formed as an absorber, it locally absorbs liquid, and thus has poor diffusivity for efficiently utilizing the entire absorber.

[0006] Further, while pulp exhibits a certain degree of compression recovery and bending recovery when it is dried, its strength is extremely reduced when it is wet, and it hardly shows those recovery properties. Therefore, when stress is applied to the wet pulp, The pulp is compressed and deformed (hereinafter referred to as “break”), and the liquid absorption space is significantly reduced. As a result, the once absorbed liquid easily returns to the body side due to the twist, which causes stickiness and liquid leakage.

Further, the liquid absorption space is reduced due to this twisting, whereby the movement resistance when the liquid moves to the polymer is increased. As a result, not only the liquid absorption efficiency of the polymer is lowered, but also the re-absorption rate of the entire absorbent body after twisting is significantly reduced, which often causes liquid leakage.

In order to improve the poor diffusibility of these fluff pulps and the reduction of the liquid absorption space due to twisting, a technique for improving the diffusivity and the liquid return property by compressing / densifying the pulp is also used. Have been reported up to. However, these techniques do not solve the essential problem that the strength of pulp becomes extremely low when it gets wet, and conversely, the distance between fibers of pulp becomes too close, so that liquid becomes a polymer. The movement resistance at the time of movement greatly increases, resulting in a disadvantage that the liquid absorption efficiency of the polymer deteriorates. That is, in the absorber made of fluff pulp, the liquid absorbency and the diffusibility were not compatible with each other, and the absorbency / leak prevention property was still insufficient.

On the other hand, most of the above-mentioned absorbent paper is absorbent paper obtained by wet-making natural pulp. However, the absorbent paper manufactured by such a method has a strong interfacial tension between water and pulp due to hydrogen bond during pulp dehydration and drying during dehydration / wet pressure / drying process during papermaking. Works. Due to this tightening force, the pulp fibers are tightly tightened. As a result, the absorbent paper obtained by wet papermaking of pulp fibers not only has a very slow liquid absorption / permeation, but also the pulp fiber space that substantially absorbs the liquid is extremely reduced.

There has also been attempted a method of improving the bulkiness of the absorbent paper by creping or embossing the absorbent paper. However, in such a method, only the apparent thickness of the absorbent paper is improved, the liquid absorption space composed of pulp fibers is hardly increased, and the liquid absorption / permeability is not improved.

Also, an absorbent paper mainly composed of bulky cellulose fibers has been proposed. Since such an absorbent paper has a large fiber-to-fiber distance, it is excellent in the liquid absorption rate and the liquid transmission rate, but is inferior in the liquid diffusivity. Therefore, when the absorbent body is composed only of the absorbent paper and the polymer, the absorbent body has a poor ability to diffuse the liquid throughout the polymer, and the ability to fix the polymer decreases. Furthermore, if pressure is applied while absorbing the liquid, liquid return easily occurs. On the other hand, absorbent paper mainly composed of softwood pulp or hardwood pulp having a small fiber diameter has also been proposed. Since such absorbent paper has a high density, it is excellent in liquid absorbability and liquid diffusibility due to the capillary phenomenon, but it is inferior in liquid permeability, so that the liquid remains retained on the surface of the absorbent paper and the salat of the absorbent paper surface is Lack of feeling. As described above, it is difficult to develop the liquid absorbing and transmitting properties and the liquid diffusing property with only one sheet of absorbent paper.

Attempts have also been made to manufacture bulky absorbent paper by using a dry method such as the air ray method for manufacturing the absorbent paper.
That is, bulky absorbent paper is manufactured by depositing pulp in bulk and binding it with an appropriate binder. According to this method, it is possible to obtain absorbent paper having a very low density when dried, a large distance between pulp fibers, and a large liquid absorption space. Such an absorbent paper has a large liquid absorbing space even when absorbing liquid, but has a drawback that its diffusivity is very poor. Further, when the absorbent paper is under pressure while being wet with a liquid, there is a problem in that, like the fluff pulp, twisting / sagging occurs.

Cellulose non-woven fabrics such as rayon spunbond are also used as absorbent paper. Since the non-woven fabric is composed of single fibers, the function of the non-woven fabric absorbent paper is such that the liquid diffusivity and the liquid absorptivity are in a contradictory relationship. That is, the diffusibility of the liquid tends to be improved by decreasing the fiber diameter of the single fiber, but this also reduces the distance between the fibers, and therefore the liquid absorption and permeability is deteriorated. On the contrary, when the fiber diameter of the single fiber is increased, the liquid absorption and permeability are improved, but the liquid diffusibility is deteriorated. As described above, the absorbent paper using the non-woven fabric cannot satisfy both the liquid diffusibility and the liquid absorption and permeability.

Japanese Patent Laid-Open No. 4-89053 discloses a highly absorbent and ultrathin structure in which an absorbent body is formed by combining various absorbent papers having different liquid absorption and liquid diffusivity and a highly absorbent polymer. Absorbent articles are disclosed. However, in such absorbent articles, temporary absorption / permeation / permeation /
Since each function of the absorbent article of diffusion / holding is assigned to each of the constituent members such as the absorbent paper and the superabsorbent polymer forming the absorbent body, there is a drawback that the structure of the absorbent body becomes complicated, and the cost is reduced. There is a problem called up.

Therefore, an object of the present invention is to provide an absorbent paper having a large liquid absorbing space, a high liquid absorbing and transmitting property, and a high liquid diffusing property, and a manufacturing method thereof.

It is another object of the present invention to provide an absorbent article which has a high liquid absorbency, a small liquid leakage, an ultrathin and comfortable wearing feeling.

[0017]

As a result of intensive studies, the inventors of the present invention have found that an absorbent paper obtained from a combination of specific fibers has both properties of liquid diffusibility and liquid absorptivity. I found out.

The present invention was made based on the above findings, and is an absorbent paper containing bulky cellulose fibers and hydrophilic fine fibers, wherein the hydrophilic fine fibers are one of the absorbent papers. Of the bulky cellulose fiber having an average fiber length of 1.5 to 20 mm and being crosslinked in its molecule or between molecules, or Fiber roughness is 0.3mg
/ M or more, and the hydrophilic fine fibers have a fiber roughness of 0.01 to 0.2 mg / m and an average fiber length of 0.
The above object is achieved by providing an absorbent paper having a thickness of 5 to 1 mm.

The present invention also provides a preferable method for producing the absorbent paper of the present invention, wherein the average fiber length is 1.5 to 20 m.
m and crosslinked in its molecule and between molecules, or bulky cellulose fiber having a fiber roughness of 0.3 mg / m or more and average fiber having a fiber roughness of 0.01 to 0.2 mg / m A step of dispersing a hydrophilic fine fiber having a length of 0.5 to 1 mm in water to form a slurry; a step of spraying the slurry on a papermaking wire to form a paper layer on the papermaking wire; And a step of dehydrating and drying the above-mentioned paper layer; and a method for producing an absorbent paper.

Furthermore, the present invention provides an absorbent article using the above-mentioned absorbent paper, a liquid-permeable surface material, a liquid-impermeable leakproof material, and a liquid interposed between the surface material and the leakproof material. In an absorbent article comprising a retentive absorbent body, the absorbent body comprises at least absorbent paper and a superabsorbent polymer, and the absorbent paper comprises bulky cellulose fibers and hydrophilic fine particles. The aforesaid hydrophilic fine fibers have a higher abundance ratio on one surface side of the absorbent paper than the abundance ratio on the other surface side of the absorbent paper, and the bulky cellulose fibers have an average fiber length of 1. 5 to 20 mm and crosslinked in the molecule or between the molecules, or the fiber roughness is 0.3 mg / m
The above is the fiber roughness of the hydrophilic fine fibers is 0.0
The present invention provides an absorbent article characterized by having an average fiber length of 1 to 0.2 mg / m and an average fiber length of 0.5 to 1 mm.

The absorbent paper of the present invention is useful as a puerperium pad, a breast milk pad, an underpad, a sweat absorbing sheet, an absorbent turban for a perm, a drip sheet, a medical pad and an undersheet for a bed. It is useful as absorbent paper for absorbent articles such as napkins and disposable diapers.

