JP2023067820A - Water swellable structure and manufacturing method thereof as well as filter containing the structure - Google Patents

Abstract

To provide a filter containing a water swellable structure capable of obtaining a sufficient water stopping effect even when the density of a water-absorbing fiber is low, by overcoming the problem of high cost and degradation of the passability of gas and organic liquid, because in a suction decompression device or an oil supply device, in a flow path of gas or an organic liquid in these devices, in order not to pass water content on a down stream side, a water absorbing filter is used, such a filter clogs, when a large amount of water flowed-in, the filter by absorption swelling to stop water supply, however, since, in order to stop water, a water absorbing fiber layer having high density is necessary, there are problems of high cost and reduced gas and organic liquid permeability.SOLUTION: A water-swellable structure in which a water-swelling layer and a porous sheet having 5 to 200 pores/cm2 and an average pore diameter of 0.05 to 2.0 mm are laminated.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a water-swellable structure obtained by laminating a water-swellable layer and a perforated sheet, and a method for producing the same.

2. Description of the Related Art In a vacuum suction device, an oil supply device, and the like, a water absorption filter is used in order to prevent moisture from passing downstream in a flow path of gas or liquid in these devices.

For example, the liquid intrusion prevention device described in Patent Document 1 is a device that is attached to a liquid collection container into which liquid is injected by creating a negative pressure with a suction pump or the like, and serves to prevent liquid from entering the suction pump. have. Such a liquid intrusion prevention device incorporates water-absorbent fibers, and under conditions such as a rise in the liquid level in the liquid collection container, liquid reaches the liquid intrusion prevention device. disappears, i.e., clogs, and stops the intrusion of liquid.

Further, Patent Document 2 discloses a water-removing filter for water-containing oil using a water-swellable fiber having a multi-layered structure of a hydrogel outer layer and an acrylonitrile polymer and/or other polymer inner layer. Such a water removal filter can remove moisture contained in organic liquids by allowing organic liquids such as insulating oil, lubricating oil and organic solvent to pass through.

JP-A-5-201452 Japanese Patent Publication No. 1-008561

A conventional liquid intrusion prevention device such as that disclosed in Patent Document 1 requires a large amount of water-absorbing fibers (high-density water-absorbing layer) in order to close the gaps between the fibers due to the swelling of the water-absorbing fibers and stop the water. Since the water-absorbent fiber is expensive, it becomes a factor of cost increase. On the other hand, if the density of the water-absorbing layer is made low in order to suppress cost increases, the gaps cannot be completely closed even if the water-absorbing layer swells. .

In addition, in conventional water removal filters such as those disclosed in Patent Document 2, there is a limit to increasing the density because it is necessary to ensure liquid permeability for organic liquids. Water cannot be stopped when it passes through, and water leaks downstream.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a water-absorbing swelling structure capable of obtaining a sufficient water-stopping effect even if the density of the water-absorbing fibers is lower than that of the conventional structure, and a filter including the structure. aim.

As a result of intensive studies in order to achieve the above object, the present inventor found that the above object can be achieved by laminating a water-swelling layer and a perforated sheet, and arrived at the present invention. That is, in such a structure, since the liquid only passes through the holes in the sheet, it is sufficient to block only the holes in the sheet when water is stopped. In addition, since the density of the water-swelling layer can be reduced, the permeability of organic liquids such as gasoline can be ensured.

