JPH09141091A - Water-absorbing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a water-absorbing sheet in which an absorbent for water can efficiently absorb water. SOLUTION: This sheet consists of a bag 11, a granular absorbent 5 for water housed only in a part P of the bag 11 and a sealing means 12 to seal the granular absorbent 5 for water to prevent the absorbent from spreading in the whole bag 11. The bag 11 is produced by laminating thermoplastic films 2a, 2b at least one of which has lots of pores 1 and then sealing the peripheral part 3. The diameter of the pores 1 of the bag is in such a range that the pores permeate water but do not leak the granular absorbent 5. The sealing means 12 is opened by absorption of water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbent sheet for absorbing and retaining water, which is used in the field of preservation of fresh foods, sanitary materials such as disposable diapers and sanitary products, and soil. It is advantageously used in the field of agriculture and civil engineering, which absorbs and retains the water contained therein.

[0002]

2. Description of the Related Art Food such as meat and fish is leached with a soup called drip when vacuum packed with a non-breathable film and stored in a chilled temperature zone, or when frozen and stored and then thawed. This drip accumulates between the food and the film and causes a problem such as discoloration of the food that has been in contact with it for a long time, which deteriorates the commercial value, and the removal of the discolored portion causes a reduction in the yield. In addition, this drip also serves as a breeding ground for bacteria, which shortens the shelf life of food.

Conventionally, a method using a water absorbing sheet has been known as a means for removing drip. In this method, food is stored by contacting it with a sheet-shaped water absorbing material, and drip leaching during storage is absorbed by this water absorbing material to be removed. This water-absorbent sheet is composed of, for example, a water-absorbent layer having water-absorbent particles carried on the entire surface of paper, pulp, or the like, between two water-permeable surface layers made of paper, nonwoven fabric, or a thermoplastic film having a large number of pores. It is sandwiched between. This water-absorbent sheet is not only for the purpose of removing drip, but also for removing moisture adhering to the surface of foods and other articles, and as a sanitary article.
It is also used as an agricultural civil engineering material that absorbs and retains water in the soil.

[0004]

The above-mentioned conventional water-absorbing sheet has a structure in which the water-absorbing material is carried on the entire surface of the water-absorbing sheet. However, when fresh food or the like is actually stored on this water-absorbing sheet. , The drip penetrates inside from a part of the water absorbent sheet and is absorbed by the water absorbent material of the permeated part, and the water absorbent material of this part swells due to the water absorption, but the other parts do not transfer the water and do not absorb the water. There is a problem of being left as it is. This is because the water that has locally passed through a part of the skin film of the water absorbent sheet is immediately absorbed by the water absorbent material in the vicinity, and the particulate water absorbent material that has absorbed the water swells and the particles quasi-assemble with each other in a dango shape. It is considered that this is because water is not distributed to other parts.

Further, since this type of water absorbent sheet is disposable, it is uneconomical that the water absorbent material which has not absorbed water remains after one use, and it also discharges more waste than necessary. It also becomes an environmental problem. The present invention has been made to solve the above problems, and an object of the present invention is to provide a water absorbing sheet that can efficiently absorb water by using a relatively small amount of water absorbing material.

[0006]

[Means for Solving the Problems]
A bag body in which a thermoplastic film having a large number of pores formed on at least one of them is overlapped and a peripheral edge is sealed, a granular water absorbent material unevenly distributed in a part of the bag body, and the granular water absorbent material is formed in the bag body. Of the sealing means so as not to spread over the whole, the pores of the bag have a pore diameter in a range that allows moisture to pass through but does not leak the granular water-absorbing material, and the sealing means is The problem can be solved by providing a water absorbing sheet formed so as to be unsealed by absorbing water.

The diameter of the pores formed in the bag is 5
It is preferably in the range of 0 μm to 150 μm. The above-mentioned sealing means is a heat-sealing part or an adhesive part formed between two thermoplastic films forming a bag, and the heat-sealing part or the adhesive part is expanded by absorbing water by the water absorbing material. It is preferably formed so as to be peeled off due to the expansion pressure when it is formed. Further, the adhesive portion may be water-soluble or water-softenable, and may be formed so as to be peeled off by the moisture that has passed through the pores of the bag.

