Composite absorber and polymer absorbent

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). The polymer absorbent (4) has a dischargeable liquid amount of 20 g / g or more in a liquid component absorbed thereto, with the dischargeable liquid rate of 65% or more.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a composite absorber and a polymer absorbent.

Background Art

[0002] As an absorber used for absorbing liquids such as aqueous solutions, those containing a superabsorbent polymer (so-called "SAP") having a high absorption amount are known. Such absorbers containing a superabsorbent polymer are applied to various fields such as disposable paper diapers, civil engineering and building materials such as dew prevention sheets and simple soils, base materials for pharmaceuticals, and materials for absorbing leaked liquids, as disclosed in Patent Documents 1 to 4, for example.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such a superabsorbent polymer (SAP) can hold a large amount of liquid components (that is, has a high liquid retention ability), but has a slow absorption rate. Therefore, in conventional absorbers such as disposable paper diapers, it is used in combination with pulp so that liquid can be quickly absorbed and retained temporarily. In such a conventional absorber, the liquid component is quickly absorbed by the pulp in the absorber and temporarily retained in the pulp, and then transferred to the SAP having a high liquid retention ability and retained in the SAP. However, in such a conventional absorber, since the liquid retention capacity of the pulp is low, the amount of liquid temporarily retained in the pulp, that is, the amount of liquid transferred from the pulp to the SAP, is small, and there is a risk that the liquid retention capacity of the SAP and thus the absorption performance of the absorber cannot be fully exhibited.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide an absorber having high absorption performance.

Means for Solving the Problems

[0006] One aspect (Aspect 1) of the present invention is a composite absorber for absorbing a liquid, comprising: a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer; The polymer absorbent is a composite absorber 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.

[0007] In the composite absorber of this aspect, the polymer absorbent that can take in a liquid such as an aqueous solution into the continuous pores by capillary action has a high liquid discharge amount and a high liquid discharge rate (that is, it has a high liquid retention capacity and excellent liquid release property (liquid separation property)), so that a large amount of liquid can be retained at one time, and a large amount of the absorbed and retained liquid can be released. Thereby, since the composite absorber of this aspect can transfer a large amount of liquid from the polymer absorbent to the superabsorbent polymer (SAP), the liquid retention capacity of the SAP can be fully utilized, and high absorption performance can be exhibited as an absorber.

[0008] Further, in another aspect (Aspect 2) of the present invention, in the composite absorber of the above Aspect 1, the polymer absorbent is characterized in that the repeated liquid discharge rate after repeating liquid absorption and liquid separation three times is 65% or more.

[0009] Since the composite absorber of the present embodiment has a high repeated liquid discharge rate of the polymer absorbent, even when liquid is repeatedly supplied, it can hold a large amount of liquid and discharge it at a high liquid discharge rate. As a result, since the composite absorber of the present embodiment can transfer a large amount of liquid from the polymer absorbent to the SAP even when liquid is repeatedly supplied, the liquid retention ability of the SAP can be further utilized, and high absorption performance can be continuously exhibited over a long period of time.

[0010] In still another aspect (Aspect 3) of the present invention, in the composite absorber of the above Aspect 1 or 2, the amount of liquid transferred from the polymer absorbent to the superabsorbent polymer is 5.0 g / g or more.

[0011] Since the amount of liquid transferred from the polymer absorbent to the SAP in the composite absorber of the present embodiment is 5.0 g / g or more, the liquid temporarily held by the polymer absorbent can be more reliably transferred to the SAP. As a result, the composite absorber of the present embodiment can more reliably exhibit high absorption performance.

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

[0013] Since the polymer absorbent of the composite absorber of the present embodiment is a monolithic absorbent, it can quickly absorb liquid and more steadily transfer the temporarily held liquid to the SAP.

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

[0015] In the composite absorber of this aspect, since the polymer absorbent has the above specific configuration, when absorbing liquid, the hydrophilic continuous skeleton is likely to stretch, and the continuous pores are also likely to expand. Therefore, more liquid can be taken into the continuous pores more quickly, and the absorber can exhibit even higher absorption performance.

[0016] Still another aspect (Aspect 6) of the present invention is a polymer absorbent used together with a superabsorbent polymer, comprising a hydrophilic continuous skeleton and continuous pores, and being 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.

[0017] Since the polymer absorbent of this aspect has the above specific high liquid discharge amount and liquid discharge rate (that is, has a high liquid retention ability and excellent liquid release property (lyophilicity)), it can hold a large amount of liquid at one time and can release a large amount of the absorbed and held liquid. Therefore, when the polymer absorbent of this aspect is used in an absorber together with a superabsorbent polymer (SAP), a large amount of liquid can be transferred from the polymer absorbent to the SAP, and the liquid retention ability of the SAP can be fully utilized. Thus, the absorber can exhibit high absorption performance.

Advantages of the Invention

[0018] According to the present invention, an absorber with high absorption performance can be provided.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0020] Hereinafter, a preferred embodiment of the present invention will be described in detail using the composite absorber 1 which is one embodiment. In this specification, unless otherwise specified, "viewing an object (for example, a composite absorber, etc.) placed on a horizontal plane in a deployed state from the upper side in the vertical direction in the thickness direction of the object" is simply referred to as "plan view".

[0021] [Composite Absorber] Figure 1 is an exploded perspective view of the composite absorber 1 which is one embodiment of the present invention. The composite absorber 1 shown in Figure 1 has a substantially rectangular outer shape in plan view, and in the thickness direction, a first holding sheet 2 forming one surface of the composite absorber 1, a second holding sheet 3 forming the other surface of the composite absorber 1, and a liquid-absorbing member composed of a mixture of a polymer absorbent 4 and a superabsorbent polymer 5 (SAP) located between these sheets are provided as the basic configuration.