That is, the present invention is achieved by the following means.
(1) A water-absorbing and swelling structure comprising a water-swelling layer and a porous sheet having 5 to 200 pores/cm ² and an average pore diameter of 0.05 to 2.0 mm laminated.
(2) The water-absorbing swelling layer according to (1), wherein the water-absorbing swelling layer is a water-absorbing fiber structure containing 50-100% by mass of water-absorbing fibers having a water absorption rate of 500-50000% by mass. gender structure.
(3) The water-absorbing and swelling structure according to (2), wherein the water-absorbing fibers enter at least a part of the pores of the perforated sheet.
(4) The water-absorbent fiber has a core-sheath structure in which the core is an acrylonitrile-based polymer, and has a salt-type carboxyl group of 0.5 to 5.5 mmol/g. The water-absorbing swelling structure according to (2).
(5) The water-absorbing and swelling structure according to (2), wherein the water-absorbing fibrous structure is a non-woven fabric structure having a thickness of 1 to 20 mm and a basis weight of 100 to 3500 g/m ² .
(6) The water-absorbing and swelling structure according to (1), wherein the perforated sheet has a thickness of 10 to 500 μm.
(7) A method for producing a water-swellable structure according to any one of (1) to (6), which comprises combining the water-swellable layer and the perforated sheet by needle punching.
(8) A filter comprising the water-absorbing swelling structure according to any one of (1) to (6).

In the water-absorbing swelling structure of the present invention, a water-absorbing swelling layer and a perforated sheet are laminated to allow liquid to flow only through the holes in the sheet. It is characterized by being able to stop water even with a water-absorbing swelling layer having a small amount of fibers (low density). In addition, since the density can be made low, organic liquids such as gasoline can be passed through at a practical level speed. The water-absorbing and swelling structure of the present invention having such characteristics can be used, for example, as a water removing/water stopping material or a water removing/water stopping filter in various fields such as living materials, medical care, construction, civil engineering, agriculture and horticulture, and sanitary materials. It is possible to develop applications such as

The water-absorbing swelling structure of the present invention is formed by laminating a water-absorbing swelling layer and a perforated sheet. In the present invention, the water-stopping effect is exhibited by closing the pores of the perforated sheet due to the water-absorbing swelling of the water-absorbing fibers and water-absorbing polymer particles constituting the water-absorbing swelling layer.

The laminated structure of the water-swellable structure of the present invention is not particularly limited as long as the effects of the present invention can be obtained. A three-layer structure of perforated sheet/water-swelling layer may be mentioned. In addition, although layers other than the water-swelling layer and the perforated sheet may be laminated, it is preferable that the water-swelling layer and the perforated sheet are adjacent to each other from the viewpoint of obtaining an excellent water stopping effect. Further, the overall shape of the water-absorbing and swelling structure of the present invention is typically plate-like or coin-like, but may be string-like or thread-like.

The perforated sheet employed in the water-absorbing and swelling structure of the present invention has 5 to 200 perforations/cm ² and an average perforation diameter of 0.05 to 2.0 mm.

If the average pore size of the perforated sheet is less than 0.05 mm, it is difficult for organic liquids such as gasoline to pass through. Conversely, when the average pore size exceeds 2.0 mm, the pores are too large, and the water-absorbing fibers and the water-absorbing polymer swell and cannot be closed completely, making it difficult to stop water. Such average pore diameter is preferably 0.08 to 1.8 mm, more preferably 0.1 to 1.5 mm.

Further, when the number of holes in the perforated sheet is less than 5, there arises a problem that it becomes difficult to pass organic liquids such as gasoline. On the other hand, if the number of pores exceeds 200, there are too many pores, and the water-absorbing fibers and polymers swell due to water absorption, making it difficult to block water. inconvenience occurs. The number of openings is preferably 10 to 180/cm ² , more preferably 20 to 160/cm ² .

Examples of such a perforated sheet include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and vinyl chloride, and metal foils such as iron, aluminum, and stainless steel, and they may be combined or laminated. From among these, it is preferable to select and use a durable material that does not dissolve in the passing liquid.

Furthermore, the thickness of such perforated sheet is preferably 10 to 500 μm. If the thickness is less than 10 μm, there is a risk that problems such as tearing may occur during processing into a water-absorbing swelling structure and use. Conversely, if the thickness exceeds 500 μm, there is a possibility that problems such as being unable to be processed into the desired shape may occur. The thickness of such perforated sheet is more preferably 13 to 450 μm, more preferably 15 to 400 μm.

