Liquid Absorbent Sheet

Abstract

To provide a liquid absorbing sheet that is made compact before absorbing liquid and can absorb a sufficient amount of liquid when absorbing the liquid.SOLUTION: A liquid absorbing sheet includes: a receiving base material which has liquid permeability and which includes a first base material, a second base material, and a bonding portion at which the first base material and the second base material are bonded to each other at margins thereof, the first base material and the second base material each being composed of a material including fibers; and a water absorbing resin which has a water absorbing property, which is swelled with water absorption, and which is received in a portion between the first base material and the second base material surrounded by the bonding portion. In the liquid absorbing sheet, the bonding portion is at least partially broken when the water absorbing resin is swelled.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a liquid absorbent sheet. [Background technology]

[0002] For example, in an inkjet printer, waste ink is generated during a head cleaning operation performed to prevent a decline in print quality due to ink clogging, and during an ink refill operation after replacing an ink cartridge. In addition, ink may leak from unintended locations in the inkjet printer. Ink absorbers that absorb such ink are known.

[0003] For example, Patent Document 1 discloses an SAP sheet in which particles of SAP, a highly absorbent polymer, are sealed between a first sheet and a second sheet made of a fibrous material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-136152 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the SAP is sealed, it will reach its swelling limit while absorbing liquid, and the swelling will be restricted, so it will no longer be able to absorb any more liquid. In other words, it will no longer be able to absorb any more liquid before the SAP reaches its maximum absorbable amount. As a result, it will not be able to absorb a sufficient amount of liquid. [Means for solving the problem]

[0006] The liquid absorbent sheet of the present invention includes a storage substrate having a first substrate, a second substrate, and a joining portion at which edges of the first substrate and the second substrate are joined to each other, the first substrate and the second substrate being each made of a material containing fiber, and having liquid permeability; a water-absorbent resin that is accommodated in a portion surrounded by the joint between the first base material and the second base material, has water absorption properties, and swells as it absorbs water; The joint is characterized in that at least a part of the joint breaks due to swelling of the water-absorbent resin. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a first embodiment of a liquid absorbent sheet of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the liquid absorbent sheet shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the liquid absorbent sheet shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the liquid absorbent sheet shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a method for producing the liquid absorbent sheet shown in FIG. [Figure 6] FIG. 6 is a sectional view illustrating a method for producing the liquid absorbent sheet shown in FIG. [Figure 7] FIG. 7 is a sectional view illustrating a method for producing the liquid absorbent sheet shown in FIG. [Figure 8] FIG. 8 is a plan view of a second embodiment of the liquid absorbent sheet of the present invention. [Figure 9] FIG. 9 is a cross-sectional view of the liquid absorbent sheet shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view of the liquid absorbent sheet shown in FIG. [Figure 11] FIG. 11 is a plan view of a third embodiment of the liquid absorbent sheet of the present invention. [Figure 12] FIG. 12 is a plan view of a modified example of the liquid absorbent sheet of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The liquid absorbent sheet of the present invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings.

[0009] First Embodiment Fig. 1 is a plan view of a first embodiment of the liquid absorbent sheet of the present invention. Figs. 2 to 4 are cross-sectional views of the liquid absorbent sheet shown in Fig. 1. Figs. 5 to 7 are cross-sectional views for explaining a method for producing the liquid absorbent sheet shown in Fig. 1.

[0010] In the following description, for convenience of explanation, the upper side in Figs. 2 to 8 (as well as Figs. 9 and 10) will be referred to as "upper (or upper side)" and the lower side as "lower (belower)".

[0011] 1 to 4, the liquid absorbent sheet 10 has a liquid-permeable storage substrate 2 and a water-absorbent resin 3 stored in the storage substrate 2. Liquid that has dropped or permeated into the storage substrate 2 from the outside permeates the storage substrate 2 and is absorbed and held by the water-absorbent resin 3 inside.

[0012] Examples of the liquid include water, ink, body fluids, etc. Examples of the ink include water-based ink in which a coloring material is dissolved in a water-based solvent, as well as solvent-based ink in which a binder is dissolved in a solvent, UV-curable ink in which a binder is dissolved in a liquid monomer that is cured by UV irradiation, and latex ink in which a binder is dispersed in a dispersion medium. In the following, the liquid absorbed by the water-absorbing resin 3 will be described as ink.

