Composite absorbents and polymeric absorbents

Abstract

To provide an absorber that has high absorption performance.SOLUTION: A composite absorber (1) according to the present invention is for absorbing liquid, the composite absorber (1) comprising: a polymer absorbent (4) having hydrophilic continuous skeletons and continuous pores; and a highly absorbent polymer (5). Three minutes after the polymer absorbent (4) having adsorbed liquid contacts the highly absorbent polymer (5), the amount of liquid transferred to the highly absorbent polymer (5) is 23.0 g / g or more.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a composite absorbent and a polymeric absorbent. [Background technology]

[0002] As an absorbent used for absorbing liquids such as aqueous solutions, there are known absorbents containing a superabsorbent polymer (so-called "SAP") having a high absorption capacity. As disclosed in, for example, Patent Documents 1 to 4, absorbents containing such superabsorbent polymers are applied in various fields such as disposable paper diapers, civil engineering and construction materials such as anti-condensation sheets and simple soil, base materials for pharmaceuticals, and materials for absorbing leaked liquids. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-36638 A [Patent Document 2] JP 2017-205225 A [Patent Document 3] Japanese Patent Application Publication No. 63-75016 [Patent Document 4] Japanese Patent Application Publication No. 8-38893 Summary of the Invention [Problem to be solved by the invention]

[0004] Although such superabsorbent polymers (SAPs) can retain a large amount of liquid (i.e., have a high liquid retention capacity), they have a slow absorption rate, and therefore, in conventional absorbents such as disposable paper diapers, they are used in combination with pulp to temporarily absorb and retain liquid. In such conventional absorbents, the liquid is quickly absorbed by the pulp in the absorbent and temporarily retained within the pulp, and then transferred to the SAP, which has a high liquid retention capacity, and retained within the SAP. However, in such conventional absorbents, the pulp has a low liquid retention capacity, and therefore the amount of liquid temporarily held in the pulp, i.e., the amount of liquid transferred from the pulp to the SAP, is small, which raises the risk that the liquid retention capacity of the SAP, and therefore the absorption performance of the absorbent body, may not be fully demonstrated.

[0005] The present invention has been made in consideration of such problems, and has an object to provide an absorbent body having high absorption performance. [Means for solving the problem]

[0006] One aspect of the present invention (Aspect 1) is a composite absorbent for absorbing liquid, comprising: The present invention includes a polymeric absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer, The polymer absorbent is a composite absorbent characterized in that the amount of liquid transferred to the superabsorbent polymer 3 minutes after the polymer absorbent comes into contact with the superabsorbent polymer after absorbing liquid is 23.0 g / g or more.

[0007] In the composite absorbent of this embodiment, the polymer absorbent, which can take up liquids such as aqueous solutions into its open pores by capillary action, has a high liquid transfer rate, and thus can retain a large amount of liquid at one time. In addition, a large amount of liquid can be transferred from the polymer absorbent to the superabsorbent polymer (SAP). This makes it possible to fully utilize the liquid retention capacity of the SAP, and thus allows the absorbent to exhibit high absorption performance.

[0008] In another aspect (Aspect 2) of the present invention, in the composite absorbent of Aspect 1 above, the polymer absorbent is characterized in that the amount of liquid transferred to the superabsorbent polymer 30 seconds after the polymer absorbent comes into contact with the superabsorbent polymer after absorbing liquid is 7.0 g / g or more.

[0009] The composite absorbent of this embodiment can deliver a large amount of liquid in a short time after the absorbent polymer comes into contact with the SAP after absorbing liquid, and therefore can more reliably exhibit high absorption performance.

[0010] In yet another aspect (Aspect 3) of the present invention, in the composite absorbent of Aspect 1 or 2 above, the polymer absorbent is characterized in that the liquid discharge amount of the absorbed liquid component is 20 g / g or more and the liquid discharge rate is 65% or more.

[0011] The composite absorbent of this embodiment is capable of retaining a large amount of liquid at one time and releasing a large amount of the absorbed and retained liquid because the polymer absorbent has a high liquid discharge volume and liquid discharge rate (i.e., high liquid retention capacity and excellent liquid release properties (liquid release properties)). As a result, the composite absorbent of this embodiment can steadily transfer a large amount of liquid from the polymer absorbent to the SAP, making it possible to more fully utilize the liquid retention capacity of the SAP and thereby enabling the absorbent to exhibit even higher absorption performance.

[0012] In still another aspect (Aspect 4) of the present invention, in the composite absorbent of any one of Aspects 1 to 3 above, the polymer absorbent is a monolithic absorbent.

[0013] In the composite absorbent of this embodiment, since the polymer absorbent is a monolithic absorbent, it is capable of absorbing liquid quickly and also of transferring the temporarily held liquid to the SAP more reliably.

[0014] In yet another aspect (Aspect 5) of the present invention, in the composite absorbent of any of Aspects 1 to 4 above, the polymer absorbent is a hydrolysate of a crosslinked polymer of a (meth)acrylic acid ester and a compound containing two or more vinyl groups in one molecule, and is characterized in that it contains at least one -COONa group.

[0015] In the composite absorbent of this embodiment, since the polymer absorbent has the above-mentioned specific configuration, when liquid is absorbed, the hydrophilic continuous skeleton is easily extended and the continuous pores are easily expanded, so that a larger amount of liquid can be taken up into the continuous pores more quickly, and the absorbent can exhibit even higher absorption performance.

[0016] Yet another embodiment (embodiment 6) of the present invention is a polymeric absorbent used together with a superabsorbent polymer, It has a hydrophilic continuous skeleton and continuous pores, The polymer absorbent is characterized in that the amount of liquid transferred to the superabsorbent polymer 3 minutes after the polymer absorbent comes into contact with the superabsorbent polymer after absorbing liquid is 23.0 g / g or more.

[0017] The polymer absorbent of this embodiment has the above-mentioned specific high liquid transfer rate, and therefore can hold a large amount of liquid at one time and can transfer a large amount of liquid from the polymer absorbent to the superabsorbent polymer (SAP), thereby making full use of the liquid retention capacity of the SAP. Therefore, when the polymer absorbent of this embodiment is used together with SAP in an absorbent body, the absorbent body can exhibit high absorption performance. Effect of the Invention

[0018] According to the present invention, an absorbent body having high absorption performance can be provided. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is an exploded perspective view of a composite absorbent body 1 according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of a composite absorbent body 1' according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram illustrating a manufacturing process of absorbent A, which is an example of a polymer absorbent. [Figure 4] FIG. 4 is an SEM photograph of absorbent A at a magnification of 50 times. [Diagram 5] FIG. 5 is a SEM photograph of absorbent A at a magnification of 100 times. [Figure 6] FIG. 6 is an SEM photograph of absorbent A at a magnification of 500 times. [Figure 7] FIG. 7 is a SEM photograph of absorbent A at a magnification of 1000 times. [Figure 8]FIG. 8 is an SEM photograph of absorbent A at a magnification of 1500 times. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A preferred embodiment of the present invention will be described in detail below using a composite absorbent body 1 as one embodiment. In this specification, unless otherwise specified, "planar view" simply means "viewing an object (e.g., a composite absorbent body) placed on a horizontal surface in an unfolded state in the thickness direction of the object from above in the vertical direction."