Next, the water-swelling layer in the present invention is a layer containing a material that swells by absorbing water. When a liquid containing water passes through such a water-absorbing swelling layer, water-absorbing swelling occurs, and the pores of the above-described perforated sheet are closed, thereby exhibiting a water stopping effect. Here, water-absorbing fibers and water-absorbing polymer particles can be used as the material that swells by absorbing water. In particular, water-absorbent fibers are preferable because they are less likely to fall off than water-absorbent polymer particles, and a fiber structure can be formed only by entangling fibers without using an adhesive or the like.

The water absorption rate of such water-absorbent fibers is preferably 500 to 50000% by mass. If the water absorption is less than 500% by mass, swelling due to water absorption will be insufficient, and there is a risk that the water removal/water stopping ability will not be exhibited sufficiently. If the amount exceeds 50,000% by mass, there is a risk that swelling due to water absorption will be too large, resulting in a problem that shape stability will be impaired. The water absorption rate of such water-absorbing fibers is more preferably 700 to 45,000% by mass, and even more preferably 1,000 to 40,000% by mass.

Moreover, the water-absorbent fiber preferably has a core-sheath structure in which the core is an acrylonitrile-based polymer, and has salt-type carboxyl groups of 0.5 to 5.5 mmol/g. Since acrylonitrile-based polymers do not have water absorbency, the core part has a core-sheath structure made of acrylonitrile-based polymer, so that the shape is stable even when water is absorbed, and problems such as the fibers falling off are less likely to occur. You get the advantage of Further, when the amount of salt-type carboxyl groups is less than 0.5 mmol/g, there is a possibility that a water-swellable structure exhibiting sufficient water-swellability cannot be obtained. Conversely, if it exceeds 5.5 mmol/g, there is a possibility that the amount of water absorption is too large, resulting in excessive swelling and loss of shape stability. The amount of salt-type carboxyl groups is more preferably 0.7 to 5.0 mmol/g, more preferably 1.0 to 4.5 mmol/g.

Furthermore, the water-absorbing fibers preferably have a fineness of 0.5 to 15.0 dtex. By setting the fineness to 0.5 dtex or more, sufficient strength can be secured, the shape is stable even when water is absorbed, and problems such as the fibers falling off are less likely to occur. If the fineness exceeds 15.0 dtex, the surface area is reduced and the contact area with water is reduced, so that the swelling speed may be reduced and the waterproof performance may be reduced.

In addition, the absorbent fibers preferably have a fiber length of 10 to 200 mm. Within such a range, it is possible to obtain good workability when producing a carded web by a carding machine in processing into a water-swellable structure. Such fiber length is preferably 15 to 170 mm, more preferably 20 to 150 mm.

The water-absorbing swelling layer in the present invention is preferably a water-absorbing fiber structure containing 50 to 100 mass % of such water-absorbing fibers. If the water-absorbent fiber content is less than 50% by mass, the pores of the perforated sheet may not be closed when swollen, resulting in insufficient water stopping effect. The content of such water-absorbing fibers is more preferably 55% by mass or more, and even more preferably 60% by mass or more.

In addition, fibers other than the above water-absorbing fibers that can be contained in such a water-absorbing fiber structure include natural fibers such as pulp, cotton, hemp, silk, and wool, regenerated fibers such as rayon and cupra, acrylic, Synthetic fibers such as polyester, polyolefin, polyurethane, polyamide, polyethylene, and polypropylene can be used.

Moreover, it is preferable to incorporate heat-fusible fibers into such a water-absorbent fibrous structure. The water-absorbing and swelling structure of the present invention can stop water by swelling the water-absorbing fibers and filling the voids. The outward swelling that increases the volume of the structure itself is suppressed, and the voids in the water-swellable structure can be filled more efficiently. Examples of such heat-fusible fibers include those using thermoplastic polymers such as polyethylene, polypropylene, polyester, polyamide, and polyolefin. In addition, as such heat-fusible fibers, two or more types of polymers with different melting points are used, and a core-sheath structure or a side-by-side structure using a high-melting polymer for the core and a low-melting polymer for the sheath may be used. can also

Furthermore, the water-absorbing fiber structure preferably has a thickness of 1 to 20 mm. If the thickness is less than 1 mm, a sufficient contact time with the passing liquid cannot be obtained, and there is a possibility that problems such as not being able to obtain the effect of water removal and water stoppage may occur. Conversely, if it exceeds 20 mm, it may be difficult to process it into the desired shape. The thickness of such a water-absorbent fibrous structure is more preferably 1.2 to 17 mm, more preferably 1.5 to 15 mm. The thickness refers to the total thickness of the laminated water-absorbing fibrous structures when a plurality of water-absorbing fibrous structures are laminated in the water-absorbing and swelling structure.