[0013] The storage substrate 2 has a first sheet 2A which is a first substrate, a second sheet 2B which is a second substrate, and a joint 2C where the edges of the first sheet 2A and the second sheet 2B are joined together. The first sheet 2A and the second sheet 2B are made of a material containing fiber.

[0014] The planar shape of first sheet 2A and second sheet 2B is substantially square in the illustrated configuration, but is not limited to this configuration and may be any shape, such as rectangular, circular, elliptical, or polygonal.

[0015] Examples of fibers include synthetic resin fibers such as polyester fibers and polyamide fibers; natural resin fibers such as cellulose fibers, keratin fibers, and fibroin fibers, and chemically modified products thereof. These can be used alone or in appropriate mixtures, but it is preferable for the fiber to be mainly cellulose fiber, and it is more preferable for almost all of the fiber to be cellulose fiber.

[0016] Cellulose is a material having suitable hydrophilicity, and therefore when ink is applied to the liquid absorbent sheet 10, it can suitably absorb the ink, and can quickly recover from a particularly high fluidity state (for example, a state in which the viscosity is 10 mPa·s or less), and can suitably deliver the ink once absorbed to the water-absorbent resin 3. As a result, the ink absorption characteristics of the liquid absorbent sheet 10 as a whole can be made particularly excellent. Furthermore, cellulose fiber is a renewable natural material, and among various fibers, it is inexpensive and easily available, and therefore is advantageous from the standpoints of reducing the production cost of the liquid absorbent sheet 10, stable production, reducing the environmental load, and the like.

[0017] In this specification, the cellulose fiber may be any fiber that contains cellulose as a main component as a compound, and may contain hemicellulose and lignin in addition to cellulose.

[0018] The average length of the fibers is not particularly limited, but is preferably 0.1 mm to 7 mm, more preferably 0.1 mm to 5 mm, and even more preferably 0.1 mm to 3 mm. The average width (diameter) of the fibers is not particularly limited, but is preferably 0.05 mm to 2 mm, and more preferably 0.1 mm to 1 mm.

[0019] The average aspect ratio of the fibers (ratio of average length to average width) is not particularly limited, but is preferably 10 or more and 1,000 or less, and more preferably 15 or more and 500 or less.

[0020] The above-mentioned numerical ranges allow more suitable carrying of the water-absorbent resin 3, retention of ink by the fibers, and delivery of the ink to the water-absorbent resin 3. As a result, the ink absorption characteristics of the liquid absorbent sheet 10 as a whole can be improved.

[0021] The first sheet 2A and the second sheet 2B may be made of the same material or different materials.

[0022] The thickness of the first sheet 2A and the second sheet 2B is not particularly limited, but is preferably 0.1 mm to 10 mm, more preferably 0.5 mm to 5 mm. This allows the ink to be more effectively held by the fibers and sent to the water-absorbent resin 3. This further improves the ink absorption properties of the liquid absorbent sheet 10 as a whole.

[0023] The thickness of the first sheet 2A and the second sheet 2B may be the same or different.

[0024] The density of the fibers in the first sheet 2A and the second sheet 2B is not particularly limited, but may be, for example, 0.01 g / cm 3 More than 0.5cm 3 / g or less, and preferably 0.05 g / cm 3 More than 0.3cm 3 / g or less. This can sufficiently increase the ink permeability through the fibers. As a result, the ink absorption characteristics of the liquid absorbent sheet 10 as a whole can be further improved. In addition, it is possible to prevent the particles of the water-absorbent resin 3 from unintentionally leaking out from between the fibers.

[0025] In addition to the above-mentioned fibers, the first sheet 2A and the second sheet 2B preferably contain a binder that binds the fibers together, which can sufficiently increase the strength of the first sheet 2A and the second sheet 2B and prevent breakage in unintended parts.