[0021] [Composite absorber] FIG. 1 is an exploded perspective view of a composite absorbent body 1 according to one embodiment of the present invention. The composite absorbent 1 shown in FIG. 1 has a generally rectangular outer shape in a plan view, and basically comprises a first retention sheet 2 forming one surface of the composite absorbent 1 in the thickness direction, a second retention sheet 3 forming the other surface of the composite absorbent 1, and a liquid-absorbent member located between these sheets and consisting of a mixture of a polymer absorbent 4 and a superabsorbent polymer 5 (SAP).

[0022] The liquid-absorbent member in the composite absorbent body 1 is configured to absorb and retain liquid that has permeated through the first retaining sheet 2, using a polymer absorbent 4 and a highly absorbent polymer 5 that have a hydrophilic continuous skeleton and continuous pores and are located between the first retaining sheet 2 and the second retaining sheet 3. Furthermore, the above-mentioned polymer absorbent 4 has a unique liquid transfer property in which the amount of liquid transferred to the superabsorbent polymer 5 3 minutes after the polymer absorbent 4 after absorbing liquid comes into contact with the superabsorbent polymer 5 is 23.0 g / g or more.

[0023] The polymer absorbent 4 can take up liquids such as aqueous solutions into its continuous pores by capillary action, and due to its unique high liquid migration property described above, it can retain a large amount of liquid at one time and transfer a large amount of liquid from the polymer absorbent 4 to the super absorbent polymer 5 (SAP). Therefore, the composite absorbent 1 containing such a polymer absorbent 4 can fully utilize the liquid retention ability of the SAP, and can exhibit high absorption performance as an absorbent.

[0024] In the present invention, the absorbent member is not limited to the form of the composite absorbent 1 in the above-mentioned embodiment, and the absorbent member may or may not contain other absorbent materials as long as it contains at least the polymer absorbent having the above-mentioned specific liquid migration properties and SAP.

[0025] Furthermore, in the present invention, the configuration of the composite absorbent is not limited to the form of the composite absorbent 1 of the above-mentioned embodiment, and the composite absorbent may have, for example, a hydrophilic fiber sheet 6 located between the first retention sheet 2 and the liquid-absorbent member (i.e., the polymer absorbent 4 and the highly absorbent polymer 5), as in a composite absorbent 1' of another embodiment of the present invention shown in Figure 2.

[0026] In the present invention, the outer shape, various dimensions, basis weight, etc. of the composite absorbent body are not particularly limited as long as they do not impair the effects of the present invention, and any outer shape (e.g., circular, elliptical, polygonal, hourglass, design shape, etc.), various dimensions, basis weight, etc. can be adopted according to various applications and usage modes, etc.

[0027] Hereinafter, various constituent members of the composite absorbent body of the present invention will be described in more detail using a composite absorbent body 1 of an embodiment shown in FIG.

[0028] (Retaining sheet) 1, a first retention sheet 2 forming one surface of the composite absorbent body 1 has a substantially rectangular outer shape in a plan view similar to the outer shape of the composite absorbent body 1. The first retention sheet 2 is formed of a liquid-permeable sheet-like member that allows liquid supplied to the composite absorbent body 1 to pass therethrough and be absorbed and retained in the liquid-absorbent member on the inside.

[0029] The first retaining sheet 2 has an overall size that is slightly larger than the liquid-absorbent member located on the inside (i.e., compared to the area where the polymer absorbent 4, etc. are located), and is joined at its peripheral portion to the second retaining sheet 3 located on the other side of the composite absorbent 1 in the thickness direction by any adhesive or heat-sealing means, etc.

[0030] On the other hand, the second retention sheet 3 forming the other surface of the composite absorbent body 1 has a substantially rectangular outer shape in a plan view similar to the outer shape of the composite absorbent body 1. The second retention sheet 3 is made of a liquid-impermeable sheet-like member that prevents liquid that has not been absorbed and retained in the inner liquid-absorbent member and liquid that has seeped out from the liquid-absorbent member from leaking out to the outside of the composite absorbent body 1.

[0031] In the present invention, the sheet-like members usable as the first and second retaining sheets are not limited to those in the above-mentioned embodiments, and the composite absorbent of the present invention may be any one of the first and second retaining sheets formed from a liquid-permeable sheet-like member. That is, the composite absorbent of the present invention may be any one of the first and second retaining sheets formed from a liquid-impermeable sheet-like member.

[0032] When a liquid-permeable sheet-like member is used as the holding sheet, the liquid-permeable sheet-like member is not particularly limited as long as it does not impair the effects of the present invention, and any liquid-permeable sheet-like member can be used according to various applications, usage modes, etc. Examples of such liquid-permeable sheet-like members include hydrophilic nonwoven fabrics such as air-through nonwoven fabrics, spunbond nonwoven fabrics, and point-bond nonwoven fabrics, woven fabrics, knitted fabrics, and porous resin films.

[0033] Furthermore, when hydrophilic nonwoven fabrics, woven fabrics, knitted fabrics, etc. (hereinafter collectively referred to as "fiber sheets") are used as the liquid-permeable sheet-like member, these fiber sheets may have a single-layer structure or a multi-layer structure of two or more layers. The type of fiber constituting such a fiber sheet is not particularly limited, and examples thereof include hydrophilic fibers such as cellulosic fibers and thermoplastic resin fibers that have been subjected to a hydrophilization treatment. These fibers may be used alone or in combination of two or more types of fibers. Furthermore, examples of cellulose-based fibers that can be used as constituent fibers of the fiber sheet include natural cellulose fibers (e.g., plant fibers such as cotton), regenerated cellulose fibers, refined cellulose fibers, and semi-synthetic cellulose fibers. Examples of thermoplastic resin fibers that can be used as constituent fibers of the fiber sheet include fibers made of known thermoplastic resins such as olefin-based resins such as polyethylene (PE) and polypropylene (PP), polyester-based resins such as polyethylene terephthalate (PET), and polyamide-based resins such as 6-nylon. These resins may be used alone or in combination of two or more types.

[0034] In addition, when a liquid-impermeable sheet-like member is used as the holding sheet, the liquid-impermeable sheet-like member is not particularly limited as long as it does not impair the effects of the present invention, and any liquid-impermeable sheet-like member can be adopted according to various applications and usage modes, etc. Examples of such liquid-impermeable sheet-like members include hydrophobic nonwoven fabrics formed from any hydrophobic thermoplastic resin fibers (for example, polyolefin fibers such as PE and PP, polyester fibers such as PET, various composite fibers such as core-sheath type, etc.); porous or nonporous resin films formed from hydrophobic thermoplastic resins such as PE and PP; laminates in which a nonwoven fabric is bonded to the resin film; laminated nonwoven fabrics such as SMS nonwoven fabrics, etc.