Further, the water-absorbing fiber structure preferably has a basis weight of 100 to 3500 g/m ² . If the basis weight is less than 100 g/m ² , problems may occur such as insufficient water removal and water stopping effects. Conversely, if it exceeds 3500 g/m ² , processing may become difficult. The basis weight of such a water-absorbent fibrous structure is more preferably 120 to 3200 g/m ² , still more preferably 150 to 3000 g/m ² . In addition, when a plurality of water-absorbent fibrous structures are laminated in the water-absorbing and swelling structure, the basis weight refers to the total basis weight of the laminated water-absorbing fibrous structures.

The form of the water-absorbing fibrous structure described above may be any form such as non-woven fabric such as card web, knitted fabric, or woven fabric, as long as it can be combined with the above-described perforated sheet in the manufacturing method described later. .

Furthermore, in the water-absorbing and swelling structure of the present invention, it is preferable that the above-described water-absorbing fibers enter into at least some of the pores of the perforated sheet. In such a state, the openings are more reliably blocked by the water-absorbing swelling of the water-absorbing fibers, so that even if the content of the water-absorbing fibers is small, water can be stopped efficiently.

Further, in the water-absorbing swelling structure of the present invention, other layers may be laminated in addition to the above-described perforated sheet and water-absorbing swelling layer. Examples of such other layers include polyester fiber nonwoven fabrics having no water absorbency. When such a polyester fiber nonwoven fabric is used as the outermost layer of the water-swellable structure, the strength of the water-swellable structure can be improved and the surface can be prevented from becoming fuzzy.

Examples of the method for producing the water-swelling structure of the present invention described above include a method of bonding the water-swelling layer and the perforated sheet described above with an adhesive or the like, and a method of combining them by needle punching. can. The latter method is particularly suitable when the water-swelling layer is a water-absorbing fiber structure containing water-absorbing fibers.

That is, in the needle punching process, since the water-absorbing swelling layer and the perforated sheet are superimposed and pierced with a large number of needles, the above-mentioned "state in which the water-absorbent fibers enter at least a part of the perforations of the perforated sheet" can be easily achieved. can be formed into In addition, in the needle punching process, even if a non-perforated sheet is used instead of the perforated sheet, the sheet can be integrated while forming perforations by penetrating the needle. Inventive water-swellable structures can also be formed.

A representative example of the water-absorbent fiber that can be employed in the present invention is a fiber having a core-sheath structure in which the core portion is an acrylonitrile-based polymer and the sheath portion is an acrylic acid-based polymer having a carboxyl group. be.
Such water-absorbing fibers can be produced by subjecting the surface layer of fibers made of an acrylonitrile-based polymer (hereinafter referred to as acrylonitrile-based fibers) to cross-linking introduction treatment and hydrolysis treatment to generate carboxyl groups. This manufacturing method will be described in detail below.

First, as the acrylonitrile-based polymer constituting the acrylonitrile-based fiber as a raw material, a polymer containing 70% by mass or more, preferably 75% by mass or more of acrylonitrile is desirable. Examples of copolymerizable monomers include vinyl halides such as vinyl chloride, vinyl bromide, and vinylidene chloride, and vinylidene halides; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; and salts thereof: ( (Meth)acrylic acid esters such as methyl methacrylate, ethyl (meth)acrylate, and butyl (meth)acrylate: vinyl esters such as vinyl acetate and vinyl propionate: vinylsulfonic acid, (meth)allylsulfone acids, ethylenically unsaturated sulfonic acids such as p-styrenesulfonic acid, and salts thereof; and vinyl compounds such as (meth)acrylamide, vinylidene cyanide, and methacrylonitrile. An acrylonitrile-based fiber can be obtained by performing wet spinning or the like using such a polymer by a known method.