Further, the sealing means is an inner bag made of paper or non-woven fabric enclosed in the bag body, and the granular water absorbing material is enclosed in the inner bag, and the inner bag is also provided. May be formed so that at least a part of the peripheral edge thereof is opened by the moisture that has passed through the pores of the bag. This inner bag is also an inner bag made of a water-soluble film,
The granular water absorbing material may be enclosed in the inner bag. The above particulate water absorbing material can be impregnated with a wetting agent made of a hydrophilic polyhydric alcohol.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the following examples. (Example 1) FIGS. 1A and 1B show a water absorbing sheet of Example 1. The water-absorbent sheet 10 comprises a polyethylene film 2a having a large number of pores 1 formed therein (hereinafter referred to as "apertured film") 2a and a non-porous polyethylene film 2b having no pores formed thereon. The bag body 11 in which the peripheral edge portion 3 is heat-sealed, the granular water absorbent material 5 (4.5 g) unevenly distributed in a part of the bag body 11 (hereinafter, referred to as “unevenly distributed region P”), and the granular water absorbent material ( Hereinafter, this will be simply referred to as a “water absorbing material” 5 and a sealing means 12 that is sealed so as not to spread in the entire bag 11.

The sealing means 12 in this embodiment is a heat seal portion (12) formed between two polyethylene films 2a and 2b.
No. 2 is weakly formed to such an extent that when the water-absorbent material 5 absorbs water and expands, it peels off due to the expansion pressure. The peel strength is, for example, in the range of 0.1 kg / 15 mm to 1.0 kg / 15 mm according to JIS-Z-1707.

The size of the bag body 11 in the first embodiment is 1
70 mm × 250 mm, and the polyethylene films 2a and 2b forming the bag body 11 each have a thickness of 50 μm.
It is. The perforated film 2a has pores 100 having a pore diameter of 100 μm within a range that allows moisture to pass therethrough without leaking the granular water-absorbing material 5.
Are formed so that the aperture ratio is 1.0%. Further, the water absorbing material 5 contained in the unevenly distributed region P of the bag body 11 is made of a crosslinked sodium polyacrylate having a maximum water absorption rate of 200 times its own weight.

In this water-absorbent sheet 10, for example, a water-absorbent material 5 is placed in the central portion (unevenly distributed region P) of a non-porous polyethylene film 2b having the above-mentioned size, and a perforated film 2a having the above-mentioned size is put on the water-absorbent material 5 to form films 2a, 2b. And heat-seal the peripheral portions of both films strongly, and the peripheral portion of the unevenly distributed region P containing the water absorbing material 5 is, for example, peeling strength within a range of 0.1 kg / 15 mm to 1.0 kg / 15 mm. It can be manufactured by weakly heat-sealing.

When the water absorbing sheet 10 of the first embodiment is used for absorbing drip of meat or fish, for example, these foods are unevenly distributed region P on the side of the perforated film 2a of the water absorbing sheet 10.
If you place it on top of it and store it, the generated drip will have pores 1,
It reaches the water absorbing material 5 through ... And is absorbed by this. Since the water-absorbent material 5 expands when it absorbs water, when the water absorption progresses and the expansion pressure thereof exceeds the peel strength of the heat-sealing portion 12, the heat-sealing portion 12 is peeled off, and at the same time, the water-absorbing material 5 which continues to expand further. A part of the water absorbent material 5 advances from the uneven distribution area P to the side portion (absence area) S of the bag body 11 due to the expansion pressure and the pressure applied by the weight of the food. As a result, the water absorption region is expanded according to the amount of water absorption, and the water absorbent material 5 contained in the water absorbent sheet 10 is used for water absorption without waste.

Example 2 A water absorbing sheet of Example 2 is shown in FIG.
Shown in In FIG. 2, the water-absorbent sheet 20 includes a bag body 21 in which two perforated films 2a similar to those used in Example 1 are overlapped and a peripheral edge portion 3 is sealed, and the bag body 2
From the water absorbent material 5 similar to that used in the first embodiment, which is unevenly distributed in the unevenly distributed area P of No. 1, and the sealing means 22 that seals the water absorbent material 5 so as not to spread in the entire bag body 21. Has become. In this case, the sealing means 22 is composed of an adhesive portion (22) formed so as to be peeled off by the expansion pressure when the water absorbent material 5 absorbs water and expands, or by being swollen by water. The adhesive part 22 in this embodiment is formed by using starch paste as an adhesive.

