JP3296521B2 - Water-absorbing composite and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-shaped composite absorbent, and more particularly, to a novel sheet-shaped composite absorbent having a large liquid absorbency while having a thin and flexible sheet-like form. And a method for producing such a sheet-shaped composite absorbent. This sheet-shaped composite absorbent can be advantageously used for sanitary products, especially sanitary products and diapers.

[0002]

2. Description of the Related Art Conventionally, materials used for absorbent products such as diapers and sanitary napkins include a top sheet from the top surface (top sheet) and an absorbent member arranged thereunder.
And a film having a leak-proof function.

[0003] As for the absorbent member to which the present invention relates, a mixture of unwoven fabric of wood pulp, so-called fluff-like pulp, and powdery superabsorbent resin (SAP) has been generally used. However, at the same time as public demands for resource saving and improvement of logistics efficiency, etc.
The market demand for ultra-compact products is increasing.

As an absorber for such an ultra-thin product, a multilayered sheet-shaped absorber has been used. These absorbers are composed of a combination of a layer (referred to as a transfer sheet or a secondary sheet) for liquid diffusion and temporary storage and a structured sheet of SAP and fluff pulp (main absorber layer). Has become.

[0005] As the transfer sheet, for example, as described in JP-A-4-27226,
A nonwoven fabric web having a hydrophilic surface, a cellulosic nonwoven fabric such as rayon or cotton, a material obtained by stabilizing the form of air-laid pulp with a binder, or the like is used. To form a main absorber layer.

At present, the development of an absorbent product which is thinner and more excellent in wearability is being promoted by these multilayer structures.

[0007]

However, in the above-described layer structure based on the prior art, the common disadvantages are that there is no connection between the layers of the multi-layer sheet and that the shape of the main absorber layer is small. Due to insufficient stability, there is a drawback that the utilization efficiency of the absorber is still insufficient and the structure tends to be fragmented after absorbing the liquid.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet-shaped composite absorbent body which eliminates the above-mentioned drawbacks of the prior art, has an extremely high liquid absorption efficiency, and can maintain excellent form stability even after liquid absorption. To provide.

[0009]

According to the present invention, there is provided a first layer comprising a nonwoven fabric web mainly composed of synthetic fibers having surface wetting characteristics with respect to moisture, and a water retention degree significantly higher than that of the first layer. A second layer comprising a highly water-absorbent polymer sheet having a high form stability and the first layer and the second layer
Are arranged at appropriate intervals and extend in parallel with each other.
It is joined by heat fusion at the joint, and this joint
Characterized in that it is integrally bonded to each other have, absorbent composite having a water absorption capacity gradient in the thickness direction is provided.

The water-absorbing composite of the present invention is basically composed of the following two layers, and these two layers are stably bonded and integrated.

First layer: A nonwoven fabric web mainly composed of synthetic fibers having surface wetting properties against moisture.

Second layer: a form-stabilized superabsorbent polymer sheet having significantly higher water retention than the first layer.

First, the characteristics of the first and second layers will be described.

The first layer is made of a synthetic fiber which has surface wetting properties against moisture but has little ability to absorb moisture, and has the ability to stably maintain the initial shape even in the wet state. In contrast, the second layer has a significantly greater liquid absorption capacity than the first layer.

The first layer and the second layer are preferably combined and integrated so as not to form a gap between the layers.
A difference in the liquid permeability between the first layer and the second layer, that is, a water absorption capacity gradient will occur. This water absorption capacity gradient indicates that when the water-absorbing composite is used with the first layer in close proximity to the skin of the human body, the excreted liquid is instantaneously received by the first layer, but is retained here. It passes quickly without being absorbed into the second layer and is stably absorbed. The first layer is always waiting for the next excretion. Also, the large water absorption capacity gradient between the first layer and the second layer reliably prevents backflow of liquid from the second layer to the first layer.

In the present invention, one of the most suitable sheet-like materials for forming the first layer is a low-density, thermally-bonded nonwoven fabric mainly composed of polypropylene fibers. In particular, the non-woven fabric that has been subjected to a surfactant treatment has surface wettability, and has the same physical strength and shape retention as a dry state even in a wet state. Accordingly, even if the second layer softens or loses shape retention due to water absorption, the initial sheet shape of the water-absorbing composite can be stably maintained.

Other suitable sheet-like materials for the first layer are mainly hydro-entangled non-woven fabrics of polyethylene or polypropylene, non-woven fabrics to which shrink-processed high-shrinkage polyester is added, and polyethylene or polypropylene-based resins having low density. Spunbond or the like as a component can also be used.