[0022]

The absorbent paper of the present invention contains bulky cellulose fibers and hydrophilic fine fibers as described above. The above-mentioned bulky cellulose fiber forms a bulky network structure in the absorbent paper of the present invention. On the other hand, the hydrophilic fine fibers have a higher abundance ratio on one side of the absorbent paper of the present invention than on the other side. As a result, on the surface side where the hydrophilic fine fibers are present in a low proportion, the liquid absorption rate and the local liquid absorptivity are excellent, and the liquid permeability is high. On the other hand, on the surface side where the hydrophilic fine fibers are present in a high proportion, since the hydrophilic fine fibers have a high surface area, the liquid diffusibility is excellent. Therefore, it is possible to quickly diffuse the liquid that has permeated the surface side where the hydrophilic fine fibers are present in a low proportion.
As described above, the absorbent paper of the present invention has both a liquid absorbing and transmitting property and a liquid diffusing property even though it has a single structure.

Further, according to the method for producing an absorbent paper of the present invention, the difference in fiber length and fiber diameter between the bulky cellulose fiber and the hydrophilic fine fiber is utilized to obtain the absorbent paper of the present invention. With respect to the existing ratio of the hydrophilic fine fibers in the thickness direction of, the gradient can be provided particularly easily.

First, the absorbent paper of the present invention will be described in detail with reference to the drawings together with a preferable manufacturing method thereof.

FIG. 1 is a schematic view showing a cross section in the thickness direction of the absorbent paper 11 of the present invention. As described above, the absorbent paper 11 of the present invention includes the bulky cellulose fibers 12 and the hydrophilic fine fibers 13, and the hydrophilic fine fibers 13 are present on one surface side of the absorbent paper 11. However, the bulky cellulose fibers 12 have an average fiber length of 1.5 to 20 mm and are crosslinked in the molecule or between the molecules, or have a fiber roughness of 0. The hydrophilic fine fibers 13 have a fiber roughness of 0.01 to 0.2 mg / m and an average fiber length of 0.5 to 1 mm.

As shown in FIG. 1, the hydrophilic fine fibers 13 contained in the absorbent paper 11 of the present invention have a gradient in the distribution in the thickness direction of the absorbent paper 11. That is, in the thickness direction of the absorbent paper 11, the hydrophilic fine fibers 13 have a higher abundance ratio on one side of the absorbent paper 11 than on the other side. In the following description, among the surfaces of the absorbent paper 11,
The surface having a lower proportion of the hydrophilic fine fibers 13 is referred to as a "front surface", and the surface having a higher proportion of the hydrophilic fine fibers 13 is referred to as a "back surface".

In FIG. 1, the upper side of the figure corresponds to the "back side" and the lower side of the figure corresponds to the "front side". However, the above "front side" to "front side" of the absorbent paper 11 of the present invention. Since the bulky cellulose fiber 12 is mainly used in the vicinity, it has a function of quickly absorbing the liquid and allowing the liquid to quickly permeate to the "back surface". That is, this region mainly functions as an "absorption-permeation layer" for the liquid. On the other hand, since the hydrophilic fine fibers 13 are mainly contained in the vicinity of the “rear surface” to the “rear surface”, it has a function of quickly diffusing the liquid that has permeated from the “front surface”. That is, this region primarily functions as a "diffusion layer" for liquids. As described above, the absorbent paper 11 of the present invention is characterized by having both the absorption and transmission layer and the diffusion layer in a single structure. As a result, the liquid absorption is high, and after absorbing the liquid, The surface is extremely dry (feeling of salat).

As described above, the "front surface" and the "back surface"
There is a large difference in the diffusibility of the liquid between. That is, on the "back surface" side (diffusion layer) where the hydrophilic fine fibers are the main constituent, the liquid diffuses quickly. On the other hand, on the "surface" side (absorption / permeation layer) where the bulky cellulose fiber is the main component, the absorption and transmission of liquid is rapid, but the diffusion of liquid is not so rapid. That is, the absorbent paper of the present invention has a diffusion gradient with respect to the diffusion of the liquid in the thickness direction. Therefore, for example, when the diffusion area when the absorbent paper of the present invention absorbs 1 g of physiological saline is used as a measure of the diffusibility of the liquid, the diffusion area on the “back surface” side is the diffusion area on the “front surface” side. It is larger than the diffusion area. In the present invention, the ratio of the diffusion area on the "back surface" side to the diffusion area on the "front surface" side in the absorbent paper of the present invention is preferably 1.2 or more, and more preferably 1.5 to. 20 and particularly preferably 2 to 20. The method of measuring the diffusion area will be described later.

The abundance ratio of the hydrophilic fine fibers in the absorbent paper of the present invention may gradually increase from the "front surface" to the "back surface", but in a stepwise manner with a certain thickness as a boundary. It may increase.

On the other hand, the bulky cellulosic fibers may be present uniformly in the thickness direction of the absorbent paper of the present invention, but it is more preferable that the cellulose fibers are present on the "back surface" side of the absorbent paper of the present invention. The existence ratio is higher on the "front surface" side. That is, it is preferable that the abundance ratio of the bulky cellulose fibers has a gradient in the thickness direction of the absorbent paper of the present invention. The existence ratio may be gradually increased from the “rear surface” to the “front surface”, or may be increased stepwise with a certain thickness as a boundary.

More specifically, the "back surface" of the absorbent paper of the present invention.
From the side to a depth of about 1/3 in the thickness direction, the hydrophilic fine fibers are preferably about 5 to about 70 based on the total amount thereof.
%, More preferably about 10 to about 50% by weight,
The diffusion layer mainly composed of the hydrophilic fine fibers is formed. On the other hand, the bulky cellulosic fibers are preferably contained in an amount of about 60 to about 100 based on the total amount of the absorbent paper of the present invention at a depth of about 2/3 in the thickness direction from the "surface" side.
%, More preferably about 70 to about 97% by weight,
The absorption-permeation layer mainly composed of the bulky cellulose fiber is formed.

As described above, the distribution of the bulky cellulose fibers and the hydrophilic fine fibers may be gradually increased in the thickness direction of the absorbent paper of the present invention. It may be increased in the shape. And
In a particularly preferred embodiment of the absorbent paper of the present invention in which both the bulky cellulose fiber and the hydrophilic fine fiber have a gradient in the distribution in the thickness direction of the absorbent paper, the liquid absorption and permeability And the diffusibility of the liquid can be more remarkably exhibited.

As described above, the absorbent paper of the present invention mainly has a "front surface" side for absorbing and transmitting liquid and a "rear surface" side for diffusing liquid. Therefore, when using the absorbent paper of the present invention, it is preferred that the "front" side of the absorbent paper be the side that comes into contact with the liquid first.

The mixing ratio of the bulky cellulose fiber and the hydrophilic fine fiber in the absorbent paper of the present invention is not particularly limited, but the bulky cellulose fiber is 100 parts by weight of the absorbent paper of the present invention. Based on the above, it is preferably contained in an amount of 50 to 97 parts by weight, more preferably 70 to 95 parts by weight. If the blending ratio of the above-mentioned bulky cellulose fibers is less than 50 parts by weight, the bulky network structure may be insufficient and an absorbent paper having both transmission and diffusion may not be obtained. If the blending ratio exceeds 97 parts by weight, the blending ratio of the hydrophilic fine fibers will be low and the diffusivity will be insufficient, so the above range is preferred.

The hydrophilic fine fibers are preferably contained in an amount of 3 to 50 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the absorbent paper of the present invention. If the blending ratio of the hydrophilic fine fibers is less than 3 parts by weight, the diffusivity becomes insufficient, and if the blending ratio of the hydrophilic fine fibers exceeds 50 parts by weight, the hydrophilic property on the "surface" side is reduced. Since the blending ratio of the fine fibers increases and the permeability becomes insufficient, the above range is preferable.

If desired, the absorbent paper of the present invention may contain heat-meltable adhesive fibers which are melted by heating and adhered to each other. By adding such a heat-meltable adhesive fiber, it is possible to maintain the structural stability of the absorbent paper of the present invention when it is wet.

It is preferable to add 2 to 30 parts by weight, and more preferably 3 to 20 parts by weight of the above-mentioned heat-meltable adhesive fiber based on 100 parts by weight of the absorbent paper of the present invention. If the amount added is less than 2 parts by weight, the strength of the absorbent paper of the present invention will be insufficient when the liquid is actually absorbed, and the bulky cellulose fibers and the hydrophilic fine fibers in the absorbent paper of the present invention will be in a mixed state. Is not preferable because the diffusion gradient may not be maintained due to changes in On the other hand, if the addition amount exceeds 30 parts by weight, the hydrophilicity of the entire absorbent paper is lowered, and the liquid absorption rate and the liquid diffusing ability may be insufficient, which is not preferable.

