JP7310377B2 - Absorber - Google Patents

Description

The present invention relates to absorbent bodies.

Sanitary material products such as disposable diapers and napkins are composed of a sheet-like absorber that absorbs and retains water-based liquids such as urine and menstrual blood, a surface sheet that is placed on one side of the absorber, and a surface sheet that is placed on the other side of the absorber. It has a coated backsheet. The topsheet is permeable to urine and menstrual blood, and the backsheet is leakproof to urine and menstrual blood. The above absorber has a structure in which a mixture of pulp fibers and a water-absorbing polymer is wrapped with a nonwoven fabric, tissue, or the like.

In the sanitary material product, the absorber, the topsheet and the backsheet are arranged in the order of the topsheet, the absorber and the backsheet from the side closest to the wearer when the sanitary material product is worn.

Here, in recent years, with the spread of sanitary material products such as paper diapers and napkins, it has been desired to improve the feeling of wearing sanitary material products by making them thinner.

The following are known sanitary material products designed to improve wearing comfort through thinning.

Patent Literature 1 discloses a sanitary material product having an absorbent body in which an absorbent polymer is sandwiched between two hydrophilic nonwoven fabrics without using bulky pulp fibers for the absorbent body.

WO2011/086841

However, the absorber included in the sanitary material product disclosed in Patent Document 1 has a problem that it cannot exhibit absorption characteristics that are sufficiently satisfactory for the wearer. For example, in the sanitary material product disclosed in Patent Document 1, a spunlace nonwoven fabric made of a mixed fiber of rayon staple fibers and polyester staple fibers is used as a hydrophilic nonwoven fabric used for the absorbent body. A spunlace nonwoven fabric is a nonwoven fabric obtained by a water jet manufacturing method in which high-pressure water jets are jetted from the surface direction of the nonwoven fabric to entangle the fibers. In the water jet manufacturing method, the spunlaced nonwoven fabric as a whole is crushed in the thickness direction by high pressure, so the fibers forming the spunlaced nonwoven fabric tend to be oriented in the plane direction as a whole. That is, the orientation angle in the thickness direction of the spunlaced nonwoven fabric is reduced. In addition, in the absorbent body described above, pulp fibers are not arranged between two hydrophilic nonwoven fabrics in order to achieve a thin structure. Therefore, as a result, the spunlace nonwoven fabric described above has a problem that it is inferior in liquid permeability to water-based liquids such as urine and menstrual blood (speed at which water-based liquids administered from the direction perpendicular to the surface of the nonwoven fabric pass in the thickness direction). be. In a sanitary material product equipped with an absorbent body using such a spunlace nonwoven fabric, in a surface liquid flow test assuming a sanitary material product when worn, the water-based liquid did not penetrate smoothly into the absorbent body, and the surface A water-based liquid leaks from the edge of the sanitary material along the sheet. Although the details will be described later, the above-mentioned surface liquid flow test is a state in which the sanitary material product is fixed on an inclined table having an inclination angle of 45°, and 25 g of 0.9% physiological saline is poured from the surface sheet side. This is a test to evaluate the distance from when the physiological saline is dripped and runs down along the topsheet until it is absorbed inside the topsheet.

In view of the above problems, an object of the present invention is to provide an absorbent body that is thin and has excellent absorption properties.

In order to solve the above problems, the present invention consists of the following configurations.
(1) A first nonwoven fabric, a second nonwoven fabric, and a water-absorbing polymer, wherein the water-absorbing polymer is sandwiched between the first nonwoven fabric and the second nonwoven fabric, and the first nonwoven fabric is the first nonwoven fabric. Including short fibers, the single filament strength of the first short fibers is 0.15 N or more, the content of the first short fibers is 10% by mass or more with respect to the entire first nonwoven fabric, The first nonwoven fabric has a basis weight of 60 g/m ² or less, an orientation angle in the thickness direction of the first nonwoven fabric of 20° or more, and a thickness of 3 mm.
(2) The first nonwoven fabric contains second staple fibers, the official moisture content of the second staple fibers is 8% or more, and the content of the second staple fibers is less than the first 50% by mass or more and 90% by mass or less with respect to the entire nonwoven fabric, and the content of the first short fibers is 10% by mass or more and 50% by mass or less with respect to the entire first nonwoven fabric. Absorber,
(3) The absorbent body of (1) or (2), wherein the first short fibers are hollow fibers and the porosity of the first short fibers is 10% or more;
(4) The water absorber according to any one of (1) to (3), wherein the water absorption height of the second nonwoven fabric in the Byrek water absorption test is higher than the water absorption height of the first nonwoven fabric in the Byrek water absorption test. can be,
(5) In the method for manufacturing an absorbent body according to any one of (1) to (4), after the first staple fibers and the second staple fibers are fed into a card machine, the first staple fibers are A step of subjecting the first staple fiber and the second staple fiber to a mixed fiber treatment and an open fiber treatment, forming a web with a cross wrap weber, and introducing the web into a water jet type nonwoven fabric forming apparatus and subjecting it to a high pressure water jet. and drying to obtain a first non-woven fabric after entangling with , and the amount of the first staple fibers input to the card machine is equal to the first staple fibers and the second staple fibers to be input to the card machine. is 10% by mass or more and 50% by mass or less with respect to the total input amount of the staple fibers, and the amount of the second staple fibers input to the card machine is equal to the first staple fibers and the second staple fibers to be input to the card machine 50% by mass or more and 90% by mass or less with respect to the total input amount of the short fibers, the single yarn strength of the first short fibers is 0.15 N or more, and the official moisture content of the second short fibers is , 8% or more.