On the other hand, since the second layer is mainly composed of a highly absorbent polymer, it has an extremely high absorbency and has a water absorbing capacity of at least 10 times, preferably 30 times or more of its own weight. Therefore, as compared with the first layer, the second layer has at least three times or more, preferably five times or more the absorption gradient of the first layer, and is made of a material having shape retention even when wet. . Such a superabsorbent layer can be formed by using a preformed sheet as a skeleton and integrating a superabsorbent polymer with the skeleton by an appropriate means.

Preferred examples of the superabsorbent polymer for forming the second superabsorbent layer include crosslinked products of sodium polyacrylate, carboxymethyl cellulose, polysaccharides and the like. As a method of forming these polymers into a sheet, a method of forming a bulky nonwoven fabric of synthetic fibers, impregnating this nonwoven fabric with an acrylic acid monomer, and then polymerizing the monomer, or easily fusing with a highly absorbent polymer fiber is used. And a method in which the heat-fusible fibers are partially melted by heat treatment to obtain an absorbent polymer sheet by the bonding force, and the like.

A particularly preferred method is to use a water-stable net-like non-woven fabric such as, for example, polypropylene dry non-woven fabric, polypropylene spunbond, polyethylene melt blown, which is hydroentangled with a precursor web of acrylic or cellulose fibers and then hydroentangled. This is a method of obtaining a highly absorbent sheet by increasing the absorption of this fiber layer by a hydrolysis treatment in the case of acrylic fibers and by a carboxymethylation and cross-linking treatment in the case of cellulose fibers.

The highly absorbent sheet having these skeletons is
It is stable even in a wet state, and can contribute to the bonding between the first layer and the second layer as described later.

In the present invention, the bonding state between the first layer and the second layer is an important factor that determines the performance as a water-absorbing composite having a large absorption capacity gradient in the thickness direction. Methods that can be applied to obtain a good bonding state are roughly classified into the following three methods.

(1) A method of bonding the two layers simultaneously with the formation of the first layer and the second layer: corresponding to the first layer, for example, to a card web of polypropylene fibers, corresponding to the second layer,
For example, a fiber staple (for example, trade name “Lanseal” manufactured by Toyobo Co., Ltd.) whose surface is treated with sodium polyacrylate to make it highly absorbent is overlapped, and the two layers are integrated by hydroentanglement.

(2) A method for making the second layer highly absorbent after bonding the first layer and the second layer: a second layer is added to a card web of, for example, polypropylene fiber corresponding to the first layer formed in advance, for example. For example, a card web of acrylic fiber (but not superabsorbent) is superimposed, and the two layers are combined by any suitable means such as hydroentanglement to form an integrated web. The fiber portion is subjected to a hydrolysis treatment to form a water-absorbing composite.

(3) Method of integrating a separately prepared first layer and a high-absorbency second layer: from a first layer consisting of a sheet such as a card web of polypropylene fibers and a sheet previously made highly absorbent. The second layer is integrated by an appropriate means. This integration can be performed using a binder such as a hot melt adhesive, but thermocompression bonding is most advantageous in that it does not use a hot melt adhesive that may change the absorption performance of the product. It is. To facilitate integration by thermocompression bonding, as a second layer,
For example, a heat-fusible spunbond made of, for example, polypropylene or polyethylene spunbond is used as a skeleton, and carboxymethylated and cross-linked wood pulp fibers are entangled with the skeleton, and the wood pulp fiber portion is subjected to carboxymethylation treatment. It is preferable to use one having high absorbency. In this case, the spunbond skeleton is
It is desirable that the second layer is ubiquitous at a position close to the surface in contact with the first layer, not at the center in the thickness direction.

In the present invention, the superabsorbent polymer sheet constituting the main component of the second layer can also be obtained by chemically treating fibers to impart high absorbency. For example, an acrylic fiber which is partially hydrolyzed to form a polyacrylate and which has high absorbency can be advantageously used. Alternatively, in the case of a cellulose fiber, high absorbency can be imparted by carboxyl methylation and cross-linking the cellulose fiber. Examples of this carboxymethylation are described in detail below.

The method itself for carboxymethylating cellulosic fibers is already widely known. Basically, it can be carried out by reacting an alkali hydroxide and a monochloroacetate with a cellulosic fiber in a solvent such as water or isopropyl alcohol.