[0035] In the present invention, the external shape, various dimensions, basis weight, etc. of the retaining sheet are not particularly limited as long as they do not impair the effects of the present invention, and any external shape (e.g., circular, oval, polygonal, hourglass, design shape, etc.), various dimensions, basis weight, etc. can be adopted according to various applications and usage modes, etc.

[0036] (Liquid-absorbent member) In the composite absorbent 1 shown in Figure 1, the liquid-absorbent member is configured to absorb and retain liquid that has permeated through the first retaining sheet 2 by using a polymer absorbent 4 having a hydrophilic continuous skeleton and continuous pores and a superabsorbent polymer 5 located between the first retaining sheet 2 and the second retaining sheet 3 as described above.

[0037] In the composite absorbent 1, the polymer absorbent 4 and the highly absorbent polymer 5 of the liquid-absorbent member are bonded to each of the above-mentioned first retaining sheet 2 and second retaining sheet 3 by any adhesive such as a hot melt adhesive, but in the composite absorbent of the present invention, the polymer absorbent does not need to be bonded to the retaining sheet.

[0038] As described above, the liquid-absorbent member contains, as essential components, a polymer absorbent having a hydrophilic continuous skeleton and continuous pores and the above-mentioned specific liquid transport property, and a superabsorbent polymer 5. The polymer absorbent will be described later, and the superabsorbent polymer is a powder or granular material made of a highly absorbent polymer such as a sodium acrylate copolymer known in the art, and is known as SAP (Super Absorbent Polymer).

[0039] In the present invention, the liquid-absorbent member located between the first and second holding sheets may contain only the above-mentioned polymer absorbent and superabsorbent polymer as the liquid-absorbent material, or may further contain a liquid-absorbent material known in the art in addition to these. Examples of such liquid-absorbent materials include hydrophilic fibers, and more specifically, pulp fibers (e.g., ground pulp, etc.), and cellulosic fibers such as cotton, rayon, and acetate. For example, in the embodiment of the composite absorbent 1 shown in Figure 1, the liquid-absorbent member located between the first retention sheet 2 and the second retention sheet 3 contains a superabsorbent polymer 5 in addition to a polymer absorbent 4 that has a hydrophilic continuous skeleton and continuous pores and has the above-mentioned unique liquid-absorbency.

[0040] In the present invention, the external shape (planar shape of the arrangement area), various dimensions, basis weight, etc. of the liquid-absorbent member are not particularly limited as long as they do not impair the effects of the present invention, and any external shape, various dimensions, basis weight, etc. can be adopted according to various applications, usage modes, etc.

[0041] (hydrophilic fiber sheet) In addition, in the present invention, the composite absorbent may have a hydrophilic fiber sheet 6 located between the first retention sheet 2 and the liquid-absorbent member (i.e., the polymer absorbent 4 and the highly absorbent polymer 5), for example, as in another embodiment of the composite absorbent 1' shown in Figure 2.

[0042] In the present invention, the hydrophilic fiber sheet that can be used in the composite absorbent is not particularly limited as long as it does not impair the effects of the present invention, and any hydrophilic fiber sheet can be used depending on various applications and usage modes. Examples of such hydrophilic fiber sheets include nonwoven fabrics, woven fabrics, knitted fabrics, etc. that have hydrophilicity. The hydrophilic fiber sheet may have a single-layer structure or a multi-layer structure of two or more layers.

[0043] The type of fibers constituting the hydrophilic fiber sheet is not particularly limited, and examples thereof include hydrophilic fibers such as cellulosic fibers and thermoplastic resin fibers that have been subjected to a hydrophilic treatment. These fibers may be used alone or in combination of two or more types of fibers. Furthermore, examples of cellulose-based fibers that can be used as constituent fibers of the hydrophilic fiber sheet include natural cellulose fibers (e.g., plant fibers such as cotton), regenerated cellulose fibers, refined cellulose fibers, and semi-synthetic cellulose fibers. Examples of thermoplastic resin fibers that can be used as constituent fibers of the hydrophilic fiber sheet include fibers made of known thermoplastic resins such as olefin resins such as PE and PP, polyester resins such as PET, and polyamide resins such as 6-nylon. These resins may be used alone or in combination of two or more types.

[0044] In the present invention, the outer shape, various dimensions, basis weight, etc. of the hydrophilic fibrous sheet are not particularly limited as long as they do not impair the effects of the present invention, and any outer shape, various dimensions, basis weight, etc. can be adopted according to various applications, usage modes, etc.

[0045] The polymer absorbent used in the composite absorbent of the present invention will be described in more detail below.

[0046] [Polymer absorbent] The polymer absorbent is not particularly limited as long as it is a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and has a unique liquid migration property in which the amount of liquid migration to SAP 3 minutes after the polymer absorbent after absorbing liquid comes into contact with SAP is 23.0 g / g or more. For example, it is a hydrolyzate of a crosslinked polymer of two or more monomers including at least (meth)acrylic acid ester, and a polymer compound having at least one hydrophilic group in the functional group. More specifically, it is a hydrolyzate of a crosslinked polymer of a compound containing a (meth)acrylic acid ester and two or more vinyl groups in one molecule, and a polymer compound having at least -COONa group. Such a polymer absorbent is an organic porous body having at least one -COONa group in one molecule, and may further have a -COOH group. The -COONa group is distributed approximately uniformly in the skeleton of the porous body.

[0047] When the polymer absorbent is a hydrolysate of a crosslinked polymer of such a (meth)acrylic acid ester and a compound containing two or more vinyl groups in one molecule and contains at least one -COONa group, as described below, the continuous hydrophilic skeleton is more likely to extend when absorbing liquid, and the continuous pores are more likely to expand, so that a larger amount of liquid can be taken in the continuous pores more quickly, and the absorbent can exhibit even higher absorption performance.

[0048] In this specification, the (meth)acrylic acid ester refers to an acrylic acid ester or a methacrylic acid ester.

[0049] In such a polymer absorbent formed by the hydrolysis product of a cross-linked polymer of a (meth)acrylic acid ester and divinylbenzene, a hydrophilic continuous skeleton is formed by an organic polymer having at least a -COONa group, and the skeleton has interconnected pores (interconnected pores) that serve as absorption fields for the liquid to be absorbed. In addition, since the hydrolysis treatment converts the -COOR groups (that is, carboxylate groups) of the crosslinked polymer into -COONa groups or -COOH groups (see FIG. 3), the polymer absorbent may have -COOR groups.

[0050] The presence of --COOH groups and --COONa groups in the organic polymer forming the hydrophilic continuous skeleton can be confirmed by analysis using infrared spectroscopy and a method for quantifying weakly acidic ion-exchange groups.