The present invention can provide an absorbent body that is thin and has excellent absorption properties.

The absorbent body of the present invention comprises a first nonwoven fabric, a second nonwoven fabric and an absorbent polymer, and has a thickness of 3 mm. Also, the water absorbing polymer is sandwiched between the first nonwoven fabric and the second nonwoven fabric. And the first nonwoven fabric contains the first short fibers,
The single filament strength of the first short fibers is 0.15 N or more, and the content of the first short fibers is 10% by mass or more with respect to the entire first nonwoven fabric. Furthermore, the first nonwoven fabric has a basis weight of 60 g/m ² or less and an orientation angle in the thickness direction of 20° or more. Although the details will be described later, the orientation angle in the thickness direction of the nonwoven fabric represents the orientation state of the fiber axes of the fibers forming the nonwoven fabric. As the value of the orientation angle in the thickness direction of the nonwoven fabric increases within the range of 90° or less, the acute angle formed between the direction of the fiber axes of the fibers constituting the nonwoven fabric and the direction perpendicular to the surface direction of the nonwoven fabric becomes smaller.

The absorbent body of the present invention having such a characteristic structure is thin and has excellent absorption properties. Although the details of the mechanism by which the above effect is obtained will be described later, it is presumed to be as follows. That is, the first nonwoven fabric included in the absorbent body of the present invention contains a specific content of first short fibers having high single filament strength, has a basis weight of 60 g/m ² or less, and is oriented in the thickness direction. An angle of 20° or more facilitates permeation of the water-based liquid from one side of the first nonwoven fabric to the other side. As a result, even if there is no pulp fiber between the first and second nonwoven fabrics, the water-absorbing polymer present between the first and second nonwoven fabrics quickly absorbs the aqueous solution. , it becomes possible to retain water. Therefore, in the absorbent body of the present invention, since it is not necessary to arrange pulp fibers between the first nonwoven fabric and the second nonwoven fabric, the absorbent body can be made as thin as 3 mm or less in thickness. Needless to say, the fact that the basis weight of the first nonwoven fabric is 60 g/m ² or less is advantageous for thinning the absorbent body.

(First nonwoven fabric)
First, the first nonwoven fabric included in the absorbent body of the present invention will be described. As described above, the first nonwoven fabric contains a specific content of the first short fibers having high single filament strength, has a basis weight of 60 g/m ² or less, and has an orientation angle of 20° or more in the thickness direction. is. This structure of the first nonwoven fabric makes it easier for the water-based liquid to permeate from one side of the first nonwoven fabric to the other side. Therefore, in the sanitary material product using the absorbent body of the present invention, the first nonwoven fabric is arranged so that the first nonwoven fabric is closer to the wearer than the second nonwoven fabric and the water-absorbing polymer when the sanitary material product is worn. As a result, water-based liquid such as urine emitted from the wearer permeates the first nonwoven fabric, is absorbed by the water-absorbing polymer, and is easily retained. That is, the absorber has excellent absorption characteristics.

Here, the first nonwoven fabric contains the first short fibers. Although the details will be described later, the single filament strength of the first staple fibers is high. Since the single filament strength of the first short fibers is high, the fiber axes of the fibers constituting the first nonwoven fabric are oriented in the desired direction in the present invention by a water jet or the like during the production of the first nonwoven fabric. becomes easier. In addition, since the single filament strength of the first staple fibers is high, the fiber axes of the fibers constituting the first nonwoven fabric oriented in a desired direction can be easily maintained until after the absorbent body is used. The content of the first short fibers in the first nonwoven fabric is 10% by mass or more with respect to the entire first nonwoven fabric. When the content of the first short fibers is 10% by mass or more, it is possible to orient the fiber axes of the fibers constituting the first nonwoven fabric in a desired direction and maintain the orientation. The content of the first short fibers is 20% by mass or more because the orientation of the fiber axes of the fibers constituting the first nonwoven fabric in the desired direction and the maintenance of the orientation are more reliable. and more preferably 30% by mass or more.

The orientation angle in the thickness direction of the first nonwoven fabric is 20° or more. That is, in the first nonwoven fabric, the acute angle between the direction of the fiber axes of the fibers constituting the first nonwoven fabric and the direction perpendicular to the surface direction of the nonwoven fabric is 70° or less. When the orientation of the fiber axes of the fibers constituting the first nonwoven fabric is as described above, the water-based liquid easily moves in the direction perpendicular to the surface direction of the nonwoven fabric inside the first nonwoven fabric, and as a result, , the water-based liquid easily permeates from one side of the first nonwoven fabric to the other side. The orientation angle in the thickness direction of the first nonwoven fabric is preferably 30° or more for the reason that the above effects are more excellent. On the other hand, although the upper limit of the orientation angle in the thickness direction of the first nonwoven fabric is not particularly limited, it is preferably 90° or less.

