Composite absorber and hygiene product

Abstract

To provide an absorber capable of stably showing absorption performance.SOLUTION: A composite absorber (4) which is a composite absorber (4) for absorbing body fluid, includes a polymer absorbent having hydrophilic continuous skeleton and continuous pores, and a highly absorbent polymer. The polymer absorbent contains at least -COOH group and -COONa group as an ion exchange group, and the total ion exchange capacity of -COOH group and -COONa group per mass in the dry state is 4.0 mg equivalent / g or more.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a composite absorber and a sanitary product having the same.

Background Art

[0002] In sanitary products such as disposable diapers and sanitary napkins, those using a superabsorbent polymer (so-called "SAP") having a high absorption amount are known. For example, Patent Document 1 discloses an absorbent article using an absorber formed by combining absorbent resin particles (superabsorbent polymer) having excellent absorption amount and hydrophilic fibers such as pulp fibers having excellent absorption speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such a superabsorbent polymer (SAP) can retain a large amount of moisture (that is, has a high water retention capacity), but has a slow water absorption speed. Therefore, in conventional absorbers, it is used in combination with pulp so that water can be quickly retained temporarily. In such a conventional absorber, when body fluids such as urine are discharged from the wearer of the sanitary product, the body fluids are quickly absorbed by the pulp in the absorber and temporarily retained in the pulp, and then transferred to the SAP having a high water retention capacity and retained in the SAP. On the other hand, body fluids such as urine to be absorbed by the absorber vary greatly in salt concentration in the body fluid due to differences in diet (for example, components of ingested food and drink) and living environment (for example, frequency of sweating and urination), and particularly divalent ions in the body fluid (for example, Ca 2+ 、Mg 2+Even in trace amounts, they will have a significant adverse effect on the absorption performance of SAP (particularly, water absorption capacity, water retention capacity, and absorption rate). However, conventional absorbents do not have the function of modifying the salt concentration in body fluids such as urine. Therefore, the body fluid temporarily retained in the pulp is directly transferred to SAP as it is, and the absorption performance of SAP varies due to the influence of the salt concentration in the body fluid (particularly, divalent ion concentration). As a result, there is a risk that the absorption performance of the absorbent cannot be stably exhibited.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide an absorbent that can stably exhibit absorption performance.

Means for Solving the Problems

[0006] One aspect (Aspect 1) of the present invention is a composite absorbent for absorbing body fluids, wherein the composite absorbent includes a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer, the polymer absorbent contains at least -COOH groups and -COONa groups as ion exchange groups, and the total ion exchange capacity of the -COOH groups and -COONa groups per unit mass in the dry state is 4.0 meq / g or more. The composite absorbent is characterized by this.

[0007] In the composite absorbent of this aspect, since the polymer absorbent has a hydrophilic continuous skeleton and continuous pores, it can quickly absorb body fluids such as urine and temporarily retain them. Furthermore, by containing a certain amount or more of -COOH groups and -COONa groups, which are ion exchange groups, when the polymer absorbent absorbs and temporarily retains body fluids, ions in the body fluid (particularly divalent ions such as Ca 2+ 、Mg 2+ etc.) can be ion-exchanged by -COOH groups and -COONa groups, and the body fluid can be modified into a body fluid that hardly affects the absorption performance of the superabsorbent polymer (SAP) (particularly, water absorption capacity, water retention capacity, and absorption rate). As a result, in the composite absorber of this aspect, since the body fluid is transferred to the SAP after being modified by the polymer absorbent, variations in the absorption performance of the SAP are less likely to occur, and the absorption performance as an absorber can be stably exhibited.

[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 ion exchange rate of polyvalent ions is 50% or more.

[0009] In the composite absorber of this aspect, the ion exchange rate of polyvalent ions (ions with a valence of 2 or more) of the polymer absorbent is 50% or more, and since the body fluid can be more reliably modified, variations in the absorption performance of the SAP can be made less likely to occur, and the absorption performance as an absorber can be more stably exhibited.

[0010] In still another aspect (Aspect 3) of the present invention, in the composite absorber of the above Aspect 1 or 2, the polymer absorbent is characterized in that the water absorption per unit mass is 30 g / g or more.