Other optional components that can be added to the absorbent paper of the present invention include, for example, other pulps such as softwood pulp, hardwood pulp and straw pulp, and dialdehyde starch, sponge and sodium carboxymethylcellulose as a strong adjuvant. Etc. can be mentioned. These components are 0% based on 100 parts by weight of the absorbent paper of the present invention.
Up to 20 parts by weight can be added.

The basis weight of the absorbent paper of the present invention is not particularly limited, but is preferably 10 to ²⁰⁰ g / m ² , and 20
More preferably, it is about 150 g / m ² . Basis weight is 1
If it is less than 0 g / m ² , the absorbent paper may be too thin to exhibit the functions of transmission and diffusion. If the basis weight exceeds 200 g / m ² , the absorbent paper may be thicker. It may be difficult for smooth passage of liquid such as passing, diffusion and diffusion to occur, so the above range is preferable.

The thickness of the absorbent paper of the present invention is not particularly limited, but the thickness under a load of 2.5 g / m ² is preferably 0.2 to 2 mm, more preferably 0.2 to 1 mm. preferable. If the thickness is less than 0.2 mm, the absorbent paper may be too thin to exhibit the functions of transmission and diffusion. If the thickness exceeds 2 mm, smooth transmission of liquid, transmission and diffusion, may occur. Since it may be difficult to occur, the above range is preferable.

In a preferred embodiment of the absorbent paper of the present invention, 50 to 97 parts by weight of the bulky cellulose fiber and 3 to 50 parts by weight of the hydrophilic fine fiber are contained based on 100 parts by weight of the absorbent paper. .

In a particularly preferred embodiment of the absorbent paper of the present invention, 70 to 95 parts by weight of the bulky cellulose fiber and 5 to 30 parts by weight of the hydrophilic fine fiber are used based on 100 parts by weight of the absorbent paper. , And 2 to 30 parts by weight of the hot-melt adhesive fiber; and the basis weight of the absorbent paper is 10 to 10.
It is 200 g / m ² .

The absorbent paper of the present invention is preferably produced by the method described below. That is, the absorbent paper of the present invention,
As shown in FIG. 2, the above-mentioned bulky cellulose fibers 12 and fibers having an average fiber length of 1.5 to 20 mm and having intramolecular and intermolecular crosslinks or a fiber roughness of 0.3 mg / m or more. The hydrophilic fine fibers 13 having a roughness of 0.01 to 0.2 mg / m and an average fiber length of 0.5 to 1 mm.
A step of dispersing and in water to form a slurry 14.
It is preferably manufactured by a method comprising the steps of spraying the slurry 14 on the papermaking wire 15 to form a paper layer 16 on the papermaking wire 15; and dehydrating and drying the paper layer 16.

Thus, the absorbent paper of the present invention is preferably produced by the wet papermaking method. The wet paper machine is not particularly limited, and for example, a round-net paper machine, a former paper machine, a twin-wire paper machine, and a Fourdrinier paper machine can be used.

The papermaking method will be described in more detail with reference to FIG. 3 which is an enlarged view of the portion (a) of FIG. When the slurry 14 is sprayed on the papermaking wire 15 (that is, in the initial stage of papermaking), the bulky cellulose fiber 12 has a fiber length larger than the opening diameter of the papermaking wire 15. While the bulky cellulose fiber 12 is deposited on the papermaking wire 15,
Since the fiber length of the hydrophilic fine fibers 13 in the slurry 14 is finer than the opening diameter of the papermaking wire 15, the hydrophilic fine fibers 13 pass through the papermaking wire 15. , Discharged with water. Therefore, in the initial stage of papermaking, a paper layer (absorption / transmission layer) mainly composed of the bulky cellulose fibers 12 is formed immediately above the papermaking wire 15.

When the paper layer (absorption / permeation layer) containing the bulky cellulose fibers 12 as a main component starts to be formed, the hydrophilic fine fibers 13 mainly have the bulky cellulose fibers 12 as the fiber length. Since it is larger than the inter-fiber distance in the paper layer, it cannot pass through the paper layer containing the bulky cellulose fibers 12 as a main component and starts to be deposited on the paper layer. This portion becomes a paper layer (diffusion layer) in which the bulky cellulose fiber 12 and the hydrophilic fine fiber 13 are mixed. That is, in the absorbent paper of the present invention, the side not in contact with the papermaking wire 15 is a paper layer (diffusion layer) in which the bulky cellulose fibers 12 and the hydrophilic fine fibers 13 are mixed. As a result, an absorbent paper having a gradient in the abundance ratio of the bulky cellulose fibers 12 and the hydrophilic fine fibers 13 in a single structure is obtained.

More specifically, the paper layer (absorption / permeation layer) mainly composed of the bulky cellulose fiber 12 is contained in the slurry 14 during the process of making the slurry 14 on the papermaking wire 15. It is formed by utilizing the difference between the fiber length of the fibers present in and the opening diameter of the papermaking wire. Then, a paper layer (diffusion layer) in which the bulky cellulose fibers 12 and the hydrophilic fine fibers 13 are continuously mixed from the paper layer (absorption / permeation layer) mainly composed of the bulky cellulose fibers 12 ) Is formed. That is, in the preferred method for producing absorbent paper of the present invention, the fiber length of the bulky cellulose fiber 12 and the papermaking wire 15 are
Between the average opening diameter, the fiber length of the hydrophilic fine fibers 13, and the average interfiber distance in the paper layer (absorption / permeation layer) mainly composed of the bulky cellulose fibers 12 described above. Fiber length of the cellulose fiber 12> Opening diameter of the papermaking wire 15> Fiber length of the hydrophilic fine fiber 13> Average fiber in the paper layer (absorption / transmission layer) mainly composed of the bulky cellulose fiber 12 Interspace] By making use of the above preferable relationship, an absorbent paper having a gradient in the abundance ratio of the bulky cellulose fibers 12 and the hydrophilic fine fibers 13 in a single structure is produced. As a result, as shown in FIG. 3, in the preferred method for producing absorbent paper of the present invention, the absorbent paper is formed on the farthest side from the papermaking wire 15 than in the paper layer formed immediately above the papermaking wire 15. The presence ratio of the hydrophilic fine fibers 13 is higher in the paper layer.

For this purpose, although the average fiber length of the hydrophilic fine fibers 13 is smaller than the opening diameter of the papermaking wire 15, a paper layer (absorption) mainly composed of the bulky cellulose fibers 12 is used. It is important to make it larger than the average inter-fiber distance in the permeable layer). The opening diameter of the paper making wire 15 is larger than the average fiber length of the hydrophilic fine fibers 13, but it is also important to make it smaller than the average fiber length of the bulky cellulose fibers 12. If the opening diameter of the papermaking wire 15 is too small, that is, the opening diameter of the papermaking wire 15 is the hydrophilic fine fiber 1
When the average fiber length is less than 3, the hydrophilic fine fibers 13 cannot pass through the papermaking wire 15 and the hydrophilic fine fibers 13 exist in the thickness direction of the absorbent paper of the present invention. It is not preferable because a gradient cannot be provided in the ratio. On the contrary, the above papermaking wire 1
If the opening diameter of 5 is too large, that is, if the opening diameter of the papermaking wire 15 is larger than the average fiber length of the bulky cellulose fibers 12, both fibers slip through the papermaking wire 15. , I can't even make paper. Therefore, the aperture diameter of the papermaking wire 15 is preferably 1 to 5 mm, and 1 to 2.
More preferably, it is 8 mm (16 to 6.5 mesh) (based on new JIS (1987)).

As described above, in the preferred method for producing an absorbent paper of the present invention, the difference in fiber length and fiber diameter between the bulky cellulose fiber 12 and the hydrophilic fine fiber 13 and the eyes of the papermaking wire 15 are obtained. By utilizing the difference in opening diameter, a gradient is provided in the abundance ratio of the hydrophilic fine fibers 13 in the thickness direction of the absorbent paper of the present invention.

According to the above-described preferred method for producing the absorbent paper of the present invention, a gradient can be provided particularly easily in the distribution of the hydrophilic fine fibers 13 in the thickness direction of the absorbent paper of the present invention.

According to the above-mentioned method, it is possible to manufacture the absorbent paper which can exhibit the liquid absorption and the permeability and the liquid diffusivity in one papermaking process, and the papermaking process can be simplified. .