Next, the basis weight of the first nonwoven fabric is 60 g/m ² or less. When the basis weight of the first nonwoven fabric is 60 g/m ² or less, the water-based liquid easily permeates from one surface to the other surface of the first nonwoven fabric. The basis weight of the first nonwoven fabric is preferably 50 g/m ² or less for the reason that the above effects are more excellent. On the other hand, although the lower limit of the basis weight of the first nonwoven fabric is not particularly limited, it is preferably 20 g/m ² or more for the reason that the water-absorbing polymer described below can be carried more reliably.

Moreover, as the first nonwoven fabric, specifically, a thermal bond nonwoven fabric, a spunbond nonwoven fabric, and a spunlace nonwoven fabric can be mentioned. Among these, the first nonwoven fabric is a spunlace nonwoven fabric because it can be made into a nonwoven fabric without a binder even when cellulose fibers are used as the second short fibers described later. is preferred.

Also, the first nonwoven fabric preferably contains second staple fibers in addition to the first staple fibers. Although the details will be described later, the second staple fibers are staple fibers having an official moisture content of 8% or more. Such second short fibers can be said to be hydrophilic short fibers. The water is temporarily retained completely by the short fibers, and then the water-based liquid tends to be finally retained by the water-absorbing polymer via the second short fibers. As a result, even when the absorbent body is pressurized by the weight of the wearer, the water-based liquid retained in the absorbent body permeates the surface sheet from the absorbent body and flows back toward the wearer. is suppressed. Furthermore, the content of the second short fibers is preferably 50% by mass or more with respect to the entire first nonwoven fabric. When the first nonwoven fabric contains 50% by mass or more of the second short fibers, it becomes easier to suppress the reversion. For the reasons described above, the content of the second short fibers in the first nonwoven fabric is more preferably 65% by mass or more. On the other hand, it becomes easier to orient the fiber axes of the fibers constituting the first nonwoven fabric in the desired direction in the present invention, and further, the fiber axes of the fibers constituting the first nonwoven fabric oriented in the desired direction are absorbed. The content of the second short fibers is preferably 90% by mass or less because it is easy to maintain until after use. The official moisture content of each short fiber is described in Sensenshi, Vol. 32, No. 3, pp. 88-86, 1991.

(Second nonwoven fabric)
Next, the second nonwoven fabric included in the absorbent body of the present invention will be described. The second nonwoven fabric is not particularly limited, and may be the same nonwoven fabric as the first nonwoven fabric, or may be a nonwoven fabric different from the first nonwoven fabric.

Here, the water absorption height of the second nonwoven fabric in the Byrek water absorption test is preferably higher than the water absorption height of the first nonwoven fabric in the Byrek water absorption test. By adopting such a mode, the water-based liquid that has entered from the side of the first nonwoven fabric of the absorbent body diffuses inside the absorbent body toward the water-absorbing polymer and the second nonwoven fabric, and reaches the second nonwoven fabric. The water-based liquid diffuses inside the second nonwoven fabric in a direction parallel to the surface direction of the second nonwoven fabric. As a result, the water-based liquid that has entered the interior of the absorbent body diffuses widely throughout the water-absorbing polymer and the second nonwoven fabric, and is absorbed and retained. Therefore, the absorption properties of the absorber are improved. In addition, the water absorption height in the Byrek method water absorption test referred to here is the one measured by the method specified in JIS L1907 (2010) 7.1.2. The method for making the water absorption height of the second nonwoven fabric in the Byrek water absorption test higher than the water absorption height of the first nonwoven fabric in the Byrek water absorption test is not particularly limited as long as the effects of the present invention are not impaired. A method of making the content of the second short fibers in the nonwoven fabric of (1) larger than the content of the second short fibers in the first nonwoven fabric can be exemplified.

Moreover, as the second nonwoven fabric, specifically, a thermal bond nonwoven fabric, a spunbond nonwoven fabric, and a spunlace nonwoven fabric can be mentioned. Among these, the second nonwoven fabric is a spunlace nonwoven fabric because it can be made into a nonwoven fabric without a binder even when cellulose fibers are used as the second short fibers described later. is preferred.

(First staple fiber)
Next, the first short fibers will be described. The single filament strength of the first short fibers contained in the first nonwoven fabric is 0.15 N or more. Since the first nonwoven fabric contains such first short fibers, the fiber axes of the fibers constituting the first nonwoven fabric can be oriented in the desired direction in the present invention by a water jet or the like during the production of the first nonwoven fabric. Further, it becomes easy to maintain the fiber axes of the fibers constituting the first nonwoven fabric oriented in a desired direction until after the absorbent body is used. For the reasons described above, the single filament strength of the first staple fibers is preferably 0.2 N or more. On the other hand, the upper limit of the single filament strength of the first staple fibers is not particularly limited, but the reason is that the first nonwoven fabric can be made to have a good touch and a sanitary material product that does not cause discomfort when worn can be obtained. Therefore, it is preferably 1.0 N or less. Here, the single filament strength of short fibers refers to the maximum load of the elongation-load curve obtained when a single short fiber is subjected to a tensile test with reference to JIS L 1015 (1999) 8.7.1. Further, short fibers refer to fibers having a fiber length in the range of 10 to 100 mm. The fiber length of the first short fibers is preferably 20 to 80 mm from the viewpoint of passability through a card machine, which will be described later.