[0011] In the composite absorber of this aspect, the polymer absorbent has a water absorption of a certain level or more, and since it can absorb more body fluid and gradually modify it, variations in the absorption performance of the SAP can be made less likely to occur, and the absorption performance as an absorber can be more stably exhibited.

[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 characterized in that the porosity per unit volume of the polymer absorbent is 85% or more.

[0013] In the composite absorber of this aspect, the polymer absorbent has a porosity of a certain level or more, and since it can absorb more body fluid and gradually modify it, variations in the absorption performance of the SAP can be made less likely to occur, and the absorption performance as an absorber can be more stably and favorably exhibited.

[0014] In yet another aspect (Aspect 5) of the present invention, in the composite absorber according to any one of the above Aspects 1 to 4, the polymer absorbent is characterized in that the average diameter of the continuous pores is 1 μm to 1000 μm.

[0015] In the composite absorber of this aspect, since the average diameter of the continuous pores of the polymer absorbent is within the above specific range, the space (pores) for the polymer absorbent to take in body fluid is less likely to collapse, and it can have a higher absorption rate, and excellent absorption performance can be stably exhibited. In particular, when the porosity per unit volume of the polymer absorbent is 85% or more and the average diameter of the continuous pores is 1 μm to 1000 μm, more pores can absorb and modify body fluid, so there is an advantage that more excellent ion exchange efficiency can be realized.

[0016] In yet another aspect (Aspect 6) of the present invention, in the composite absorber according to any one of the above Aspects 1 to 5, the polymer absorbent is characterized in that it is a monolithic absorbent.

[0017] In the composite absorber of this aspect, since the polymer absorbent is a monolithic absorbent, it can quickly absorb body fluid and more steadily transfer the temporarily held liquid to the SAP, so more excellent absorption performance can be stably exhibited.

[0018] In yet another aspect (Aspect 7) of the present invention, in the composite absorber according to any one of the above Aspects 1 to 6, the polymer absorbent is characterized in that 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.

[0019] In the composite absorber of this aspect, since the polymer absorbent has the above specific configuration, when absorbing body fluid, the hydrophilic continuous skeleton is likely to elongate and the continuous pores are also likely to expand, so more body fluid can be taken into the continuous pores more quickly, and higher absorption performance can be exhibited as an absorber. At the same time, more body fluid can be steadily modified, and the variation in the absorption performance of the SAP can be further reduced.

[0020] In still another aspect (Aspect 8) of the present invention, in the composite absorber according to any one of Aspects 1 to 7 above, the superabsorbent polymer is an acrylic acid-based superabsorbent polymer having cations on its surface.

[0021] An acrylic acid-based superabsorbent polymer (SAP) having cations on its surface is particularly susceptible to adverse effects on the absorption performance (especially, the amount of water absorbed, the amount of water retained, and the absorption rate) by ions in body fluids. However, even when the composite absorber of this aspect contains such SAP, when the polymer absorbent absorbs and temporarily retains body fluids, the ions in the body fluids can be ion-exchanged by -COOH groups and -COONa groups to modify the body fluids. Therefore, variations in the absorption performance of SAP are less likely to occur, and the absorption performance as an absorber can be stably exhibited.

[0022] Still another aspect (Aspect 9) of the present invention is a sanitary product characterized by having the composite absorber according to any one of Aspects 1 to 8 above.

[0023] Since the sanitary product of this aspect has the composite absorber according to any one of Aspects 1 to 8 above, it can exhibit high absorption performance as a sanitary product (for example, absorption performance such as being less likely to cause rewetting and having a high absorption rate).

Effects of the Invention

[0024] The present invention can provide an absorber that can stably exhibit absorption performance.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Hereinafter, a preferred embodiment of the composite absorber of the present invention will be described in detail using a light incontinence pad 1, which is an example of a sanitary product to which the composite absorber is applied. In this specification, unless otherwise specified, "looking at an object (e.g., a light incontinence pad, a composite absorber, etc.) placed on a horizontal plane in a deployed state from the upper side in the vertical direction (the surface sheet side in the case of a sanitary product) in the thickness direction of the object" is simply referred to as "plan view".