As the alkali hydroxide, an alkali metal hydroxide is generally used, and sodium hydroxide is preferred from the viewpoint of cost. As the monochloroacetate, an alkali metal salt or an ammonium salt is used. In general, sodium monochloroacetate and potassium monochloroacetate are used.

The method for introducing the cross-linking is not particularly limited. However, the cross-linking agent may be reacted with the cellulosic fiber in advance and then carboxymethylated. The agent may be acted on at the same time, or the crosslinking agent may be acted on after carboxymethylation. Examples of the crosslinking agent include aldehydes such as formaldehyde and glyoxal; N-methylol compounds such as dimethylol urea, dimethylol ethylene urea, and dimethylol imidazolidone; oxalic acid, maleic acid, succinic acid, and polyacrylic acid. Polycarboxylic acids; polyepoxy compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and diepoxybutane; divinyl compounds such as divinyl sulfone and methylenebisacrylamide; dichloroacetone, dichloropropanol, and dichloro Polyvalent halogen compounds such as acetic acid; halohydrin compounds such as epichlorohydrin and epipromohydrin; and polyvalent aziridine compounds can be used.

The amount of the crosslinking agent varies depending on the type of the crosslinking agent or the reaction conditions.
Preferably it is 1 to 10% by weight.

The pure water absorption of a cellulosic fiber having a cross-linking bond and a carboxymethyl group is determined mainly by the degree of substitution of the carboxymethyl group and the cross-link density. Although the pure water absorption theoretically increases as the degree of substitution of the carboxymethyl group increases, a degree of substitution of 0.35 to 1.6 is appropriate in practice. Even if the substitution degree is increased beyond 1.6, the water absorption becomes almost saturated, and the cost of the obtained sheet increases, which is disadvantageous. In addition, when carboxymethylation is performed, a phenomenon that depolymerization of cellulose molecules occurs and conversely, a phenomenon that water absorption decreases may occur. On the other hand, if the degree of substitution is less than 0.35, a sufficient amount of pure water absorption cannot be obtained.

The cellulose-based layer, ie, the second layer, thus carboxylated and crosslinked, is bonded and integrated with the first layer described above.
This integration is achieved by means commonly used for bonding a plurality of sheets or webs mainly composed of fibers to each other, such as bonding with an adhesive, heat fusion, high frequency fusion,
Although it is possible to perform this using means such as hydroentanglement and needle punching, it is preferable to perform heat fusion of a part of the skeletal fiber constituting the second layer and the fiber portion of the first layer. Will be The heat fusion between the first layer and the second layer is different from the entanglement bonding, and if the whole surface is adhered, the rigidity is increased as a whole, so that the flexibility is maintained and the diffusivity is controlled. It is desirable to apply a bond with a partial pattern.

FIG. 1 is a perspective view of a water-absorbing composite to which such a connection is applied, FIG. 2 is a partial cross-sectional view taken along the line PP ′ (MD direction) of FIG. 1, and FIG. It is a partial sectional view in the S 'direction (CD direction). 1 to 3, a first layer 1 and a second layer 2 are connected to each other at a plurality of connecting portions 3 arranged at appropriate intervals and extending in the MD direction parallel to each other. As shown in FIG. 2, the width A of each connecting portion 3 and the interval B between adjacent connecting portions 3 can be freely set, but the width A is 1 to 5 mm and the interval B is 5 to 20 m.
About m is appropriate.

The connecting portion 3 may extend over the entire surface of the water-absorbing composite as shown in FIG.
Alternatively, as shown in FIG. 4 (B), it may be provided except for a peripheral portion. In addition, when the water-absorbing composite is used for a specific application such as a sanitary napkin, as shown in FIG. 4 (C), an elliptical central portion (sweet The coupling portion 3 may be provided in a portion other than the (spot) 4 portion. Further, as shown in FIG. 4D, the coupling portions 3 can be arranged in one or a plurality of rings surrounding the central portion 4.

The water-absorbing composite of the present invention comprising the first layer and the second layer bonded and integrated with each other has a relatively small water retention degree that the first layer has, and a water-absorbing composite that the second layer has. Due to the extremely high water retention, the water absorption capacity has a steep gradient in the thickness direction. This water absorption capacity gradient acts to move the liquid quickly from the first layer to the second layer when the liquid is supplied onto the first layer, and then to stably hold the liquid in the second layer. Therefore, when the water-absorbing composite of the present invention is used as an absorbent for sanitary napkins, for example,
In addition to exhibiting a sufficiently large absorption capacity, the first layer in contact with the skin has very little moisture and therefore gives a very good feel. Also, even if the second layer absorbs a large amount of water and becomes swollen, the first layer joined to it retains the same strength as when dried,
The overall shape of the water-absorbing composite is extremely stable.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail.