The water absorbing sheet 20 has a water absorbing material 5 (4.5) in the uneven distribution region P of the perforated film 2a having the above-mentioned size.
g) is placed, and the starch glue aqueous solution is applied in a strip shape to the peripheral portion of the unevenly distributed region P where the water absorbing material 5 is placed, and then the other perforated film 2a is covered and the films 2a and 2a are overlapped, The peripheral edge of the film is strongly heat-sealed, and the starch glue application part is pressure-bonded and dried to form an adhesive part 2.
It can be manufactured by forming 2.

When the water absorbing sheet 20 of the second embodiment is used for absorbing drip of meat or fish, for example, the food can be placed in the uneven distribution area P of any one of the sheet surfaces without paying attention to the front and back of the water absorbing sheet. When left for storage, the generated drip reaches the water absorbent 5 through the pores 1, ... And is absorbed by the water absorbent 5.

On the other hand, the adhesive portion 22 joins the perforated films 2a, 2a while maintaining a sufficient peeling strength during drying, but when water penetrates through the pores 1, ..., The starch paste is water-soluble. Therefore, it swells due to moisture, and the peel strength is significantly reduced. Therefore, when the water-absorbent material 5 expands due to water absorption, the expansion pressure causes the swelled adhesive portion 22 to be unsealed,
A part of the water absorbent material 5 advances to the side portion S of the bag body 21 due to the expansion pressure and the gravity of the food. As a result, the water absorbing sheet 20 has an expanded water absorbing area in accordance with the amount of water absorbed, and the water absorbing material 5 is used for absorbing water without waste.

(Embodiment 3) A water absorbing sheet of Embodiment 3 is shown in FIG.
(A) and (b). 3A and 3B, the water absorbing sheet 30 includes a bag body 31 in which two perforated films 2a similar to those used in Example 1 are superposed and a peripheral edge portion 3 is sealed, and the bag body 31. A water absorbent material 5 similar to that used in Example 1 and unevenly distributed inside 31 and a thin paper inner bag 32 sealed so that the water absorbent material 5 does not spread throughout the bag body 31. Has become. The inner bag 32 has a size of, for example, 95 mm × 110 mm, and a pair of opposing peripheral portions of the inner bag 32 are bonded with a water-soluble adhesive 33, for example, starch paste.

This water absorbing sheet 30 is obtained by putting a predetermined amount (4.5 g) of the water absorbing material 5 in the inner bag 32 having one adhesive portion opened and sealing the opening with a water-soluble adhesive 33. The inner bag 32 thus obtained can be manufactured by putting it in the bag body 31 formed by the two perforated films 2a, 2a and strongly heat-sealing the peripheral portion thereof.

When the water absorbent sheet 20 of the second embodiment is used for absorbing drip of meat or fish, for example, the inner bag 32 of the bag body 31 does not care about the front and back of the water absorbent sheet.
When food is placed on the uneven distribution area P where is stored,
The generated drip passes through the pores 1, ... And further permeates the paper fiber gap of the inner bag 32 by the capillary phenomenon to reach the water absorbing material 5, and is absorbed by this.

On the other hand, the adhesive 3 that seals the opening of the inner bag 32
Sample No. 3 seals its opening with a sufficient peel strength when dried, but when water penetrates through the pores 1, ..., the adhesive 33 is water-soluble, so that the adhesive 33 is softened by the water and has a peel strength. Markedly reduced. Therefore, when the water-absorbent material 5 expands due to water absorption, the opening of the inner bag 32 is unsealed by the expansion pressure, and a part of the water-absorbent material 5 is removed from the inner bag 32 by the expansion pressure and the weight of the food. Advance into the bag 31. By this, the water absorption area is expanded according to the amount of water absorption,
The water absorbing material 5 contained in the water absorbing sheet 20 is used for absorbing water without waste.

