JP2006056160A - Water absorptive composite sheet for water barrier sheet, its manufacturing method and water barrier sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water barrier sheet excellent in water barrier property and handling capability. <P>SOLUTION: The water absorptive composite sheet 1 for the water barrier sheet has a substrate 2 and approximately spherical, water absorptive resin particles 3 that are bonded intermittently on the substrate 2. The water barrier sheet 10A has this water absorptive composite sheet 1 and covering sheets 11, 12 consisting of a water permeable sheet or a water non-permeable sheet. The manufacturing method of this water absorptive composite sheet 1 for the water barrier sheet is provided, which comprises attaching the droplets containing a polymerizable monomer and a substance in course of polymerization thereof to the substrate 2 and then polymerizing the monomer and the substance in which polymerization is on-going. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-absorbent composite sheet for a water-impervious sheet excellent in water absorbability and handleability, a method for producing the same, and a water-impervious sheet using the water-absorbent composite sheet for a water-impervious sheet.

  Conventionally, as a water shielding sheet used to prevent water leakage and exudation and intrusion at seawalls, rivers and other revetments, underground structures, waste disposal sites and reservoirs, water-permeable gelling substances for water shielding purposes are permeated. A water shielding sheet sandwiched between a water-permeable sheet or a water-impermeable sheet is used.

  For example, Japanese Patent Laid-Open No. 60-240446 discloses a waterproof material in which particles of a water-absorbing gelling substance are bonded and fixed between sheets of water-permeable material. However, with this waterproof material, there is a problem in that the water-absorbing substance is fixed by the adhesive so that the adhesive adheres to and embeds the water-absorbing substance, thereby inhibiting water absorption and preventing sufficient water shielding. . Japanese Patent Application Laid-Open No. 63-30809 and Japanese Patent Application Laid-Open No. 1-207375 disclose a technique using a water-absorbing substance as a binder component. In this method, the water-absorbing amount of the binder component is not sufficient, and the water-absorbing material after swelling is poorly fixed due to water-absorbing swelling and water dissolution of the binder. There is a problem that the water shielding effect cannot be shown. That is, when the water-absorbing substance moves and the water-absorbing substance is unevenly distributed or agglomerated, for example, when the water-absorbing substance is agglomerated as it is in the agglomerated state, the water-absorbing substance becomes mamako and becomes a water shielding material. Cannot go well, or a part of it swells greatly, making it impossible to apply it to the target area. In addition, in the case of using an adhesive or a binder, there is also a problem that the water shielding sheet is particularly hard, is not flexible, and is difficult to fit into a structure.

  On the other hand, in JP-A-7-207851 and JP-A-9-47736, a water-impervious sheet in which a water-absorbing substance is present between the water-permeable sheets and is integrated by needle punching and quilting. Is disclosed. Although this water-impervious sheet has improved flexibility, there is a problem that the water-absorbing substance easily passes through the fibers and is scattered outside the fiber layer due to an impact force applied by needle punching or quilting. Spattered water-absorbing substances reduce workability, and in addition to the problem that a large amount of water-absorbing substances need to be used in anticipation of the amount of water-absorbing substances being reduced by scattering, in addition, water-absorbing substances are made permeable to water. There are drawbacks that it is difficult to exist uniformly between the sheets, and that they are likely to be non-uniform. As a result, the water pressure resistance of the water-impervious sheet is lowered, resulting in a problem that a sufficient water-insulating effect cannot be exhibited.

In Japanese Patent Laid-Open No. 2003-25472, in order to prevent scattering of the water-absorbing substance, a technique of a laminated water-impervious sheet using a water-absorbing swellable substance having a particle structure with a specific particle size in which the amount of fine powder mixed is reduced. Is disclosed. With this method, a uniform water shielding sheet can be obtained without scattering fine powders. However, in this technique, the nonwoven fabric of the surface layer of the water shielding sheet and the sheet-like fiber molded body of the intermediate layer, and the sheet-like fiber molded body of the intermediate layer and the woven fabric or nonwoven fabric of the base layer are fused and bonded to each other by heat-sealing fibers. In addition, since a thick fiber web is used, the rigidity is high and there is no flexibility. Therefore, there is a problem that the place where water shielding is desired is a curved surface, cannot be applied to a place where there is a narrow space or a protrusion, and the water shielding sheet is difficult to be folded or folded.
JP-A-60-240446 JP-A-63-30809 JP-A-1-207375 JP 7-207851 A JP 9-47736 A JP 2003-25472 A

  An object of the present invention is to solve the above-mentioned conventional problems and to provide a water shielding sheet excellent in water shielding and handling properties.

  In particular, the present invention is that the water-absorbent resin is stably present in the water-impervious sheet without moving, has good shape retention and flexibility before water absorption, and quickly and uniformly absorbs and swells during water absorption. It is another object of the present invention to provide a water shielding sheet that can stably block water even in a state, and can efficiently absorb water even with water having a high metal ion concentration.

  The water-absorbent composite sheet for a water-impervious sheet according to claim 1 is characterized by having a base material and substantially spherical water-absorbent resin particles fixed intermittently on the base material.

  The water-absorbent composite sheet for water-impervious sheet according to claim 2 is characterized in that, in claim 1, the water-absorbent resin particles have an average particle size of 10 to 5,000 μm.

The water-absorbent composite sheet for a water-impervious sheet according to claim 3 is the water-absorbent composite sheet according to claim 1 or 2, wherein the water-absorbent resin particles are fixed on the substrate at a rate of 50 to 1,000 g / m ^2. Features.

  The water-absorbent composite sheet for a water-impervious sheet according to a fourth aspect is characterized in that, in any one of the first to third aspects, a substance having a metal ion capturing ability is supported on the base material.

  A water-absorbent composite sheet for a water-impervious sheet according to a fifth aspect is characterized in that, in any one of the first to fourth aspects, the base material is a water-permeable network structure.

  Since the water-absorbent composite sheet for a water-impervious sheet of the present invention has water-absorbing resin particles fixed to the base material, the water-absorbent composite sheet for the water-impervious sheet can be applied to the base material both before and after water absorption. Thus, the water-absorbent resin particles are stably fixed, and the water-absorbent resin particles exist stably without moving in the water-impervious sheet. For this reason, the water-absorbing resin particles move and agglomerate so that the water-absorbing resin particles do not become mako at the time of water absorption. Water can be smoothly blocked without diffusing or leaking (water leaks from the sheet without blocking water).

  In addition, since the water-absorbent resin particles are fixed intermittently to the base material, that is, in a discontinuous manner, the water-absorbent resin particles are flexible, can be easily deformed, and are curved surfaces that are desired to be water-blocked, narrow spaces, It can be easily applied to a place with a protrusion, and can be easily bent.

  In the water-absorbent composite sheet for a water-impervious sheet according to the present invention, a substrate may be loaded with a substance having a metal ion scavenging ability, whereby water with high metal ion concentration such as seawater can also efficiently absorb and swell. Will be able to. The substance having the ability to capture metal ions may be a water-absorbing resin or other chelating agent.

  As a base material of the water-absorbent composite sheet for water-impervious sheet used in the water-impervious sheet of the present invention, a water-permeable network structure is preferable.

  The water-impervious sheet according to claim 6 is provided on the water-absorbent composite sheet for water-impervious sheet according to any one of claims 1 to 5 and at least the water-absorbent resin particle fixing surface side of the water-absorbent composite sheet. It has the coating sheet which consists of a water-impermeable sheet or a water-permeable sheet, It is characterized by the above-mentioned.