[0051] Here, Fig. 3 is a diagram for explaining the manufacturing process of absorbent A, which is an example of a polymer absorbent. In Fig. 3, the upper diagram shows the constituent raw materials for polymerization, the middle diagram shows monolith A, which is a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene, and the lower diagram shows absorbent A obtained by subjecting monolith A in the middle diagram to hydrolysis and drying treatment.

[0052] Hereinafter, an explanation will be given using absorbent A, which is an example of a polymer absorbent and is formed from a hydrolysate of a crosslinked polymer of a (meth)acrylic acid ester and divinylbenzene.

[0053] The polymer absorbent is not limited to the absorbent A, but may be a hydrolysate of a cross-linked polymer of a (meth)acrylic acid ester and a compound having two or more vinyl groups in one molecule, or a hydrolysate of a cross-linked polymer of two or more monomers including at least a (meth)acrylic acid ester. However, if the polymer absorbent is a monolithic absorbent, it has the advantage that it can absorb liquid quickly and that the liquid temporarily held in the polymer absorbent can be transferred to the SAP more reliably.

[0054] In the following description, "Monolith A" refers to an organic porous material consisting of a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene before hydrolysis treatment, and may be referred to as a "monolithic organic porous material." In addition, "absorbent A" is a hydrolyzate of a crosslinked polymer (monolith A) of (meth)acrylic acid ester and divinylbenzene after hydrolysis and drying. In the following description, absorbent A refers to the absorbent in a dry state.

[0055] First, the structure of absorbent A will be described. As described above, absorbent A has a hydrophilic continuous skeleton and continuous pores. As shown in Fig. 3, absorbent A, which is an organic polymer having a hydrophilic continuous skeleton, is obtained by cross-linking polymerizing (meth)acrylic acid ester, which is a polymerization monomer, and divinylbenzene, which is a cross-linking monomer, and further hydrolyzing the obtained cross-linked polymer (monolith A).

[0056] The organic polymer that forms a hydrophilic continuous skeleton has, as structural units, a polymerized residue of an ethylene group (hereinafter referred to as "structural unit X") and a cross-linked polymerized residue of divinylbenzene (hereinafter referred to as "structural unit Y"). Furthermore, the polymerized residue of the ethylene group (structural unit X) in the organic polymer forming the hydrophilic continuous skeleton has a -COONa group generated by hydrolysis of the carboxylate group, or both a -COOH group and a -COONa group. When the polymerized monomer is a (meth)acrylic acid ester, the polymerized residue of the ethylene group (structural unit X) has a -COONa group, a -COOH group, and an ester group.

[0057] In the absorbent A, the ratio of the crosslinked polymer residue of divinylbenzene (structural unit Y) in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0.1 to 30 mol %, preferably 0.1 to 20 mol %, relative to the total structural units. In the absorbent A in which butyl methacrylate is used as the polymerization monomer and divinylbenzene is used as the crosslinking monomer, the ratio of the crosslinked polymer residue of divinylbenzene (structural unit Y) in the organic polymer forming the hydrophilic continuous skeleton is, for example, about 3 mol %, preferably 0.1 to 10 mol %, more preferably 0.3 to 8 mol %, relative to the total structural units. Furthermore, when the ratio of cross-linked polymerized residues of divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is 0.1 mol % or more, the strength of absorbent A is less likely to decrease, and when the ratio of cross-linked polymerized residues of divinylbenzene is 30 mol % or less, the absorption amount of the liquid to be absorbed is less likely to decrease.

[0058] In addition, in the absorbent A, the organic polymer forming the hydrophilic continuous skeleton may be composed only of the structural unit X and the structural unit Y, or may have, in addition to the structural unit X and the structural unit Y, a structural unit other than the structural unit X and the structural unit Y, that is, a polymerized residue of a monomer other than a (meth)acrylic acid ester and divinylbenzene.

[0059] Examples of structural units other than the structural unit X and the structural unit Y include polymerized residues of monomers such as styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, isobutene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate.

[0060] The proportion of structural units other than the structural unit X and the structural unit Y in the organic polymer that forms the hydrophilic continuous skeleton is, for example, 0 to 50 mol %, and preferably 0 to 30 mol %, relative to all structural units.

[0061] The thickness of the hydrophilic continuous skeleton of the absorbent A is preferably 0.1 to 100 μm. When the thickness of the hydrophilic continuous skeleton of the absorbent A is 0.1 μm or more, the spaces (pores) for absorbing liquid in the porous body are less likely to collapse during absorption, and the amount of absorbed liquid is less likely to decrease. On the other hand, when the thickness of the hydrophilic continuous skeleton is 100 μm or less, an excellent absorption speed is easily obtained.

[0062] In addition, since the pore structure of the hydrophilic continuous skeleton of absorbent A is an open-cell structure, the thickness of the continuous skeleton is measured by evaluating the cross section of the skeleton that appears on the test piece for electron microscope measurement. The continuous skeleton is often polygonal in shape because it is formed by the gaps between water (water droplets) removed by the dehydration and drying process after hydrolysis. Therefore, the thickness of the continuous skeleton is the average value of the diameter (μm) of the circle circumscribing the polygonal cross section. In rare cases, there may be small holes in the polygon, in which case the circumscribing circle of the polygonal cross section surrounding the small holes is measured.

[0063] Furthermore, the absorbent A preferably has an average diameter of interconnected pores of 1 to 1000 μm. When the average diameter of interconnected pores in the absorbent A is 1 μm or more, the spaces (pores) for absorbing liquid in the porous body are less likely to collapse during absorption, and the absorption rate is less likely to decrease. On the other hand, when the average diameter of interconnected pores is 1000 μm or less, an excellent absorption rate is more likely to be obtained.

[0064] The average diameter (μm) of the interconnected pores of absorbent A can be measured by mercury intrusion porosimetry, and the maximum value of the pore distribution curve obtained by the mercury intrusion porosimetry is used. Regardless of the ionic form of absorbent A, samples for measuring the average diameter of interconnected pores are those dried for 18 hours or more in a reduced pressure dryer set at a temperature of 50°C. The final pressure reached is 0 Torr.

[0065] Here, FIG. 4 is an SEM photograph of absorbent A at a magnification of 50 times, FIG. 5 is an SEM photograph of absorbent A at a magnification of 100 times, FIG. 6 is an SEM photograph of absorbent A at a magnification of 500 times, FIG. 7 is an SEM photograph of absorbent A at a magnification of 1000 times, and further, FIG. 8 is an SEM photograph of absorbent A at a magnification of 1500 times. The absorbents A shown in these Figs. 4 to 8 are examples of absorbents that use butyl methacrylate as a polymerization monomer and divinylbenzene as a cross-linking monomer, and each has a cubic structure with a side length of 2 mm.

[0066] 4 to 8 has a large number of cellular macropores and further has portions where these cellular macropores overlap. Absorbent A has an open cell structure in which the overlapping portions of the macropores form common openings (mesopores), i.e., it has an open cell structure (open macropore structure).