[0022] And the liquid-absorbing member in the composite absorber 1 is configured to be able to absorb and hold the liquid that has passed through the first holding sheet 2 by the polymer absorbent 4 having a hydrophilic continuous skeleton and continuous pores and the superabsorbent polymer 5 located between the first holding sheet 2 and the second holding sheet 3. Furthermore, the above-mentioned polymer absorbent 4 has a unique liquid discharge property 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.

[0023] The polymer absorbent 4 can take in a liquid such as an aqueous solution into the continuous pores by capillary action, and furthermore, by having the above-mentioned specific high liquid discharge amount and liquid discharge rate (that is, having a high liquid retention ability and excellent liquid release property (liquid separation property)), it can hold a large amount of liquid at once and can release a large amount of the absorbed and held liquid. Therefore, since the composite absorber 1 containing such a polymer absorbent 4 can transfer a large amount of liquid from the polymer absorbent 4 to the superabsorbent polymer 5 (SAP), the liquid retention ability of SAP can be fully utilized, and high absorption performance can be exhibited as an absorber.

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

[0025] Also, in the present invention, the configuration of the composite absorber is not limited to the form of the composite absorber 1 of the above-described embodiment, and the composite absorber may have a hydrophilic fiber sheet 6 positioned between the first holding sheet 2 and the liquid-absorbing member (that is, the polymer absorbent 4 and the superabsorbent polymer 5), for example, like the composite absorber 1' of another embodiment of the present invention shown in FIG. 2.

[0026] In the present invention, the outer shape, various dimensions, basis weight, etc. of the composite absorber are not particularly limited as long as the effects of the present invention are not impaired, and any outer shape (for example, circular shape, oval shape, polygonal shape, hourglass shape, design shape, etc.), various dimensions, basis weight, etc. corresponding to various uses and usage modes can be adopted.

[0027] Hereinafter, various components of the composite absorber of the present invention will be described in more detail using the composite absorber 1 of the embodiment shown in FIG. 1.

[0028] (Retention Sheet) In the composite absorber 1 shown in FIG. 1, the first retention sheet 2 forming one surface of the composite absorber 1 has a substantially rectangular outer shape similar to the outer shape of the composite absorber 1 in plan view. Such a first retention sheet 2 is formed of a liquid-permeable sheet-like member that can allow the liquid supplied to the composite absorber 1 to permeate and be absorbed and retained by the inner liquid-absorbing member.

[0029] The first retention sheet 2 has a slightly larger size overall than the liquid-absorbing member disposed inside (that is, compared to the area where the polymer absorbent 4 and the like are disposed), and is joined to the second retention sheet 3 located on the other side in the thickness direction of the composite absorber 1 at the peripheral edge by any adhesive or heat-sealing means or the like.

[0030] On the other hand, the second retention sheet 3 forming the other surface of the composite absorber 1 has a substantially rectangular outer shape similar to the outer shape of the composite absorber 1 in plan view. Such a second retention sheet 3 is formed of a liquid-impermeable sheet-like member that prevents the liquid not absorbed and retained by the inner liquid-absorbing member or the liquid exuded from the liquid-absorbing member from leaking to the outside of the composite absorber 1.

[0031] In the present invention, each sheet-like member that can be used as the first retention sheet and the second retention sheet is not limited to those of the above-described embodiment, and in the composite absorber of the present invention, at least one of the first retention sheet and the second retention sheet may be formed of a liquid-permeable sheet-like member. That is, in the composite absorber of the present invention, either one of the first retention sheet and the second retention sheet may be formed of a liquid-impermeable sheet-like member.

[0032] In addition, 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 inhibit the effects of the present invention, and any liquid-permeable sheet-like member corresponding to various applications, usage modes, etc. can be adopted. Examples of such liquid-permeable sheet-like members include non-woven fabrics such as hydrophilic air-through non-woven fabrics, spunbond non-woven fabrics, and point-bond non-woven fabrics, woven fabrics, knitted fabrics, porous resin films, and the like.

[0033] Furthermore, when using a hydrophilic non-woven fabric, woven fabric, knitted fabric, etc. (hereinafter collectively referred to as "fiber sheet") 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 constituent fibers of such fiber sheets is not particularly limited, and examples include hydrophilic fibers such as cellulose-based fibers and thermoplastic resin fibers subjected to 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 for the constituent fibers of the fiber sheet include natural cellulose fibers (such as plant fibers such as cotton), regenerated cellulose fibers, purified cellulose fibers, semi-synthetic cellulose fibers, and the like. Examples of thermoplastic resin fibers that can be used for the 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 of resins.

[0034] Also, when using a liquid-impermeable sheet-like member as the holding sheet, the liquid-impermeable sheet-like member is not particularly limited as long as it does not inhibit the effects of the present invention, and any liquid-impermeable sheet-like member corresponding to various applications, usage modes, etc. can be adopted. Examples of such liquid-impermeable sheet-like members include hydrophobic nonwoven fabrics formed by any hydrophobic thermoplastic resin fibers (e.g., polyolefin fibers such as PE and PP, polyester fibers such as PET, various composite fibers such as core-sheath type, etc.); porous or non-porous resin films formed by hydrophobic thermoplastic resins such as PE and PP; laminates obtained by laminating a nonwoven fabric to the resin film; laminated nonwovens such as SMS nonwovens, etc.

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

[0036] (Liquid-absorbing member) In the composite absorber 1 shown in FIG. 1, the liquid-absorbing member is configured to be able to absorb and hold the liquid that has passed through the first holding sheet 2 by the polymer absorbent 4 and the superabsorbent polymer 5 having a hydrophilic continuous skeleton and continuous pores located between the first holding sheet 2 and the second holding sheet 3 as described above.