[0027] In this specification, the "longitudinal direction" refers to "the longer direction of the length of a vertically long object (e.g., a light incontinence pad, a composite absorber, etc.) in plan view", the "width direction" refers to "the shorter direction of the length of a vertically long object in plan view", and the "thickness direction" refers to "the direction perpendicular to an object placed on a horizontal plane in a deployed state". These longitudinal direction, width direction, and thickness direction are in orthogonal relationships with each other.

[0028] In addition, in this specification, unless otherwise specified, in the thickness direction of the light incontinence pad 1, "the relatively proximal side with respect to the wearer's skin surface when the light incontinence pad 1 is worn" is referred to as the "skin-facing surface side", and "the relatively distal side with respect to the wearer's skin surface when the light incontinence pad 1 is worn" is referred to as the "non-skin-facing surface side".

[0029] [Light incontinence pad] FIG. 1 is a schematic plan view of the light incontinence pad 1 in a deployed state to which the composite absorber 4 according to an embodiment of the present invention is applied. As shown in FIG. 1, the light incontinence pad 1 has a longitudinal outer shape that, in plan view, has a longitudinal direction L and a width direction W, and in which two longitudinal edges protrude in an arc shape toward the outer side in the longitudinal direction. Note that the outer shape of the light incontinence pad 1 is not limited to such a form, and any shape (for example, an oval shape, a rectangular shape, an hourglass shape, etc.) according to various uses and usage modes can be adopted as long as it is a longitudinal shape.

[0030] The light incontinence pad 1 basically includes, in the thickness direction, a liquid-permeable surface sheet 2 that forms the surface on the skin-facing surface side of the light incontinence pad 1, a back sheet 3 that forms the surface on the non-skin-facing surface side of the light incontinence pad 1, and a composite absorber 4 located between these sheets. In addition, the light incontinence pad 1 further includes an adhesive portion (not shown) that is disposed on the surface on the non-skin-facing surface side of the back sheet 3 and adhesively fixes the light incontinence pad 1 to the inner surface of clothing such as the wearer's underwear.

[0031] Note that the light incontinence pad 1 is not limited to such a configuration. For example, a pair of side sheets for forming a leakage-preventing wall that are located at both ends in the width direction W of the light incontinence pad 1 at a position closer to the skin-facing surface side than the surface sheet 2 and are arranged to extend in the longitudinal direction L, and a plurality of elastic members arranged along the longitudinal direction L in each of the pair of side sheets may be provided.

[0032] And in the light incontinence pad 1, the composite absorber 4 is located between the top sheet 2 and the back sheet 3, and is formed of a water-absorbent member capable of absorbing body fluids such as urine discharged from the wearer and passing through the top sheet 2. Such a composite absorber 4 contains a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer (SAP). Furthermore, the above-mentioned polymer absorbent contains at least -COOH groups and -COONa groups as ion-exchange groups, and has a specific ion-exchange ability that the total ion-exchange capacity of -COOH groups and -COONa groups per unit mass in the dry state is 4.0 meq / g or more.

[0033] Since the polymer absorbent of the composite absorber 4 has a hydrophilic continuous skeleton and continuous pores, it can quickly absorb and temporarily hold body fluids such as urine. Furthermore, by containing a certain amount or more of -COOH groups and -COONa groups, which are ion-exchange groups, when the polymer absorbent absorbs and temporarily holds body fluids, ions in the body fluids (especially divalent ions such as Ca 2+ and Mg 2+ etc.) can be ion-exchanged by -COOH groups and -COONa groups, and the body fluids can be modified into body fluids that are less likely to adversely affect the absorption performance of SAP (especially the water absorption amount, water retention amount, and absorption rate). Thereby, since the composite absorber 4 can transfer the body fluids to SAP after modifying them with the polymer absorbent, the absorption performance of SAP is less likely to vary, and the absorption performance as an absorber can be stably exhibited.

[0034] Therefore, the light incontinence pad 1 provided with such a composite absorber 4 can also exhibit high absorption performance as a light incontinence pad (for example, absorption performance such as being less likely to cause rewetting and having a high absorption rate).