Next, an aqueous solution in which a hydrazine compound and an alkaline metal compound coexist is attached to the acrylonitrile fiber and heated to simultaneously introduce cross-linking and hydrolysis by the hydrazine compound.

Specifically, an aqueous solution in which a hydrazine-based compound and an alkaline metal compound coexist is applied, and the adhesion amount with respect to the dry mass of the acrylonitrile-based fiber is 1.0 to 20.0 meq/g, preferably 1.0 to 20.0 meq/g for the alkaline metal compound. is 2.5 to 15.0 meq/g, and for hydrazine-based compounds, 0.01 to 2.0% by mass, preferably 0.05 to 1.5% by mass in terms of pure N ₂ H ₄ It is desirable to adopt a means of adjusting the adhered fibers so as to be so that the fibers are heated at a temperature of 80 ° C. or higher for 1 to 120 minutes, preferably in a moist heat atmosphere of 100 to 150 ° C. for 5 to 40 minutes. .

Here, if the amount of hydrazine attached to the dry fiber mass is less than the above lower limit, the obtained gel strength of the fibers having a core-sheath structure becomes low when water is absorbed, and the gel may fall off. be. On the other hand, if the upper limit is exceeded, the resulting fiber having a core-sheath structure may have insufficient water absorption performance.

Examples of the hydrazine compound used here include hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, hydrazine carbonate, and hydrazine hydrobromide. Further, an alkaline metal compound refers to a substance exhibiting a pH of 7.5 or more when made into a 1.0% by mass aqueous solution, and examples of such substances include hydroxides of alkali metals such as Na, K and Li. Alternatively, alkali metal salts such as Na, K and Li of organic acids such as carbonic acid, acetic acid and formic acid can be used. As a solvent for preparing an aqueous solution, water is preferable from an industrial point of view, but a mixed solvent of water and a water-miscible organic solvent such as alcohol, acetone, or dimethylformamide may also be used.

The above-described water-absorbing and swelling structure of the present invention can be used in various applications, and can be used, for example, as a water-removing filter for oil, a water-removing filter for organic solvents, an oil-water separation filter, and a liquid-intrusion prevention filter. .

Examples of use as a water-removing filter for oil include molding the water-absorbing and swelling structure of the present invention into a sheet, folding it into a bellows shape, and fitting it into a filter frame. For example, it is cut according to the size of the holder and used by setting it in the filter holder. In such an example, a liquid such as an insulating oil, a lubricating oil, or an organic solvent is passed through the sheet-shaped water-absorbing and swelling structure to remove water mixed in the liquid, and to remove a large amount of water from the liquid. In this case, the water-absorbent fibers swell and fill the voids of the filter to stop the passage of the liquid, thereby preventing the liquid containing water from passing through the downstream side of the filter.

Further, as an example of use as a liquid intrusion prevention filter, the water-absorbing and swelling structure of the present invention is molded into a coin shape and set in a filter holder provided in a blood aspirator used in surgery or the like. is mentioned. In such an example, blood or the like is aspirated, and when the liquid collection container of the aspirator becomes full, the blood or the like comes into contact with the coin-shaped water-absorbing swelling structure, swelling occurs, and the aspiration is stopped by filling the void. be able to. As a result, blood or the like can be prevented from leaking into vacuum pipes, vacuum pumps, or the like.

EXAMPLES Examples are shown below to facilitate understanding of the present invention, but these are merely illustrative and the gist of the present invention is not limited by these.

<Method for evaluating hole diameter>
The perforated sheet is taken out from the water-swellable structure and cut into 2 cm squares. The cut perforated sheet is observed with a microscope, the longest diameter of each of 20 arbitrarily selected perforations is measured, and the average value is defined as the perforation diameter.

<Method for evaluating the number of pores>
The perforated sheet is taken out from the water-swellable structure and cut into 1 cm square pieces. Observe the cut perforated sheet with a loupe and count the number of perforations.