In addition, since it is possible to suppress the decrease in the strength of the first nonwoven fabric due to water absorption and to make it easier to orient the fiber axes of the fibers constituting the first nonwoven fabric in the desired direction in the present invention, the first short Preferably, the official moisture content of the fibers is less than 8%. For the above reasons, the official moisture content of the first short fibers is preferably 1% or less. For the reason of minimizing the decrease in strength of the first nonwoven fabric due to water absorption, the lower limit of the official moisture content of the first short fibers is preferably 0%.

Here, the first short fibers include polyolefin short fibers such as polyethylene and polypropylene; polyester short fibers such as polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate; nylon short fibers; acrylic fibers such as acrylonitrile; vinylon fibers such as Among these staple fibers, polyester staple fibers are preferable from the viewpoint of being excellent in strength and versatility. Furthermore, short fibers of polyethylene terephthalate are more preferred.

Also, the first short fibers are preferably hollow fibers. Moreover, the porosity of the hollow fibers is preferably 10% or more. Since the first short fibers are hollow fibers having a porosity of 10% or more, the bulk of the first short fibers increases, and as a result, the fiber axes of the fibers constituting the first nonwoven fabric are adjusted to the desired values in the present invention. Further, it becomes easy to maintain the fiber axes of the fibers constituting the first nonwoven fabric oriented in the desired direction until after the absorbent body is used. For the above reasons, the porosity is preferably 20% or more. On the other hand, the upper limit of the porosity is preferably 50% or less for the reason that the strength of the first nonwoven fabric can be maintained.

(Second staple fiber)
Next, the second short fibers will be explained. The official moisture content of the second staple fibers is 8% or more. Since the second staple fibers are hydrophilic staple fibers with an official moisture content of 8% or more, the water-based liquid can more easily permeate from one surface to the other surface of the first nonwoven fabric.

Specific examples of the second staple fibers include wool fibers, silk fibers, and cellulosic fibers such as cotton, linen, and rayon fibers. Among these fibers, the second short fibers are preferably cellulose fibers, and more preferably rayon fibers. Here, since the second short fibers are cellulose fibers, the absorbent body has excellent storage stability against insect damage, etc., and the second short fibers are rayon with an official moisture content of 10% or more. By being a fiber, it is possible to further suppress backflow of the aqueous liquid from the absorbent body through the first nonwoven fabric. The fiber length of the second short fibers is preferably in the range of 10 to 100 mm as in the case of the first short fibers. A range of 20 to 80 mm is preferred.

(Absorber)
The absorber of the present invention has a thickness of 3 mm or less. Since the thickness of the absorbent body is 3 mm or less, when the absorbent body of the present invention is used in a sanitary material product such as a diaper, the sanitary material product using the absorbent body of the present invention is flexible and suppresses stiffness. Furthermore, it can be made to be excellent in a feeling of wearing. For the reason that the sanitary material product is more comfortable to wear, the absorbent body is preferably thin, and the thickness of the absorbent body is preferably 2.5 mm or less. On the other hand, the thickness of the absorbent body is preferably 1 mm or more in order to improve the absorption characteristics of the absorbent body. In addition, the thickness of the absorber referred to herein is measured based on JIS L1913 (1998) 6.1.2 A method.

A method for making the absorber of the present invention 3 mm or less will be described. Here, in a conventional absorber, a water-absorbing polymer and a large amount of pulp fibers are sandwiched between two non-woven fabrics such as tissues in order to improve the absorption characteristics of the absorber. Since the pulp fiber is bulky, the thickness of the conventional absorber greatly exceeds 3 mm, which is thick. On the other hand, in the absorbent body of the present invention, due to the above circumstances, it is necessary to ensure excellent absorption properties of the absorbent body without arranging bulky pulp fibers between the first nonwoven fabric and the second nonwoven fabric. can be done. Therefore, in the absorbent body of the present invention, the content of the pulp fibers arranged between the first nonwoven fabric and the second nonwoven fabric is 50 g/m ² or less, so that the thickness of the absorbent body is 3 mm or less. can do. The pulp content is preferably 10 g/m ² or less, particularly preferably 0 g/m ² , because the thickness of the absorbent body of the present invention can be made thinner.

(water absorbing polymer)
The absorbent body of the present invention contains a water-absorbing polymer. The water-absorbing polymer used in the present invention includes, for example, starch, crosslinked carboxymethylated cellulose, polymers of acrylic acid or alkali metal acrylate salts or copolymers thereof, polyacrylates such as sodium polyacrylate, and polyacrylates. Examples thereof include acid-acid graft polymers. Among these, the water-absorbing polymer is preferably sodium polyacrylate. From a different point of view, the water-absorbing polymer has an absorption capacity of 40 to 80 times normal saline per 1 g of the water-absorbing polymer and an absorption rate of normal saline per 1 g of the water-absorbing polymer of 50 seconds or less. Some are preferred from the standpoint of better absorption characteristics. Moreover, the water-absorbing polymer is preferably particulate from the viewpoint of handleability in the production process and the like. When the water absorbing polymer is particulate, the number average particle diameter is preferably 50 μm or more and 800 μm or less. When the number average particle size of the water absorbing polymer is 50 µm or more and 800 µm or less, it is possible to suppress the water absorbing polymer from permeating the first nonwoven fabric or the second nonwoven fabric. Here, the absorption capacity of the water-absorbing polymer for physiological saline is measured by the tea pack method specified in JIS K7223 (1996), and the absorption speed of the water-absorbing polymer for physiological saline is specified in JIS K7224 (1996). measured by the Vortex method. The number-average particle size of the water-absorbing polymer is calculated by observing 10 water-absorbing polymer particles with an SEM or the like and averaging the diameters obtained by circular approximation of each particle. In the present invention, when a sodium polyacrylate-based water-absorbing polymer is used as the water-absorbing polymer, "Sanwet IM-930" manufactured by SDP Global can be employed.