[0035] Hereinafter, various constituent members of the sanitary product to which the composite absorber of the present invention is applied will be described in more detail using the above-mentioned light incontinence pad 1.

[0036] (Top Sheet) In the above-mentioned light incontinence pad 1, as shown in FIG. 1, in plan view, the surface sheet 2 extends from one side edge to the other side edge in the longitudinal direction L of the light incontinence pad 1, and also extends from the vicinity of one side edge to the vicinity of the other side edge in the width direction W of the light incontinence pad 1, and has a vertically long outer shape. Such a surface sheet 2 is disposed at a position on the skin-facing surface side in the thickness direction of the light incontinence pad 1, and is composed of a liquid-permeable sheet-like member that forms a contact surface that can contact the wearer's skin, that is, the surface on the skin-facing surface side of the light incontinence pad 1.

[0037] Further, as shown in FIG. 1, the surface sheet 2 has a size that is slightly larger in the longitudinal direction L and the width direction W than the composite absorber 4 disposed on the non-skin-facing surface side of the surface sheet 2, and is joined to the back sheet 3 located on the non-skin-facing surface side at the peripheral portion.

[0038] In the present invention, the outer shape, various dimensions, basis weight, etc. of the surface sheet are not particularly limited as long as they can be used as the surface sheet of a sanitary product, and any outer shape, various dimensions, basis weight, etc. corresponding to desired liquid permeability, skin feel, flexibility, strength, etc. can be adopted.

[0039] (Back sheet) In the above-mentioned light incontinence pad 1, the back sheet 3 extends from one side edge to the other side edge in the longitudinal direction L of the light incontinence pad 1 in plan view, and also extends from one side edge to the other side edge in the width direction W of the light incontinence pad 1, and has a vertically long outer shape. Such a back sheet 3 is disposed at a position on the non-skin-facing surface side in the thickness direction of the light incontinence pad 1, forms the non-skin-facing surface of the light incontinence pad 1, and is composed of a liquid-impermeable sheet-like member that prevents body fluids such as urine that have passed through the composite absorber 4 from leaking to the outside of the light incontinence pad 1.

[0040] In the present invention, the outer shape, various dimensions, basis weight, etc. of the back sheet are not particularly limited as long as they can be used as the back sheet of a sanitary product, and any outer shape, various dimensions, basis weight, etc. corresponding to desired leak prevention performance, air permeability, strength, etc. can be adopted.

[0041] (Composite absorber) In the above-mentioned light incontinence pad 1, as shown in FIG. 1, in plan view, the composite absorber 4 extends over a wide area in the longitudinal direction L from the vicinity of one longitudinal end edge to the vicinity of the other longitudinal end edge around the central part in the longitudinal direction L and the width direction W of the light incontinence pad 1, and also in the width direction W, it extends over a wide area from the vicinity of one widthwise end edge to the vicinity of the other widthwise end edge, and further has a vertically long outer shape in which two longitudinal end edges protrude in an arc shape toward the outer side in the longitudinal direction.

[0042] More specifically, the composite absorber 4 has a constricted portion in the longitudinal central part in plan view, in which the widthwise length is relatively small compared to other parts. Further, in this constricted portion, there are a minimum width portion having the minimum width of the composite absorber 4 and a maximum width portion having the maximum width of the composite absorber 4 on the outer side in the longitudinal direction of the constricted portion.

[0043] The composite absorber 4 is disposed between the surface sheet 2 and the back sheet 3 in the thickness direction of the light incontinence pad 1, and is formed of a predetermined water-absorbing member that can absorb and hold body fluids such as urine that has passed through the surface sheet 2. Such a water-absorbing member is composed of a water-absorbing material such as a polymer absorbent, hydrophilic fiber, superabsorbent polymer, etc. described later, and a sheet such as a tissue that holds it. That is, the composite absorber means a water-absorbing member composed of a water-absorbing material that can absorb and hold body fluids and a sheet that holds it.

[0044] In the light incontinence pad 1, the composite absorber 4 is joined to each of the surface sheet 2 and the back sheet 3 by an arbitrary adhesive such as a hot melt adhesive.