The concentration of the bulky cellulose fibers 12 in the slurry 14 is preferably 0.02 to 1% by weight, more preferably 0.03 to 0.7% by weight, based on the total amount of the slurry. %. If the concentration of the bulky cellulose fibers 12 is less than 0.02% by weight, the desired permeation rate becomes insufficient, or the amount of waste water for obtaining the desired basis weight becomes too large, resulting in energy loss. Cellulosic fiber 12 which has a large loss and is bulky
If the concentration exceeds 1% by weight, the dispersibility of the fibers deteriorates and unevenness of the paper layer may occur. Therefore, the above range is preferable.

The concentration of the hydrophilic fine fibers 13 in the slurry 14 is based on the total amount of the slurry.
The amount is preferably 0.002 to 0.5% by weight, and more preferably 0.003 to 0.3% by weight. If the concentration of the hydrophilic fine fibers 13 is less than 0.002% by weight, the desired diffusivity may not be obtained, and the concentration of the hydrophilic fine fibers 13 may be 0.5% by weight. If it exceeds, the hydrophilic fine fibers 13 may be present also on the "surface" side, and the desired diffusion gradient may not be obtained, so
The above range is preferable.

The concentration of the above-mentioned heat-meltable adhesive fiber which is optionally used in the absorbent paper of the present invention is preferably 0.001 to 0.3% by weight in the above slurry, and 0.002 to 0.002% by weight. More preferably, it is 0.2% by weight. If the above concentration is less than 0.001% by weight, the purpose of keeping the structure of the absorbent paper stable may not be achieved, and if the above concentration exceeds 0.3% by weight, the hydrophilicity of the entire absorbent paper will be reduced. In some cases, the above range is preferable.

Next, the bulky cellulose fiber will be described in detail.

In the absorbent paper of the present invention, it is preferable to form a network structure of the bulky cellulose fibers. Such a network structure is a particularly preferred structure because it quickly absorbs liquid and allows liquid to quickly permeate to the "back" side. For this purpose, the bulky cellulose fibers have an average fiber length of 1.5 to 20 m.
m is necessary, and the preferable average fiber length is 2 to
10 mm, more preferable average fiber length is 2 to 5 mm
Is. If the average fiber length is less than 1.5 mm, the bulky network structure cannot be formed, and if it is smaller than the opening diameter of the papermaking wire,
The papermaking wire cannot be slipped through to make paper. When the average fiber length exceeds 20 mm, the dispersibility in water deteriorates and a uniform network structure cannot be formed. It is important that the bulky cellulosic fibers are cellulosic fibers capable of forming a bulky structure as the paper layer formed on the papermaking wire and as the resulting absorbent paper. If a bulky structure cannot be formed, the obtained absorbent paper will have a dense structure, and it will not be possible to obtain excellent absorption rate and transmission rate, or the diffusion gradient will not be obtained, which is not preferable.

As the bulky cellulose fiber, any cellulose fiber may be used as long as it is bulky.
As the cellulose fiber, for example, natural cellulose such as wood pulp or cotton, regenerated cellulose such as rayon or cupra can be used. From the viewpoint of cost, it is preferable to use wood pulp, especially softwood pulp (NBK).
P) is preferably used. These cellulose fibers may be used alone or in combination of two or more.

The above-mentioned bulky cellulose fiber has a fiber length within the above range and is cross-linked within or between its molecules; or, when a network of cellulose fibers is formed, the fiber itself. Is bulky, that is, it is thick as a structure, and specifically, the fiber roughness must be 0.3 mg / m or more.
In particular, it is preferable that the above-mentioned bulky cellulose fiber has both the above conditions and the condition that the average fiber length is 1.5 to 20 mm. Further, the bulky cellulose fibers have an average fiber length of 1.5 to 20.
In addition to having the condition of mm and the above or condition, the following condition, that is, the cross-sectional shape of the fiber is round, specifically, the roundness of the fiber cross section is 0.5 to 1. It is more preferable to satisfy certain conditions. Still further, the bulky cellulose fiber has an average fiber length of 1.5 to 20 mm and the above.
It is even more preferable to satisfy all the conditions (1) and (2). Hereinafter, the above conditions 1 to 3 will be described.

First, the above conditions will be described.
The bulky cellulose fibers have an average fiber length of 1.5 to
It is a crosslinked cellulose fiber having a length of 20 mm and having intramolecular and intermolecular crosslinking of the cellulose fiber. Such crosslinked cellulose fibers can maintain a bulky structure even in a wet state. A more preferred bulky cellulose fiber is a crosslinked pulp obtained by crosslinking a pulp having an average fiber length of 2 to 5 mm. Further, the fiber roughness is 0.3 mg / m or more (more preferably 0.
It is also preferable that 3 to 2 mg / m, more preferably 0.32 to 1 mg / m) of pulp is crosslinked. Further, it is also preferable that pulp having a roundness of the fiber cross section of 0.5 to 1 is cross-linked. Furthermore, Merce

Next, the absorbent article of the present invention using the absorbent paper of the present invention will be described with reference to FIGS. 4 and 5.

Here, FIG. 4 is a schematic view showing a cross section in the width direction of a sanitary napkin as one embodiment of the absorbent article of the present invention. FIG. 5: is a schematic diagram which shows the cross section of the sanitary napkin as another aspect of the absorbent article of this invention in the width direction (FIG. 4).
(Corresponding figure).

The absorbent article of the present invention comprises a liquid-permeable surface material, a liquid-impermeable leak-proof material, and a liquid-retaining absorber interposed between the surface material and the leak-proof material. It is characterized in that the above-mentioned absorber comprises at least the absorbent paper of the present invention and a superabsorbent polymer.

A sanitary napkin 10 as one embodiment of the absorbent article of the present invention shown in FIG. 4 has a liquid-permeable surface material 2
1. A liquid impermeable leak preventer 23 and a liquid retaining absorbent 22 interposed between the surface member and the leak preventer.

More specifically, the sanitary napkin 10 described above.
Is substantially vertically long, and when the sanitary napkin 10 is worn, the surface material 21 is located on the side in contact with the skin, and the leak preventer 23 is located on the side in contact with the underwear. The absorber 22 is interposed between the surface material 21 and the leak preventer 23.

Further, as shown in FIG. 4, the absorbent body 22 has the lower surface, all side surfaces, and the peripheral edge portions of the upper surface, which are the leakage preventing material 2.
It is covered by 3. Furthermore, the entire surface of the combination of the absorber 22 and the leak preventer 23 is the surface material 2 described above.
It is covered by 1. As a result, the absorber 22
The central portion of the upper surface of is directly covered with the surface material 21. Therefore, the liquid directly permeates the absorber 22 through the surface material 21.

On the side of the surface material 21 that does not come into contact with the skin, three adhesive portions 24 are formed in a stripe shape in the longitudinal direction. The adhesive section 24 is protected by a release paper 25. In FIG. 4, reference numeral 26 is an adhesive that fixes the surface material 21, the absorber 22, and the leak preventer 23 to each other.

The surface material 21 is not particularly limited as long as it allows liquid to pass through the absorbent body 22, but a material having a feeling close to that of underwear is preferable. Examples of such a surface material include, for example, woven fabric, non-woven fabric, and porous film of thermoplastic resin. In particular, an apertured film made of polyolefin such as low density polyethylene can be preferably used.

The apertured film can be manufactured, for example, by the following method. That is, a polyolefin such as low-density polyethylene is melted and extruded from a T-die to form a film on the spiral braided wire net 31 composed of the wire rod 31a shown in FIGS. 6 (A) and 6 (B). Then, by aspirating such a film, FIG.
The apertured film 42 having the apertures 44 shown in (A) is obtained. As shown in FIGS. 7 (B) and 7 (C), the perforated film 42 has a large number of tops 45 formed of convex curved surfaces.
And a large number of apertures 44 located between the tops 45.

The leakage preventive material 23 is not particularly limited as long as it is liquid impermeable, but it is particularly preferable that it has moisture permeability and a feel close to that of underwear. The liquid impermeable leak preventer having moisture permeability is, for example, a thermoplastic resin to which a filler of an inorganic compound or an organic compound is added, is melt-extruded from a T die or a circular die to form a film, and then, It can be obtained by uniaxially or biaxially stretching the film.

As shown in FIG. 4, the absorbent body 22 of the absorbent article of the present invention comprises at least the absorbent paper 22A of the present invention and the superabsorbent polymer 22B. Such an absorber 22
Since its thickness is extremely thin, it can be worn comfortably, and it is highly absorbent and less likely to leak.