(Embodiment 4) The water absorbing sheet of Embodiment 4 is shown in FIG.
Shown in In FIG. 4, the water-absorbent sheet 40 includes a bag body 41 in which two perforated films 2a similar to those used in Example 1 are superposed and a peripheral edge portion 3 is sealed, and a bag body 4
The water absorbent material 5 is unevenly distributed in the inside of the container 1, and the inner bag 42 made of a water-soluble starch film is sealed so that the water absorbent material 5 does not spread in the entire bag body 41. Inner bag 42
The dimension is, for example, 95 mm × 110 mm.

The water-absorbing material 5 in this example is a granular sodium polyacrylate cross-linked product (4.5 g) having a maximum water absorption rate of 200 times its own weight impregnated with glycerin (3 g) as a wetting agent. is there.

In the water absorbent sheet 40, a predetermined amount of the water absorbent material 5 is put in the inner bag 42, one of which is opened, and the opening is sealed. The water absorbent sheet 40 is sealed with two perforated films 2a, 2a.
It can be manufactured by placing it in the bag 41 formed by and heat-sealing the peripheral portion strongly.

The water absorbing sheet 40 of the fourth embodiment is used, for example, for absorbing drip of meat or fish, without worrying about the front and back of the water absorbing sheet.
When food is placed and stored on the portion where the water is placed, the generated drip passes through the pores 1, ... And at least partially dissolves the inner bag 42, reaches the water absorbent material 5, and is absorbed therein. become.

On the other hand, since the inner bag 42 is water-soluble, it is dissolved or softened by the infiltration of water, and therefore the water-absorbent material 5
When it expands due to water absorption, it collapses due to its expansion pressure,
A part of the water absorbent material 5 advances into the bag body 41 from the inner bag 42 by the expansion pressure and the pressure of the weight of the food. Thereby, the water absorption area is expanded according to the amount of water absorption, and the water absorption sheet 4
The water absorbing material 5 contained in 0 will be used for water absorption without waste.

In each of the embodiments of the present invention described above, the thermoplastic film (eg, 2a, 2b in FIG. 1) forming the bag is a hydrophobic film that does not change its shape even when it comes into contact with moisture. Therefore, it is preferable to use a material that can maintain flexibility and strength even at low temperatures. Examples of suitable thermoplastic films from this viewpoint include, for example, polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, polyamides, ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, single-layer films or laminates such as polystyrene. A film can be mentioned.

The film thickness is preferably in the range of 20 μm to 100 μm. Film thickness less than 20 μm or 100
If it exceeds μm, uniform water absorption may not be possible through the pores 1, ... When the perforated film 2a is formed.

As a method for producing the perforated film 2a by forming pores in the above-mentioned thermoplastic film, it is possible to carry out melt perforation with a needle which is conventionally known, for example, a needle heated above the melting point of the thermoplastic film, or at room temperature. There is a method of punching with a punch, or a method of punching with a laser, etc., but a method of heating a roll in which a needle is planted to a temperature equal to or lower than the melting point and perforating with a physical force is particularly preferable. According to this method,
Protrusion edges, so-called burrs, are formed on the back surface of the pores 1, ... When a bag is manufactured with the surface on which the burrs are exposed facing inside, the burrs act as a kind of valve to allow the infiltration of water from the outside to the inside. Has the effect of being promoted by the capillary phenomenon and preventing the fine powder of the water absorbing material 5 from leaking to the outside through the pores 1, ....

The film thickness is preferably 20 μm to 100 μm
In the perforated film 2a produced from a thermoplastic film having a size within the range of m, the preferable pore diameters of the pores 1, ...
It is in the range of 50 μm to 150 μm. Within this range, not only the external moisture can flow through the pores 1, ... At any time, but also the fine particles of the water-absorbing material 5 stored inside the pores 1 ,.
It can be prevented from leaking to the outside through.

The porosity of the pores 1, ... Is important because it greatly affects the water absorption rate, and it is desirable to make it as large as possible from this point of view. It is preferably in the range of 1% to 2.0%.