[0067] The overlapping portions of the macropores form common openings (mesopores) having an average diameter in a dry state of 1 to 1000 μm, preferably 10 to 200 μm, and particularly preferably 20 to 100 μm, and most of them have an open pore structure. When the average diameter of the mesopores in a dry state is 1 μm or more, the absorption rate of the liquid to be absorbed is improved. On the other hand, when the average diameter of the mesopores in a dry state is 1000 μm or less, the absorbent A is less likely to become embrittled. The number of overlapping macropores in each macropore is about 1 to 12, and in most cases, about 3 to 10.

[0068] In addition, since absorbent A has such an open cell structure, macropores and mesopores can be uniformly formed, and there is an advantage in that the pore volume and specific surface area can be significantly increased compared to the particle agglomeration type porous bodies as described in JP-A-8-252579 and the like.

[0069] The total pore volume of the pores (voids) of the absorbent A is preferably 0.5 to 50 mL / g, more preferably 2 to 30 mL / g. When the total pore volume of the absorbent A is 0.5 mL / g or more, the spaces (voids) for absorbing liquid in the porous body are less likely to collapse during absorption, and the amount of absorbed liquid and the absorption rate are less likely to decrease. On the other hand, when the total pore volume of the absorbent A is 50 mL / g or less, the strength of the absorbent A is less likely to decrease.

[0070] The total pore volume can be measured by mercury intrusion porosimetry. The sample for measuring the total pore volume is dried for 18 hours or more in a vacuum dryer set at a temperature of 50°C, regardless of the ion form of absorbent A. The final pressure is 0 Torr.

[0071] Hereinafter, the state when the absorbent A comes into contact with a liquid will be described, but the same applies to the case when a liquid comes into contact with a liquid-absorbent member or a composite absorbent body containing the absorbent A.

[0072] First, the continuous pores of the absorbent A shown in Figs. 4 to 8 are pores in which a plurality of pores (voids) are interconnected, and it is possible to visually confirm with the naked eye that a large number of voids are provided from the outside. When liquid comes into contact with the absorbent A having such a large number of voids, a certain amount of liquid enters the large number of voids by capillary action and is absorbed into the absorbent A. At this time, a part of the liquid absorbed into the absorbent A is absorbed into the hydrophilic continuous skeleton by osmotic pressure, and the continuous skeleton is extended. On the other hand, the liquid absorbed into the absorbent A that is not absorbed into the hydrophilic continuous skeleton is absorbed while remaining in the pores.

[0073] In this way, absorbent A has the property that its hydrophilic continuous skeleton expands when it absorbs liquid. This expansion of the continuous skeleton occurs in almost all directions. Furthermore, as the external shape of absorbent A increases due to this expansion of the continuous skeleton, the size of each pore also increases. When the size of the pores increases in this way, the volume of the pores increases, and the amount of liquid that can be retained in the pores also increases. In other words, absorbent A, which has expanded by absorbing a certain amount of liquid, can absorb a further predetermined amount of liquid into the expanded pores due to capillary action. Furthermore, since absorbent A absorbs liquid by capillary action, it can quickly absorb liquid.

[0074] Furthermore, of the liquid absorbed by absorbent A, more remains in the pores than in the hydrophilic continuous skeleton. Most of the liquid absorbed by absorbent A is achieved by retaining the liquid in the pores through capillary action, so the greater the porosity (the volume of the pores relative to the volume of absorbent A), which is the ratio of the volume of the voids in the pores (total pore volume), the more liquid can be absorbed. It is preferable that this porosity is 85% or more.

[0075] For example, when the porosity of the absorbent A shown in the above-mentioned Figs. 4 to 8 is calculated, it is as follows. First, the specific surface area of ​​absorbent A obtained by mercury porosimetry is 400 m 2 / g, and the pore volume is 15.5 mL / g. This pore volume of 15.5 mL / g means that the volume of the pores in 1 g of absorbent A is 15.5 mL. Here, assuming that the specific gravity of absorbent A is 1 g / mL, the volume occupied by pores in 1 g of absorbent A, i.e., the pore volume, is 15.5 mL, and the volume of 1 g of absorbent A is 1 mL. In this case, the total volume (volume) of 1 g of absorbent A is 15.5 + 1 (mL), and the ratio of the pore volume to that is the porosity, so the porosity of absorbent A is 15.5 / (15.5 + 1) × 100 ≒ 94%.

[0076] In the present invention, such an absorbent A having a hydrophilic continuous skeleton and continuous pores, that is, a polymer absorbent, is applied to a composite absorbent in the form of, for example, particles or sheets. Furthermore, as described above, this polymer absorbent has a specific liquid transfer property that the liquid transfer amount to SAP 3 minutes after the polymer absorbent after liquid absorption comes into contact with SAP is 23.0 g / g or more.

[0077] Such a polymer absorbent can take in liquid into the continuous pores by capillary action, and furthermore, due to having the above-mentioned specific high liquid transfer property, it can hold a large amount of liquid at once and transfer a large amount of liquid from the polymer absorbent to SAP. Therefore, the composite absorbent of the present invention containing such a polymer absorbent can fully utilize the liquid retention ability of SAP and exhibit high absorption performance as an absorbent. In this specification, the liquid transfer amount to the superabsorbent polymer 3 minutes after the polymer absorbent after liquid absorption comes into contact with the superabsorbent polymer may be simply referred to as the liquid transfer amount from the polymer absorbent to the superabsorbent polymer (SAP).

[0078] In the present invention, the liquid transfer amount from the polymer absorbent to SAP is more preferably 27.0 g / g or more, and particularly preferably 33.0 g / g or more. The liquid transfer amount from this polymer absorbent to SAP can be measured as follows.