[0037] In the composite absorber 1, the polymer absorbent 4 and the superabsorbent polymer 5 of the liquid-absorbing member are joined to each of the first holding sheet 2 and the second holding sheet 3 described above by an arbitrary adhesive such as a hot melt adhesive, but in the composite absorber of the present invention, the polymer absorbent may not be joined to the holding sheet.

[0038] And, as described above, the liquid-absorbing member contains, as essential constituent components, a polymer absorbent having a hydrophilic continuous skeleton and continuous pores and having the above-described specific liquid discharge property, and a superabsorbent polymer 5. Although the polymer absorbent will be described later, the superabsorbent polymer is a powdery or granular material composed of a superabsorbent polymer such as a sodium acrylate copolymer known in the art, and is referred to as SAP (Super Absorbent Polymer).

[0039] In the present invention, the liquid-absorbing member located between the first holding sheet and the second holding sheet may contain only the above-described polymer absorbent and superabsorbent polymer as the liquid-absorbing material, or may further contain a liquid-absorbing material known in the art in addition to these. Examples of such a liquid-absorbing material include hydrophilic fibers, and more specifically, pulp fibers (for example, ground pulp, etc.), cellulose-based fibers such as cotton, rayon, and acetate. For example, in the composite absorber 1 of the embodiment shown in FIG. 1, the liquid-absorbing member located between the first holding sheet 2 and the second holding sheet 3 contains, in addition to the polymer absorbent 4 having a hydrophilic continuous skeleton and continuous pores and having the above-described specific liquid-absorbing property, a superabsorbent polymer 5.

[0040] In the present invention, the outer shape (planar shape of the arrangement region), various dimensions, basis weight, etc. of the liquid-absorbing member are not particularly limited as long as the effects of the present invention are not impaired, and any outer shape, various dimensions, basis weight, etc. corresponding to various uses and usage modes can be adopted.

[0041] (Hydrophilic fiber sheet) Further, in the present invention, the composite absorber may have a hydrophilic fiber sheet 6 located between the first holding sheet 2 and the liquid-absorbing member (that is, the polymer absorbent 4 and the superabsorbent polymer 5), for example, like the composite absorber 1' of another embodiment shown in FIG. 2.

[0042] In the present invention, the hydrophilic fiber sheet that can be used for the composite absorber is not particularly limited as long as it does not inhibit the effects of the present invention, and any hydrophilic fiber sheet corresponding to various applications, usage modes, etc. can be adopted. Examples of such hydrophilic fiber sheets include non-woven fabrics, woven fabrics, knitted fabrics, etc. having hydrophilicity. Note that the hydrophilic fiber sheet may have a single-layer structure or a multi-layer structure of two or more layers.

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

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

[0045] Hereinafter, the high molecular absorbent used for the composite absorber of the present invention will be described in more detail.

[0046] [High molecular absorbent] The polymer absorbent is a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and is not particularly limited as long as it 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. For example, it is a hydrolyzate of a cross-linked polymer of two or more monomers containing at least (meth)acrylic acid ester, and examples of the polymer compound having at least one or more hydrophilic groups in the functional group can be given. More specifically, it is a hydrolyzate of a cross-linked polymer of (meth)acrylic acid ester and a compound containing two or more vinyl groups in one molecule, and examples of the polymer compound having at least -COONa group can be given. Such a polymer absorbent is an organic porous body having at least one or more -COONa groups in one molecule, and may further have -COOH groups. In the skeleton of the porous body, -COONa groups are distributed substantially uniformly.

[0047] When the polymer absorbent is a hydrolyzate of such (meth)acrylic acid ester and a cross-linked polymer of a compound containing two or more vinyl groups in one molecule, and contains at least one or more -COONa groups, as will be described later, the hydrophilic continuous skeleton is likely to expand when absorbing liquid, and the continuous pores are also likely to expand. Therefore, more liquid can be taken into the continuous pores more quickly, and higher absorption performance can be exhibited as an absorber.

[0048] In this specification, (meth)acrylic acid ester means acrylic acid ester or methacrylic acid ester.

[0049] In the polymer absorbent formed by the hydrolyzate of such (meth)acrylic acid ester and divinylbenzene, a hydrophilic continuous skeleton is formed by an organic polymer having at least -COONa group, and continuous pores (continuous pores) serving as a liquid absorption field for the liquid to be absorbed are provided between the skeletons. Since the hydrolysis treatment is to convert the -COOR group (that is, carboxylic acid ester group) of the cross-linked polymer into -COONa group or -COOH group (see Figure 3), the polymer absorbent may have -COOR group.

[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 spectrophotometry 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 this 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 the monolith A in the middle diagram to hydrolysis and drying treatments.

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

[0053] Note that the polymer absorbent is not limited to such absorbent A, and may be, for example, a hydrolyzate of a crosslinked polymer of (meth)acrylic acid ester and a compound having two or more vinyl groups in one molecule, or a hydrolyzate of a crosslinked polymer of two or more types of monomers including at least (meth)acrylic acid ester. However, when the polymer absorbent is a monolithic absorbent, it has the advantages that it can quickly absorb a liquid and can more steadily transfer the liquid temporarily held in the polymer absorbent to the SAP.

[0054] Note that in the following description, "monolith A" is an organic porous body composed of a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene before hydrolysis treatment, and may be referred to as a "monolithic organic porous body". Also, "absorbent A" is a hydrolyzate of a crosslinked polymer (monolith A) of (meth)acrylic acid ester and divinylbenzene after hydrolysis treatment and drying treatment. Note that in the following description, absorbent A refers to the 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. Absorbent A, which is an organic polymer having a hydrophilic continuous skeleton, is obtained by cross-linking and polymerizing a (meth)acrylate ester, which is a polymerization monomer, and divinylbenzene, which is a cross-linking monomer, as shown in Fig. 3, and further hydrolyzing the obtained cross-linked polymer (monolith A).