More specifically, the above superabsorbent polymer 22
B is wrapped inside the absorbent paper 22A of the present invention, and the super absorbent polymer 22B is sandwiched between the absorbent paper 22A of the present invention. In this case, it is preferable to sandwich the superabsorbent polymer 22B between the absorbent papers 22A of the present invention so that the superabsorbent polymer 22B contacts the "back surface" of the absorbent paper 22A of the present invention. With such a configuration, the liquid that has passed through the surface material 21 is quickly absorbed and permeated by the “surface” of the absorbent paper 22A of the present invention,
The "rear surface" of the absorbent paper 22A is more smoothly reached.
The liquid that has reached the "back surface" of the absorbent paper 22A is diffused throughout the absorbent paper 22A of the present invention and then fixed to the superabsorbent polymer 22B.

As described above, in the absorbent article of the present invention, absorption / permeation / diffusion / holding of liquid is performed extremely smoothly. As a result, the absorbent article of the present invention can more reliably immobilize the liquid, and moreover, the surface material 2 described above.
The liquid does not remain on the surface 1 and the liquid does not return to the surface material 21. Further, when the absorbent body 22 is composed of only one sheet of absorbent paper 22A and the superabsorbent polymer 22B, the absorbent article can be made extremely thin and have a comfortable fit.

The superabsorbent polymer 22B is preferably a polymer capable of absorbing and retaining 20 times or more of its own weight of liquid and gelling. The super absorbent polymer 22B
The shape is not particularly limited, and for example, a spherical shape, a flaky shape, or a particle shape can be used. Examples of such superabsorbent polymers include starch-acrylic acid (salt) graft copolymers, saponified starch-acrylonitrile copolymers, crosslinked sodium carboxymethyl cellulose and acrylic acid (salt) polymers. Can be mentioned.

Another embodiment of the absorbent article of the present invention using the absorbent paper of the present invention will be described with reference to FIG. 5 by taking a sanitary napkin as an example. The same points as those in FIG. 4 will not be described in detail, but the description in detail regarding FIG. 4 will be applied as appropriate. Further, in FIG. 5, the same members as those in FIG. 4 are designated by the same reference numerals.

The absorbent body 22 in the sanitary napkin 10 as another embodiment of the absorbent article of the present invention shown in FIG.
The absorbent paper 22 of the present invention comprises two absorbent papers 22A and 22C of the present invention and the super absorbent polymer 22B.
The super absorbent polymer 22B is sandwiched between A and 22C. In this case, it is preferable that the "back surface" of the absorbent paper 22A is in contact with the superabsorbent polymer 22B. Further, it is preferable that the "back surface" of the absorbent paper 22C is also in contact with the superabsorbent polymer 22B. Particularly preferably, the "back surface" of the absorbent paper 22A is in contact with the superabsorbent polymer 22B, and the "back surface" of the absorbent paper 22C is in contact with the superabsorbent polymer 22B. With such a structure, absorption / permeation / diffusion / holding of liquid can be performed extremely smoothly.

The absorbent article of the present invention using the absorbent paper of the present invention has been described based on its preferred embodiment.
The absorbent article of the present invention is not limited to the above aspect, for example,
It goes without saying that the same can be applied to other absorbent articles such as paper diapers and incontinence pads.

[0077]

EXAMPLES Next, the absorbent paper of the present invention and its manufacturing method will be described in more detail with reference to Examples and Comparative Examples.

First, production of bulky cellulose fibers and hydrophilic fine fibers used in Examples and Comparative Examples will be described. In the following description, "%" means "% by weight" unless otherwise specified.

Production Example 1 Production of Bulky Cellulose Fibers The average fiber length is 2.35 mm and the fiber roughness is 0.36.
mercerized pulp with a roundness of 0.80 in the fiber cross section of 0.80 mg / m (“POROSA” manufactured by ITT RAYONIER INC.
NIER-J "(trade name) 100 g, 5% dimethylol dihydroxyethylene urea (crosslinking agent," Sumitex Resin NS-19 "(trade name) manufactured by Sumitomo Chemical Co., Ltd.) and 3% metal salt Catalyst (Sumitex manufactured by Sumitomo Chemical Co., Ltd.
Aqueous solution containing Accelerator X-110 "(trade name) 10
The mercerized pulp was dispersed in 00 g to impregnate the crosslinking agent.

Then, after the aqueous solution of the crosslinking agent was separated from the mercerized pulp until the amount of the aqueous solution of the crosslinking agent with respect to the mercerized pulp reached 200%, it was heated in an electric dryer at 135 ° C. for 10 minutes, The cellulose in the mercerized pulp was crosslinked to obtain a mercerized crosslinked pulp. This is designated as cellulose fiber (A).

Production Example 2 Production of Bulky Cellulose Fibers The average fiber length is 2.56 mm and the fiber roughness is 0.35.
mg / m and 100 g of coniferous Krato pulp (“INDORAYON” (trade name) manufactured by PT Inti Indorayon Utama) having a roundness of the fiber cross section of 0.28, 5% dimethylol dihydroxyethylene urea (crosslinking agent) "Sumitex Resin NS-19" (trade name) manufactured by Sumitomo Chemical Co., Ltd. and 3% metal salt catalyst ("Sumite manufactured by Sumitomo Chemical Co., Ltd."
x Accelerator X-110 "(trade name))
After being dispersed in 000 g, the mercerized pulp was impregnated with the crosslinking agent.

Then, the aqueous solution of the crosslinking agent was removed from the softwood kraft pulp until the amount of the aqueous solution of the crosslinking agent with respect to the softwood kraft pulp reached 200%, and then heated in an electric dryer at 135 ° C. for 10 minutes. The cellulose in the softwood kraft pulp was crosslinked to obtain a crosslinked pulp. This is designated as cellulose fiber (B).

Production Example 3 Production of Bulky Cellulose Fibers The average fiber length is 2.35 mm and the fiber roughness is 0.36.
mercerized pulp with a roundness of 0.80 in the fiber cross section of 0.80 mg / m (“POROSA” manufactured by ITT RAYONIER INC.
NIER-J "(product name)) was prepared. This is designated as cellulose fiber (C). The cellulose fiber (C) is not crosslinked.

Production Example 4 Production of Bulky Cellulose Fibers The average fiber length is 2.38 mm and the fiber roughness is 0.32.
Cross-linked pulp (“High Bulk Additive HBA-S” (trade name) manufactured by Weyerhauser Paper) having mg / m and a roundness of a fiber cross section of 0.30 was prepared. This is designated as cellulose fiber (D).

Production Example 5 Production of Bulky Cellulose Fiber The average fiber length is 2.56 mm and the fiber roughness is 0.24.
Coniferous kraft pulp NBKP (MacMillanBloedel L) with mg / m and a roundness of fiber cross section of 0.34
"HARMAC-R" (trade name) of td. was prepared. This is designated as cellulose fiber (E). The cellulose fiber (E) is not crosslinked.

Production Example 6 Production of Bulky Cellulose Fibers The average fiber length is 2.56 mm and the fiber roughness is 0.35.
A softwood Krato pulp (“INDORAYON” (trade name) manufactured by PT Inti Indorayon Utama) having mg / m and a roundness of a fiber cross section of 0.28 was prepared. This is called cellulose fiber (F). The cellulose fiber (F) is not crosslinked.

Production Example 7 Production of Bulky Cellulose Fiber The average fiber length is 0.75 mm and the fiber roughness is 0.13.
Hardwood kraft pulp with a roundness of 0.35 mg / m and a fiber cross section of 0.35 (“BAHIA SUL Co.
Crosslinked pulp was obtained in the same manner as in Production Example 1 except that "SUL CELULOSE SA" (trade name) was used. This is designated as cellulose fiber (G).

The average fiber length, the fiber roughness and the roundness of the fiber cross section of the above cellulose fibers (A) to (G) were measured by the following methods. Table 1 shows the results.

<Measurement of Average Fiber Length and Fiber Roughness> It was measured using a fiber roughness meter FS-200 (manufactured by KAJAANI ELECTRONICS LTD.). First, in order to determine the true weight of the cellulose fiber, the cellulose fiber is dried in a vacuum dryer at 100 ° C.
And dried for 1 hour to remove water present in the cellulose fiber.