[0026] The binder is not particularly limited, and examples of the binder that can be used include thermoplastic resins, curable resins, starch, dextrin, glycogen, amylose, hyaluronic acid, kudzu, konjac, potato starch, etherified starch, esterified starch, natural gum paste (etherified tamarind gum, etherified locust bean gum, etherified guar gum, acacia arabic gum), fiber-derived paste (etherified carboxymethylcellulose, hydroxyethylcellulose), seaweed (sodium alginate, agar), animal protein (collagen, gelatin, hydrolyzed collagen, sericin), etc., but it is preferable to use a thermoplastic resin.

[0027] Examples of the thermoplastic resin include polyolefins such as AS resin, ABS resin, polyethylene, polypropylene, and ethylene-vinyl acetate copolymer (EVA), modified polyolefins, acrylic resins such as polymethyl methacrylate, polyesters such as polyvinyl chloride, polystyrene, polyethylene terephthalate, and polybutylene terephthalate, polyamides (nylons) such as nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 6-12, and nylon 6-66, liquid crystal polymers such as polyphenylene ether, polyacetal, polyether, polyphenylene oxide, polyether ether ketone, polycarbonate, polyphenylene sulfide, thermoplastic polyimide, polyetherimide, and aromatic polyester, and various thermoplastic elastomers such as styrene-based, polyolefin-based, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, polybutadiene-based, trans-polyisoprene-based, fluororubber-based, and chlorinated polyethylene-based. One or more types selected from these may be used in combination. Preferably, the thermoplastic resin used is polyester or a material containing polyester.

[0028] In addition to the binder, the composition may contain, for example, a colorant for coloring the fibers, an aggregation inhibitor for inhibiting aggregation of the fibers and the binder, a flame retardant for making the fibers etc. less flammable, and a paper strength agent for increasing the paper strength of the first sheet 2A and the second sheet 2B.

[0029] The joint 2C is a portion where the edges of the first sheet 2A and the second sheet 2B are joined together. In this embodiment, the entire peripheries of the edges of the first sheet 2A and the second sheet 2B are joined together so as to form a frame shape in a plan view.

[0030] The joining method for the joint portion 2C is not particularly limited, and examples thereof include fusion such as thermal fusion and ultrasonic fusion, adhesion via an adhesive, and pressure bonding, and one or a combination of two or more of these can be used.

[0031] Furthermore, since at least one of the first sheet 2A and the second sheet 2B contains the binder as described above, the first sheet 2A and the second sheet 2B can be bonded by thermal fusion. Furthermore, the bonding strength can be easily adjusted by appropriately setting the particle size and amount of the binder contained in the first sheet 2A or the second sheet 2B.

[0032] In the case of bonding using an adhesive, the adhesive to be used is not particularly limited and may be a water-soluble adhesive, an organic adhesive, or the like, but among them, a water-soluble adhesive is preferable. In this way, if the ink is water-based, the water-soluble adhesive will dissolve when the ink comes into contact with the adhesive, and this can promote the breaking of the joint 2C.

[0033] Examples of water-soluble adhesives include proteins such as casein, soy protein, and synthetic protein; various starches such as starch and oxidized starch; polyvinyl alcohols including modified polyvinyl alcohols such as polyvinyl alcohol, cationic polyvinyl alcohol, and silyl-modified polyvinyl alcohol; cellulose derivatives such as carboxymethyl cellulose and methyl cellulose; aqueous polyurethane resins; and aqueous polyester resins.

[0034] In this embodiment, the joint strength at the joint 2C is approximately the same over the entire area.

[0035] The water-absorbent resin 3 is stored in the portion surrounded by such a joint 2C. The water-absorbent resin 3 is a resin that has water absorption and swells with water absorption. The water-absorbent resin 3 is not particularly limited, but examples thereof include carboxymethyl cellulose, polyacrylic acid, polyacrylamide, starch-acrylic acid graft copolymer, hydrolyzate of starch-acrylonitrile graft copolymer, vinyl acetate-acrylic acid ester copolymer, copolymer of isobutylene and maleic acid, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer, polyethylene oxide, polysulfonic acid compound, polyglutamic acid, salts (neutralized products) thereof, crosslinked bodies, etc. Here, water absorption refers to a function of having hydrophilicity and retaining moisture. Many water-absorbent resins 3 gel when they absorb water.

[0036] Among them, a resin having a functional group on the side chain is preferable as the water-absorbent resin 3. Examples of the functional group include an acid group, a hydroxyl group, an epoxy group, and an amino group.