  The water-impervious sheet according to claim 7 is characterized in that, in claim 6, the covering sheet is a water-impermeable sheet.

  Thus, the water-impervious sheet of the present invention is provided with a water-permeable or water-impermeable cover sheet on one surface (adsorbent resin particle fixing surface) or both surfaces of the water-absorbent composite sheet for water-impervious sheet of the present invention. It is excellent in water absorption and handling.

  The method for producing a water-absorbent composite sheet for a water-impervious sheet according to claim 8, wherein a droplet containing a polymerizable monomer capable of producing a water-absorbent resin and / or a polymerized product of the monomer is attached to a substrate, It is characterized in that substantially spherical water-absorbing resin particles are intermittently fixed onto the substrate by polymerizing the monomer and / or the polymerized product.

  The method for producing a water-absorbent composite sheet for a water-impervious sheet according to claim 9 includes: a polymerizable monomer capable of forming a second water-absorbent resin after arranging the first water-absorbent resin on the substrate; and / or the monomer The first water-absorbing resin is polymerized by the second water-absorbing resin by causing the monomer and / or the polymerization-promoting material to polymerize by dropping droplets containing the polymerization progressing material on the substrate. It is characterized by being fixed intermittently on the material.

  According to the method for producing a water-absorbent composite sheet for water-impervious sheet of the present invention, such a water-absorbent composite sheet for water-impervious sheet of the present invention can be industrially advantageously produced.

  In the water-absorbent composite sheet for water-impervious sheet of the present invention, the water-absorbent resin particles are stably fixed to the substrate regardless of before and after water absorption, and the shape stability is high over a long period of time, and the flexibility is high. Moreover, it is excellent in the water absorption by a water absorbing resin. Accordingly, the water-absorbing composite sheet for a water-impervious sheet of the present invention is constituted by sandwiching and storing it from one side (water-absorbing resin particle fixing surface) or both sides with a water-permeable or water-impermeable coating sheet. If it is the water-proof sheet | seat of invention, it can be easily bend | folded thru | or folded into a desired shape by the softness | flexibility, and can be easily applied to arbitrary places.

  In addition, the water-absorbent composite sheet for water-impervious sheet of the present invention can be used as it is without being completely sandwiched between water-permeable or water-impermeable coating sheets, and has a high water-absorbing and swelling performance. An effect can be obtained. In addition, it is possible to provide various functions such as improving the water shielding performance against seawater by supporting a substance having the ability to capture metal ions and other functional materials on the base material. There is expected.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[Water-absorbent composite sheet for water shielding sheets]
Fig.1 (a) is typical sectional drawing which shows embodiment of the water absorptive composite sheet for water-impervious sheets of this invention, FIG.1 (b) is the perspective view.

  A water-absorbing composite sheet 1 for a water shielding sheet shown in FIGS. 1A and 1B is obtained by intermittently fixing substantially spherical water-absorbing resin particles 3 to a base material 2.

  As the base material 2, in the manufacturing process of the water-absorbent composite sheet for a water-impervious sheet of the present invention described later, droplets in the course of polymerization can be adhered, and flexibility that is an important characteristic of the water-impervious sheet, for example, When applied to narrow spaces, it must be flexible enough to change its shape easily by human power, and must be made of a highly permeable material so that the water-impervious sheet can immediately contact the water to be absorbed. Although a perforated film may be used, a water-permeable network structure is particularly preferable.

  Here, the network structure includes a planar or two-dimensional network structure and a spatial or three-dimensional network structure. Examples of the two-dimensional network structure include a thin nonwoven fabric, a fabric, a net structure obtained by extrusion molding of a thermoplastic plastic, a network structure of a thermoplastic fiber, and a metal network structure. Examples of the three-dimensional network structure include a laminate of the two-dimensional network structure, a thick nonwoven fabric, a fiber cotton, and a porous plastic plate having independent or open cells.

  As the substrate 2, a nonwoven fabric or a fabric is particularly preferable.

  Regardless of the regular shape or indefinite shape of the outer shape, the base material exhibits the network structure composed of a large number of voids and through-holes and a skeleton portion for molding them. In the case of a nonwoven fabric, regardless of whether the fiber entanglement is fusion, adhesion, or simple mechanical entanglement, the strength of the entanglement is not limited, but a strength that can be easily deformed manually is desirable.

  The material of the base material is preferably fiber, and the fiber is natural fiber (cellulosic as plant fiber, for example, pulp, waste paper, paper, cotton, hemp, straw, bamboo, sawdust, etc., animal fiber is silk, wool Etc.), artificial fibers (cellulosic materials such as acetate and rayon), synthetic fibers (polyethylene, polypropylene, polyester, acrylic, polyamide, etc.), inorganic fibers (glass fiber, quartz fiber, asbestos, perlite, etc.), etc. . Further, in view of environmental problems, synthetic fibers such as biodegradable polylactic acid fibers and aliphatic polyesters may be used instead of synthetic fibers that are not biodegradable. Two or more of these may be mixed and used.

  The substrate is not limited to fibers, and may be a woven fabric woven with slit yarn having slits made of a water-permeable film or sheet.

  When a thermoplastic resin is used for the substrate, it can be heat sealed and fixed or folded to form a bag.

  The thickness, basis weight, etc. of the base material are appropriately determined in consideration of the required strength, water permeability, etc., but the thickness is preferably 1 to 200 mm (under 0.2 psi pressure), In particular, it is preferably 1 to 100 mm, particularly 1 to 50 mm.

  The water-absorbing resin constituting the water-absorbing resin particles 3 is a resin that can quickly absorb water several tens to several hundreds times its own weight. The water absorption performance of the water absorbent resin is preferably 5 to 60 g-water / g-water absorbent resin, more preferably 10-55 g-water / g-water absorbent resin per water absorbent resin. If the water absorption performance of the water absorbent resin is lower than this range, a large amount of water absorbent resin is required to obtain the required water absorption, which is uneconomical. Moreover, when water absorption is higher than this range, the strength of the water-absorbing gel of the water-absorbent resin becomes too low, and the water-impervious sheet using the water-absorbing sheet may run and leak.

  The particle size of the water-absorbent resin particles 3 is not particularly limited, but is preferably 10 to 5,000 μm in average particle size, more preferably 50 to 3,000 μm, and particularly preferably 100 to 2,000 μm. . If the average particle diameter of the water-absorbing resin particles 3 is too small, the water-absorbing resin particles 3 may not be fixed on the base material. If the average particle size is too large, the fixing strength to the base material 2 per particle will be low. It is easy to fall off.

  The water absorbent resin particles 3 are fixed to the base material 2 intermittently, that is, discontinuously. The water-absorbent resin particles 3 are intermittently fixed to the base material 2, whereby the flexibility required for the water shielding sheet can be obtained. If the water-absorbent resin particles are continuously fixed on the base material and connected to form a plate shape, the flexibility of the water shielding sheet is impaired, and the intended flexibility of the present invention cannot be obtained.

  The water-absorbent resin particles 3 are fixed to the base material 2 after, for example, attaching a droplet containing a polymerizable monomer and / or a polymerized product of the monomer to the base material, as will be described later. It means that the water-absorbent resin is fixed on the substrate by polymerizing the polymerizable monomer and / or the polymerized product of the monomer.