Accurately weigh approximately 1 g of cellulose fiber to an accuracy of ± 0.1 mg. Next, in order not to damage the cellulose fiber, the cellulose fiber was completely disintegrated in 150 ml of water with a mixer attached to the fiber roughness meter, diluted with water to 5000 ml, and diluted with 50 ml of the diluted solution. Was accurately measured and used as a fiber roughness measuring solution, and the average fiber length and the fiber roughness were determined according to the operation procedure of the fiber roughness meter. As the average fiber length, a value calculated by the following formula based on the above operation was used.

[0091]

[Equation 1]

<Measurement of Roundness of Fiber Cross Section> To measure the roundness of the cellulose fiber cross section, first, the cellulose fiber is sliced perpendicularly to the cross section direction so that the area of the cross section of the cellulose fiber does not change, and the electron A cross-sectional photograph was taken with a microscope, and the cross-sectional photograph was analyzed by an image analyzer (“Avio EXCEL” (trade name) manufactured by Nippon Avionics Co., Ltd.), and the roundness of the cellulose fiber cross section was obtained using the formula shown below. . The roundness was an average value obtained by measuring 100 cross sections of an arbitrary cellulose fiber.

[0093]

[Equation 2]

[0094]

[Table 1]

[Production Example 8] Production of hydrophilic fine fibers The average fiber length was 0.75 mm, and the fiber roughness was 0.09.
Hardwood pulp (mg / m EUCA manufactured by RIO CELL SA Co.
LYPTUS (product name)) was prepared. This is referred to as hydrophilic fine fiber (A).

[Production Example 9] Production of hydrophilic fine fibers The average fiber length was 0.80 mm and the fiber roughness was 0.13.
Hardwood pulp (Kitami (trade name) manufactured by Mitsubishi Paper Mills, Ltd.) of mg / m was prepared. This is a hydrophilic fine fiber (B).

[Production Example 10] Production of hydrophilic fine fibers The average fiber length was 2.34 mm and the fiber roughness was 0.13.
Softwood kraft pulp (Skeena Cellulose)
"Skeena PRIME" (trade name) manufactured by Co. was prepared. This is a hydrophilic fine fiber (C).

[Production Example 11] Production of hydrophilic fine fiber The finely selected pulp was acid-hydrolyzed, washed with water and dried, and then finely pulverized by mechanical pulverization. Average fiber length 0.02 mm, fiber roughness 0.08 mg. / M of cellulose fine fiber (“KC Flock W-400” (trade name) manufactured by Sanyo Kokusaku Pulp Co., Ltd.) was prepared. This is a hydrophilic fine fiber (D).

Example 1 Production of absorbent paper Cellulose fiber (A) concentration was 0.16% by weight, hydrophilic fine fiber (A) concentration was 0.05% by weight, and thickness 1
The density of denier of polyvinyl alcohol fiber having an average fiber length of 3 mm (heat-melting adhesive fiber, hereinafter referred to as PVA, Fibribond (trade name) manufactured by Sansho Co., Ltd.) is 0.0.
1% by weight (0.022
% By weight), and these were uniformly dispersed in water to obtain a slurry. This slurry has a wire opening diameter of 1.4 mm (1
(2 mesh) and sprayed onto a papermaking wire to form a paper layer on the papermaking wire. Using the suction box,
The paper layer was dehydrated. In the dehydrated aqueous solution, about 0.
It contained 02% by weight of fibers, and most of them were hydrophilic fine fibers (A). Then, after the paper layer was dried with a dryer, 10% of crepe was applied and the basis weight was 8
An absorbent paper of 0 g / m ² was obtained. This absorbent paper is absorbent paper 10
80 parts by weight of cellulose fiber (A) based on 0 parts by weight,
It contained 15 parts by weight of hydrophilic fine fibers (A) and 5 parts by weight of the PVA fibers. Moreover, this absorbent paper had a gradient in the abundance ratio of hydrophilic fine fibers in the thickness direction.

[Example 2] Production of absorbent paper Cellulose fiber (B) concentration was 0.16% by weight, hydrophilic fine fiber (B) concentration was 0.05% by weight, and thickness 1
Denier concentration of 3 mm PVA (heat-melting adhesive fiber, Fibribond (trade name) manufactured by Sansho Co., Ltd.) is 0.
Absorbing paper having a basis weight of 80 g / m ² was obtained by performing the same operation as in Example 1 except that these were uniformly dispersed in water to form a slurry so that the amount of the absorbent paper was 006% by weight. The dehydrated aqueous solution contained about 0.016% by weight of fibers, and most of them were hydrophilic fine fibers (B).
This absorbent paper contains 80 parts by weight of cellulose fiber (B) and 1 part of hydrophilic fine fiber (B) based on 100 parts by weight of absorbent paper.
It contained 7 parts by weight and 3 parts by weight of the PVA fiber. Moreover, this absorbent paper had a gradient in the abundance ratio of hydrophilic fine fibers in the thickness direction.

Example 3 Production of absorbent paper Cellulose fiber (C) concentration was 0.16% by weight, hydrophilic fine fiber (A) concentration was 0.05% by weight, and thickness was 1.1 denier. In order to make the concentration of polyethylene terephthalate fiber having an average fiber length of 5 mm (heat-melting adhesive fiber, hereinafter referred to as PET, "TMOTNSB" (trade name) of Teijin Ltd.) 0.01% by weight, The same operation as in Example 1 was performed, except that the absorbent paper was uniformly dispersed in water to obtain a slurry, to obtain an absorbent paper having a basis weight of 80 g / m ² . The dehydrated aqueous solution contained about 0.02% by weight of fibers, and most of them were hydrophilic fine fibers (A).
This absorbent paper contains 80 parts by weight of cellulose fiber (C) and 1 part of hydrophilic fine fiber (A) based on 100 parts by weight of absorbent paper.
5 parts by weight and 5 parts by weight of the PET fiber were contained. Moreover, this absorbent paper had a gradient in the abundance ratio of hydrophilic fine fibers in the thickness direction.

Example 4 Production of Absorbent Paper Cellulose fiber (D) concentration was 0.16% by weight, hydrophilic fine fiber (B) concentration was 0.05% by weight, and thickness 1
Denier concentration of 3 mm PVA (heat-melting adhesive fiber, Fibribond (trade name) manufactured by Sansho Co., Ltd.) is 0.
Absorbing paper having a basis weight of 80 g / m ² was obtained by performing the same operation as in Example 1 except that these were uniformly dispersed in water to form a slurry so that the amount of the absorbent paper was 006% by weight. The dehydrated aqueous solution contained about 0.016% by weight of fibers, and most of them were hydrophilic fine fibers (B).
This absorbent paper contains 80 parts by weight of cellulose fiber (D) and 1 part of hydrophilic fine fiber (B) based on 100 parts by weight of absorbent paper.
It contained 7 parts by weight and 3 parts by weight of the PVA fiber. Moreover, this absorbent paper had a gradient in the abundance ratio of hydrophilic fine fibers in the thickness direction.

Comparative Example 1 Production of Absorbent Paper An absorbent paper was obtained in the same manner as in Example 1 except that cellulose (E) was used instead of cellulose fiber (A). The dehydrated aqueous solution contained about 0.02% by weight of fibers, and most of them were hydrophilic fine fibers (A). Then, after the paper layer was dried with a dryer, 10% of crepe was applied to obtain an absorbent paper having a basis weight of 80 g / m ² . This absorbent paper contained 80 parts by weight of the cellulose fibers (E), 15 parts by weight of the hydrophilic fine fibers (A), and 5 parts by weight of the PVA fibers based on 100 parts by weight of the absorbent paper.

Comparative Example 2 Production of Absorbent Paper Cellulose (F) was used instead of cellulose fiber (B), and hydrophilic fine fiber (C) was used instead of hydrophilic fine fiber (B). Perform the same operation as in Example 2,
An absorbent paper having a basis weight of 80 g / m ² was obtained. The dehydrated aqueous solution contained almost no fibers. This absorbent paper contains cellulose fiber (F) based on 100 parts by weight of the absorbent paper.
74 parts by weight, hydrophilic fine fibers (C) 23 parts by weight,
It contained 3 parts by weight of the PVA fiber.

Comparative Example 3 Production of Absorbent Paper The same operation as in Example 2 was carried out except that the hydrophilic fine fibers (D) were used instead of the hydrophilic fine fibers (B), and the basis weight was 80 g / m 2. ² absorbent paper was obtained. The dehydrated aqueous solution contained about 0.048% by weight of fibers, and most of them were hydrophilic fine fibers (D). This absorbent paper is based on 100 parts by weight of absorbent paper (Cellulose fiber (B))
In an amount of 95 parts by weight, 1 part by weight of the hydrophilic fine fiber (D), and 4 parts by weight of the PVA fiber.