[0037] In particular, the water-absorbent resin 3 is preferably a resin having an acid group on the side chain, and more preferably a resin having a carboxyl group on the side chain.

[0038] Examples of the carboxyl group-containing unit constituting the side chain include those derived from monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, fumaric acid, sorbic acid, cinnamic acid, and anhydrides and salts thereof.

[0039] When the water absorbent resin 3 has an acid group in its side chain, the ratio of the acid groups neutralized to form salts among the acid groups contained in the water absorbent resin 3 is preferably 30 mol% to 100 mol%, more preferably 50 mol% to 95 mol%, and even more preferably 60 mol% to 90 mol%. This makes it possible to improve the ink absorption by the water absorbent resin 3 (liquid absorbent sheet 10).

[0040] The type of neutralization salt is not particularly limited, and examples thereof include alkali metal salts such as sodium salts, potassium salts, and lithium salts, and salts of nitrogen-containing basic substances such as ammonia, among which sodium salts are preferred. This can improve the ink absorption of the water-absorbent resin 3 (liquid-absorbing sheet 10).

[0041] The water-absorbent resin 3 having acid groups in the side chains is preferable because electrostatic repulsion occurs between the acid groups when absorbing ink, which increases the absorption speed. In addition, if the acid groups are neutralized, the ink is easily absorbed into the water-absorbent resin 3 due to osmotic pressure.

[0042] The water absorbent resin 3 may have a structural unit that does not contain an acid group in the side chain. Examples of such a structural unit include a hydrophilic structural unit, a hydrophobic structural unit, and a structural unit that serves as a polymerizable crosslinking agent.

[0043] Examples of the hydrophilic constituent units include constituent units derived from nonionic compounds such as acrylamide, methacrylamide, N-ethyl(meth)acrylamide, Nn-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxypolyethylene glycol(meth)acrylate, polyethylene glycol mono(meth)acrylate, N-vinylpyrrolidone, N-acryloylpiperidine, and N-acryloylpyrrolidine.

[0044] Examples of the hydrophobic structural unit include structural units derived from compounds such as (meth)acrylonitrile, styrene, vinyl chloride, butadiene, isobutene, ethylene, propylene, stearyl (meth)acrylate, and lauryl (meth)acrylate.

[0045] Examples of the structural unit that serves as the polymerizable crosslinking agent include structural units derived from diethylene glycol diacrylate, N,N-methylenebisacrylamide, polyethylene glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane diallyl ether, trimethylolpropane triacrylate, allyl glycidyl ether, pentaerythritol triallyl ether, pentaerythritol diacrylate monostearate, bisphenol diacrylate, isocyanuric acid diacrylate, tetraallyloxyethane, and diallyloxyacetate.

[0046] The water-absorbent resin 3 preferably contains a polyacrylate copolymer or a cross-linked polyacrylic acid polymer, which has the advantages of improving the liquid absorption performance and reducing the manufacturing cost, for example.

[0047] The crosslinked polyacrylic acid polymer is preferably one in which the proportion of structural units having a carboxyl group in all structural units constituting the molecular chain is 50 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more.

[0048] If the proportion of structural units containing a carboxyl group is too low, it may be difficult to achieve sufficiently excellent ink absorption performance.

[0049] The carboxyl groups in the crosslinked polyacrylic acid polymer are preferably partly neutralized (partially neutralized) to form a salt.

[0050] The proportion of neutralized carboxyl groups in the total carboxyl groups in the crosslinked polyacrylic acid polymer is preferably 30 mol % or more and 99 mol % or less, more preferably 50 mol % or more and 99 mol % or less, and even more preferably 70 mol % or more and 99 mol % or less.

[0051] The water-absorbent resin 3 may have a structure crosslinked with a crosslinking agent other than the above-mentioned polymerizable crosslinking agent.

[0052] When the water-absorbent resin 3 is a resin having an acid group, for example, a compound having a plurality of functional groups that react with the acid group can be preferably used as the crosslinking agent.

[0053] When the water-absorbent resin 3 is a resin having a functional group that reacts with an acid group, a compound having a plurality of functional groups that react with an acid group in the molecule can be suitably used as the crosslinking agent.