In the absorbent body of the present invention, the weight per unit area of the water-absorbing polymer is preferably 100 g/m ² or more and 500 g/m ² or less. When water-absorbing polymers are densely present and come into contact with an aqueous liquid, the expanded water-absorbing polymers come into contact with each other, inhibiting contact between other unabsorbed/unswollen water-absorbing polymers and the aqueous liquid. However, when the weight of the water-absorbing polymer is within the above range, the particles of the water-absorbing polymer are present at appropriate intervals, avoiding the "gel block phenomenon" and making the water-absorbing polymer efficient. function more easily.

(Method for producing first nonwoven fabric and second nonwoven fabric)
Next, the method for producing the first nonwoven fabric and the second nonwoven fabric used in the absorbent body of the present invention will be specifically described. The manufacturing method is not limited to these.

The first staple fibers and optionally the second staple fibers used to obtain the first nonwoven fabric of the present invention are placed in a card machine at a ratio that makes the content of the first nonwoven fabric within the desired range. After throwing, mixing and opening the fibers, a uniform web is formed with a cross-lap weber. Subsequently, the web is put into a water jet type nonwoven fabric forming apparatus and entangled with a high-pressure water jet to form a nonwoven fabric. After that, the nonwoven fabric is dried in a hot air oven to obtain a first nonwoven fabric.

A more specific method for producing the first nonwoven fabric is exemplified below. A first staple fiber and a second staple fiber are fed into a card machine. At this time, the input amount of each short fiber is as follows. The input amount of the first staple fibers is 10% by mass or more and 50% by mass or less with respect to the total mass of the first staple fibers and the second staple fibers, and the input amount of the second staple fibers is 50% by mass or more and 90% by mass or less with respect to the total mass of the first short fibers and the second short fibers. Next, the first staple fibers and the second staple fibers are subjected to fiber mixing treatment and fiber opening treatment, and formed into a web having a uniform thickness with a cross-lap weber. Further, the obtained web is put into a water jet type nonwoven fabric forming apparatus and entangled with a high-pressure water jet to form a nonwoven fabric. After that, the nonwoven fabric is dried in a hot air oven to obtain a first nonwoven fabric.

Also when obtaining the second nonwoven fabric, the same manufacturing method as for the first nonwoven fabric can be adopted, except that the composition and content of the short fibers are changed.

(Method for manufacturing absorber)
Next, the method for producing the absorbent body of the present invention will be specifically described, but the method for producing the absorbent body of the present invention is not limited to the following. An absorbent body is obtained by fixing a water absorbing polymer between the first nonwoven fabric and the second nonwoven fabric. As a method for fixing the water absorbing polymer, (1) a hot melt adhesive is sprayed or spirally sprayed on one side of the first nonwoven fabric, and the water absorbing polymer is sprayed thereon; (2) A method in which the hot-melt adhesive and the water-absorbing polymer are in contact with each other, and (2) a method in which the heat-fusible resin powder and the water-absorbing polymer are uniformly mixed in advance. For example, after spraying on one side of the first nonwoven fabric, the water-absorbing polymer is covered with the second nonwoven fabric, heated to a temperature equal to or higher than the melting point of the heat-fusible powder, and then thermocompressed. As the hot-melt adhesive used at this time, styrene-based hot-melt adhesives and olefin-based hot-melt adhesives suitable for use in sanitary products can be suitably used. As the heat-fusible resin powder, polyethylene powder and ethylene-vinyl acetate copolymer powder can be suitably used from the viewpoint that heat-fusibility can be achieved at a relatively low temperature. .

(Manufacturing method for sanitary material products)
A method for manufacturing sanitary products such as disposable diapers and napkins using the absorbent body of the present invention will be described. After cutting the absorbent body of the present invention into a substantially rectangular shape, the absorbent body is inserted between the top sheet and the back sheet, which are substantially rectangular like the cut absorbent body and have a larger area than the cut absorbent body. Clamp and fix. At this time, the absorbent body is preferably sandwiched between the topsheet and the backsheet so that the first nonwoven fabric of the absorbent body is in contact with the topsheet. Since the first nonwoven fabric has the characteristic of facilitating the permeation of water-based liquids from one side of the first nonwoven fabric to the other side, the contact of the topsheet with the first nonwoven fabric allows water-based liquids that permeate the inside of the topsheet. The liquid quickly permeates the first nonwoven fabric and is easily absorbed by the water-absorbing polymer to retain the water. Therefore, the absorption properties of the absorber are improved. Examples of the method of fixing the parts in which the top sheet and the absorbent body, the back sheet and the absorbent body, and the top sheet and the back sheet are in direct contact include a method using a hot-melt adhesive and a method using heat-sealable resin powder. can be done. In addition, as the surface sheet used when the absorbent body of the present invention is used as a sanitary material product, it is preferable to adopt a nonwoven fabric, for example, a wet nonwoven fabric or a In addition to resin bond dry nonwoven fabric, thermal bond dry nonwoven fabric, spunbond dry nonwoven fabric, needle punch dry nonwoven fabric, water jet punch dry nonwoven paper fabric, flash spinning dry nonwoven fabric, etc., uniform basis weight and thickness can be achieved. A nonwoven fabric manufactured by a papermaking method can also be preferably used. Among them, it is preferable to use a thermal-bonded dry-type nonwoven fabric as the topsheet because it is located in a place where it comes into contact with human skin. In addition, the back sheet used when the absorbent body of the present invention is used as a sanitary material product has the viewpoint that the water vapor accumulated inside the sanitary material product can be released to the outside and the comfort of the wearer can be given, and the back sheet is waterproof. A laminated sheet of a moisture-permeable and waterproof film and a non-woven fabric is preferable from the viewpoint that it can provide excellent properties and touch. Examples of the moisture-permeable waterproof film include a porous polyethylene film, a moisture-permeable urethane film, a moisture-permeable polyester elastomer film, and the like. As the nonwoven fabric, the same nonwoven fabric as the surface sheet can be used, but a spunbond dry-laid nonwoven fabric is preferable from the viewpoint of cost and strength.