<Evaluation method for water absorption rate of water-absorbent fiber>
About 0.5 g of the sample is immersed in pure water, kept at 25° C. for 30 minutes, wrapped in a nylon filter cloth (200 mesh), and centrifuged (160 G × 5 minutes, where G is the acceleration of gravity) to separate the fibers. Remove water. The weight of the sample thus prepared is measured (W2 [g]). Next, the sample is dried in a vacuum dryer at 80° C. to a constant weight and weighed (W3 [g]). From the above measurement results, it is calculated by the following formula.
Water absorption = (W2-W3)/W3

<Evaluation method for total carboxyl group content>
About 1 g of a fiber sample is immersed in 50 ml of 1 mol/l hydrochloric acid aqueous solution for 30 minutes. The fiber sample is then immersed in water at a bath ratio of 1:500. After 15 minutes, when it is confirmed that the bath pH is 4 or more, it is dried (if the bath pH is less than 4, it is washed with water again). Next, about 0.4 g of the sufficiently dried fiber sample was precisely weighed (W1 [g]), 100 ml of water was added, and 15 ml of 0.1 mol/l sodium hydroxide aqueous solution and 0.4 g of sodium chloride were added. and phenolphthalein are added and stirred. After 15 minutes, titrate with a 0.1 mol/l aqueous solution of hydrochloric acid until the color of phenolphthalein disappears, and the consumption of the aqueous solution of hydrochloric acid (V1 [ml]) is determined. From the measured values obtained, the total carboxyl group content is calculated according to the following formula.
Total amount of carboxyl groups [mmol / g] = (0.1 × 15-0.1 × V1) / W1

<Method for evaluating the amount of H-type carboxyl groups and the amount of salt-type carboxyl groups>
The amount of H-type carboxyl groups is calculated in the same manner as in the above method for measuring the total amount of carboxyl groups, except that the initial immersion in a 1 mol/l hydrochloric acid aqueous solution and subsequent washing with water are not performed. The amount of salt-type carboxyl groups is calculated by subtracting the amount of H-type carboxyl groups from the total amount of carboxyl groups.

<Confirmation method of core-sheath structure>
After dyeing the sample with a cationic dye, the cross section of the fiber is observed with an optical microscope. In the case of the core-sheath structure, it can be confirmed that the color depth and hue are different between the surface layer and the center.

<Fineness>
The sample is placed in a constant temperature and humidity chamber under an atmosphere of 20° C. and 65% RH for 24 hours. The fibers thus moistened are measured according to the JIS L 1015:2010 standard fineness A method.

<Fiber length>
The sample is placed in a constant temperature and humidity chamber under an atmosphere of 20° C. and 65% RH for 24 hours. The fibers thus moistened are measured according to the average fiber length staple diagram method (method A) of JIS L1015:2010.

<Method for evaluating the thickness of the water-absorbing fiber structure>
After a water-swellable structure sample is cut into a size of 10 cm×10 cm, it is dried, and the thickness of the water-swellable structure is measured using a vernier caliper without compressing it. The same measurement is performed at two other arbitrary locations, and the average value of the measurement results at all three locations is calculated. The thickness of the water-absorbing fibrous structure is calculated by subtracting the thickness of the layers other than the water-absorbing fibrous structure from the average value.

<Method for evaluating basis weight of water-absorbent fiber structure>
After cutting a card web sample into 10 cm×10 cm, it is dried at 105° C. for 2 hours, and the weight (W6 [g]) of the sample is measured. Based on the above results, the numerical value calculated by the following formula is used as the fabric weight of the water-absorbing fibrous structure.
Weight (g/m ² ) = W6/(0.1 x 0.1)

<Evaluation method for water stopping performance>
A filter manufactured by Shibata Science Co., Ltd. (product number: 061630-4705) was used as an apparatus for evaluating the water stopping performance. A filter is a suction filtration bottle with a glass filter base attached and a filter holder set thereon. A water-absorbing fiber structure cut into 10 cm squares is sandwiched between the glass filter base and the filter holder of this filter, and 400 ml of water is supplied from above while being sucked at -80 kPa. to measure. If this value exceeds 15 ml, water will pass through the filter even in actual use, making it unsuitable for use as a filter.