[0054] Examples of the compound (crosslinking agent) having a plurality of functional groups that react with the acid group include glycidyl ether compounds such as ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, (poly)glycerin polyglycidyl ether, diglycerin polyglycidyl ether, and propylene glycol diglycidyl ether; polyhydric alcohols such as (poly)glycerin, (poly)ethylene glycol, propylene glycol, 1,3-propanediol, polyoxyethylene glycol, triethylene glycol, tetraethylene glycol, diethanolamine, and triethanolamine; and polyvalent amines such as ethylenediamine, diethylenediamine, polyethyleneimine, and hexamethylenediamine. In addition, polyvalent ions such as zinc, calcium, magnesium, and aluminum can also be suitably used because they react with the acid group of the water absorbent resin 3 to function as a crosslinking agent.

[0055] The water-absorbent resin 3 may have any shape, such as, for example, a scale-like, needle-like, fibrous, or particulate shape, but it is preferable that the majority of the water-absorbent resin 3 is particulate. When the water-absorbent resin 3 is particulate, the ink permeability can be easily ensured. The average particle size of the particles is preferably 10 μm or more and 1000 μmm or less, more preferably 50 μm or more and 800 μm or less, and even more preferably 100 μm or more and 600 μm or less.

[0056] The storage substrate 2 may contain components (other components) other than the water-absorbent resin 3. Examples of such components include surfactants, lubricants, antifoaming agents, fillers, ion-exchange resins, activated carbon, zeolite, antiblocking agents, UV absorbers, colorants such as pigments and dyes, flame retardants, and flowability improvers.

[0057] Here, when ink penetrates the liquid absorbent sheet 10 and the absorbent resin 3 absorbs the ink, the absorbent resin 3 swells as shown in FIG. 3. When the liquid absorbent sheet 10 absorbs more ink, the swollen absorbent resin 3 pushes the first sheet 2A and the second sheet 2B apart from each other as shown in FIG. 4, and the joint 2C breaks. Therefore, the swollen absorbent resin 3 overflows toward the outside of the storage substrate 2 through the broken portion. With this configuration, when the liquid absorbent sheet 10 is not absorbing ink or when the amount of ink absorbed is relatively small, the absorbent resin 3 can be stored in the storage substrate 2 to achieve a compact size, while preventing the absorbent resin 3 from leaking outward. When the amount of ink absorbed exceeds a predetermined amount, the joint 2C breaks, and the absorbent resin 3 can further absorb ink and swell, so that the absorbent resin 3 as a whole can sufficiently absorb ink. As described above, the liquid absorbent sheet 10 can achieve a compact size before sufficiently absorbing ink, and can absorb a sufficient amount of ink when absorbing ink.

[0058] In particular, in the case of this embodiment, since the joint strength is approximately the same at the joint 2C, as the swelling of the water-absorbent resin 3 progresses, the first sheet 2A and the second sheet 2B become more likely to separate from each other over the entire joint 2C. Therefore, the swelling of the water-absorbent resin 3 in the thickness direction of the liquid absorbent sheet 10 is not hindered. Therefore, the ink absorption amount of the water-absorbent resin 3 as a whole can be increased more efficiently.

[0059] Furthermore, when the volume of the water-absorbing resin 3 when dry, i.e., before absorbing ink, is V1 and the volume after absorbing the maximum amount of ink is V2, V1 / V2 is preferably 2 to 1000, more preferably 5 to 250. This allows a sufficient amount of ink to be absorbed and allows the joint portion 2C to be broken more reliably.

[0060] In addition, the joint 2C has a water-absorbent resin 3 of 0.5 g / cm 3 More than 20.0g / cm 3 It is preferable that the water-absorbent resin 3 has a structure in which at least a part of the water-absorbent resin 3 breaks when the water-absorbent resin 3 absorbs a liquid of 2.0 g / cm 3 More than 10.0g / cm 3 It is more preferable that the ink-absorbing layer is configured so that at least a part of the ink-absorbing layer breaks when the ink-absorbing layer absorbs the liquid. This allows the ink-absorbing layer to absorb a sufficient amount of ink.