[Comparative Example 4] Production of absorbent paper The opening diameter of the papermaking wire was 1.4 mm (12 mesh).
To 0.09 mm (166 mesh), an absorbent paper having a basis weight of 80 g / m ² was obtained in the same manner as in Example 3. The dehydrated aqueous solution contained almost no fibers. This absorbent paper contained 73 parts by weight of the cellulose fibers (C), 23 parts by weight of the hydrophilic fine fibers (A), and 4 parts by weight of the PET fibers based on 100 parts by weight of the absorbent paper.

[Comparative Example 5] Production of absorbent paper Cellulose fiber (G) concentration was 0.16% by weight, hydrophilic fine fiber (D) concentration was 0.05% by weight, and thickness 1
Denier concentration of 3 mm PVA (heat-melting adhesive fiber, Fibribond (trade name) manufactured by Sansho Co., Ltd.) is 0.
01% by weight (0.02 as a whole slurry)
2% by weight), and these were uniformly dispersed in water to obtain a slurry. Wire diameter of this slurry is 0.09mm
It was sprinkled on a (166 mesh) paper making wire to form a paper layer on the paper making wire. The paper layer was dehydrated using a suction box. In the dehydrated aqueous solution,
It contained almost no fiber. This absorbent paper contains 73 parts by weight of cellulose fiber (G) based on 100 parts by weight of the absorbent paper.
Parts by weight, 23 parts by weight of hydrophilic fine fiber (D), P
It contained 4 parts by weight of VA fiber.

[Comparative Example 6] Production of absorbent paper The opening diameter of the papermaking wire was 1.4 mm (12 mesh).
From 5.6 mm (3.5 mesh) to
Papermaking was carried out in the same manner as in Example 2, but most of the fibers slipped from the papermaking wire, and papermaking was not possible.

The following measurements were performed on the absorbent papers obtained in Examples 1 to 4 and Comparative Examples 1 to 6 above. The results are shown in Table 2.

<Measurement of Absorption Time> As shown in FIG. 8, an absorption paper 51 (200 mm × 75 mm) is placed horizontally, an acrylic plate 52 having an injection port 54 with a diameter of 10 mm is placed thereon, and further on top of that. Place the weight 53 on the absorbent paper 51
A load of g / cm ² was applied. Next, 6 g of defibrinated horse blood (manufactured by Japan Biotest Institute Co., Ltd.) was injected from the injection port 54, and the time until the defibrinated horse blood was completely absorbed was measured. The absorption time was defined as the average of 5 measurements.

<Measurement of Diffusion Area> As shown in FIG. 9, the absorbent paper 1 was horizontally installed so that the “front surface” of the absorbent paper 51 (200 × 75 mm) was on the upper side, and the diameter of 2 mm from the microtube pump 60. 1 g of physiological saline 62 was injected into the absorbent paper 51 at a speed of 1 g / 10 seconds through a tube 61 having an injection port of. The distance between the tip of the tube 61 and the absorbent paper was about 10 mm. Saline is 0.0
It was colored with 1% food blue No. 1 (Tokyo Chemical Industry Co., Ltd.) and used. About 1 minute after injection of physiological saline, the diffusion area (cm ² ) on the “surface” of the absorbent paper was accurately traced and measured by an image analyzer. The same operation is performed by horizontally setting the absorbent paper 1 so that the “rear surface” of the absorbent paper 51 is on the upper side, accurately tracing the diffusion area (cm ² ) of the “rear surface”, and measuring with an image analyzer. did. Next, the diffusion area ratio between the "front side" and the "back side" of the absorbent paper was obtained by rounding off to the second decimal place according to the following formula.

[0112]

(Equation 3)

<Evaluation of Surface State after Absorption of Liquid> As shown in FIG. 6, the absorption paper 51 is horizontally installed so that the “surface” of the absorption paper 51 (200 × 75 mm) is on the upper side, and the microtube pump 60 is used. Then, 3 g of physiological saline was injected into the absorbent paper 51 at a speed of 1 g / 10 seconds through a tube 61 having an injection port with a diameter of 2 mm. Approximately 1 minute after the injection of physiological saline, a sensory evaluation of the "latency" of the "surface" of the absorbent paper was performed. The same operation was performed by horizontally installing the absorbent paper 1 so that the “back surface” of the absorbent paper 51 was on the upper side. The evaluation criteria are as follows.

◯: Physiological saline is hardly retained on the absorbent paper, and there is a feeling of slat. Δ: A little saline is retained on the absorbent paper, but there is some sensation of slat. X: A considerable amount of physiological saline remains on the absorbent paper, and it feels sticky.

[0115]

[Table 2]

As is clear from the results shown in Table 2, the absorbent paper of the present invention has a fast absorption time, has a liquid diffusion gradient, and is excellent in slatiness. On the other hand, in the absorbent paper of the comparative example, since there is no diffusion gradient related to the diffusibility of the liquid in the thickness direction, since the absorbed liquid remains on the surface forever, an absorbent paper excellent in the surface slat feel is obtained. I can't. In addition, Example 3
As is clear from the comparison between Comparative Example 4 and Comparative Example 4 and the comparison between Example 2 and Comparative Example 6, if the selection of the mesh opening diameter of the paper making mesh to be used is not appropriate, the absorbent paper obtained will have the above hydrophilicity. It is not possible to obtain a gradient in the proportion of fine fibers or to make paper itself.

Next, the production of the absorbent article provided with the absorbent paper of the present invention will be described.

[Example 5] Production of absorbent article A sanitary napkin 10 shown in Fig. 4 was produced. The absorbent paper (length 195 mm, width 160 mm) obtained in Example 1 was used as the absorbent paper 22A. The superabsorbent polymer 22B was dispersed substantially uniformly on the area of the back surface side of the absorbent paper 22A having a length of 195 mm and a width of 70 mm so that the spray amount was 50 g / m ² . Then, the absorbent paper 22A is folded inward, and the superabsorbent polymer 22B is wrapped with the absorbent paper 22A to manufacture the absorbent body 22 (therefore, the "surface" of the absorbent paper 22A).
The side corresponds to the outside of the absorber 22). The width of the absorber 22 is 7
It was 5 mm. Sodium polyacrylate (Polymer Q (trade name) manufactured by Kao Corporation) was used as the superabsorbent polymer 22B. The absorbent body 22 was wrapped with polyethylene laminated paper (leak-proof material 23), and the combination of the absorbent body 22 and the leak-proof material 23 was further wrapped with the surface material 21. Then, the surface material 21, the absorber 22, and the leak preventer 23 were fixed to each other with an adhesive 26. As the surface material 21, the perforated film shown in FIG. 7 was used. The perforated film is formed by melt-extruding low-density polyethylene through a T die to form a film on the spiral braided wire net shown in FIG. 6 and then sucking the film. Furthermore,
On the lower surface side of the sanitary napkin 10, three adhesive portions 24 were formed in a stripe shape in the longitudinal direction. The adhesive section 24 is provided on the release paper 2
Protected by 5.

Example 6 Manufacture of Absorbent Article The procedure of Example 5 was repeated except that the absorbent paper obtained in Example 2 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

Example 7 Production of Absorbent Article The procedure of Example 5 was repeated except that the absorbent paper obtained in Example 3 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

Example 8 Production of Absorbent Article The procedure of Example 5 was repeated except that the absorbent paper obtained in Example 4 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

[Comparative Example 7] Production of absorbent article The same operation as in Example 5 was carried out except that the absorbent paper obtained in Comparative Example 1 was used in place of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

[Comparative Example 8] Production of absorbent article The same operation as in Example 5 was carried out except that the absorbent paper obtained in Comparative Example 2 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

[Comparative Example 9] Production of absorbent article Physiology was performed in the same manner as in Example 5 except that the absorbent paper obtained in Comparative Example 3 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

[Comparative Example 10] Production of absorbent article Physiology was performed in the same manner as in Example 5 except that the absorbent paper obtained in Comparative Example 4 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

Comparative Example 11 Production of Absorbent Article Physiology was performed in the same manner as in Example 5 except that the absorbent paper obtained in Comparative Example 5 was used instead of the absorbent paper obtained in Example 1. A napkin for use was manufactured.