<Evaluation method for liquid permeability>
Evaluation of liquid permeability is performed in the same manner as the evaluation method of water stopping performance. However, the liquid used is xylene, and the time it takes to pass 400 ml of liquid is measured. If xylene does not flow, or if it takes more than 30 seconds to flow, it is not suitable for practical use because the organic liquid, which is the original purpose, cannot flow or it takes too much time.

<Method for producing water-absorbent fiber>
A spinning dope prepared by dissolving 10 parts of an acrylonitrile-based polymer consisting of 90% acrylonitrile and 10% methyl acrylate in 90 parts of a 48% sodium thiocyanate aqueous solution is spun, washed with water, stretched, dried, crimped, and heat-treated according to conventional methods. , and cut to obtain an acrylonitrile-based fiber as a raw material. Next, after attaching a mixed aqueous solution containing 0.10% hydrazine and 35.0% sodium hydroxide to the acrylonitrile-based fiber, it was squeezed so that the liquid absorption amount to the fiber mass was 100%. A cross-linking hydrolysis treatment was performed for a minute and washed with water. The washed fiber is immersed in a 0.1% sulfuric acid aqueous solution at 30°C for 1 hour, then dehydrated, oiled, dehydrated, opened, and dried by spraying ammonia gas to make the core part acrylonitrile. A water-absorbent fiber having a core-sheath structure, which is a polymer and the sheath portion is an acrylic polymer having a carboxyl group, was obtained. The water-absorbing fiber had a fineness of 5.6 dtex, a fiber length of 51 mm, a water absorption rate of 20000% by mass, and a salt-type carboxyl group amount of 1.6 mmol/g.

[Examples 1 to 3]
Two card webs having a basis weight half that of the fiber structure shown in Table 1 were produced using only the water-absorbing fibers obtained by the method described above. Next, a spunbond nonwoven fabric of polyester fibers (Ecoure (registered trademark) 3201A manufactured by Toyobo Co., Ltd., thickness 0.15 mm, basis weight 20 g/m ² )/the card web/polyethylene sheet (thickness 50 μm)/the card web/polyester fibers of spunbond nonwoven fabric (Ecoure (registered trademark) 3201A manufactured by Toyobo Co., Ltd., thickness 0.15 mm, basis weight 20 g / m ² ) in this order, and needle punching is performed three times in the order of front, back, front 5 Water-absorbing and swelling structures of Examples 1 to 3 having a layered structure were obtained. Table 1 shows the evaluation results of these water-absorbing swelling structures. For needle punching, a needle punch machine manufactured by Yamato Kiko Co., Ltd. was used, and FPD-1 40C manufactured by Organ Needle Co., Ltd. was used as the needle.

[Example 4]
In Example 1, instead of 2 carded webs, 4 carded webs of 525 g/m ² using the above water-absorbing fibers and the same spunbond nonwoven fabric used in Example 1 / 2 card webs / polyethylene sheet (thickness 50 μm) / 2 card webs / the same spunbond nonwoven fabric as used in Example 1, except that it has a 7-layer structure. A swellable structure was obtained. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 5]
A water-absorbing and swelling structure of Example 5 was obtained in the same manner as in Example 2, except that needle punching was performed five times in the order of front, back, front, back, front. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 6]
A water-absorbing swellable structure of Example 6 was obtained in the same manner as in Example 2, except that the front and back were subjected to needle punching twice in this order. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 7]
Two card webs having a basis weight half that of the fiber structure shown in Table 1 were produced using water-absorbent fibers. Next, the same spunbond nonwoven fabric used in Example 1/the card web/polyethylene sheet having 8 holes/cm ² of 1.0 mm (thickness 50 μm)/the card web/used in Example 1 The same spunbonded nonwoven fabrics were laminated in the same order as above, and the layers were point-bonded with an adhesive to obtain a water-absorbing and swelling structure of Example 7 having a five-layer structure. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 8]
In Example 2, instead of the water-absorbent fiber obtained by the method described above, a water-absorbent fiber (Teijin Frontier A water-absorbing and swelling structure of Example 8 was obtained in the same manner except that "Bell Oasis (registered trademark)" manufactured by Co., Ltd., fineness 11 dtex, fiber length 52 mm) was used. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 9]
In Example 2, except that instead of using only the water-absorbing fibers, 60% by weight of the water-absorbing fibers obtained by the method described above and 40% by weight of polyester fibers were blended to create a card web. A water-absorbing swelling structure of Example 9 was obtained. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 10]
In Example 2, instead of using only water-absorbent fibers, 60% by weight of water-absorbent fibers and 40% by weight of heat-sealable polyester fibers were blended to create a card web, and after needle-punching, at 130 ° C. for 5 minutes. A water-absorbing swelling structure of Example 10 was obtained in the same manner as above, except that the structure was heat-sealed. Table 1 shows the evaluation results of this water-absorbing swelling structure.