[0061] Moreover, the weight (total amount) of the water-absorbing resin 3 is preferably 20% to 95% of the total weight of the liquid absorbent sheet 10 when no liquid is absorbed, and more preferably 30% to 70%. This allows a sufficient amount of ink to be absorbed.

[0062] The weight of the water-absorbent resin 3 per unit area of ​​the liquid absorbent sheet 10 is 100 g / m 2 More than 1000g / m 2 It is preferable that the thickness is less than 200 g / m 2 More than 800g / m 2 It is more preferable that the thickness is equal to or less than 100 mm. This allows a sufficient amount of ink to be absorbed, and makes it easier for the joint portion 2C to break.

[0063] The water-absorbent resin 3 may or may not be supported on the storage substrate 2, but is preferably bonded to at least one of the first sheet 2A, which is the first substrate, and the second sheet 2B, which is the second substrate. This makes it possible to prevent the stored water-absorbent resin 3 from moving excessively within the storage substrate 2. As a result, the ink can be absorbed evenly.

[0064] The method of supporting the water-absorbent resin 3 on the storage substrate 2 is not particularly limited, and examples thereof include a method of bonding the water-absorbent resin 3 to the storage substrate 2 using an adhesive, a method of adding moisture to the water-absorbent resin 3 to make it sticky, and a method of adhering the water-absorbent resin 3 by using this sticky property. When an adhesive is used, the adhesive to be used is not particularly limited, and the adhesives described above can be used. Among them, a water-soluble adhesive is preferable. As a result, when the ink is water-based, the water-soluble adhesive dissolves when the ink comes into contact with the adhesive, and therefore it is possible to prevent the penetration of the ink into the water-absorbent resin 3 from being hindered.

[0065] As described above, the liquid absorbent sheet 10 includes the first sheet 2A, which is the first substrate, the second sheet 2B, which is the second substrate, and the joint 2C, where the edges of the first sheet 2A and the second sheet 2B are joined together. The first sheet 2A and the second sheet 2B are each made of a material containing fiber, and the liquid-permeable storage substrate 2 includes the water-absorbent resin 3, which is stored in the portion surrounded by the joint 2C between the first sheet 2A and the second sheet 2B, has water absorption properties, and swells as it absorbs water. The joint 2C is at least partially broken by the swelling of the water-absorbent resin 3. With this configuration, when no liquid is absorbed or when the amount of ink absorbed is relatively small, the water-absorbent resin 3 can be stored in the storage substrate 2 to achieve a compact size, while preventing the water-absorbent resin 3 from leaking outward. When the amount of absorbed liquid exceeds a predetermined amount, the joints 2C break, allowing the water-absorbent resin 3 to absorb more liquid and swell, so that the water-absorbent resin 3 as a whole can sufficiently absorb liquid. As described above, the liquid absorbent sheet 10 is compact before it has sufficiently absorbed liquid, and yet can absorb a sufficient amount of liquid when it has absorbed liquid.

[0066] Next, an example of a method for producing the liquid absorbent sheet 10 will be described.

[0067] First, the first sheet 2A, the second sheet 2B, the water-absorbent resin 3, the mask 4 and the heating and pressing jig 5 are prepared.

[0068] Next, as shown in Fig. 5, a water-soluble adhesive or water is applied to at least one of the first sheet 2A and the second sheet 2B. Next, as shown in Fig. 6, a water-absorbent resin 3 is sprayed onto the surface on which the water-soluble adhesive or water has been applied. At this time, a mask 4 such as masking tape is placed on the portion that will later become the joint 2C.

[0069] Next, the mask 4 is removed, and a water-soluble adhesive or water is applied to the first sheet 2A and the second sheet 2B with the absorbent resin supported thereon. Then, as shown in Fig. 7, the first sheet 2A and the second sheet 2B are overlapped so that the water-absorbent resin 3 is positioned therebetween, and heating and pressing are performed using a heating and pressing tool 5. At this time, the part where the mask 4 was placed is heated and pressed.

[0070] Either the heating or the pressing may be omitted. Also, an adhesive may be applied between the first sheet 2A and the second sheet 2B.

[0071] <Second embodiment> Fig. 8 is a plan view of a second embodiment of the liquid absorbent sheet of the present invention, Fig. 9 and Fig. 10 are cross-sectional views of the liquid absorbent sheet shown in Fig. 8.