The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

[Measurement and evaluation method]
(1) Fabric weight of non-woven fabric
Based on JIS L1913 (1999) 6.2, take three test pieces of 25 cm × 25 cm from the nonwoven fabric, weigh the mass (g) in each standard state, and calculate the mass per 1 m ² (g / m ² ) was obtained, and the average weight per unit area was calculated according to the following formula.
Sm = W/A
Sm: basis weight (g/m ² )
W: mass (g) of the test piece in the standard state
A: Area of test piece (m ² ).

(2) Orientation angle in the thickness direction of the non-woven fabric The orientation angle of the fibers was obtained with reference to the method described in Emae et al. . As an evaluation procedure, a cross-sectional image obtained by X-ray CT or a scanning electron microscope is subjected to binarization and two-dimensional Fourier transform processing to obtain a power spectrum. The angular distribution of the average amplitude width was obtained from the obtained power spectrum, and its elliptical approximation was performed. Specifically, using a scanning electron microscope (S-3400N, manufactured by Hitachi High-Technologies Corporation), a cross section formed in the width direction-thickness direction of the nonwoven fabric was observed at a magnification of 1,000. Note that cross-sectional images were taken at 5 points per nonwoven fabric sample. After converting the obtained image into a bmp file format so that the number of pixels on one side is a multiple of 4 and the horizontal direction of the image is the width direction, the five images are analyzed by the non-destructive paper surface fiber orientation analysis program " FiberOri8single03” was used to collectively read the data, binarization, Fourier transform, and automatic processing of elliptical approximation of the angular distribution of the average amplitude width of the power spectrum were performed to calculate the orientation angle and degree of orientation. Considering the symmetry of the non-woven fabric, when the orientation angle was 90° or more, the value was subtracted from 180° and converted to a value of 90° or less to obtain the orientation angle.

(3) Water absorption height in Byrek method water absorption test of nonwoven fabric It was measured based on JIS L1907 (2010) 7.1.2. Specifically, five test pieces of 200 mm × 25 mm were collected from the nonwoven fabric, and after fixing the test piece on a horizontal bar supported on the water surface of a water tank, the horizontal bar was lowered to lower the lower end of the test piece. 20 mm is immersed in water and left for 10 minutes. After standing, the height to which the water rose due to capillary action was measured with a scale to 1 mm, and the average value of 5 test pieces was obtained.

(4) Content of fibers constituting nonwoven fabric JIS L 1030-1 (2006) "Test method for mixing rate of textile products - Part 1: Fiber identification" and JIS L 1030-2 (2005) "Mixing of textile products Rate Test Method-Part 2: Fiber Mixing Rate", the positive mixing rate (mass ratio of each fiber in the standard state) was measured, and this was used as the content (mass%) of the fibers constituting the nonwoven fabric. .

(5) Single filament strength of staple fiber Measured with reference to JIS L1015 (1999) 8.7.1. Specifically, one fiber was loosely stretched, and both ends of the fiber were attached to paper with an adhesive. At this time, a region of 20 mm was secured only for fibers between gripped portions. The grip portion of this sample is attached to the grip of a tensile tester (Tensilon universal testing machine model RTG-1210 manufactured by Orientec), and pulled at a grip interval of 10 mm and a tensile speed of 10 mm / min. The maximum load in the load (N) curve was taken as the single yarn strength (N). Ten samples were measured, and the average value was calculated.

(6) Official moisture content of staple fibers If the composition of staple fibers is known, the official moisture content value described for the same composition in Sensen Magazine 1991 Vol. 32 No. 3 P. 88-86 The official moisture content of the fiber was used. If the composition of the short fibers is unknown, the composition of the short fibers is specified by the method described in (4) Content of fibers constituting the nonwoven fabric, and similarly Sensho Magazine 1991, Vol. 32, No. 3, P.88. The official moisture content value described for the same composition in -86 was taken as the official moisture content of the short fibers.