The water absorption, the wet tensile strength, and the degree of carboxymethyl group substitution in each of Examples and Comparative Examples were measured by the following methods.

[Amount of Pure Water Absorption] Four test samples of 2.5 cm × 2.5 cm square were placed on a 10 cm × 10 cm square of 250
It is sealed in a bag made of mesh nylon wire, immersed in pure water obtained by distilling deionized water through an ion exchange resin for 10 minutes to absorb water, and then pulled up, suspended and drained for 10 minutes. After performing the above, the weight of the test sample was measured, and the amount of water absorption was indicated by the weight (g) of pure water absorbed per 1 g of the test sample.

[Wet tensile strength] According to the method of JIS P8135, the value in the longitudinal direction was measured using a test piece having a width of 25 mm.

[Degree of carboxymethyl group substitution] 2.5 cm
After drying four test samples of 2.5 cm square in a vacuum dryer at 60 ° C. for 4 hours, the weight was measured, and the value obtained by subtracting the weight of the synthetic fiber nonwoven fabric from this value was used as the carboxy content in the composite sheet. The weight was defined as methylcellulose. The sample after weight measurement was transferred to a petri dish, and a methanolic hydrochloric acid solution (70% by weight)
50 ml of a mixed solution of hydrogen chloride dissolved at a concentration of 1 mol / l in an aqueous methanol solution) was added, and the mixture was allowed to stand for 1 hour. After that, it was sufficiently washed with methanol to completely remove hydrochloric acid, and air-dried. Then, 300 ml of the air-dried sample
After adding about 20 ml of 0.1 N sodium hydroxide solution and 100 ml of pure water and slowly stirring for 1 hour, titration was performed with 0.1 N hydrochloric acid using phenolphthalein as an indicator. Was used to calculate the degree of substitution.

Y = 0.1A-0.1B (1) Degree of substitution = 162Y / (1000W-80Y) (2) In the formula, A: Amount of 0.1 N sodium hydroxide solution (ml) B: 0. Amount of 1N hydrochloric acid (ml) Y: amount of carboxymethyl group (milliequivalent) W: weight of carboxymethylcellulose (g) (Example 1) From a staple (2.2d × 51 mm) of a polypropylene fiber having a basis weight of 30 g / m ^2. Card web was prepared. On the other hand, a card web made of staples (1.5 d × 45 mm) of polynosic fiber having a basis weight of 40 g / m ² was prepared.

The two types of card webs were overlapped, and a high-pressure columnar water stream of about 80 kg / cm ² was jetted to entangle and integrate the fibers of the card web with the fiber staples to obtain a laminated sheet.

Next, this laminated sheet was 20 cm × 30 c
m (weight 4 g), cut into sodium hydroxide 1
After immersing for one minute in a mixed solution consisting of 0.4% by weight, potassium monochloroacetate 34.6% by weight, epichlorohydrin 1.0% by weight and water 54.0% by weight, the mixture was pressed between filter papers and pressed. 2 g of the mixed solution was attached to 1 g of the sheet. Put this in a polyethylene bag,
The polynosic fiber was carboxymethylated and cross-linked by placing it in a dryer kept at 60 ° C. for 4 hours.

Next, the operation of dipping in a 70% by weight aqueous solution of methanol and pressing between filter papers was repeated four times to sufficiently wash the laminated sheet. Finally, it was immersed in 100% methanol, pressed between filter papers and pressed, and then air-dried to obtain a water-absorbent nonwoven fabric. In addition, the substitution degree of the carboxymethyl group of the polynosic fiber part in the obtained water-absorbent nonwoven fabric was 0.47.

The resulting water-absorbing composite has a structure as shown in the schematic diagram of FIG. In FIG. 5, reference numeral 11 denotes a layer formed of staples of polypropylene fibers, and reference numeral 12 denotes a layer of carboxymethylated polynosic fibers.

After immersing the water-absorbing composite in distilled water for 10 minutes, the structure changed as shown in FIG.
The pure water absorption of this water-absorbing composite was 35 g / g, the tensile strength (MD) in a dry state was 4.5 kgf, the wet strength was 3.0 kgf, and the dry strength ratio was about 67%. In this state of water absorption, the shape was substantially the same as before water absorption.