  In general, the water-absorbent resin particles 3 are preferably fixed uniformly and intermittently on the base material 2, but may be fixed non-uniformly and intermittently on the base material 2, for example, The arrangement part of the water-absorbent resin particles 3 may be formed in a gradation, stripe, houndstooth or checkered pattern. Further, the water-absorbent resin particles 3 may be intermittently fixed on the base material 2 one by one, and a plurality of particles adhering to each other in a bowl shape are fixed intermittently. Also good. By doing in this way, it is possible to prevent the mamako phenomenon during water absorption, improve the water absorption speed, and ensure flexibility.

If the amount of water-absorbing resin particles 3 fixed to the substrate 2 is too small, sufficient water absorption cannot be obtained, and if it is excessively large, the water-absorbing resin particles are connected to each other to form a hard plate, Flexibility is impaired. Therefore, the fixed amount of the water-absorbent resin particles 3 varies depending on the structure of the substrate 2 and the required water absorption, but the basis weight is 50 to 1,000 g / m ² , particularly 50 to 500 g / m ² . It is preferable to do. However, even when the amount of the water-absorbent resin particles 3 fixed to the base material 2 is large, the water-absorbent resin particles 3 are aggregated and fixed in a bowl shape on the base material 2 so as to be flexible due to intermittent fixing. In addition, the water absorption can be increased by increasing the fixing amount.

  In addition to the water-absorbing resin fixed to the base material, the water-impervious sheet of the present invention has a water-absorbing resin that is free, that is, not fixed to the base material and can be easily peeled off. You may do it. In this case, the shape of the free water-absorbing resin is not particularly limited, and is not limited to a granular shape, and may be a fibrous shape or a film shape.

  The water-impervious sheet of the present invention has a high concentration of metal ions such as seawater, hard water and other alkali metal ions and alkaline earth metal ions by supporting a material having the ability to capture metal ions on the base material. For example, it is possible to increase the water absorption of water having a metal ion concentration of 10 ppm or more. The substance having the ability to capture metal ions may be water-absorbing resin particles or a chelating agent that captures metal ions.

Chelating agents include ethylenediaminetetraacetic acid, hydroxyethylethylenediaminediacetic acid, dihydroxyethylethylenediaminediacetic acid, 1,3-propanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, hydroxyethyliminodiacetic acid, Examples include gluconic acid metal salts. These derivatives can also be used. Two or more of these chelating agents may be used in combination. An ethylenediaminetetraacetic acid metal salt is preferred from the standpoint of availability and economy. Supported amount of these chelating agents is preferably 10~1,000g / ^{m 2} as a weight per unit area with respect to the substrate, more preferably from 50 to 500 g / ^{m 2,} especially 50 to 300 g / ^{m 2} is preferred.

  In addition, the water-impervious sheet of the present invention may carry a water-absorbing resin different from the water-absorbing resin particles 3 fixed to the base material 2, and thus carry another water-absorbing resin. Thus, the water absorption performance can be improved. In this case, as described later, a liquid containing a polymerizable monomer capable of forming the second water-absorbent resin after the first water-absorbent resin is disposed on the substrate and / or a polymerization product of the monomer. The first water-absorbent resin is equivalent to the second water-absorbent resin (the above-mentioned water-absorbent resin particles 3) by causing droplets to adhere onto the substrate and polymerizing the monomer and / or the polymerization product. ) Can be fixed intermittently on the substrate.

Examples of the first water-absorbing resin for improving the water absorption include the following.
(1) Anionic water-absorbing resin As the anionic water-absorbing resin, a commercially available anionic water-absorbing resin can be used. For example, there are the following water-soluble ethylenically unsaturated monomer homo- or copolymer resins. Examples of such monomers include acrylic acid, methacrylic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinyl Examples thereof include sulfonic acid, (meth) allylsulfonic acid, and alkali metal salts and ammonium salts thereof, and one or more of these can be used. Acrylic acid and 2- (meth) acryloylethanesulfonic acid or a salt thereof are preferred.
(2) Cationic water-absorbing resin Commercially available cationic water-absorbing resins can also be used as the cationic water-absorbing resin. For example, polyallylamine, polyalkylenepolyamine, polyethyleneimine, polyvinylamine, Mannich reaction product of poly (meth) acrylamide, poly (meth) acrylamine, dialkylaminoalkyl (meth) acrylate: N, N-dimethylaminoethyl (meth) Acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminobutyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate homo resin or copolymer resin with (meth) acrylamide, Dialkylaminoalkyl (meth) acrylates made from quaternized ammonium salts with alkyl halides (for example, methyl chloride, ethyl chloride, methyl bromide, etc.) or copolymer resins thereof with (meth) acrylamide, polydia Kill allylamine quaternary ammonium salts, quaternized vinyl benzyl amine resin, acetylated chitosan, crosslinked polycationic condensation reaction product of epichlorohydrin and polyvalent amine or monoamine.
(3) Nonionic water-absorbing resin Nonionic water-absorbing resins include polyethylene oxide, polypropylene oxide, ethylene oxide / propylene oxide copolymer, N-vinylcarboxylic acid amide polymer, polyvinyl alcohol, and polyvinyl acetate. A crosslinked body can be used. In particular, a crosslinked polyalkylene oxide such as polyethylene oxide is preferred. For the purpose of holding the molded body in the presence of water, these resins may be used before or after the sheet molding and after crosslinking.

  By supporting the anionic water-absorbing resin on a base material, a metal having a valence of 2 or more can be captured to increase the water absorption capacity. Moreover, the water absorption capacity of the aqueous solution containing metal ions can be increased by supporting the cationic water absorbent resin. Further, by supporting the nonionic water-absorbing resin, the water absorption ability of the aqueous solution containing the electrolyte can be increased. These water absorbent resins (first water absorbent resins) may be used alone or in combination of two or more.

  The shape of the first water-absorbent resin is arbitrary, and particles having various shapes such as a granular shape, a fibrous shape, a flake shape, a crushed shape, and the like can be used.

  Even if the first water-absorbing resin is in the form of fine powder, it can be stably fixed on the substrate by the adhesion force of the droplets during polymerization as described later. Further, a water-absorbing resin having the same or larger average particle size as that of droplets in the polymerization process described later may be used. For example, a water-absorbing resin having better water-absorbing performance than particles in the process of polymerization, a non-manufactured product, and a recovered water-absorbing resin such as used paper diapers and pet sheets may be used.

  However, if the first water-absorbing resin is too large, the second water-absorbing resin particles may not be stably fixed to the base material. The average particle size is preferably 1,000 μm or less, and is preferably about 300 to 800 μm, for example, when handleability is considered.

The amount of the first water-absorbing resin supported on the substrate varies depending on the required water absorption capacity and the amount of the second water-absorbing resin used, but the basis weight is 10 to 500 g / m with respect to the substrate. ^2, more preferably 10 to 400 g / m ² , and particularly preferably 10 to 200 g / m ² .

  Further, the base material may be further supported with an antibacterial agent, a bactericide, a bacteriostatic agent, a stabilizer for preventing resin alteration, a fragrance, and the like to enhance functionality.

  Furthermore, fibrous materials such as pulp and chemical fibers, silica powders used for preventing blocking of known water-absorbing resins, and the like may be disposed on the substrate.

[Production method of water-absorbent composite sheet for water shielding sheet]
Hereinafter, preferred embodiments of the method for producing the water-absorbent composite sheet for water-impervious sheet of the present invention will be described, but the method for producing the water-absorbent composite sheet for water-impervious sheet of the present invention is limited to the following methods. It is not something.