The water absorbing material used in the water absorbing sheet of the present invention may be any granular material generally used in the field of disposable diapers, sanitary products, agricultural civil engineering and the like. These are generally three-dimensionally cross-linked water-soluble polymers, and many types are known. The preferred water absorbing material is
Acrylic acid, methacrylic acid, acrylic acid salt, methacrylic acid salt, acrylic acid ester, methacrylic acid ester, acrylic acid amide, on polysaccharides such as starch and cellulose
Methacrylic acid amide, acrylonitrile, methacrylonitrile, maleic acid, sulfonated styrene, polyvinyl pyridine, or any one or more selected from the group consisting of oligomers or cooligomers thereof is graft-polymerized, or is graft-polymerized and then hydrolyzed. Crosslinked product of the obtained polymer, polyethylene oxide, polypropylene oxide, polyvinylpyrrolidone, sulfonated polyethylene, polyvinylpyridine, polyacrylate,
Cross-linked product of at least one selected from the group consisting of polymethacrylate, polyacrylic acid amide, polymethacrylic acid amide, vinyl acetate / acrylic acid salt copolymer, isobutylene / maleic anhydride copolymer, polyvinyl alcohol /
Examples thereof include maleic acid copolymers and carboxymethyl cellulose crosslinked products. Examples of preferred commercially available water-absorbing materials used for the water-absorbing sheet of the present invention include PX-402A (manufactured by Showa Denko KK), Sunwet IM-300 (manufactured by Sanyo Kasei Co., Ltd.), AquaKeep 10SH (steel chemistry industry). And manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.).

Since the particle diameter of the water-absorbing material needs to be larger than the pore diameters of the pores 1, ..., For example, when the pore diameters of the pores 1, ... Are 100 μm, they remain on the 150-mesh sieve. It is preferable that the particle size is about the same.

The above particulate water-absorbing material may be impregnated with a wetting agent composed of a hydrophilic polyhydric alcohol. When the granular water-absorbing material is impregnated with the wetting agent, the fluidity of the water-absorbing material unevenly distributed in the bag body is improved, and more uniform water absorption becomes possible.

Examples of hydrophilic polyhydric alcohols that can be used as wetting agents are, for example, ethylene glycol, propylene glycol, diethylene glycol monoethyl ether, 1,3-butylene glycol, glycerin, polyethylene glycol, polypropylene glycol, polyglycerin, xylitol, Examples thereof include sorbitol, maltitol, methyl cellulose, carboxymethyl cellulose and the like.

The mixing ratio of the particulate water absorbing material and the wetting agent is preferably within the range of 20 to 200 parts by weight of the wetting agent with respect to 100 parts by weight of the particulate water absorbing material.
Outside of this range, the fluidity of the water absorbent material and the uniformity of water absorption will be reduced.

Water absorbing sheet 2 shown in Example 2 and FIG.
In No. 0, the adhesive part 22 is formed by using starch paste as an adhesive. In this case, the starch paste is a water-soluble adhesive, but the adhesive 22 does not necessarily need to be water-soluble or water-softenable as long as it can release the seal when absorbing water.

When the adhesive portion 22 is not water-soluble or water-softenable, the adhesive amount is adjusted to adjust the adhesive portion 2
The water absorbing material 5 may be formed so as to be separated by the expansion pressure when the water absorbing material 5 absorbs water and expands. The adhesive at this time is not particularly limited, but it is preferable to use a synthetic resin adhesive that can adhere the thermoplastic films used for the bag body 21 to each other.

It is further preferable that the adhesive portion 22 is water-soluble or water-softening. The adhesive that can be used in this case is one that is water-soluble or water-softening and that can adhere the thermoplastic films used for the bag body 21 to each other. Preferable examples thereof include starch paste, natural polysaccharides, glue, gum arabic, alginic acid, polyvinyl alcohol (PVA) and the like. In particular, starch paste and natural polysaccharides are preferable from the viewpoint of food hygiene.

Water absorbing sheet 3 shown in Example 3 and FIG.
In 0, the inner bag 32 is made of paper or non-woven fabric. Water can pass through the surface of these materials by capillarity. Therefore, the water that has passed through the pores 1, ... Can further penetrate the surface of the inner bag 32 and reach the water absorbent material 5. From the viewpoint of water permeability and economy, the inner bag 32 is preferably made of tissue paper-like thin paper.