Example 2 [First Layer] Polyester fiber staple (15d × 4)
5 mm) 60 parts, sea core type composite fiber staple of polypropylene and polyethylene (2.0 d × 45 mm) 4
A 25 g / m ² card web is prepared from 0 parts of the mixed fiber, and the web is dried by passing through a hot air dryer at 130 ° C. to obtain a dry nonwoven fabric, which is used as a first layer.

[Second Layer] Softwood bleached kraft pulp (NBKP) was hydroentangled with a polypropylene spunbond nonwoven fabric having a basis weight of 12 g / m ² (denier 2.5 denier) so as to have an amount of 80 g / m ² . A composite sheet was produced. The obtained composite sheet is 20 cm × 30 cm (weight 5.4).
g) and immersed in a mixed solution consisting of 10.4% by weight of sodium hydroxide, 34.6% by weight of potassium monochloroacetate, 1.0% by weight of epichlorohydrin and 54.0% by weight of water for 1 minute Then, the mixture was pressed between filter papers and pressed so that 2 g of the mixed solution adhered to 1 g of the composite sheet. This was placed in a polyethylene bag and placed in a drier kept at 60 ° C. for 4 hours to carry out carboxymethylation and crosslinking of NBKP.

Next, the operation of dipping in a 70% by weight methanol aqueous solution, sandwiching between filter papers and pressing was repeated four times to sufficiently wash the composite sheet. Finally, it was immersed in 100% methanol, pressed between filter papers and pressed, and then air-dried to obtain a water-absorbent nonwoven fabric. In addition, the substitution degree of the carboxymethyl group of NBKP in the obtained water-absorbent nonwoven fabric was 0.47.

The first layer and the second layer obtained as described above are superimposed, passed through a pair of grooved rolls heated to 140 ° C. and thermocompressed to obtain a waveform as shown in FIG. A water-absorbing composite having the following pattern was obtained.

The amount of pure water absorbed by the first layer used was 4.8 g.
/ G nonwoven fabric and the second layer had a pure water absorption of 35 g / g absorber. The pure water absorption of the resulting water-absorbing composite was 27.
g / g complex.

When the physical properties of the water-absorbing composite were evaluated, the dry tensile strength (MD) was 5.5 kgf, and the wet tensile strength (MD) after immersion in pure water for 10 minutes was 4.0 kgf.
Met. Therefore, the dry-wet strength ratio was about 72%, and the water-absorbing composite maintained substantially the same shape as before the water absorption even in the water-absorbing state.

[0053] is prepared (Example 3) [First layer] Commercially available polypropylene nonwoven having a basis weight of 32 g / m ² (Fiber Tech Corporation, trade name "Ultra Dry soft"). The pure water absorption of this nonwoven fabric is 5.2
g / g nonwoven fabric.

[Second layer] Polypropylene / polyethylene sea-score type composite fiber staple (2.0 mm) was used as easily meltable fiber in 75 parts of a 3d × 51 mm polyacryl superabsorbent fiber staple (trade name “Lanseal” manufactured by Toyobo).
(d × 45 mm) was added to prepare a mixed fiber card web having a basis weight of 50 g / m ² . 135 ° C
And dried by passing through a hot air drier, to form a highly absorbent sheet, which is used as the second layer. The pure water absorption of this second layer was 25 g / g nonwoven fabric.

The first layer and the second layer obtained as described above are superimposed, passed through a pair roll composed of a grooved roll and a flat roll heated to a surface temperature of 150 ° C., and thermocompressed. As a result, a water-absorbing composite having a corrugated pattern as shown in FIG.

The pure water absorption of the obtained water-absorbing composite was 20.
g / g complex. The composite had a dry tensile strength (MD) of 6.2 kgf and a wet tensile strength (MD) of 4.0 kgf after immersion in pure water for 10 minutes. Therefore, the wet / dry strength ratio was about 65%.

(Example 4) The water-absorbing composites obtained in Examples 1, 2 and 3 were placed between a top sheet and a back sheet to form a sanitary napkin having a total thickness of about 1.0 mm. It was created. After testing each napkin,
It exhibited excellent water absorption, and kept its surface extremely dry even after water absorption, and had excellent performance as a sanitary napkin.