With respect to the sanitary napkins obtained in Examples 5 to 8 and Comparative Examples 7 to 11, the absorption time, the amount of dynamic liquid return and the leak test (number of leak occurrences) were measured by the following methods.
Table 3 shows the results.

<Absorption time and dynamic liquid return amount> In the apparatus for measuring the liquid absorption time of absorbent paper shown in FIG. 8, the sanitary napkin 10 is placed horizontally instead of the absorbent paper 51, and the diameter is 10 m.
The acrylic plate 52 having the injection port 54 of m is placed thereon, and the weight 53 is further placed thereon, and the sanitary napkin 10
A load of 5 g / cm ² was applied to. Next, 6 g of defibrinated horse blood (manufactured by Japan Biotest Institute Co., Ltd.) from the inlet 54
Was injected, and the time until the defibrinated horse blood was completely absorbed was measured.

After defibrinated horse blood is completely absorbed, it is left for 20 minutes. Then, this sanitary napkin 10
Paper (length 195 mm x width 75 m) on the upper surface (skin contact surface side) of
10 sheets of m and a basis weight of 30 g / m ² were stacked and the sanitary napkin 10 and paper in this state were mounted on the female waist model 70 shown in FIG. 10 as shown in FIG. Next, the female waist model 70 was fitted with shorts, and then walked at a walking speed of 100 steps / minute (50 m / minute). After walking
The sanitary napkin 10 and 10 sheets of paper were taken out, and the weight of defibrinated horse blood absorbed in the paper was measured. This is defined as the dynamic liquid return amount (g).

The absorption time and the amount of dynamic liquid return were measured 10 times, and the average value was used as the absorption time and the amount of dynamic liquid return.

<Leak Test (Number of Leak Occurrences)> Examples 5 to 5
8 and the sanitary napkins obtained in Comparative Examples 7 to 11 are shown in FIG.
The female waist model 70 shown in FIG. 0 was attached as shown in FIG. Next, the female waist model 70 was fitted with shorts, and then walked at a walking speed of 100 steps / minute (50 m / minute).

Then, after injecting 3 g of defibrinated horse blood into the sanitary napkin through the tube 71 while walking, walking at the same speed for 10 minutes (total amount of 3 g), and then defibrinated horse blood was applied to the sanitary napkin. After injecting 3g into
At the time of walking at the same speed for 10 minutes (total amount of 6 g), after further injecting 3 g of defibrinated horse blood into the sanitary napkin, at the same speed of walking for 10 minutes (total amount of 9 g), the number of samples was 10 at each time point. The number of leaks was counted.

[0133]

[Table 3]

As is clear from the results shown in Table 3, the absorbent article of the present invention comprising the absorbent paper of the present invention has a very simple structure but has a short liquid absorption time and It is a very high performance product with a small amount of return and a small number of leaks. This is because the absorbent paper of the present invention has a liquid absorption / diffusion gradient in its single structure, so that it absorbs liquid quickly, allows liquid to smoothly pass through the absorbent paper, and absorbs liquid. This is due to the sufficient diffusion of liquid on the "back" side of the paper.

[0135]

Since the absorbent paper of the present invention has a liquid absorption / diffusion gradient in its single structure, the liquid absorption rate is high, and the liquid spot absorptivity and liquid permeability and It has excellent diffusibility, and as a result, the surface has a very high feeling of slat. Further, according to the method for manufacturing absorbent paper of the present invention, the absorbent paper can be easily manufactured by a single process. Furthermore, the absorbent article of the present invention using the absorbent paper of the present invention has extremely high absorbency and little liquid leakage,
Moreover, it is extremely thin and has excellent wearing comfort.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section in the thickness direction of an absorbent paper of the present invention.

FIG. 2 is a schematic diagram showing a preferred method for producing the absorbent paper of the present invention.

FIG. 3 is an enlarged view of part (a) of FIG.

FIG. 4 is a schematic view showing a cross section in the width direction of a sanitary napkin as an embodiment of the absorbent article of the present invention using the absorbent paper of the present invention.

FIG. 5 is a schematic view (corresponding to FIG. 4) showing a cross section in the width direction of a sanitary napkin as another embodiment of the absorbent article of the present invention using the absorbent paper of the present invention.

FIG. 6 is a view showing a spiral braided wire mesh for producing a liquid-permeable surface material.

FIG. 7 is a schematic view showing a liquid-permeable surface material.

FIG. 8 is a schematic view showing an absorption time measuring device.

FIG. 9 is a schematic view showing a device for measuring a diffusion area.

FIG. 10 is a schematic diagram showing a female waist model.

FIG. 11 is a schematic view showing a state in which the absorbent article of the present invention is attached to a female waist model.

[Explanation of symbols]

 10 Sanitary Napkins 11 Absorbing Paper 12 Bulky Cellulose Fibers 13 Hydrophilic Fine Fibers 14 Slurry 15 Paper Making Wire 16 Paper Layer 17 Network Structure 21 Liquid Permeable Surface Material 22 Liquid Retaining Absorber 23 Liquid Impermeable Leak preventive material 24 Adhesive part 25 Release paper 26 Adhesive

Front Page Continuation (72) Minor Nakanishi Minoru Nakanishi 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Prefecture Kao Corporation Stock Research Institute

Claims (11)

[Claims] 1. An absorbent paper comprising bulky cellulosic fibers and hydrophilic fine fibers, wherein the hydrophilic fine fibers are present in a proportion of one side of the absorbent paper to the other side of the absorbent paper. The bulky cellulose fiber has an average fiber length of 1.5 to
20 mm and crosslinked in the molecule or between the molecules or has a fiber roughness of 0.3 mg / m or more, and the hydrophilic fine fibers have a fiber roughness of 0.01 to 0.2 mg / m.
An absorbent paper characterized in that the fiber length is m and the average fiber length is 0.5 to 1 mm. 2. The absorbent paper according to claim 1, which contains at least 50 to 97 parts by weight of the bulky cellulose fibers and 3 to 50 parts by weight of the hydrophilic fine fibers based on 100 parts by weight of the absorbent paper. 3. A heat-fusible adhesive fiber is further included; 70 to 95 parts by weight of at least the bulky cellulose fiber, 5 to 30 parts by weight of the hydrophilic fine fiber, and 100 parts by weight of the absorbent paper. The heat-meltable adhesive fiber is 2 to 30
Including parts by weight; and the basis weight of the absorbent paper is 10 to 200 g
The absorbent paper according to claim 1 or 2, wherein the absorbent paper is / m ² . 4. The bulky cellulose fiber is 0.5
The absorbent paper of claim 1 having a circularity of ˜1. 5. The absorbent paper according to claim 1, wherein the bulky cellulose fiber is mercerized pulp. 6. The bulky cellulose fibers are 2 to 5
Absorbent paper according to any of claims 1 to 5, having an average fiber length of mm. 7. The absorbent paper according to claim 1, wherein when the absorbent paper absorbs 1 g of physiological saline, the diffusion area ratio between the front surface side and the back surface side is 1.2 or more. 8. A bulky cellulose fiber having an average fiber length of 1.5 to 20 mm and being cross-linked in its molecule or between molecules, or having a fiber roughness of 0.3 mg / m or more and a bulky cellulose fiber and a fiber roughness. 0.01-0.2 mg / m and an average fiber length of 0.
Dispersing hydrophilic fine fibers of 5 to 1 mm in water to form a slurry; spraying the slurry onto a papermaking wire to form a paper layer on the papermaking wire; and the paper layer And a step of dehydrating and drying the absorbent article. 9. The method according to claim 8, wherein the opening diameter of the papermaking wire is 1 to 5 mm. 10. An absorbent article comprising a liquid-permeable surface material, a liquid-impermeable leak-proof material, and a liquid-retaining absorber interposed between the surface material and the leak-proof material. The absorbent body comprises at least absorbent paper and a superabsorbent polymer, the absorbent paper contains bulky cellulose fibers and hydrophilic fine fibers, and the hydrophilic fine fibers are the absorbent particles. The abundance ratio on one surface side of the paper is higher than the abundance ratio on the other surface side, and the average fiber length of the bulky cellulose fibers is 1.5 to 2
0 mm and the inside and the inside of the molecule are cross-linked or the fiber roughness is 0.3 mg / m or more, and the fiber roughness of the hydrophilic fine fibers is 0.01 to 0.2 mg.
/ M and the average fiber length is 0.5 to 1 mm. 11. The absorbent article according to claim 10, wherein the absorbent body comprises the absorbent paper sandwiched between the absorbent papers.