[0079] <Method for Measuring Liquid Transfer Amount to SAP> (1) 0.3 g of the measurement sample (polymer absorbent) is placed in a plastic cylinder (inner diameter: 60 mm, outer diameter: 70 mm, height: 52 mm, mass: 64 g) with a nylon mesh material (NBC Meshtec Co., Ltd., N-NO255HD 115 (standard width: 115 cm, 255 mesh / 2.54 cm, opening: 57 μm, wire diameter: 43 μm, thickness: 75 μm)) attached to the bottom, and the mass (g) of the cylinder is measured. This measurement method is performed under conditions of a temperature of 25°C and a humidity of 60%. In addition, when the measurement sample (polymer absorbent) is recovered from a composite absorbent product and used, it can be obtained according to the <Recovery method of the measurement sample (polymer absorbent)> described later. (2) Place a plastic cylinder (inner diameter: 60 mm, outer diameter: 70 mm, height: 52 mm, mass: 64 g) into a petri dish (inner diameter: 85 mm, depth: 20 mm) and sprinkle 0.3 g of superabsorbent polymer (SAP) evenly inside the cylinder. Then remove the cylinder and measure the mass (g) of the petri dish. (3) Place 60 mL of 0.9% sodium chloride solution into a petri dish with a pedestal (inner diameter: 85 mm, depth: 20 mm, pedestal arrangement: two pedestals arranged parallel to each other with an interval of 24 mm in the center of the bottom (inner side), pedestal width: 2 mm, pedestal height: 2 mm, pedestal length: 25 mm). (4) Place the cylinder containing the sample to be measured (polymer absorbent) on the base in the center of a petri dish with a base, immerse the bottom of the cylinder in the above-mentioned sodium chloride aqueous solution, and allow the sample in the cylinder to absorb the sodium chloride aqueous solution for 3 minutes. (5) After absorbing the liquid for 3 minutes, the cylinder is pulled out, tilted 45° and allowed to drain for 1 minute, and then the mass (g) of the cylinder is measured. (6) Calculate the amount of liquid absorbed by the sample (g) by subtracting the mass (g) of the cylinder after absorbing the liquid, measured in (5) above, from the mass (g) of the cylinder before absorbing the liquid, measured in (1) above. Further, divide this amount of liquid absorbed by the mass of the sample (=0.3 g) to obtain the amount of liquid absorbed per unit mass of the sample (g / g). (7) Then, the cylinder after draining in (5) above is placed on the petri dish containing the SAP, and the sample in the cylinder and the SAP in the petri dish are brought into contact with each other via the bottom surface (mesh material) of the cylinder. (8) After a predetermined time has elapsed since the sample was brought into contact with the SAP (for example, 30 seconds or 3 minutes), the cylinder is removed and the mass (g) of the dish is measured. (9) The mass (g) of the Petri dish measured in (8) above is subtracted by the mass (g) of the Petri dish measured in (2) above to calculate the amount of liquid absorbed by SAP (g). This amount of liquid absorbed is then divided by the mass of the sample (=0.3 g) to obtain the amount of liquid absorbed by SAP per unit mass of the sample (g / g), i.e., the amount of liquid transferred to SAP per unit mass of the sample (g / g). The amount of liquid transferred to the superabsorbent polymer 30 seconds after contact with the superabsorbent polymer described below means the amount of liquid transferred (g / g) to the SAP 30 seconds after contacting the sample (8) with the SAP.

[0080] When the above-mentioned measurement sample (polymer absorbent) is to be recovered from a composite absorbent product, it can be obtained as follows.

[0081] <How to collect the measurement sample (polymer absorbent)> (1) Peel off the retaining sheet or the like from the composite absorbent product to expose the liquid-absorbent member. (2) All absorbent materials including the object to be measured (polymer absorbent) are dropped from the exposed absorbent member, and the absorbent materials other than the (particulate) object to be measured (e.g., pulp, synthetic resin fibers, etc.) are removed using tweezers or the like. (3) A microscope or a simple magnifying glass is used as a magnifying observation means, and the measurement object is collected using tweezers or the like while observing at a magnification at which the difference from SAP can be recognized or at which the pores of the porous body can be visually recognized. The magnification of the simple magnifying glass is not particularly limited as long as the pores of the porous body can be visually recognized, and may be, for example, 25 to 50 times. (4) The objects to be measured thus collected are used as samples for measurement in various measurement methods.

[0082] Here, a polymer absorbent as an example of the present invention, pulp fiber (fluff pulp) as a comparative example, Infinity particles as a comparative example, and superabsorbent polymer (SAP) as a comparative example were prepared, and these samples were allowed to absorb liquid for 3 minutes, and then the amount of liquid transferred to the SAP was measured 30 seconds and 3 minutes after contact with the SAP. The measurement results of the amount of liquid transferred to the SAP are shown in Table 1 below. The Infinity particles mentioned above are absorbents manufactured by P&G, and have a structure (foam structure) similar to that of polymer absorbents. However, unlike polymer absorbents, they do not have the ability to absorb liquid and expand.

[0083] [Table 1]

[0084] As shown in Table 1, pulp fibers, Infinity particles, and SAP tend to increase the amount of liquid transferred to the SAP as the contact time with SAP increases, but the amount is small. On the other hand, the polymer absorbent shows a higher liquid transfer amount than any of the conventional pulp fibers, Infinity particles, and SAP. In particular, it can be seen that the polymer absorbent shows a relatively high liquid transfer amount even for a relatively short contact time of 30 seconds after the polymer absorbent after absorbing liquid was brought into contact with the SAP. In other words, it is clear that the polymer absorbent has unique and excellent liquid migration properties that are not available in conventional pulp fibers, Infinity particles, SAP, etc.

[0085] In the present invention, the polymer absorbent preferably has a liquid transfer amount to SAP of 7.0 g / g or more 30 seconds after the polymer absorbent after absorbing liquid comes into contact with SAP. If the polymer absorbent has such liquid transferability, the polymer absorbent after absorbing liquid can transfer a large amount of liquid in a short time after contacting SAP, and therefore can more steadily exhibit high absorption performance. The amount of liquid transfer of the polymer absorbent to the SAP 30 seconds after contact with the SAP is more preferably 7.5 g / g or more, even more preferably 8.0 g / g or more, and particularly preferably 9.0 g / g or more.

[0086] Furthermore, in the present invention, it is preferable that the polymer absorbent has a specific liquid discharge property in which the liquid discharge amount of the absorbed liquid component is 20 g / g or more and the liquid discharge rate is 65% or more. Such a polymer absorbent can take in liquid into the continuous pores by capillary action, and further, by having the specific high liquid discharge amount and liquid discharge rate (i.e., by having high liquid retention capacity and excellent liquid release property (liquid syneresis)), it can hold a large amount of liquid at one time and can release a large amount of the absorbed and held liquid. Therefore, a composite absorbent containing such a polymer absorbent can steadily transfer a large amount of liquid from the polymer absorbent to the SAP, making it possible to more fully utilize the liquid retention capacity of the SAP and thus to exhibit even higher absorption performance as an absorbent. The liquid discharge amount of the polymer absorbent is particularly preferably 35 g / g or more, and the liquid discharge rate is more preferably 70% or more, and particularly preferably 75% or more. The liquid discharge amount and liquid discharge rate of these polymer absorbents can be measured as follows.