[0045] The composite absorber 4 contains, as essential components, a polymer absorbent having the above-described specific ion-exchange ability with a hydrophilic continuous skeleton and continuous pores as described above, and a superabsorbent polymer. 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). Note that the specific type of the superabsorbent polymer (SAP) is not particularly limited. For example, an acrylic acid-based SAP having cations on its surface can be preferably used. Such an acrylic acid-based SAP having cations on its surface is particularly susceptible to adverse effects on the absorption performance (especially, the water absorption amount, water retention amount, and absorption rate) by ions in body fluids. However, even when the composite absorber 4 contains such SAP, when the polymer absorbent absorbs and temporarily holds body fluids, the ions in the body fluids can be ion-exchanged by -COOH groups and -COONa groups to modify the body fluids. Therefore, it is difficult for variations to occur in the absorption performance of SAP, and the absorption performance as an absorber can be stably exhibited.

[0046] Note that the composite absorber 4 may contain only the above-described polymer absorbent and SAP as water-absorbing materials, or may further contain water-absorbing materials known in the art in addition to these. Examples of such water-absorbing materials include hydrophilic fibers. More specifically, examples include pulp fibers (e.g., ground pulp, etc.), cellulose-based fibers such as cotton, rayon, and acetate.

[0047] Note that the composite absorber 4 may have a configuration in which such a polymer absorbent, SAP, and any water-absorbing material are covered with a wrap sheet such as a tissue having hydrophilicity.

[0048] 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 inhibited, and any outer shape, various dimensions, basis weight, etc. corresponding to desired water absorption, flexibility, strength, etc. can be adopted.

[0049] Hereinafter, the polymer absorbent used in the composite absorber of the present invention will be described in more detail.

[0050] [Polymer absorbent] In the present invention, the polymer absorbent is not particularly limited as long as it has a hydrophilic continuous skeleton and continuous pores, contains at least -COOH groups and -COONa groups as ion exchange groups, and has a specific ion exchange ability that the total ion exchange capacity of -COOH groups and -COONa groups per unit mass in the dry state is 4.0 meq / g or more. Such polymer absorbents include, for example, hydrolyzates of cross-linked polymers of two or more monomers containing at least (meth)acrylate esters, and polymer compounds having at least one or more hydrophilic groups in the functional groups. More specifically, hydrolyzates of cross-linked polymers of (meth)acrylate esters and compounds containing two or more vinyl groups in one molecule, and polymer compounds having at least -COOH groups and -COONa groups can be mentioned. Such a polymer absorbent is an organic porous body having at least one or more -COONa groups in one molecule, and further has -COOH groups. In the skeleton of the porous body, -COONa groups are distributed substantially uniformly.

[0051] When the polymer absorbent is a hydrolyzate of a cross-linked polymer of such (meth)acrylate esters and a compound containing two or more vinyl groups in one molecule, as will be described later, when absorbing body fluids such as urine, the hydrophilic continuous skeleton is likely to elongate (that is, it is likely to expand), and the continuous pores are also likely to expand. Therefore, more body fluids can be taken into the continuous pores more quickly. As a result, the composite absorber containing such a polymer absorbent can exhibit higher absorption performance as an absorber, can steadily modify more body fluids, and can further reduce the variation in the absorption performance of the SAP.

[0052] In this specification, (meth)acrylate ester means acrylate ester or methacrylate ester.

[0053] In such a polymer absorbent formed by the hydrolyzate of a crosslinked polymer of such a (meth)acrylate and divinylbenzene, a hydrophilic continuous skeleton is formed by an organic polymer having at least -COONa groups and -COOH groups, and there are continuous pores (continuous voids) serving as absorption sites for the liquid to be absorbed (i.e., body fluids such as urine) between the skeletons. Note that since the hydrolysis treatment converts the -COOR group (i.e., carboxylic acid ester group) of the crosslinked polymer into a -COONa group or a -COOH group (see Fig. 2), the polymer absorbent may have a -COOR group.

[0054] The presence of -COOH groups and -COONa groups in the organic polymer forming the hydrophilic continuous skeleton and the total ion exchange capacity of -COOH groups and -COONa groups per unit mass in the dry state can be confirmed by analysis using infrared spectrophotometry and a method for quantifying weakly acidic ion exchange groups.