  Usually, the water-absorbent composite sheet for a water-impervious sheet of the present invention is produced by sequentially performing a step of fixing water-absorbent resin particles to a substrate and a surface cross-linking step of the water-absorbent resin. In the case where a substance having a metal ion scavenging ability or other functional substance is supported on the base material, a step of applying these substances on the base material before the step of fixing the water absorbent resin particles on the base material I do. Hereinafter, each step will be described.

[1] Step of applying a metal ion scavenging substance or other functional substance on the base material As described above, the base material has a water absorbent resin (first water absorbent resin) for improving water absorption performance. And chelating agents that have the ability to capture metal ions, antibacterial agents, bactericides, bacteriostatic agents, stabilizers to prevent resin alteration, fragrances, fibrous materials such as pulp and chemical fibers, and known water-absorbing resins Silica powders used for blocking prevention can be added. In this case, these functional substances can be arranged on the base material in advance and fixed to the base material so that the below-described droplets during polymerization are attached. That is, since the droplets in the course of polymerization have adhesiveness, the first water-absorbing resin and other functional materials such as other liquids are engulfed and attached to the base material, and these are easily put on the base material. Can be fixed.

  Therefore, it is possible to stably fix a functional substance smaller than the average particle diameter of particles obtained by polymerizing droplets in the course of polymerization to a large functional substance on the substrate. That is, in a normal water-impervious sheet, fine powder or the like leaks from the surface sheet, aggregates due to easy mobility, or scatters as dust, but cannot be used. Since it can adhere to a functional substance and be fixed to a base material, it can be used without leaking from a covering sheet (such as a water-impermeable sheet described later).

[2] Step of fixing water-absorbing resin particles on a substrate The step of fixing water-absorbing resin particles on a substrate is preferably an aqueous solution of a polymerizable monomer that gives a water-absorbing resin, for example, an aliphatic unsaturated carboxylic acid. A redox polymerization initiator is arranged in an aqueous solution of a polymerizable monomer mainly composed of an acid or a salt thereof to initiate the polymerization of the monomer, and the reaction mixture during polymerization including the monomer and the produced polymer after the reaction is started is monitored. It is carried out by forming a droplet in the phase, bringing it into contact with the substrate, forming a precursor of the water-absorbent resin particles, and completing the polymerization, whereby the water-absorbent resin particles adhere to the substrate. A water-absorbing composite sheet for a water shielding sheet is used.

  One preferred method for polymerizing droplets in the gas phase is to use a first liquid composed of an aqueous solution of a polymerizable monomer containing one of an oxidizing agent and a reducing agent constituting a redox polymerization initiator, and a redox polymerization initiator. On the other hand, the polymerization is started by mixing in a gas phase with a second liquid consisting of an aqueous solution containing a polymerizable monomer if desired.

  As specific means, for example, as shown in the examples described later, the first liquid and the second liquid that collide with the liquid flowing out of the nozzle collide with each other at an angle of 15 degrees or more and in a liquid column state. Thus, there is a method of ejecting from separate nozzles. In this way, by causing the two liquids to collide with each other at an intersecting angle, a part of the outflow energy from the nozzle is used for mixing. The crossing angle between the first liquid and the second liquid flowing out from each nozzle is appropriately selected according to the properties of the polymerizable monomer to be used, the flow rate ratio, and the like. For example, if the linear velocity of the liquid is high, the crossing angle can be reduced.

  In this case, the temperature of the first liquid is usually 10 to 80 ° C., preferably 20 to 60 ° C., more preferably 25 to 50 ° C., and the temperature of the second liquid is also usually room temperature to 80 ° C., preferably It is 20-60 degreeC, More preferably, it is 25-50 degreeC.

  In this way, the respective aqueous solutions ejected from the nozzles collide in a liquid column state to combine both liquids. After the coalescence, a liquid column is formed and the state is maintained for a certain period of time, but the liquid column is then disassembled into droplets. The generated droplets undergo polymerization in the gas phase.

  In order for the polymerization of the droplets to proceed and contact the substrate to form suitable water-absorbent resin particles, the droplet diameter is particularly preferably in the range of 10 to 10,000 μm. That is, when the diameter of the droplet is less than 10 μm, the fine droplet adheres to the reactor or is flowed by an air current and cannot be stably fixed to the substrate. If it exceeds 10,000 μm, the spherical shape may not be maintained by its own weight when the droplet reaches the substrate.

  The gas phase gas that provides a reaction field for starting the polymerization and forming droplets during the polymerization is preferably inert to the polymerization, such as nitrogen, helium, and carbon dioxide, but may be air. In addition, there is no particular limitation on the humidity in the gas, including the case of only water vapor, but if the humidity is too low, the water in the aqueous monomer solution evaporates and the monomer precipitates before the polymerization proceeds. There is a possibility that the polymerization rate is remarkably reduced or the polymerization is stopped midway. The temperature condition of the gas is 20 ° C. or higher and 150 ° C. or lower, desirably 100 ° C. or lower. The gas flow direction may be either counter-current or co-current with respect to the liquid column and the traveling direction of the droplets. However, when it is necessary to increase the residence time of the droplets in the gas phase, that is, the polymerization rate of the polymerizable monomer is increased. If it is necessary to increase the viscosity of the droplets and thus increase the viscosity of the droplets, the countercurrent (antigravity direction) is better.

  The reaction raw materials used in the polymerization step will be described below.

(1) Polymerizable monomer The polymerizable monomer to be used is not particularly limited as long as it provides a water-absorbing resin, but it is particularly preferable to use a polymerizable monomer whose polymerization is initiated by a redox initiator. In general, the polymerizable monomer is preferably water-soluble.

  A typical example of such a polymerizable monomer, which is preferable for the present invention, is an aliphatic unsaturated carboxylic acid or a salt thereof. Specific examples include unsaturated monocarboxylic acids or salts thereof such as acrylic acid or salts thereof, methacrylic acid or salts thereof; or unsaturated dicarboxylic acids or salts thereof such as maleic acid or salts thereof, itaconic acid or salts thereof, etc. These may be used alone or in combination of two or more. Among these, acrylic acid or a salt thereof and methacrylic acid or a salt thereof are preferable, and acrylic acid or a salt thereof is particularly preferable.

  As the polymerizable monomer that gives the water-absorbent resin used in the present invention, an aliphatic unsaturated carboxylic acid or a salt thereof is preferable as described above. Therefore, an aliphatic unsaturated carboxylic acid or a salt thereof is mainly used as the aqueous solution of the polymerizable monomer. An aqueous solution as a component is preferred. Here, “the main component is an aliphatic unsaturated carboxylic acid or salt thereof” means that the aliphatic unsaturated carboxylic acid or salt thereof is 50 mol% or more, preferably 80 mol%, based on the total amount of the polymerizable monomers. This means that it is included.

  As the salt of the aliphatic unsaturated carboxylic acid, a water-soluble salt such as an alkali metal salt or an ammonium salt is usually used. The degree of neutralization is appropriately determined according to the purpose, but in the case of acrylic acid, 20 to 90 mol% of the carboxyl group is preferably neutralized with an alkali metal salt or ammonium salt. When the degree of partial neutralization of the acrylic acid monomer is less than 20 mol%, the water absorption ability of the water absorbent resin to be produced tends to be remarkably lowered.