(7) Porosity of short fibers A fiber cross section exposed by cutting out a short fiber sample from a direction perpendicular to the fiber axis using an ultramicrotome is examined with a scanning electron microscope (S-3400N manufactured by Hitachi High-Technologies Corporation). Observation was carried out at a magnification of 500 to 1,500 times. When a space inside the fiber can be confirmed in the obtained fiber cross-sectional image, the area of the fiber component part (S1) and the area of the space part inside the fiber (S2) are obtained by applying Otsu's binarization process, The porosity was calculated by the following formula.
Porosity (%) = S1 / (S1 + S2) × 100
(8) Thickness of absorber Measured based on JIS L1913 (1998) 6.1.2 A method. Specifically, five test pieces of 50 mm × 50 mm were taken from the nonwoven fabric sample, and a thickness measurement device (TECLOCK constant pressure thickness measurement device, model PG11J) was used to measure the thickness of the test piece at a standard state of 0.36 kPa. Pressure was applied for 10 seconds and the thickness was measured. The measurement was performed for each test piece (five pieces), and the average value was calculated.

(9) Water absorption height in Byrek method water absorption test of nonwoven fabric A value measured by the method specified in JIS L1907 (2010) 7.1.2.

(10) Reversion amount of sanitary material product, reversion amount after repeated use A water-based liquid imitating urine from the top sheet side of a sample of a sanitary material product in which a top sheet, an absorbent body, and a back sheet are adhered and integrated. 20 ml of physiological saline (9% sodium chloride aqueous solution) prepared as above was administered. Five minutes after administering the saline solution, a pre-weighed filter paper (qualitative filter paper No. 1, 110φ manufactured by Advantech) was placed on the surface sheet where the saline solution was administered, and a 110φ stainless steel column was placed thereon. A shape weight was placed and held for 5 minutes. After the end of the test, the weight was removed and the weight of the filter paper that had absorbed water due to reversion was measured. Using the weight of the filter paper after the test (W1) and the weight of the filter paper before the test (W0), the reversion amount was calculated by the following equation.
Amount of reversion (mg) = W1 - W0
Thirty minutes after the weight was removed, 20 ml of physiological saline was administered again to the position where the physiological saline was administered last time, and the amount of regurgitation was measured using the same weight retention time and method using newly prepared filter paper. This operation was repeated twice, and the amount of reversion for the second time and the amount of reversion for the third time were calculated. The amount of reversion at the third time was taken as the amount of reversion during repeated use.

The lower the reversal amount, the better. Those with a regurgitation amount of 60 mg or less are comfortable and preferable because reversion of the aqueous liquid to the skin side is suppressed even if the absorbent article continues to be worn after absorbing the aqueous liquid such as urine or menstrual blood. Similarly, the lower the amount of regurgitation after repeated use, the better, and the regurgitation amount after repeated use of 100 mg or less is preferable because it maintains comfort even after repeated use.

(11) Surface Liquid Flow Distance in Tilt State A substantially rectangular sanitary material product in which a top sheet, an absorbent body, and a back sheet are bonded and integrated is used as a sample, and the sample is placed on an inclined table having an inclination angle of 45°. The sample was fixed so that the longitudinal direction coincided with the tilt direction. At this time, the sample was stretched and fixed in order to eliminate wrinkles on the surface sheet. Subsequently, a total of 25 g of 0.90% physiological saline (colored with a blue dye) was dropped at a rate of 1.5 g/sec from a microtube pump or a burette at a position 1 cm below the upper edge of the surface sheet. At this time, it is observed that the physiological saline runs down along the topsheet in the oblique direction, is absorbed into the topsheet at a certain position, and disappears from the topsheet. The surface liquid flow distance is defined as the distance from the dropping position to the disappearance of the saline solution, and the maximum surface liquid flow distance observed while dropping the whole amount of 25 g of the saline solution is defined as the maximum surface liquid flow distance in the inclined state. It was taken as the surface liquid flow distance.

The lower the surface liquid flow distance, the better the liquid leakage prevention property. If the surface liquid flow distance is greater than 45 mm, leakage is noticeable when the sanitary material product is tilted, such as when the sanitary material product is in a lying position, and it was determined that it does not have practical level of absorption properties. .

(Example 1)
40 hollow short fibers (single fiber fineness: 6.6 T, fiber length: 51 mm, porosity: 30%) made of polyethylene terephthalate (official moisture content: 0.4%) as the first short fibers of the first nonwoven fabric % by mass and 60% by mass of short fibers (single fiber fineness: 1.4 dtex, fiber length: 51 mm) made of rayon (official moisture content: 11%) as second staple fibers are mixed with a card and spread. After that, it was webbed with a cross-lap weber. This web was entangled with a high-pressure water jet under conditions of a pressure of 3 MPa and a speed of 1.0 m/min, and dried at 150° C. for 3 minutes to obtain a first nonwoven fabric of 40 g/m ² . On one side of the first non-woven fabric, a styrene-based hot melt was applied in a spray form to 1 g/m ² , and a water-absorbing polymer (SDP Global IM930) was evenly applied to 300 g/m ² . disseminated. Subsequently, a nonwoven fabric was produced by the same staple fiber composition and manufacturing method as the first nonwoven fabric to obtain a second nonwoven fabric of 40 g/m ² , and 1 g/m ² of styrene hot melt was applied to one side of the second nonwoven fabric. After the hot-melt-coated surface of the second nonwoven fabric is in contact with the water-absorbing polymer dispersed on the first nonwoven fabric, the absorber is obtained by press-bonding. rice field. Furthermore, the absorbent body is cut into a substantially rectangular shape of 30 cm x 10 cm, and a thermal bond type dry nonwoven fabric made by using polyethylene / polypropylene short fibers with a core-sheath structure having polyethylene in the core and polypropylene in the sheath as the surface sheet. was cut into a substantially rectangular shape of 35 cm × 14 cm, and a porous polyethylene film and polypropylene spunbond dry nonwoven fabric were cut into a substantially rectangular shape of 35 cm × 20 cm as the back sheet, and both sides of the absorbent body were prepared. A styrene-based hot melt was applied to each surface in a spray form so as to be 1 g/m ² on each surface. Subsequently, the top sheet/absorbent body/back sheet were stacked in the order of the rectangular shape and pressed together so that the center of gravity of each material was aligned while aligning the longitudinal direction, to obtain a sanitary material product. At this time, the absorber was sandwiched between the first nonwoven fabric and the second nonwoven fabric so that the first nonwoven fabric included in the absorber was placed on the topsheet side. Table 1 shows the properties of the short fibers constituting the first and second nonwoven fabrics, the compositions of the obtained first and second nonwoven fabrics, the absorbent bodies, and the sanitary material products, and the evaluation results.