[0087] <Method of measuring liquid discharge amount and liquid discharge rate> (1) 1 g of the measurement sample (polymer absorbent) is cut into a 10 cm square mesh bag (NBC Meshtec Co., Ltd., N-NO255HD 115 (standard width: 115 cm, 255 mesh / 2.54 cm, opening: 57 μm, wire diameter: 43 μm, thickness: 75 μm)) and enclosed. The mass (g) of the mesh bag is measured in advance. This measurement method is performed under conditions of a temperature of 25°C and a humidity of 60%. Furthermore, when the measurement sample (polymer absorbent) is to be recovered from a composite absorbent product and used, it can be obtained according to the above-mentioned <Recovery method of measurement sample (polymer absorbent)>. (2) The mesh bag containing the sample is immersed in a 0.9% sodium chloride solution for one hour. (3) Hang the mesh bag for 5 minutes and drain, then measure its mass (g). (4) The amount of liquid absorbed by the sample (g) is calculated by subtracting the total mass of the sample (= 1 g) and the mesh bag from the mass of the mesh bag after draining measured in (3) above, and this amount of liquid absorbed is further divided by the mass of the sample (= 1 g) to obtain the amount of liquid absorbed per unit mass of the sample (polymer absorbent) (g / g). (5) Furthermore, the mesh bag after draining in (3) above is centrifuged at 150 G for 90 seconds, and the mass (g) of the mesh bag after the centrifugation is measured. (6) Subtract the mass of the sample (=1 g) and the total mass of the mesh bag from the mass of the mesh bag after centrifugation measured in (5) above. The mass (g) of the sample was subtracted from the amount of absorbed liquid (g) of the sample calculated in (4) above. The liquid discharge amount (g) of the sample is calculated by dividing the liquid discharge amount by the mass of the sample (=1g) to obtain the liquid discharge amount per unit mass of the sample (polymer absorbent) (g / g). (7) The liquid discharge amount per unit mass obtained in (6) above is divided by the liquid absorption amount per unit mass obtained in (4) above, and the result is multiplied by 100 to obtain the liquid discharge amount relative to the liquid absorption amount of the sample (polymer absorbent), i.e., the liquid discharge rate (%).

[0088] Hereinafter, the method for producing such a polymer absorbent will be described in detail using the above-mentioned absorbent A as an example.

[0089] [Method of manufacturing polymer absorbent] The above-mentioned absorbent A can be obtained through a cross-linking polymerization step and a hydrolysis step, as shown in Fig. 3. Each of these steps will be described below.

[0090] (Crosslinking polymerization process) First, an oil-soluble monomer for crosslinking polymerization, a crosslinkable monomer, a surfactant, water, and optionally a polymerization initiator are mixed to obtain a water-in-oil emulsion, which is an emulsion in which the oil phase is the continuous phase and water droplets are dispersed within it.

[0091] In the above-mentioned absorbent A, as shown in the upper diagram of Figure 3, butyl methacrylate, which is a (meth)acrylic acid ester, is used as the oil-soluble monomer, divinylbenzene is used as the cross-linking monomer, sorbitan monooleate is used as the surfactant, and isobutyronitrile is used as the polymerization initiator to cause cross-linking polymerization to obtain monolith A.

[0092] Specifically, for absorbent A, as shown in the upper diagram of Figure 3, first, 9.2 g of t-butyl methacrylate as an oil-soluble monomer, 0.28 g of divinylbenzene as a cross-linking monomer, 1.0 g of sorbitan monooleate (hereinafter abbreviated as "SMO") as a surfactant, and 0.4 g of 2,2'-azobis(isobutyronitrile) as a polymerization initiator are mixed and dissolved uniformly. Next, the mixture of t-butyl methacrylate / divinylbenzene / SMO / 2,2'-azobis(isobutyronitrile) is added to 180 g of pure water and stirred under reduced pressure using a planetary stirring device, a vacuum stirring and degassing mixer (manufactured by EME), to obtain a water-in-oil emulsion.

[0093] Furthermore, this emulsion is quickly transferred to a reaction vessel, sealed, and polymerized at 60°C for 24 hours under stationary conditions. After the polymerization is completed, the contents are removed, extracted with methanol, and then dried under reduced pressure to obtain Monolith A, which has a continuous macropore structure. The internal structure of Monolith A was observed by SEM, and it was found that Monolith A had a continuous cell structure and the thickness of the continuous skeleton was 5.4 μm. The average diameter of the continuous pores measured by mercury intrusion porosimetry was 36.2 μm, and the total pore volume was 15.5 mL / g.

[0094] The content of divinylbenzene in the total monomers is preferably 0.3 to 10 mol%, more preferably 0.3 to 5 mol%. The ratio of divinylbenzene to the total of butyl methacrylate and divinylbenzene is preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%. In the above-mentioned absorbent A, the ratio of butyl methacrylate to the total of butyl methacrylate and divinylbenzene is 97.0 mol%, and the ratio of divinylbenzene is 3.0 mol%.

[0095] The amount of surfactant added can be set depending on the type of oil-soluble monomer and the desired size of emulsion particles (macropores), and is preferably in the range of about 2 to 70% of the total amount of the oil-soluble monomer and surfactant.

[0096] In order to control the shape and size of the bubbles in Monolith A, alcohols such as methanol and stearyl alcohol; carboxylic acids such as stearic acid; hydrocarbons such as octane, dodecane, and toluene; cyclic ethers such as tetrahydrofuran and dioxane, etc. may be allowed to coexist in the polymerization system.

[0097] In addition, the mixing method for forming the water-in-oil emulsion is not particularly limited, and any mixing method can be used, such as a method of mixing all the components at once, or a method of separately and uniformly dissolving oil-soluble components such as the oil-soluble monomer, surfactant, and oil-soluble polymerization initiator, and water-soluble components such as water and the water-soluble polymerization initiator, and then mixing the respective components.

[0098] Furthermore, the mixing device for forming the emulsion is not particularly limited, and any device such as a normal mixer, homogenizer, or high-pressure homogenizer can be used depending on the desired emulsion particle size. Furthermore, a so-called planetary mixing device can also be used in which the material to be treated is placed in a mixing container and rotated while revolving around the revolution axis while tilting the mixing container, thereby stirring and mixing the material to be treated.

[0099] In addition, there are no particular limitations on the mixing conditions, and the stirring rotation speed, stirring time, etc. can be set as desired according to the desired emulsion particle size. Note that, with the above planetary stirring device, water droplets in the W / O emulsion can be uniformly generated, and the average diameter can be set as desired within a wide range.

[0100] The polymerization conditions for the water-in-oil emulsion can be various, depending on the type of monomer and initiator, etc. For example, when azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, etc. are used as the polymerization initiator, the polymerization can be carried out by heating in a sealed container under an inert atmosphere at a temperature of 30 to 100°C for 1 to 48 hours, and when hydrogen peroxide-ferrous chloride, sodium persulfate-acidic sodium sulfite, etc. are used as the polymerization initiator, the polymerization can be carried out in a sealed container under an inert atmosphere at a temperature of 0 to 30°C for 1 to 48 hours.

[0101] After the polymerization is completed, the contents are taken out and subjected to Soxhlet extraction with a solvent such as isopropanol to remove unreacted monomers and residual surfactants, thereby obtaining monolith A shown in the center diagram of Figure 3.

[0102] (Hydrolysis process) Next, the step of hydrolyzing the monolith A (crosslinked polymer) to obtain the absorbent A (hydrolysis step) will be described.

[0103] First, monolith A is immersed in dichloroethane containing zinc bromide and stirred at 40° C. for 24 hours, then contacted with methanol, 4% hydrochloric acid, 4% aqueous sodium hydroxide solution, and water in that order to carry out hydrolysis, and then dried to obtain a block-shaped absorbent A. Furthermore, this block-shaped absorbent A is crushed to a predetermined size to obtain a particulate absorbent A. The form of this absorbent A is not limited to particulate, and for example, it may be formed into a sheet during or after drying.