[0058]

As described above, the water-absorbing composite of the present invention has a first layer composed of a nonwoven fabric web mainly composed of synthetic fibers having a surface wetting property against water, The liquid supplied to the first layer is applied to the first layer because the second layer composed of the highly water-absorbing polymer sheet whose form is stabilized has a structure in which the liquid supplied to the first layer is extremely high. Although absorbed instantaneously, it passes quickly without being retained here, is sucked into the second layer, and is stably absorbed. Therefore, the first layer is always in a state of waiting for the next excretion, and can be advantageously used as a sheet absorbent in many uses including diapers and sanitary napkins.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a part of a water absorbent composite according to one embodiment of the present invention.

FIG. 2 is a partial cross-sectional view taken along the line P-P 'of FIG.

FIG. 3 is a partial cross-sectional view taken along the line S-S ′ of FIG. 1;

FIGS. 4A, 4B, 4C, and 4D are plan views showing examples of a joint pattern provided in the water-absorbent composite of the present invention.

FIG. 5 is a partial longitudinal sectional view showing a configuration of a water-absorbing composite in Example 1 of the present invention.

FIG. 6 is a partial longitudinal sectional view showing a state where the water-absorbing composite of FIG. 5 has absorbed water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st layer 2 2nd layer 3 Joining part 4 Central part 11 Layer consisting of the staple of a polypropylene fiber 12 Layer consisting of the staple of a polynosic fiber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI A61F 13/53 A61F 13/18 307C D04H 1/48 360 1/54 (72) Inventor Toshio Maekawa Kita Terao, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture 3-15 Mitsuike Heights C-502 (72) Inventor Kozo Tajiri 2-5-13 Matsugaoka, Nakano-ku, Tokyo Shin-Oji Paper and Matsugaoka Apartment 203 (56) References JP-A-61-48359 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 20/00-20/34 A61F 13/15 A61L 15/00

Claims (12)

(57) [Claims] 1. A first layer composed of a nonwoven fabric web mainly composed of synthetic fibers having surface wetting characteristics with respect to moisture, and a form-stabilized high water absorption having a significantly higher moisture retention than the first layer. A second layer made of a conductive polymer sheet, wherein the first layer and the second layer are arranged at an appropriate distance from each other.
Bonded by heat fusion at multiple joints extending parallel to
And a water-absorbing composite having a water-absorbing capacity gradient in a thickness direction, wherein the water-absorbing composite is integrated at the connecting portion . 2. The connecting portion is provided on the entire surface of the water-absorbing composite.
The water-absorbing composite according to claim 1, wherein the composite extends. 3. The joint has the greatest absorption power.
Claims provided in parts other than those where it is desired to
Item 2. The water-absorbing composite according to Item 1. 4. The connecting portion includes a plurality of phosphors surrounding a central portion.
The water-absorbing composite according to claim 1, which is provided in the shape of a rug. 5. The water-absorbing composite according to claim 1, wherein the first layer and the second layer are connected to each other by hydroentanglement. 6. The synthetic fiber as a main component of the first layer,
The second layer is composed of a heat-fusible net-like nonwoven fabric having a skeleton as a skeleton, and a high-water-absorbing polymer fiber composited with the skeleton. The water-absorbing composite according to claim 1, wherein the first layer and the second layer are integrated by heat fusion. Wherein said first layer is composed of polypropylene fiber web, and the backbone of the second layer of polypropylene spunbond claim 6 comprising a superabsorbent treated fibers complexed to Water-absorbing complex. 8. The water-absorbent composite according to claim 7 , wherein the fiber subjected to the high absorbency treatment is a hydrolyzed acrylic fiber or a cellulose fiber subjected to carboxymethylation and crosslinking. 9. water uptake capacity of the second layer, the water-absorbing composite according to any one of the first layer according to claim 1-8 is 3 times or more of water absorption capacity of the. 10. The strength when wet is 50% of the strength when dry
The water-absorbing composite according to any one of claims 1 to 9 , which is the above. 11. A method for producing a water-absorbing composite having a water-absorbing capacity gradient in a thickness direction, comprising the steps of: forming a first layer comprising a nonwoven fabric web mainly composed of synthetic fibers having a surface wetting property against moisture; A preparing step, comprising a skeleton made of heat-fusible fibers, and a highly absorbent fiber entangled with the skeleton, having a significantly higher water retention than the first layer, and a form-stabilized high water absorption. Preparing a second layer made of a conductive polymer sheet , and disposing the first layer and the second layer at appropriate intervals.
And joining by heat fusion at a plurality of joining portions extending in parallel with each other . 12. The skeleton consists spunbond fusible fusible, the superabsorbent fibers, according to claim 11 which is hydrolyzed acrylic fibers or carboxyl methylated and cross-linked cellulosic fibers the method of.