(Examples 2-8, Comparative Examples 1-2)
The first nonwoven fabric was produced in the same manner as in Example 1, except that the short fiber content, type, and basis weight of the nonwoven fabric were set to the contents shown in Tables 1 and 2, respectively, for the first nonwoven fabric and the second nonwoven fabric. , a second nonwoven, an absorbent article and a sanitary article were obtained. Tables 1 and 2 show the evaluation results of the first and second nonwoven fabrics, absorbent bodies, and sanitary material products.
By comparing Examples 1, 5, and 6 with Comparative Example 1, it was found that the single filament strength of the first short fibers was 0.15 N or more, so that the orientation angle was 20° or more and the surface liquid flow distance was practically reduced. It turns out that a range of values is possible.

In comparison between Examples 1 and 7 and Comparative Example 2, by setting the basis weight of the first nonwoven fabric to 60 g/m ² or less, the thickness can be kept to 3 mm or less and the wearing feeling can be excellent.

Further, in a comparison between Example 1 and Example 5, the hollow fibers having a porosity of 10% or more in the first short fibers have a high orientation angle even if the single fiber strength is low, and the surface liquid flow distance can be increased. can be set to a low value.

In comparison between Examples 1 to 3 and Example 4, the content of the second short fibers is 50% by mass or more with respect to the entire first nonwoven fabric, so that the surface liquid flow distance and the backflow amount are within the preferable range. It can be seen that the value of Furthermore, by comparing Example 1 and Example 8, the water absorption height in the Byrek method water absorption test of the second nonwoven fabric was higher than the water absorption height in the Byrek method water absorption test of the first nonwoven fabric. It will be appreciated that the amount can be any value within the preferred range.

INDUSTRIAL APPLICABILITY The absorbent body of the present invention is thin and has excellent absorption characteristics, and can be suitably used as various sanitary material products such as tape-type disposable diapers, pants-type disposable diapers, sanitary napkins, and incontinence pads. .

Claims (5)

comprising a first nonwoven and a second nonwoven and an absorbent polymer;
The water-absorbing polymer is sandwiched between the first nonwoven fabric and the second nonwoven fabric,
The first nonwoven fabric comprises first staple fibers,
The single filament strength of the first staple fibers is 0.15 N or more,
The content of the first short fibers is 10% by mass or more with respect to the entire first nonwoven fabric,
The first nonwoven fabric has a basis weight of 60 g/m ² or less,
The orientation angle in the thickness direction of the first nonwoven fabric is 20° or more,
An absorbent body having a thickness of 3 mm or less. The first nonwoven fabric contains second staple fibers,
The official moisture content of the second short fibers is 8% or more,
The content of the second short fibers is 50% by mass or more and 90% by mass or less with respect to the entire first nonwoven fabric,
The absorbent body according to claim 1, wherein the content of said first short fibers is 10% by mass or more and 50% by mass or less with respect to said entire first nonwoven fabric. The first short fibers are hollow fibers,
3. The absorbent body according to claim 1, wherein said first short fibers have a porosity of 10% or more. The water absorbent body according to any one of claims 1 to 3, wherein the water absorption height of the second nonwoven fabric in the Byrek water absorption test is higher than the water absorption height of the first nonwoven fabric in the Byrek water absorption test. A method for manufacturing an absorbent body according to any one of claims 1 to 4,
After the first staple fibers and the second staple fibers are put into a card machine, the first staple fibers and the second staple fibers are subjected to a fiber-mixing treatment and a fiber-opening treatment, and then subjected to a cross-lap weber. forming a web;
A step of introducing the web into a water jet type nonwoven fabric forming apparatus, entangling it with a high pressure water stream, and drying it to obtain a first nonwoven fabric,
The amount of the first short fibers put into the card machine is 10% by mass or more and 50% by mass or less with respect to the total amount of the first short fibers and the second short fibers put into the card machine,
The amount of the second staple fibers fed into the card machine is 50% by mass or more and 90% by mass or less with respect to the total amount of the first staple fibers and the second staple fibers fed into the card machine,
The single filament strength of the first staple fibers is 0.15 N or more,
A method for manufacturing an absorbent body, wherein the official moisture content of the second short fibers is 8% or more.