  For neutralization of the acrylic acid monomer, one or more of alkali metal hydroxide, bicarbonate, etc. or ammonium hydroxide can be used, preferably alkali metal hydroxide, Specific examples thereof include sodium hydroxide and potassium hydroxide.

  In the present invention, in addition to the aliphatic unsaturated carboxylic acid or a salt thereof, a polymerizable monomer copolymerizable with these, for example, (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, 2- Although it is hydroxyethyl (meth) acrylate and other low water-soluble monomers, alkyl acrylates such as methyl acrylate and ethyl acrylate may be used in amounts that do not deteriorate the performance of the resulting water-absorbent resin. There is no problem. In the present specification, the term “(meth) acryl” means both “acryl” and “methacryl”. Of these polymerizable monomers, those that give a water-absorbing resin are not used as auxiliary components for aliphatic unsaturated carboxylic acids or salts thereof, but as the main monomer of an “aqueous solution of a polymerizable monomer that gives a water-absorbing resin”. You can also

  The concentration of the polymerizable monomer in the polymerizable monomer aqueous solution containing the above-mentioned aliphatic unsaturated carboxylic acid or a salt thereof as a main component is 20% by weight or more, preferably 25% by weight or more. If this concentration is less than 20% by weight, the water-absorbing ability of the water-absorbent resin after polymerization cannot be obtained sufficiently, which is not preferable. The upper limit is preferably about 80% by weight from the handling of the polymerization reaction solution.

(2) Cross-linking agent Aliphatic unsaturated carboxylic acid or its salt, especially acrylic acid or its salt, may form a self-crosslinking polymer by itself. It can also be formed. When a crosslinking agent is used in combination, the water absorption performance of the water absorbent resin that is generally produced is improved. As a crosslinking agent, it reacts with a polyvalent vinyl compound copolymerizable with the polymerizable monomer, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol poly (meth) acrylates, and carboxylic acid. A water-soluble compound having two or more functional groups that can be used, such as polyglycidyl ethers such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether, is preferably used. These may be used alone or in combination of two or more. Among these, N, N′-methylenebis (meth) acrylamide and (poly) ethylene glycol di (meth) acrylate are particularly preferable. The amount of the crosslinking agent used is usually 0.001 to 10% by weight, preferably 0.01 to 5% by weight, more preferably 0.01 to 3% by weight, based on the charged amount of the polymerizable monomer.

(3) Polymerization initiator As the polymerization initiator, those generally used in aqueous radical polymerization can be used. Examples of such initiators include inorganic and organic peroxides such as persulfates such as ammonium and alkali metals, particularly potassium, hydrogen peroxide, t-butyl peroxide, and acetyl peroxide. Furthermore, initiators known as azo compounds can also be used. For example, 2,2′-azobis (2-amidinopropane) dihydrochloride, which shows water solubility to some extent, can be mentioned. These may be used alone or in combination of two or more.

  Polymerization is initiated by decomposition of the radical polymerization initiator. A commonly known technique is pyrolysis. Often, a polymerization initiator that has not been heated is added to the polymerizable monomer in the reaction solution that has been heated to the decomposition temperature of the polymerization initiator in advance to initiate the polymerization. Belongs.

  The radical polymerization initiator particularly preferably used in the present invention is a combination of an oxidizing agent and a reducing agent that forms a water-soluble redox system to some extent.

  Examples of the oxidizing agent include hydrogen peroxide, persulfates such as ammonium persulfate and potassium persulfate, t-butyl hydroperoxide, cumene hydroperoxide, ceric salt, permanganate, and chlorite. 1 type, or 2 or more types, such as a salt and hypochlorite, are mentioned. Among these, hydrogen peroxide is particularly preferable. The amount of these oxidizing agents used is usually 0.01 to 10% by weight, preferably 0.1 to 2% by weight, based on the polymerizable monomer.

  The reducing agent is capable of forming a redox system with the above oxidizing agent, specifically, sulfites such as sodium sulfite and sodium bisulfite, sodium thiosulfate, cobalt acetate, copper sulfate, ferrous sulfate, L- 1 type (s) or 2 or more types, such as ascorbic acid or an alkali metal salt of L-ascorbic acid, can be mentioned. Among these, L-ascorbic acid or L-ascorbic acid alkali metal salt is particularly preferable. The amount of these reducing agents to be used is usually 0.001 to 10% by weight, preferably 0.01 to 2% by weight, based on the polymerizable monomer.

[3] Surface cross-linking step The surface of the water-absorbent resin can be cross-linked with a cross-linking agent for the purpose of improving water absorption performance. In general, it is known to improve the properties of resin particles by applying an appropriate amount of moisture together with a crosslinking agent to the surface of powdered water-absorbent resin particles, and then heating to crosslink the surface. As a result of the formation of a crosslinked structure, it is considered that the shape can be maintained without inhibiting the swelling when water is absorbed and swollen. In this step, first, a solution of a surface cross-linking agent is applied on a substrate on which water-absorbing resin particles are supported. As the surface cross-linking agent, polyfunctional compounds that can be copolymerized with polymerizable monomers such as N, N′-methylenebis (meth) acrylamide and (poly) ethylene glycol di (meth) acrylate, (poly) ethylene glycol diglycidyl ether, etc. A compound having a plurality of functional groups capable of reacting with the carboxylic acid group is used. These surface crosslinking agents are usually used in an amount of 0.1 to 1% by weight, preferably 0.2 to 0.5% by weight, based on the water-absorbent resin particles. These surface cross-linking agents are diluted with water, ethanol, methanol or the like so as to be uniformly applied to the water-absorbent resin particles, and 0.1 to 1% by weight, particularly 0.2 to 0.5% by weight. It is preferable to use it as a solution. The application of the crosslinking agent solution is usually preferably carried out by spraying the crosslinking agent solution onto the water-absorbent resin particles on the substrate using a sprayer or applying the crosslinking agent solution with a roll brush. In addition, after providing a crosslinking agent solution excessively, you may make it remove excessive surplus crosslinking agent solution by squeezing lightly to such an extent that a resin particle is not crushed with a pressing roll, or blowing a wind. The application of the crosslinking agent solution may be performed at room temperature. The water-absorbing resin particles to which the cross-linking agent solution has been applied are then heated to cause a cross-linking reaction to selectively form a cross-linking structure on the water-absorbing resin surface. The conditions for the cross-linking reaction may be appropriately selected depending on the cross-linking agent to be used.

  In the present invention, an unsaturated carboxylic acid polymer crosslinked product is particularly preferable as the water absorbent resin, and a partially neutralized acrylic acid polymer crosslinked product is particularly preferable.

[Water shielding sheet]
Next, the water shielding sheet of the present invention using the water absorbent composite sheet for a water shielding sheet of the present invention as described above will be described.

  2 and 3 are schematic views showing an example of an embodiment of the water-impervious sheet according to the present invention, in which (a) is a partially cutaway perspective view, and (b) is BB in (a). It is an enlarged view of a section along a line. FIG. 4 is a cross-sectional view showing another embodiment of the water shielding sheet of the present invention. In addition, in Fig.2 (a), the below-mentioned ear | edge part of a water-impervious sheet has shown the state before bending in J shape.