At least a part of the peripheral edge of the inner bag 32 made of paper or nonwoven fabric is sealed with a water-soluble adhesive 33. The water-soluble adhesive that can be used here may be any as long as it can bond the material of the inner bag 32, and preferred examples thereof include starch paste, natural polysaccharides, glue, gum arabic, alginic acid, PVA etc. can be mentioned. In particular, starch paste and natural polysaccharides are preferable from the viewpoint of food hygiene.

Water absorbing sheet 4 shown in Example 4 and FIG.
In No. 0, the inner bag 42 enclosing the water absorbing material 5 is formed of a water-soluble film. It is preferable that the water-soluble film has a thickness and flexibility such that the water-absorbent material 5 will not be broken even if the water-absorbent material 5 is included therein in a dry state, and that it is hygienically safe. When the water absorbing material 5 contains a wetting agent, it is necessary that this water-soluble film does not dissolve in the wetting agent.

Suitable examples of water-soluble films that can be used include starch films, wafer films, water-soluble polyvinyl alcohol films, natural polysaccharide films, collagen films, pullulan films and the like.

The water-absorbent sheet of the present invention, regardless of any of the above-mentioned embodiments, is manufactured by using a punching machine, a bag-making machine, a filling machine, a heat sealer, etc., which are conventionally used in this field. It is possible.

The water-absorbent sheet of the present invention is not only used for absorbing water in foods, but can also be effectively used in the fields of disposable diapers, sanitary goods, agricultural civil engineering, etc., if necessary. Further, the water-absorbent sheet of the present invention is generally thrown away after being used for absorbing water, but in this case, it can be discarded as ordinary waste such as incineration waste.

(Water Absorption Test) With respect to each of the water absorption sheets of Examples 1 to 4 and the conventional type water absorption sheet of Comparative Example 1, a water absorption test was conducted under the following conditions. The structure of the water absorbing sheet of Comparative Example 1 used for comparison here is shown in FIG.
It will be explained by. In FIG. 5, the water absorbing sheet 50 of Comparative Example 1 has a bag body 54 in which a 170 mm × 250 mm polypropylene non-woven fabric 51 and a polyethylene film 52 having the same size as that of the non-woven fabric are superposed on each other and the peripheral edge portion 53 is heat-sealed. , Inside the bag body 54, two sheets of water-permeable paper 55, 5 each having a size of 150 mm × 220 mm
5, the water-absorbent material 5 (4.5 g) is evenly sandwiched between the two water-permeable papers 55, 55.

The conditions of the water absorption test are as follows. A filter paper (manufactured by Kiriyama Seisakusho Co., Ltd., diameter: 60 mm, retained particle diameter: 4 μm) was placed at the center of each water-absorbing sheet that was placed on a horizontal table, and a funnel-type funnel with a capacity scale was placed on it. 250 ml of pure water was placed in the funnel and dropped on the filter paper, and the time required for a predetermined volume of pure water to pass through the filter paper and be absorbed by the water absorbing sheet was measured. Table 1 shows the test results.

[0048]

[Table 1]

As is clear from the results in Table 1, Example 1
Each of the water absorbing sheets of Example 4 absorbs 250 ml of pure water in a shorter time than the water absorbing sheet of Comparative Example 1. This indicates that the water-absorbent sheets of the respective examples effectively consumed the water-absorbent material for water absorption without waste by expanding the water-absorbing region according to the amount of water absorption. On the other hand, in the water absorbent sheet of Comparative Example 1, only the permeated portion swells due to water absorption and the water does not migrate to other portions, so the absorption time is equivalent to that of each example if a small amount of water is used. It can be seen that as the water content increases, the time required for water absorption is extended and the water absorption efficiency is reduced.

[0050]

The water-absorbent sheet of the present invention has two bags, at least one of which is provided with a thermoplastic film having a large number of pores formed thereon, and the periphery of which is sealed, and a part of the bag body. It consists of unevenly distributed granular water-absorbing material and sealing means that seals this granular water-absorbing material so that it does not spread throughout the bag body, and the pores of the bag body allow moisture to pass through and leak the granular water-absorbing material. Having a hole diameter in the range of not, and since the sealing means is formed so as to be unsealed by water absorption, this water-absorbing sheet is unsealed when it absorbs water, A part of the water-absorbent material extends to a region where the water-absorbent material is absent, whereby the water-absorbent area is expanded in the bag according to the amount of water-absorbed material, and the water-absorbent material can be used for water absorption without waste.