[0072] Hereinafter, the second embodiment of the liquid absorbent sheet of the present invention will be described with reference to these drawings, but the differences from the above-described embodiment will be mainly described, and a description of the similar points will be omitted.

[0073] 8 and 9, in the liquid absorbent sheet 10 of this embodiment, the storage base material 2 is formed by folding one sheet in half. Of the two sheets folded and overlapped, one is the first sheet 2A and the other is the second sheet 2B. In other words, the first sheet 2A and the second sheet 2B are connected at part of their edges.

[0074] In this embodiment, the joint 2C is formed by joining the edges of the first sheet 2A and the second sheet 2B together except for the portion where the edges of the first sheet 2A and the second sheet 2B are joined together. Therefore, as shown in Fig. 10, when the joint 2C breaks, the water-absorbent resin 3 protrudes in the directions of the arrows in Fig. 8, i.e., in the three directions, but does not protrude from the portion where the edges of the first sheet 2A and the second sheet 2B are joined together.

[0075] In this way, according to this embodiment, it is possible to control the protruding direction of the water-absorbent resin 3. Therefore, for example, when the liquid absorbent sheet 10 is placed in a narrow space and it is desired to make the water-absorbent resin 3 protrude in a desired direction, this can be realized by selecting the installation direction.

[0076] <Third embodiment> FIG. 11 is a plan view of a third embodiment of the liquid absorbent sheet of the present invention.

[0077] Hereinafter, the third embodiment of the liquid absorbent sheet of the present invention will be described with reference to this figure, but the differences from the previously described embodiments will be mainly described, and a description of the similar points will be omitted.

[0078] As shown in FIG. 11, in this embodiment, the width of a portion 2D of the joint 2C corresponding to the edge on the lower side in FIG. 11 is narrower. This portion 2D is more likely to break than other portions of the joint 2C. In this way, the joint 2C has the portion 2D, which is a preferential breaking portion that breaks preferentially over other portions of the joint 2C due to swelling of the water-absorbent resin 3. This makes it possible to control the direction in which the water-absorbent resin 3 protrudes. Therefore, for example, when the liquid absorbent sheet 10 is installed in a narrow space and it is desired to have the water-absorbent resin 3 protrude in a desired direction, this can be achieved by selecting the installation direction.

[0079] Moreover, the portion 2D which is the preferential breaking portion has a smaller width than other portions of the joint portion 2C. With this configuration, the portion 2D which is the preferential breaking portion can be formed by the simple method of adjusting the width of the portion to be heated and pressed by the heating and pressing jig 5 shown in FIG.

[0080] As shown in Fig. 12, a portion having a narrower width than other portions may be formed by forming a notch 2E in a portion corresponding to the joint 2C. In this case, the portion where the notch 2E is formed becomes a preferential breaking portion.

[0081] Furthermore, without being limited to the above configuration, even if all the joints 2C have the same width, a preferential breaking portion may be formed by making the joint strength weaker than the other portions.

[0082] The liquid absorbent sheet of the present invention has been described above in terms of the illustrated embodiment, however, the present invention is not limited to this, and each part constituting the liquid absorbent sheet can be replaced with any other configuration capable of performing the same function.

[0083] The liquid absorbent sheet of the present invention may be a combination of any two or more of the structural features of the above-described embodiments. [Explanation of symbols]

[0084] 2...storage base material, 2A...first sheet, 2B...second sheet, 2C...joint, 2D...part, 2E...cutout, 3...water-absorbent resin, 4...mask, 5...heating and pressurizing tool, 10...liquid-absorbing sheet

Claims

[Claim 1] A sheet folded in half, the edges of which are not connected. The sheet has a joint where the overlapping portions are joined at the edges, and the sheet is made of a material containing fiber. and a liquid-permeable storage substrate; The container is housed in the area surrounded by the container base and the joint, has water absorption properties, and swells as it absorbs water. and a water-absorbing resin that moisturizes the surface of the substrate. The joint portion is at least partially formed preferentially over the sheet due to swelling of the water-absorbent resin. A liquid absorbent sheet characterized in that it breaks when pressed.

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