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

[0057] In absorbent A, the proportion of the cross-linking polymerization residue of divinylbenzene (constituent unit Y) in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0.1 to 30 mol% with respect to all constituent units, preferably 0.1 to 20 mol%. For example, in absorbent A using butyl methacrylate as the polymerization monomer and divinylbenzene as the cross-linking monomer, the proportion of the cross-linking polymerization residue of divinylbenzene (constituent unit Y) in the organic polymer forming the hydrophilic continuous skeleton is, for example, about 3% with respect to all constituent units, preferably 0.1 to 10 mol%, and more preferably 0.3 to 8 mol%. Note that when the proportion of the cross-linking polymerization residue 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 proportion of this cross-linking polymerization residue of divinylbenzene is 30 mol% or less, the liquid absorption amount of the liquid to be absorbed is less likely to decrease.

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

[0059] Examples of the constituent unit other than the constituent unit X and the constituent unit Y include polymerization 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, trimethylolpropane tri(meth)acrylate, and the like.

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

[0061] Also, it is preferable that the absorbent A has a thickness of the hydrophilic continuous skeleton of 0.1 to 100 μm. When the thickness of the hydrophilic continuous skeleton of the absorbent A is 0.1 μm or more, the space (pores) for taking in the liquid in the porous body is less likely to collapse during absorption, and the liquid absorption amount 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 rate is easily obtained.

[0062] Note that since the pore structure of the hydrophilic continuous skeleton of absorbent A is a continuous bubble structure, when measuring the thickness of the continuous skeleton, the cross-section of the skeleton appearing on the test piece for electron microscopy measurement is used as the location for thickness evaluation. Since the continuous skeleton is formed at intervals between the water droplets (water) removed by hydrolysis and subsequent dehydration and drying treatments, it is often polygonal in shape. Therefore, the thickness of the continuous skeleton is taken as the average value of the diameters (μm) of the circles circumscribing the polygonal cross-section. Also, although there are rare cases where small holes are open within the polygon, in such cases, the circumscribed circle of the cross-section of the polygon surrounding the small hole is measured.

[0063] Furthermore, for absorbent A, it is preferable that the average diameter of the continuous pores is 1 to 1000 μm. When the average diameter of the continuous pores of absorbent A is 1 μm or more, the space (pores) for taking in liquid in the porous body is less likely to collapse during absorption, and the absorption rate is less likely to decrease. On the other hand, when the average diameter of the continuous pores is 1000 μm or less, it is easier to obtain an excellent absorption rate.

[0064] Note that the average diameter (μm) of the continuous pores of absorbent A can be measured by the mercury intrusion method, and the maximum value of the pore size distribution curve obtained by such a mercury intrusion method is adopted. For the sample used to measure the average diameter of the continuous pores, regardless of the ionic form of absorbent A, a sample dried in a vacuum dryer set at a temperature of 50°C for 18 hours or more is used as the sample. Note that the final pressure reached is 0 Torr.

[0065] Here, Figure 4 is an SEM photograph of absorbent A at a magnification of 50 times, Figure 5 is an SEM photograph of absorbent A at a magnification of 100 times, Figure 6 is an SEM photograph of absorbent A at a magnification of 500 times, Figure 7 is an SEM photograph of absorbent A at a magnification of 1000 times, and furthermore, Figure 8 is an SEM photograph of absorbent A at a magnification of 1500 times. Absorbent A shown in these Figures 4 to 8 is an example of an absorbent using butyl methacrylate as the polymerization monomer and divinylbenzene as the cross-linking monomer, and each has a structure of a 2 mm square cube.

[0066] The absorbent A shown in FIGS. 4 to 8 has a large number of bubble-shaped macropores, and further has portions where these bubble-shaped macropores overlap. The absorbent A has a continuous bubble structure in which the overlapping portions of these macropores form a common opening (mesopore), that is, it is a continuous bubble structure (continuous macropore structure).

[0067] The overlapping portions of these macropores form a common opening (mesopore) with an average diameter in the dry state of 1 to 1000 μm, preferably 10 to 200 μm, particularly preferably 20 to 100 μm, and most of them have an open pore structure. When the average diameter of the mesopores in the dry state is 1 μm or more, the absorption rate of the liquid to be absorbed becomes better. On the other hand, when the average diameter of the mesopores in the dry state is 1000 μm or less, the absorbent A is less likely to become brittle. In addition, such an overlap of macropores is about 1 to 12 per macropore, and many are about 3 to 10.

[0068] Moreover, since the absorbent A has such a continuous bubble structure, macropore groups and mesopore groups can be formed uniformly, and there is an advantage that the pore volume and specific surface area can be significantly increased compared to particle-aggregated porous bodies described in, for example, Japanese Patent Laid-Open No. 8-252579.

[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 space (voids) for taking in the liquid in the porous body is less likely to collapse during absorption, and the liquid absorption amount and 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] In addition, the total pore volume can be measured by the mercury intrusion method. As the sample for measuring the total pore volume, regardless of the ionic form of the absorbent A, a sample dried in a vacuum dryer set at a temperature of 50°C for 18 hours or more is used. The final pressure reached is set to 0 Torr.

[0071] Next, the state when the absorbent A comes into contact with a liquid will be described. The same applies when a liquid comes into contact with a liquid-absorbing member or a composite absorber containing the absorbent A.