The above-mentioned sealing means is a weak heat-sealing part or an adhesive part formed so as to be peeled off by the expansion pressure of the water-absorbing material, a water-soluble or water-softening adhesive part, or a paper or If the inner bag is made of a non-woven fabric and is formed such that at least a part of its peripheral portion is peeled off by water to open, or if it is an inner bag made of a water-soluble film, moisture from the outside By this, the seal is easily and rapidly released, and quick water absorption becomes possible.

When the water-absorbent sheet of the present invention is manufactured, a punching machine, a bag-making machine, a filling machine, a heat sealer and the like conventionally used in this field can be used, so that no special equipment is required and the cost is low. It can be manufactured in large quantities. Further, after being used for absorbing water, it can be discarded as ordinary waste such as incineration waste, so that problems such as environmental pollution do not occur.

[Brief description of the drawings]

FIG. 1 shows an example of a water absorbent sheet of the present invention (a)
The top view and the (b) sectional view.

FIG. 2 is a sectional view showing another embodiment of the water absorbent sheet of the present invention.

FIG. 3A is a plan view and FIG. 3B is a sectional view showing still another embodiment of the water-absorbent sheet of the present invention.

FIG. 4 is a sectional view showing still another embodiment of the water absorbent sheet of the present invention.

FIG. 5 is a cross-sectional view showing a water absorbent sheet of a comparative example.

[Explanation of symbols]

 1 ... Pores 2a ... Perforated film 2b ... Non-perforated film 3 ... Peripheral part 5 ... Granular water absorbing material 10 ... Water absorbing sheet 11 ... Bag 12 ... Sealing means P ... Uneven distribution area

Claims (8)

[Claims] 1. A water-absorbent sheet containing a granular water-absorbing material for absorbing and retaining water, wherein the water-absorbent sheet comprises two sheets, at least one of which is laminated with a thermoplastic film having a large number of pores formed therein. A bag body having a sealed peripheral edge portion, and a granular water-absorbing material unevenly distributed in a part of the bag body,
This granular water-absorbing material is composed of a sealing means that is sealed so as not to spread throughout the bag body, and the pores of the bag body have a pore diameter in a range that allows moisture to pass through but does not leak the granular water-absorbing material, Further, the water absorbing sheet, wherein the sealing means is formed so as to be released by water absorption. 2. The size of the pores formed in the bag is 50 μm.
The water absorbing sheet according to claim 1, wherein the water absorbing sheet has a thickness in the range of m to 150 μm. 3. The sealing means is a heat-sealing portion formed between two thermoplastic films forming a bag body, and the heat-sealing portion expands due to absorption of water by the granular water absorbent material. The water-absorbent sheet according to claim 1, wherein the water-absorbent sheet is formed so as to be peeled off due to the expansion pressure when the water-absorbing sheet is formed. 4. The above-mentioned sealing means is an adhesive portion formed between two thermoplastic films forming a bag body,
The water absorbent sheet according to claim 1, wherein the adhesive portion is formed so as to be peeled off by the expansion pressure when the granular water absorbent material absorbs water and expands. 5. The above-mentioned sealing means is a water-soluble or water-softening adhesive part formed between two films forming a bag body, and this adhesive part is a pore of the bag body. The water-absorbent sheet according to claim 1, wherein the water-absorbent sheet is formed so as to be peeled off by the moisture that has passed through. 6. The sealing means is an inner bag made of paper or non-woven fabric sealed inside the bag body, wherein the granular water absorbing material is sealed in the inner bag, and the inner bag is sealed. The water absorbent sheet according to claim 1, wherein at least a part of a peripheral edge portion of the water absorbent sheet is formed so as to be peeled off and opened by the moisture that has passed through the pores of the bag body. 7. The sealing means is an inner bag made of a water-soluble film sealed inside the bag body, and the granular water-absorbing material is sealed in the inner bag. The water absorbent sheet according to claim 1. 8. The water absorbing sheet according to claim 1, wherein the granular water absorbing material is impregnated with a wetting agent made of a hydrophilic polyhydric alcohol.