[Example 11]
A water-absorbing and swelling structure of Example 11 having a three-layer structure was obtained in the same manner as in Example 2, except that the spunbond nonwoven fabric was not laminated. Table 1 shows the evaluation results of these water-absorbing swelling structures.

[Comparative Example 1]
A water-absorbing swelling structure of Comparative Example 1 was obtained in the same manner as in Example 2, except that the perforated sheet was not used. Table 1 shows the evaluation results of this water-absorbing swelling structure. In Comparative Example 1, since the perforated sheet was not laminated, sufficient water stopping performance could not be obtained.

[Comparative Examples 2 and 3]
Water-absorbing and swelling structures of Comparative Examples 2 and 3 were obtained in the same manner as in Example 7, except that polyethylene sheets with different pore sizes and numbers of pores were used. 1 shows the evaluation results of these water-absorbing swelling structures. As for Comparative Example 2, since the pore size was too small, although it had water stopping performance, it lacked liquid permeability and was not suitable for practical use. In Comparative Example 3, since the pore diameter was large, sufficient water stopping performance could not be obtained.

[Comparative Examples 4 and 5]
Water-absorbing and swelling structures of Comparative Examples 4 and 5 were obtained in the same manner as in Example 2, except that the basis weight of the fiber structure was changed to the value shown in Table 1. 1 shows the evaluation results of these water-absorbing swelling structures. In Comparative Example 4, sufficient water stop performance could not be obtained because the fabric weight of the water-absorbing fibrous structure was low. With regard to Comparative Example 5, there was concern that since the basis weight was too high, the liquid permeability would be low, and at the same time, it would be too thick, making processing such as pleating and punching difficult.

Claims (8)

A water-absorbing and swelling structure comprising a water-absorbing swelling layer and a porous sheet having 5 to 200 pores/cm ² and an average pore size of 0.05 to 2.0 mm laminated. 2. The water-absorbing and swelling structure according to claim 1, wherein the water-absorbing swelling layer is a water-absorbing fibrous structure containing 50-100% by mass of water-absorbing fibers having a water absorption rate of 500-50000% by mass. . 3. The water-absorbing and swelling structure according to claim 2, wherein the water-absorbing fibers enter at least some of the pores of the perforated sheet. Claim 2, wherein the water-absorbent fiber has a core-sheath structure in which the core is an acrylonitrile-based polymer, and has a salt-type carboxyl group of 0.5 to 5.5 mmol/g. 3. The water-absorbing swelling structure according to . 3. The water-absorbing and swelling structure according to claim 2, wherein the water-absorbing fibrous structure is a non-woven fabric structure having a thickness of 1-20 mm and a basis weight of 100-3500 g/m ² . 2. The water-absorbing and swelling structure according to claim 1, wherein the perforated sheet has a thickness of 10 to 500 μm. 7. The method for producing a water-swellable structure according to any one of claims 1 to 6, comprising a step of combining the water-swellable layer and the perforated sheet by needle punching. A filter comprising the water-absorbing swelling structure according to any one of claims 1 to 6.