[0072] First, the continuous pores provided in the absorbent A shown in FIGS. 4 to 8 are pores in which a plurality of pores (voids) communicate with each other, and it can be visually confirmed with the naked eye that a large number of pores are provided even from the appearance. When a liquid comes into contact with the absorbent A having such a large number of pores, due to capillary action, a certain amount of the liquid enters into these numerous pores and is absorbed by the absorbent A. At this time, a part of the liquid absorbed by the absorbent A is absorbed into the hydrophilic continuous skeleton by osmotic pressure, and the continuous skeleton elongates. On the other hand, the liquid that has not been absorbed into the hydrophilic continuous skeleton among the liquid absorbed by the absorbent A is absorbed while being retained in the pores.

[0073] In this way, the absorbent A has the property that the hydrophilic continuous skeleton elongates when absorbing a liquid. The elongation of this continuous skeleton occurs almost omnidirectionally. Furthermore, as the outer shape of the absorbent A increases due to the elongation of such a continuous skeleton, the size of each pore also increases. When the size of the pores increases in this way, the volume inside the pores increases, so the amount of liquid that can be retained in the pores also increases. That is, the absorbent A that has become larger by absorbing a certain amount of liquid can absorb a further predetermined amount of liquid into the enlarged pores by capillary action. Furthermore, since the absorbent A absorbs a liquid by capillary action, the liquid can be absorbed quickly.

[0074] In addition, more liquid remains in the pores than the liquid absorbed by the absorbent A within the hydrophilic continuous skeleton. Since most of the liquid absorption by the absorbent A is achieved by retaining the liquid in the pores through capillary action, the larger the porosity (the volume of the pore voids relative to the volume of the absorbent A), which is the ratio of the volume of the pore voids (total pore volume) to the volume of the pores, the more liquid can be absorbed. Note that this porosity is preferably 85% or more.

[0075] For example, when determining the porosity of the absorbent A shown in FIGS. 4 to 8 described above, the following results are obtained. First, the specific surface area of the absorbent A obtained by the mercury intrusion method 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 the absorbent A is 15.5 mL. Here, assuming that the specific gravity of the absorbent A is 1 g / mL, the volume occupied by the pores in 1 g of the absorbent A, that is, the pore volume, is 15.5 mL, and the volume of 1 g of the absorbent A is 1 mL. Then, the total volume (volume) of 1 g of the absorbent A is 15.5 + 1 (mL). Since the ratio of the pore volume among them is the porosity, the porosity of the 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 unique liquid discharge property 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.

[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 discharge amount and liquid discharge rate, it can hold a large amount of liquid at once and can discharge a large amount of the absorbed and held liquid. Therefore, since the composite absorber of the present invention containing such a polymer absorbent can transfer a large amount of liquid from the polymer absorbent to the SAP, the liquid retention ability of the SAP can be fully utilized, and high absorption performance can be exhibited as an absorber. In addition, 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.

[0078] <Measurement Method for Liquid Discharge Amount and Liquid Discharge Rate of Polymer Absorbent> (1) Enclose 1 g of the sample for measurement (polymer absorbent) in a mesh bag cut into a 10 cm square ((manufactured by NBC Mesh Tech Co., Ltd., N-NO255HD 115 (standard width: 115 cm, 255 meshes / 2.54 cm, opening: 57 μm, wire diameter: 43 μm, thickness: 75 μm))). Note that the mass (g) of the mesh bag is measured in advance. In addition, this measurement method is performed under the conditions of a temperature of 25°C and a humidity of 60%. Furthermore, when the sample for measurement (polymer absorbent) is recovered from the product of the composite absorber and used, it can be obtained according to the <Method for Recovering Sample (Polymer Absorbent) for Measurement> described later. (2) Immerse the mesh bag containing the sample in a 0.9% sodium chloride aqueous solution for 1 hour. (3) Measure the mass (g) after hanging the mesh bag for 5 minutes to drain the water. (4) Calculate the liquid absorption amount (g) of the sample 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 further divide this liquid absorption amount by the mass of the sample (= 1 g) to obtain the liquid absorption amount per unit mass (g / g) of the sample (polymer absorbent). (5) Further, perform a centrifugal treatment on the mesh bag drained in (3) above at 150G for 90 seconds, and measure the mass (g) of the mesh bag after the centrifugal treatment. (6) Subtract the total mass of the sample (= 1 g) and the mesh bag from the mass of the mesh bag after the centrifugal treatment measured in (5) above.Subtract the mass (g) of the fiber from the liquid absorption amount (g) of the sample calculated in the above (4). Calculate the liquid discharge amount (g) of the sample, and further divide this liquid discharge amount by the mass of the sample (= 1 g) to obtain the liquid discharge amount per unit mass (g / g) of the sample (polymer absorbent). (7) Divide the liquid discharge amount per unit mass obtained in (6) above by the liquid absorption amount per unit mass obtained in (4) above and multiply by 100 to obtain the liquid discharge amount with respect to the liquid absorption amount of the sample (polymer absorbent), that is, the liquid discharge rate (%). Note that the repeated liquid discharge rate after repeating the liquid absorption and liquid separation described later three times means the liquid discharge rate (%) after repeating the steps (2) to (6) above three times.

[0079] Note that when the above-mentioned sample for measurement (polymer absorbent) is recovered from the product of the composite absorbent, it can be obtained as follows.

[0080] <Method for recovering the sample for measurement (polymer absorbent)> (1) Peel off the holding sheet etc. from the product of the composite absorbent to expose the liquid-absorbing member. (2) Drop all the liquid-absorbing materials including the measurement object (polymer absorbent) from the exposed liquid-absorbing member, and remove the liquid-absorbing materials other than the measurement object (in particulate form) (for example, pulp, synthetic resin fibers, etc.) using tweezers or the like. (3) Using a microscope or a simple magnifying glass as the means for magnified observation, observe at a magnification that can recognize the difference from SAP or a magnification that can visually recognize the pores of the porous body, and recover the measurement object using tweezers or the like. The magnification of the simple magnifying glass is not particularly limited as long as it is a magnification that can visually recognize the pores of the porous body, and for example, a magnification of 25 to 50 times can be mentioned. (4) Use the measurement object recovered in this way as the sample for measurement in various measurement methods.