  The water-impervious sheet 10A in FIG. 2 is a water-permeable sheet or non-coated on the fixing surface (hereinafter sometimes referred to as “water-absorbing surface”) of the water-absorbent resin sheet 3 of the water-absorbent composite sheet 1 for water-impervious sheets of the present invention. A covering sheet made of a water permeable sheet (hereinafter referred to as “(non) water permeable sheet”) 11 is arranged, and the surface opposite to the water absorbing surface (hereinafter sometimes referred to as “base material surface”). The (non-) water-permeable sheet 12 is arranged on the side.

  In the water-impervious sheet 10A of FIG. 2, the (non-) water-permeable sheet 11 and the (non-) water-permeable sheet 12 are folded back into a J shape by overlapping the peripheral ear portions 11A and 12A.

  A water-impervious sheet 10C in FIG. 3 is obtained by disposing a (non-) water-permeable sheet 13 on the water-absorbing surface side of the water-absorbent composite sheet 1 for a water-impervious sheet of the present invention. The peripheral edge 13 </ b> A of the (non-) water-permeable sheet 13 is fixed to the substrate surface by going around the substrate surface side of the water-absorbent composite sheet 1 for water-impervious sheet.

  The water-impervious sheet 10C of FIG. 4 uses two water-absorbent composite sheets 1 for a water-impervious sheet according to the present invention, and is laminated with the water-absorbing surfaces facing each other. A water-permeable sheet 14 is arranged, and the peripheral edge 14A of the (non-) water-permeable sheet 14 is fixed around the other surface.

  As described above, the water-impervious sheet of the present invention is obtained by sandwiching the water-absorbent composite sheet for water-impervious sheet of the present invention from one side (water-absorbing surface) or both sides with a water-permeable or water-impermeable sheet. The water-absorbing sheet is aligned on the inner side, and a water-impermeable sheet is disposed on one side, followed by adhesion, heat sealing, stitching, or the like. 2 and 3, one sheet of the water-absorbent composite sheet 1 for water-impervious sheet according to the present invention is used, but two or three or more sheets may be laminated. Moreover, in FIG. 4, you may laminate | stack three or more water-absorbing composite sheets for water-impervious sheets. Moreover, you may cut | disconnect and use the water-absorbing composite sheet for water-impervious sheets of the present invention at a position where it is desired to partially absorb.

  The material of the water-permeable sheet as the covering sheet is not particularly limited as long as it has strength and water permeability according to the required characteristics, as described above as the base material of the water-absorbent composite sheet for water-impervious sheet of the present invention. Can be used.

On the other hand, the water-impermeable sheet is not particularly limited as long as it has sufficient strength and can prevent permeation of water. Polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polymethyl methacrylate, polyamide Thermoplastic resin sheets such as resins, and those having both stretchability, for example, styrene elastomers such as styrene-isobutylene block copolymers and styrene-butadiene block copolymers, or polyolefin elastomers such as ethylene-vinyl acetate copolymers Etc., rubber sheets, and other metal sheets such as aluminum foil can also be used, and the thickness is usually about 10 to 2000 μm and the basis weight is about 10 to 500 g / m ² .

  As shown in FIG. 1, the water-impervious sheet of the present invention fixes the water-absorbent resin particles 3 to the base material 2 together with the functional material such as the first water-absorbent resin and the chelating agent as necessary. In addition to using the water-absorbent composite sheet for the water-impervious sheet, the water-permeable sheet itself of the water-impervious sheet is used as a base material for fixing the water-absorbent resin particles, and the water-absorbent resin particles are directly fixed to the inside of the water-permeable sheet. It can also be made into a form. That is, the substrate to which the water-absorbing resin particles are fixed can be directly molded and used as a water-permeable sheet of the water-impervious sheet. In this case, the water-absorbent composite sheet for the water-impervious sheet is used as the water-permeable sheet and / or The work process of laminating with a water-impermeable sheet to form a water-impervious sheet can be omitted.

  Moreover, the water-impervious sheet of the present invention can be used after being cut, crushed, pulverized, and compression-molded as necessary. Of course, cutting, crushing, and crushing can also be used to recycle non-standard products of the water shielding sheet. When using by cutting, crushing, and pulverizing, it is preferable that the size is such that it does not easily move in the water-permeable sheet and / or the water-impermeable sheet. Known cutting, crushing, crushing, and compressing equipment can be used for cutting, crushing, crushing, and compressing.

  Further, the water-impervious sheet of the present invention, in addition to the water-absorbent composite sheet for the water-impervious sheet of the present invention, a substance having the ability to capture metal ions such as the aforementioned chelating agent and the first water-absorbent resin, Antibacterial agents, bactericides, bacteriostatic agents, stabilizers that prevent resin alteration, fragrances, and the like may be included.

  In the water-impervious sheet of the present invention, as long as both or one side of the water-absorbent composite sheet for water-impervious sheet of the present invention is covered with a water-impermeable sheet, the water-impervious sheet and the water-impermeable effect are obtained. The water shielding effect by water absorption of the water-absorbing composite sheet for a water shielding sheet when the sheet is damaged can be obtained. Further, in the water-impervious sheet of the present invention, if both or one side of the water-absorbent composite sheet for water-impervious sheet of the present invention is coated with the water-permeable sheet, the water that has permeated the water-permeable sheet Water-absorbing effect can be obtained by absorbing water with the conductive composite sheet.

[Method of manufacturing impermeable sheet]
Next, although the method to manufacture the water shielding sheet of this invention is demonstrated, the manufacturing method of the water shielding sheet of this invention is not limited to the following methods at all.

  In order to manufacture the water-impervious sheet 10A of FIG. 2, the two sheets are appropriately left on the peripheral side of the sheets 11 and 12 between the two (non-) water-permeable sheets 11 and 12 of the square shape. The water-absorbing composite sheet 1 for a water-impervious sheet of the present invention is interposed with a contour smaller than the contour of 11, 12, and then the peripheral edges (ear portions 11A, 12A) of both the sheets 11, 12 are heat-sealed. It joins and seals by appropriate methods, such as sewing. More preferably, means for embossing and integrating the (non-) water-permeable sheets 11 and 12 interposing the water-absorbent composite sheet for water-impervious sheet of the present invention, or the water-absorbent composite sheet for water-impervious sheet of the present invention 1 is preliminarily sprinkled with water to slightly swell the water-absorbent resin particles and then inserted, and the water-absorbent resin particles under light pressure and wetness are temporarily attached to the (non-) water-permeable sheets 11 and 12. You may employ | adopt the means to integrate. However, it is necessary to seal with a sealing pressure that is not damaged by the swelling pressure when the water-absorbing resin swells by absorbing water.

  In order to manufacture the water-impervious sheet 10B of FIG. 3, one rectangular (non-) water-permeable sheet 13 has an outline smaller than the outline of the sheet 13, leaving an appropriate margin on the peripheral side of the sheet 13. Then, the water-absorbing composite sheet 1 for water-impervious sheet of the present invention is installed with the water-absorbing surface side aligned, and then the peripheral edge 13A of the sheet 13 is folded into the base-material surface side of the water-absorbing composite sheet 1 for water-impervious sheet. Bonding and sealing are performed by an appropriate method such as heat sealing, adhesion, and stitching. Even in this case, it is more preferable that the (non-) water-permeable sheet 13 is embossed and integrated, or the water-absorbing composite sheet 1 for the water-impervious sheet of the present invention is preliminarily lightly sprayed with water in advance. After the resin particles are slightly swollen, a means for temporarily integrating the wet water-absorbing resin particles with the (non-) water-permeable sheet 13 by applying light pressure may be employed. However, it is necessary to seal with a sealing pressure that is not damaged by the swelling pressure when the water-absorbing resin swells by absorbing water.