[0104] In addition, the method of hydrolysis of monolith A is not particularly limited, and various methods can be adopted. For example, aromatic solvents such as toluene and xylene, halogen-based solvents such as chloroform and dichloroethane, ether-based solvents such as tetrahydrofuran and isopropyl ether, amide-based solvents such as dimethylformamide and dimethylacetamide, alcohol-based solvents such as methanol and ethanol, carboxylic acid-based solvents such as acetic acid and propionic acid, or water as a solvent are contacted with a strong base such as sodium hydroxide, or a hydrohalic acid such as hydrochloric acid, a Bronsted acid such as sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, and p-toluenesulfonic acid, or a Lewis acid such as zinc bromide, aluminum chloride, aluminum bromide, titanium (IV) chloride, cerium chloride / sodium iodide, and magnesium iodide.

[0105] Furthermore, among the polymerization raw materials of the organic polymer that forms the hydrophilic continuous skeleton of the absorbent A, the (meth)acrylic acid ester is not particularly limited, but is preferably a C1 to C10 (i.e., carbon number 1 to 10) alkyl ester of (meth)acrylic acid, and more preferably a C4 (i.e., carbon number 4) alkyl ester of (meth)acrylic acid. Examples of C4 alkyl esters of (meth)acrylic acid include t-butyl (meth)acrylic acid ester, n-butyl (meth)acrylic acid ester, and iso-butyl (meth)acrylic acid ester.

[0106] Furthermore, the monomers used in the crosslinking polymerization may be only (meth)acrylic acid esters and divinylbenzene, or may contain, in addition to (meth)acrylic acid esters and divinylbenzene, other monomers other than (meth)acrylic acid esters and divinylbenzene. In the latter case, the other monomers are not particularly limited, but examples thereof include styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobutene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. The proportion of monomers other than (meth)acrylic acid ester and divinylbenzene in all monomers used in the crosslinking polymerization is preferably from 0 to 80 mol %, more preferably from 0 to 50 mol %.

[0107] The surfactant is not limited to the above-mentioned sorbitan monooleate, and may be any surfactant capable of forming a water-in-oil type (W / O) emulsion when the monomer for crosslinking polymerization is mixed with water. Examples of such surfactants include nonionic surfactants such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, and polyoxyethylene sorbitan monooleate, anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, and dioctyl sodium sulfosuccinate, cationic surfactants such as distearyl dimethyl ammonium chloride, and amphoteric surfactants such as lauryl dimethyl betaine. These surfactants may be used alone or in combination of two or more.

[0108] In addition, the polymerization initiator is preferably a compound that generates radicals by heat and light irradiation. Furthermore, the polymerization initiator may be water-soluble or oil-soluble, and examples thereof include azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, azobiscyclohexanecarbonitrile, azobis(2-methylpropionamidine)dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-acidic sodium sulfite, and tetramethylthiuram disulfide. However, in some cases, there are systems in which polymerization proceeds only by heating or light irradiation without the addition of a polymerization initiator, and in such systems, the addition of a polymerization initiator is not necessary.

[0109] The composite absorbent of the present invention is not particularly limited, but can be applied to various fields of composite absorbents such as dew condensation prevention sheets, simple soil, and other civil engineering and construction materials, base materials for medicines, and materials for absorbing leaked liquids. Therefore, the liquid to be absorbed by the composite absorbent is not particularly limited, and examples thereof include water and aqueous solutions (e.g., seawater, etc.), acids (e.g., hydrochloric acid, etc.), bases (e.g., sodium hydroxide, etc.), organic solvents (e.g., alcohols such as methanol and ethanol, ketones such as acetone, ethers such as tetrahydrofuran (THF) and 1,4-dioxane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc.). These liquids may be mixtures of two or more liquids.

[0110] Furthermore, the present invention is not limited to the above-described embodiments, and appropriate combinations, substitutions, modifications, etc. are possible within the scope of the object and intent of the present invention. Note that in this specification, ordinal numbers such as "first" and "second" are used to distinguish the items to which the ordinal numbers are attached, and do not indicate the order, priority, importance, etc. of each item. [Explanation of symbols]

[0111] 1 Composite absorber 2. First retaining sheet 3 Second Retaining Sheet 4. Polymer absorbents 5. Superabsorbent polymer (SAP) 6 Hydrophilic fiber sheet

Claims

1. A composite absorbent for absorbing liquids for civil engineering materials, building materials, or materials for absorbing leaked liquids consisting of organic solvents (excluding cases where the use is for absorbent articles such as pants-type disposable diapers, tape-type disposable diapers, sanitary napkins, absorbent pads, disposable diapers for pets, and absorbent pads for pets), The present invention includes a polymeric absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer, The polymer absorbent is a hydrolyzate of a crosslinked polymer of a (meth)acrylic acid ester and divinylbenzene, which is a compound containing two or more vinyl groups in one molecule, and contains at least one -COONa group; a ratio of crosslinked polymer residues of the divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is 0.1 to 30 mol % based on all constitutional units, The (meth)acrylic acid ester contains a C4 alkyl ester of (meth)acrylic acid, The composite absorbent is characterized in that the amount of liquid transferred to the superabsorbent polymer 3 minutes after the polymer absorbent comes into contact with the superabsorbent polymer after absorbing liquid is 35.9 g / g or more.

2. The composite absorbent according to claim 1, characterized in that the polymer absorbent has a liquid transfer amount to the superabsorbent polymer of 7.0 g / g or more 30 seconds after the polymer absorbent comes into contact with the superabsorbent polymer after absorbing liquid.

3. 3. The composite absorbent according to claim 1, wherein the polymer absorbent has a discharge amount of absorbed liquid of 20 g / g or more and a discharge rate of 65% or more.

4. The composite absorbent according to any one of claims 1 to 3, wherein the polymer absorbent is a monolithic absorbent.

5. A polymer absorbent used together with a superabsorbent polymer for civil engineering materials, building materials, or materials for absorbing leaked liquids consisting of organic solvents (excluding cases where the use is for absorbent articles such as pants-type disposable diapers, tape-type disposable diapers, sanitary napkins, absorbent pads, disposable diapers for pets, and absorbent pads for pets), It has a hydrophilic continuous skeleton and continuous pores, The polymer absorbent is a hydrolyzate of a crosslinked polymer of a (meth)acrylic acid ester and divinylbenzene, which is a compound containing two or more vinyl groups in one molecule, and contains at least one -COONa group; a ratio of crosslinked polymer residues of the divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is 0.1 to 30 mol % based on all constitutional units, The (meth)acrylic acid ester contains a C4 alkyl ester of (meth)acrylic acid, A polymer absorbent characterized in that the amount of liquid transferred to the superabsorbent polymer 3 minutes after the polymer absorbent has come into contact with the superabsorbent polymer after absorbing liquid is 35.9 g / g or more.

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