[0081] Here, a polymer absorbent as an example of the present invention, pulp fibers (fluff pulp) as a comparative example, Infinity particles also as a comparative example, and a superabsorbent polymer (SAP) also as a comparative example were prepared, and the liquid discharge amount and liquid discharge rate after repeating liquid absorption and liquid separation 1 to 3 times were measured respectively. The measurement results of this liquid discharge amount and liquid discharge rate are shown in Table 1 below. The above-mentioned Infinity particles are an absorbent manufactured by Procter & Gamble. Although it has a structure (foam structure) similar to that of the polymer absorbent, unlike the polymer absorbent, it does not have the function of absorbing liquid and swelling.

[0082]

Table 1

[0083] As shown in Table 1, although the pulp fibers and Infinity particles show a high liquid discharge rate, the liquid discharge amount is small because the liquid absorption amount itself is small. In particular, the pulp fibers show a tendency that both the liquid discharge amount and the liquid discharge rate decrease as the number of repetitions of liquid absorption and liquid separation (「liquid absorption / liquid separation times」 in Table 1) increases. Also, since SAP has a large liquid absorption amount, although it shows a liquid discharge amount above a certain level, its liquid discharge rate is small due to its liquid retention ability. For these liquid-absorbing materials, the polymer absorbent shows a high liquid discharge amount and liquid discharge rate (that is, it shows a high liquid retention ability and excellent liquid release property (liquid separation property)), can hold a large amount of liquid at one time, and it can be seen that a large amount of the absorbed and retained liquid can be released. Furthermore, the polymer absorbent shows a stable high liquid discharge amount and liquid discharge rate regardless of whether the number of repetitions of liquid absorption and liquid separation is 1 to 3 times. Even in the case where liquid is repeatedly supplied, it can be seen that a large amount of liquid can be held and released at a high liquid discharge rate. That is, it can be seen that the polymer absorbent has an excellent liquid discharge property unique to it and not found in conventional pulp fibers, Infinity particles, SAP, etc.

[0084] In the present invention, it is preferable that the polymer absorbent has a repeated liquid discharge rate of 65% or more after repeating liquid absorption and liquid separation three times. When the polymer absorbent has such a high repeated liquid discharge rate, even when liquid is repeatedly supplied, a large amount of liquid can be retained and discharged at a high liquid discharge rate. Thus, a composite absorbent containing such a polymer absorbent can transfer a large amount of liquid from the polymer absorbent to the SAP even when liquid is repeatedly supplied. Therefore, the liquid retention capacity of the SAP can be further utilized, and high absorption performance can be continuously exhibited over a long period of time. In addition, it is more preferable that the repeated liquid discharge rate of the polymer absorbent after repeating liquid absorption and liquid separation three times is 70% or more, and particularly preferably 75% or more.

[0085] Furthermore, in the present invention, it is preferable that the amount of liquid transferred from the polymer absorbent to the SAP in the composite absorbent is 5.0 g / g or more. When the amount of liquid transferred from the polymer absorbent to the SAP is 5.0 g / g or more, the liquid temporarily retained by the polymer absorbent can be more reliably transferred to the SAP. Therefore, as an absorbent, high absorption performance can be more reliably exhibited. In addition, the amount of liquid transferred from the polymer absorbent to the SAP is more preferably 23.0 g / g or more, further preferably 27.0 g / g or more, and particularly preferably 33.0 g / g or more. The amount of liquid transferred from this polymer absorbent to the SAP can be measured as follows.

[0086] <Method for Measuring the Amount of Liquid Transferred from Polymer Absorbent to SAP> (1) Place 0.3 g of the sample for measurement (polymer absorbent) into a plastic cylinder (inner diameter: 60 mm, outer diameter: 70 mm, height: 52 mm, mass: 64 g) with a nylon mesh material (manufactured by NBC Mesh Tech Co., Ltd., N-NO255HD 115 (standard width: 115 cm, 255 meshes / 2.54 cm, opening: 57 μm, wire diameter: 43 μm, thickness: 75 μm)) attached to the bottom surface, and level it evenly. Then measure the mass (g) of the cylinder. This measurement method is carried out under the conditions of a temperature of 25°C and a humidity of 60%. When the sample for measurement (polymer absorbent) is recovered from the product of the composite absorber and used, it can be obtained according to the aforementioned <Method for Recovering the Sample for Measurement (Polymer Absorbent)>. (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). After evenly sprinkling 0.3 g of superabsorbent polymer (SAP) into the cylinder, remove the cylinder and measure the mass (g) of the petri dish. (3) Pour 60 mL of 0.9% sodium chloride aqueous solution into a petri dish with a pedestal (inner diameter: 85 mm, depth: 20 mm, pedestal arrangement: two pedestals are arranged in parallel at a 24 mm interval at the center of the bottom surface (inner side), pedestal width: 2 mm, pedestal height: 2 mm, pedestal length: 25 mm). (4) Place the cylinder containing the sample for measurement (polymer absorbent) on the pedestal at the center of the petri dish with a pedestal, immerse the bottom surface of the cylinder in the above sodium chloride aqueous solution, and allow the sodium chloride aqueous solution to absorb into the sample in the cylinder for 3 minutes. (5) After 3 minutes of liquid absorption, lift the cylinder, tilt the cylinder at 45° for 1 minute to drain the liquid, and then measure the mass (g) of the cylinder. (6) Calculate the liquid absorption amount (g) of the sample by subtracting the mass (g) of the cylinder after liquid absorption measured in (5) above from the mass (g) of the cylinder before liquid absorption measured in (1) above. Further, divide this liquid absorption amount by the mass of the sample (=0.3 g) to obtain the liquid absorption amount per unit mass of the sample (g / g). (7) Then, place the cylinder drained in (5) above on the petri dish containing SAP, and bring the sample in the cylinder into contact with the SAP in the petri dish through the bottom surface (mesh material) of the cylinder. (8) After contacting the sample with SAP, remove the cylinder 3 minutes later and measure the mass (g) of the petri dish. (9) Subtract the mass (g) of the petri dish measured in (8) above from the mass (g) of the petri dish measured in (2) above to calculate the liquid absorption amount (g) of SAP. Further, divide this liquid absorption amount by the mass of the sample (= 0.3 g) to obtain the liquid absorption amount of SAP per unit mass of the sample (g / g), that is, the liquid transfer amount to SAP per unit mass of the sample (g / g).