  4C can be manufactured in the same manner as described above except that two water-absorbing composite sheets 1 for a water-impervious sheet of the present invention are laminated.

  In addition, in FIGS. 1-4, although the square thing was shown as the water-absorbing composite sheet for water-impervious sheets and the water-impervious sheet of the present invention, the water-absorbent composite sheet for water-impervious sheets and the water-impervious sheet of the present invention are not limited. The shape is not limited to a square shape, and may be a circle, an ellipse, or other irregular shapes depending on the application.

  Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Test Examples. The materials, reagents, ratios, operations, and the like shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Example 1>
(Manufacture of water-absorbent composite sheet for water-impervious sheet)
A partially neutralized aqueous acrylic acid solution having a monomer concentration of 50% by weight and a neutralization degree of 60 mol% was added to 100 parts by weight of acrylic acid, 133.3 parts by weight of 25% by weight sodium hydroxide aqueous solution and 3.3 parts by weight distilled water. Was prepared. To 100 parts by weight of the partially neutralized acrylic acid aqueous solution, 0.14 parts by weight of N, N′-methylenebisacrylamide as a crosslinking agent and 4.55 parts by weight of a 31% by weight hydrogen peroxide aqueous solution as an oxidizing agent were added. Solution A was prepared.

  Separately, 0.14 parts by weight of N, N′-methylenebisacrylamide as a cross-linking agent and 0.57 parts by weight of L-ascorbic acid as a reducing agent were added to 100 parts by weight of the partially neutralized acrylic acid aqueous solution. Was prepared.

  The prepared solution A and solution B were mixed using the mixing apparatus shown in FIG. In this mixing apparatus, five jet nozzles 21a and 22a are provided at intervals of 1 cm in the monomer solution supply pipes 21 and 22, respectively, and the inner diameters of the nozzles 21a and 22a are 0.13 mm. The intersection angle θ between the solution A and the solution B flowing out from the nozzles 21a and 22a was adjusted to 30 °, and the distance d between the nozzle tips was adjusted to 4 mm. Solution A and solution B were each heated to a temperature of 40 ° C. and supplied with a pump at a flow rate of 5 m / sec (20 ml / min each, total volume 40 ml / min).

The solution A and the solution B merge when they exit the nozzles of the respective nozzle pairs, and after forming the liquid column 23 by about 10 mm each, the droplets 24 become droplets 24 in the gas phase (in air, The polyethylene terephthalate nonwoven fabric (fineness of 20 dtex, fiber length of 50 mm) is bonded by heat bonding, and the weight per unit area is 200 g / m ^2. (The amount of droplets was 500 g / m 2) to complete the polymerization. After that, it was dried until the water content became 5% to obtain a water absorbent resin composite sheet (50 cm × 50 cm) for a water shielding sheet. The water-absorbent resin particles have a substantially spherical shape with an average particle size of 300 μm (an average value obtained by arbitrarily measuring 50 particles from a micrograph magnified 20 times) and measuring the major axis intermittently with respect to the polyethylene terephthalate nonwoven fabric. The basis weight was 300 g / m ² .

(Manufacture of water shielding sheets)
Polyethylene sheets (thickness: 100 μm) are placed on both sides of the resulting water-absorbent composite sheet for water-impervious sheet, and the ear part is folded back to the sheet body side and fixed to the sheet body by adhesion, fusion, etc. Thus, a water shielding sheet shown in FIG. 2 was obtained.

<Example 2>
In Example 1, an anionic water-absorbent resin powder (“Aqua Pearl DS50” manufactured by Sundia Polymer Co., Ltd., average particle size 300 μm) was previously present on the polyethylene terephthalate resin nonwoven fabric so as to have a basis weight of 50 g / m ² . Water absorption for the water-impervious sheet by the same operation and method except that it was supplied by a pump so that the monomer flow rate was 4.1 m / sec (total amount 33 ml / min, equivalent to 250 g / m ^{2 of} water-absorbent resin particles). A composite sheet was produced, and a water-impervious sheet was produced in the same manner as in Example 1 using the produced water-absorbent composite sheet for water-impervious sheet.

<Example 3>
In Example 1, a cationic water-absorbing resin powder (average particle size 300 μm) produced in advance by the following method was used on a polyethylene terephthalate nonwoven fabric so as to have a basis weight of 100 g / m ² and the monomer flow rate. A water-absorbing composite sheet for a water-impervious sheet was manufactured by the same operation and method except that the water was supplied by a pump so that the pressure was 4.1 m / sec (total amount 33 ml / min, equivalent to 250 g / m ^{2 of} water-absorbing resin particles). A water-impervious sheet was produced in the same manner as in Example 1 using the produced water-absorbent composite sheet for water-impervious sheet.

(Preparation of cationic water-absorbing resin powder)
Single unit consisting of 200 g of N, N-dimethylaminoethyl acrylate methyl chloride quaternary salt (79 wt% aqueous solution), 0.98 g of trimethylolpropane triacrylate, 2.4 g of hydroxyethyl cellulose, 0.66 g of potassium persulfate and 91 g of distilled water The aqueous body solution was polymerized by holding at 100 ° C. for 10 minutes under a nitrogen atmosphere, and dried at 100 ° C. in a vacuum dryer for 6 hours. The dried resin was crushed with a coffee mill, passed through 20 mesh, and particles placed on 80 mesh were used as the cationic water-absorbing resin powder.

<Example 4>
In Example 1, the nonionic water-absorbent resin powder (average particle size 300 μm) produced in advance by the following method was used in a polyethylene terephthalate resin nonwoven fabric so as to have a basis weight of 100 g / m ² and the monomer flow rate A water-absorbing composite sheet for a water-impervious sheet was manufactured by the same operation and method except that the water was supplied by a pump so that the pressure was 4.1 m / sec (total amount 33 ml / min, equivalent to 250 g / m ^{2 of} water-absorbing resin particles). A water-impervious sheet was produced in the same manner as in Example 1 using the produced water-absorbent composite sheet for water-impervious sheet.

(Preparation of nonionic water-absorbing resin powder)
100 parts by weight of fully dehydrated polyethylene oxide having a number average molecular weight of 20,000, 100 g of ethylene oxide / propylene oxide (copolymerization ratio 8/2) copolymer having a number average molecular weight of 15,000, 3.15 g of 1,4-butanediol, dibutyltin dilaurate 0.1 g was kept at 70 ° C. in a nitrogen atmosphere, uniformly mixed, and stored in a storage tank A made of SUS. Separately, 1,6-hexamethylene diisocyanate was placed in a SUS storage tank B kept at 30 ° C. and stored in a nitrogen atmosphere. The mixture in storage tank A and the isocyanate in storage tank B are continuously fed to a twin-screw extruder set at 170 to 200 ° C. at a rate of 250 g / min and 9.64 g / min, respectively, by a metering pump, and mixed reaction And pelletized from the outlet of the extruder by a pelletizer, and the obtained pellets were mixed with dry ice and frozen and pulverized in a coffee mill, passed through 20 mesh, and the particles placed on 80 mesh were changed to polyalkylene oxide modified product. Nonionic water-absorbing resin powder was obtained.