[0087] Hereinafter, such a method for producing a polymer absorbent will be described in detail using the above absorbent A as an example.

[0088] [Method for Producing Polymer Absorbent] As shown in FIG. 3, the above absorbent A can be obtained through a crosslinking polymerization step and a hydrolysis step. Hereinafter, each of these steps will be described.

[0089] (Crosslinking Polymerization Step) First, mix an oil-soluble monomer for crosslinking polymerization, a crosslinkable monomer, a surfactant, water, and a polymerization initiator as required to obtain a water-in-oil emulsion. This water-in-oil emulsion is an emulsion in which the oil phase is the continuous phase and water droplets are dispersed therein.

[0090] And in the above absorbent A, as shown in the upper figure of FIG. 3, butyl methacrylate, which is a (meth)acrylate ester, is used as the oil-soluble monomer, divinylbenzene is used as the crosslinkable monomer, sorbitan monooleate is used as the surfactant, and isobutyronitrile is used as the polymerization initiator for crosslinking polymerization to obtain monolith A.

[0091] Specifically, in the case of absorbent A, as shown in the upper figure of Fig. 3, first, 9.2 g of t-butyl methacrylate as an oil-soluble monomer, 0.28 g of divinylbenzene as a crosslinkable 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 uniformly dissolved. 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 vacuum stirring and degassing mixer (manufactured by EMI Co., Ltd.) which is a planetary stirring device to obtain a water-in-oil emulsion.

[0092] Furthermore, this emulsion is quickly transferred to a reaction vessel and sealed, and polymerized under static conditions at 60 °C for 24 hours. After the polymerization is completed, the content is taken out, extracted with methanol, and then dried under reduced pressure to obtain monolith A having a continuous macroporous structure. As a result of observing the internal structure of monolith A by SEM, monolith A has a continuous bubble structure, and the thickness of the continuous skeleton is 5.4 μm. Also, 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.

[0093] Note that the content of divinylbenzene with respect to all monomers is preferably 0.3 to 10 mol%, more preferably 0.3 to 5 mol%. Also, 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%.

[0094] The addition amount of the surfactant can be set according to the type of the oil-soluble monomer and the size of the desired emulsion particles (macropores), and is preferably in the range of about 2 to 70% with respect to the total amount of the oil-soluble monomer and the surfactant.

[0095] In addition, in order to control the bubble shape, size, etc. of the 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 may coexist in the polymerization system.

[0096] Moreover, the mixing method for forming the water-in-oil emulsion is not particularly limited. For example, a method of mixing all components at once, a method of separately and uniformly dissolving the oil-soluble components, which are an oil-soluble monomer, a surfactant, and an oil-soluble polymerization initiator, and the water-soluble components, which are water and a water-soluble polymerization initiator, and then mixing the respective components, and any other mixing method can be adopted.

[0097] Furthermore, the mixing device for forming the emulsion is not particularly limited, and any device such as a normal mixer, a homogenizer, or a high-pressure homogenizer can be adopted according to the desired emulsion particle size. Moreover, a so-called planetary stirring device, in which the object to be treated is placed in a mixing container and the object to be treated is stirred and mixed by rotating it around the rotation axis while revolving around the rotation axis with the mixing container tilted, can also be used.

[0098] Also, the mixing conditions are not particularly limited, and the stirring rotation speed, stirring time, etc. can be arbitrarily set according to the desired emulsion particle size. In the above-mentioned planetary stirring device, water droplets in the W / O emulsion can be uniformly generated, and their average diameter can be arbitrarily set within a wide range.

[0099] The polymerization conditions of the water-in-oil droplet emulsion can adopt various conditions according to the types of monomers and initiators, etc. For example, when using azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, etc. as the polymerization initiator, it can be heated and polymerized at a temperature of 30 to 100 °C for 1 to 48 hours in a sealed container under an inert atmosphere. When using hydrogen peroxide-ferrous chloride, sodium persulfate-sodium acid sulfite, etc. as the polymerization initiator, it can be polymerized at a temperature of 0 to 30 °C for 1 to 48 hours in a sealed container under an inert atmosphere.

[0100] After the polymerization is completed, the content is taken out and Soxhlet extraction is performed with a solvent such as isopropanol to remove unreacted monomers and residual surfactants, and the monolith A shown in the middle figure of Figure 3 can be obtained.

[0101] (Hydrolysis step) Subsequently, the step of hydrolyzing the monolith A (crosslinked polymer) to obtain the absorbent A (hydrolysis step) will be described.

[0102] First, the monolith A is immersed in dichloroethane added with zinc bromide and stirred at 40 °C for 24 hours, and then contacted with methanol, 4% hydrochloric acid, 4% sodium hydroxide aqueous solution and water in this order for hydrolysis, and then dried to obtain a block-shaped absorbent A. Further, this block-shaped absorbent A is crushed into 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 shape during or after drying.

[0103] Also, the method for hydrolyzing the monolith A is not particularly limited, and various methods can be adopted. For example, using an aromatic solvent such as toluene or xylene, a halogenated solvent such as chloroform or dichloroethane, an ether solvent such as tetrahydrofuran or isopropyl ether, an amide solvent such as dimethylformamide or dimethylacetamide, an alcohol solvent such as methanol or ethanol, a carboxylic acid solvent such as acetic acid or propionic acid, or water as the solvent, contacting with a strong base such as sodium hydroxide, or contacting with a Bronsted acid such as a hydrohalic acid like hydrochloric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, or a Lewis acid such as zinc bromide, aluminum chloride, aluminum bromide, titanium(IV) chloride, cerium chloride / sodium iodide, magnesium iodide, etc.

[0104] Among the polymerization raw materials of the organic polymer that forms the hydrophilic continuous skeleton of the absorbent A, the (meth)acrylate ester is not particularly limited, but an alkyl ester of C1 - C10 (i.e., having 1 to 10 carbon atoms) of (meth)acrylic acid is preferred, and an alkyl ester of C4 (i.e., having 4 carbon atoms) of (meth)acrylic acid is particularly preferred. Examples of the C4 alkyl ester of (meth)acrylic acid include t-butyl (meth)acrylate, n-butyl (meth)acrylate, and iso-butyl (meth)acrylate.

[0105] Also, the monomer used for crosslinking polymerization may be only (meth)acrylate ester and divinylbenzene, or may contain other monomers in addition to (meth)acrylate ester and divinylbenzene. In the latter case, other monomers are not particularly limited, and 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, trimethylolpropane tri(meth)acrylate, and the like. The proportion of monomers other than (meth)acrylate esters and divinylbenzene in all the monomers used for crosslinking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

[0106] Also, the surfactant is not limited to the above-mentioned sorbitan monooleate, and any surfactant may be used as long as it can form a water-in-oil (W / O) emulsion when the monomers for crosslinking polymerization and water are mixed. 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 sodium dioctyl sulfosuccinate; cationic surfactants such as distearyldimethylammonium chloride; and amphoteric surfactants such as lauryldimethylbetaine. These surfactants may be used alone or in combination of two or more.

[0107] In addition, as the polymerization initiator, a compound that generates radicals by heat and light irradiation is preferably used. Furthermore, the polymerization initiator may be water-soluble or oil-soluble. 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-sodium acid sulfite, tetramethylthiuram disulfide, and the like. However, in some cases, there are systems in which polymerization proceeds only by heating or only by light irradiation without adding a polymerization initiator. In such systems, the addition of a polymerization initiator is unnecessary.

[0108] The composite absorber of the present invention is not particularly limited, and can be applied to composite absorbers in various fields such as dew condensation prevention sheets, civil engineering and building materials such as simple soils, base materials for pharmaceuticals, and materials for absorbing leaked liquids. Therefore, the liquid to be absorbed by the composite absorber is not particularly limited, and examples thereof include water and aqueous solutions (e.g., seawater), acids (e.g., hydrochloric acid), bases (e.g., sodium hydroxide), and 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)). These liquids may be a mixture of two or more liquids.

[0109] In addition, the present invention is not limited to the above-described embodiments and the like, and appropriate combinations, substitutions, changes, etc. are possible without departing from the object and gist of the present invention. In this specification, ordinal numbers such as "first" and "second" are for distinguishing the matters to which the ordinal numbers are attached, and do not mean the order, priority, importance, etc. of each matter.

Explanation of Reference Numerals

[0110] 1 Composite absorber 2 First holding sheet 3 Second holding sheet 4 Polymer absorbent 5 Superabsorbent polymer (SAP) 6 Hydrophilic fiber sheet

Claims

A composite absorber for absorbing liquid, for use in civil engineering materials, building materials, or materials for absorbing leaked liquid composed of organic solvents (excluding the cases where the application is for disposable pants-type diapers, tape-type disposable diapers, sanitary napkins, absorbent pads, disposable diapers for pets, or absorbent pads for pets). It contains a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer. The polymer absorbent is a hydrolyzate of a cross-linked polymer of (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. The proportion of the cross-linked polymerization residue of divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is 0.1 to 30 mol% based on all constituent units. The (meth)acrylic acid ester contains a C4 alkyl ester of (meth)acrylic acid. The polymer absorbent is characterized in that the liquid discharge amount of the absorbed liquid component is 39 g / g or more, and the liquid discharge rate is 75% or more, which is a composite absorber.

2. The polymer absorbent is characterized in that the repeated liquid discharge rate after repeating liquid absorption and liquid separation three times is 75% or more, which is the composite absorber according to claim 1.

3. The composite absorber according to claim 1 or 2, characterized in that the liquid transfer amount from the polymer absorbent to the superabsorbent polymer is 5.0 g / g or more.

4. The polymer absorbent is a monolithic absorbent, which is the composite absorber according to any one of claims 1 to 3. A polymer absorbent used together with a superabsorbent polymer, for use in civil engineering materials, building materials, or materials for absorbing leaked liquid composed of organic solvents (excluding the cases where the application is for disposable pants-type diapers, tape-type disposable diapers, sanitary napkins, absorbent pads, disposable diapers for pets, or absorbent pads for pets). It has a hydrophilic continuous skeleton and continuous pores. It is a hydrolyzate of a cross-linked polymer of (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. The proportion of the cross-linked polymerization residue of divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is 0.1 to 30 mol% based on all constituent units. The (meth)acrylic acid ester contains a C4 alkyl ester of (meth)acrylic acid, A superabsorbent polymer characterized in that the liquid discharge amount of the absorbed liquid component is 39 g / g or more and the liquid discharge rate is 75% or more.

Images