<Example 5>
In Example 1, on a polyethylene terephthalate resin nonwoven, pre ethylenediaminetetraacetic acid disodium salt dihydrate (Chelest Corp. "Chelest B") that were used in the presence to be 100 g / m ² weight per unit area A water-absorbing composite sheet for a water-impervious sheet was produced by the same operation and method, and a water-impervious sheet was produced in the same manner as in Example 1 using the produced water-absorbent composite sheet for a water-impervious sheet.

<Example 6>
A polyethylene sheet (thickness: 100 μm) is provided only on the water-absorbing surface of the water-absorbing composite sheet for water-impervious sheet obtained in the same manner as in Example 1, and the ear portion is on the substrate side of the water-absorbing composite sheet for water-impervious sheet. The sheet was folded and fixed to the sheet main body by adhesion, fusion, or the like to obtain a water shielding sheet shown in FIG.

<Comparative Example 1>
Heat-bonded fiber nonwoven fabric (polypropylene resin (melting point: 165 ° C.) as a high melting point core component, high density polyethylene (melting point: 130 ° C.) as a low melting point sheath component, fiber: 20 dtex in sheath: core (weight ratio = 1: 1) fiber length 50mm of the intersection of the composite fibers as basis weight 100 g / m ² obtained by thermal bonding with crimp) the superabsorbent resin (San-Dia polymers Ltd. "AQUAPEARL DS50" average particle size 300 [mu] m) Was uniformly spread so as to be 300 g / m ² , and the same heat-bonding fiber non-woven fabric was laminated thereon, and further sandwiched between two hot rolls and thermocompression bonded to produce a plate-shaped water-proof sheet. .

  A water-impervious sheet was produced in the same manner as in Example 1 using this water-absorbent composite sheet for water-impervious sheet.

<Comparative example 2>
In Example 1, without using the water-absorbing composite sheet for the water-impervious sheet, two polyethylene sheets (thickness 100 μm) were laminated and integrated to produce a water-impervious sheet.

<Test example>
The following evaluation was performed about each water-absorbing composite sheet for water-impervious sheet and water-impervious sheet obtained in each Example and Comparative Example, and the results are shown in Table 1. The blank in the table indicates that no measurement was performed.

<Evaluation of water absorbent composite sheet for water shielding sheet>
(1) Flexibility measurement Whether or not the water-absorbent composite sheet for water-impervious sheet produced in Examples 1 to 5 and Comparative Example 1 can be wound by hand around a tube having an outer diameter of 10 cm, respectively. , And those that can be wound are marked with ◯, and those that can be folded without being wound are marked with ×. If the flexibility is high, it can be tightly wound around the tube without any problem, but if it is not flexible, it cannot be wound because it is bent or warped.

<Evaluation of water shielding sheet>
(1) Water-absorbing resin dropout test Each of the water shielding sheets produced in each example was cut to a size of 15 × 15 cm, placed in a transparent plastic bag, placed on a vibration table, and shaken for 15 minutes at 50 Hz and an amplitude of 3 mm. Thereafter, the amount of water-absorbing resin dropped out from the degree of splashing of the water-swelling material from the side surface (the cut surface of the water-impervious sheet) was measured, and the degree of shedding was determined according to the following formula.

(2) Nail hole water-impervious test As shown in FIG. 6A, a sample 30 is placed on an 8-mesh wire mesh 31 and a nail for a colonial tile (length 30 mm, maximum diameter 3.3 mm, minimum diameter 2.9 mm). As shown in FIG. 6B, a maximum diameter (minimum diameter) and a maximum diameter (minimum diameter) of 1.3 mm) were struck at 5 cm intervals to open holes 30A at five locations. Further, it was sandwiched from above and below by a flanged acrylic pipe having an inner diameter of 20 cm, and the flanges 32A and 33A were fixed with bolts. Put 1000 g of tap water or artificial seawater (“Aquamarine” manufactured by Hachishu Yakuhin Co., Ltd.) as the test water 35 into the upper acrylic pipe 32 and cover it, and the amount of water reduction (g) after 24 hours. Measurement was performed at n = 10, and an average value was obtained (this water reduction amount is preferably 1 g or less).

  From Table 1, it can be seen that the water-impervious sheet of the present invention is excellent in water impermeability, water absorption, and handleability.

  The water-absorbent composite sheet for water-impervious sheet and the water-impervious sheet of the present invention are suitably used for water-impervious purposes such as prevention of water leakage and exudation / leakage in seawalls, rivers and other revetments, underground structures, waste disposal sites and reservoirs. can do.

Fig.1 (a) is typical sectional drawing which shows an example of embodiment of the water absorptive composite sheet for water-impervious sheets of this invention, FIG.1 (b) is the perspective view. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of embodiment of the water-impervious sheet | seat of this invention, Comprising: (a) A figure is a partially cutaway perspective view, (b) An enlarged view of the cross section which follows the BB line of (a) figure FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of other embodiment of the water-impervious sheet of this invention, Comprising: (a) A figure is a partially cutaway perspective view, (b) A figure is a cross section along the BB line of (a) figure. FIG. It is typical sectional drawing which shows an example of another embodiment of the water-impervious sheet of this invention. In an Example, it is a perspective view which shows the mixing apparatus used for manufacture of the water-absorbing composite sheet for water-impervious sheets. (A) A figure is sectional drawing which shows the structure of a nail-hole impermeable tester, (b) figure is a top view which shows the drilling part of a sample.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water-absorbing composite sheet for water-impervious sheet 2 Base material 3 Water-absorbing resin particles 10A, 10B, 10C Water-impervious sheet 11, 12, 13, 14 (Non) water-permeable sheet 21, 22 Piping 21a, 22a Nozzle 23 Liquid column 24 Droplet 30 Sample 30A Hole 31 Wire mesh 32,33 Acrylic pipe 35 Test water

Claims (9)

  A water-absorbing composite sheet for a water-impervious sheet, comprising: a base material; and substantially spherical water-absorbing resin particles fixed intermittently on the base material.   The water-absorbent composite sheet according to claim 1, wherein the water-absorbent resin particles have an average particle diameter of 10 to 5,000 µm. According to claim 1 or 2, the water absorbent resin particles, water-impervious absorbent composite sheet sheet, characterized in that it is fixed on the substrate at a rate of 50~1,000g / m ^2.   The water-absorbent composite sheet for water-impervious sheet according to any one of claims 1 to 3, wherein a substance having a metal ion capturing ability is supported on the base material.   The water-absorbent composite sheet for water-impervious sheet according to any one of claims 1 to 4, wherein the base material is a water-permeable network structure.   From the water-absorbent composite sheet for water-impervious sheet according to any one of claims 1 to 5, and a water-impermeable sheet or a water-permeable sheet provided on at least the water-absorbent resin particle fixing surface side of the water-absorbent composite sheet. A water-impervious sheet comprising: a covering sheet.   The water shielding sheet according to claim 6, wherein the covering sheet is a water-impermeable sheet.   After attaching a droplet containing a polymerizable monomer capable of forming a water-absorbent resin and / or a polymerization product of the monomer to a substrate, the monomer and / or the polymerization product are polymerized to form the group. A method for producing a water-absorbing composite sheet for a water-impervious sheet, characterized in that substantially spherical water-absorbing resin particles are intermittently fixed on a material.   After disposing the first water-absorbing resin on the base material, droplets containing a polymerizable monomer capable of forming the second water-absorbing resin and / or a polymerized product of the monomer are adhered to the base material. The monomer and / or the polymerized product is polymerized to intermittently fix the first water-absorbent resin on the base material by the second water-absorbent resin. A method for producing a water-absorbent composite sheet.

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