[0055] Here, Fig. 2 is a diagram for explaining the manufacturing process of absorbent A which is an example of the polymer absorbent. In this Fig. 2, the upper diagram shows the constituent raw materials of the polymerization, the middle diagram shows monolith A which is a crosslinked polymer of (meth)acrylate and divinylbenzene, and the lower diagram shows absorbent A obtained by subjecting the monolith A in the middle diagram to hydrolysis and drying treatments.

[0056] Hereinafter, an explanation will be given using absorbent A formed by the hydrolyzate of a crosslinked polymer of (meth)acrylate and divinylbenzene, which is an example of the polymer absorbent.

[0057] Note that the polymer absorbent is not limited to such absorbent A, and may be, for example, the hydrolyzate of a crosslinked polymer of (meth)acrylate and a compound having two or more vinyl groups in one molecule, or the hydrolyzate of a crosslinked polymer of two or more kinds of monomers containing at least (meth)acrylate. However, when the polymer absorbent is a monolithic absorbent, it can quickly absorb body fluids and can more steadily transfer the body fluids temporarily held in the polymer absorbent to the SAP. Therefore, a composite absorbent containing such a polymer absorbent can stably exhibit even better absorption performance.

[0058] In the following description, "Monolith A" is an organic porous body composed of a cross-linked polymer of (meth)acrylate 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 cross-linked polymer (Monolith A) of (meth)acrylate ester and divinylbenzene after hydrolysis treatment and drying treatment. In the following description, Absorbent A refers to the dry state.

[0059] First, the structure of Absorbent A will be described. Absorbent A has a hydrophilic continuous skeleton and continuous pores as described above. Absorbent A, which is an organic polymer having a hydrophilic continuous skeleton, is obtained by cross-linking and polymerizing (meth)acrylate ester, which is a polymerization monomer, and divinylbenzene, which is a cross-linking monomer, as shown in FIG. 2, and further hydrolyzing the obtained cross-linked polymer (Monolith A).

[0060] 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-linked 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 both -COOH groups and -COONa groups generated by hydrolysis of the carboxylic acid ester group. When the polymerization monomer is (meth)acrylate ester, the polymerization residue of the ethylene group (constituent unit X) has -COONa groups, -COOH groups, and ester groups.

[0061] In absorbent A, the proportion of the cross-linked polymerization residue (structural unit Y) of divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0.1 to 30 mol% with respect to all the structural 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-linked polymerization residue (structural unit Y) of divinylbenzene in the organic polymer forming the hydrophilic continuous skeleton is, for example, about 3% with respect to all the structural units, preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%. In addition, when the proportion of the cross-linked 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. Also, when the proportion of the cross-linked polymerization residue of divinylbenzene is 30 mol% or less, the absorption amount of the liquid to be absorbed is less likely to decrease.

[0062] In absorbent A, the organic polymer forming the hydrophilic continuous skeleton may consist only of structural unit X and structural unit Y, or may have, in addition to structural unit X and structural unit Y, structural units other than structural unit X and structural unit Y, that is, polymerization residues of monomers other than (meth)acrylate and divinylbenzene.

[0063] Examples of the structural units other than structural unit X and structural 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, etc.

[0064] In addition, the proportion of the structural units other than structural unit X and structural unit Y in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0 to 50 mol% with respect to all the structural units, preferably 0 to 30 mol%.

[0065] Further, it is preferable that the absorbent A has a hydrophilic continuous skeleton with a thickness 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 to be absorbed (body fluid) in the porous body is less likely to collapse during absorption, and the absorption amount is less likely to decrease. On the other hand, when the thickness of the hydrophilic continuous skeleton is 100 μm or less, it is easier to obtain an excellent absorption rate.

[0066] In addition, since the pore structure of the hydrophilic continuous skeleton of the absorbent A is a continuous bubble structure, for measuring the thickness of the continuous skeleton, the cross-section of the skeleton appearing in the test piece for electron microscope measurement is taken as the location for evaluating the thickness. Since the continuous skeleton is formed by the intervals between the water (water droplets) removed by dehydration and drying after hydrolysis, 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 may be cases where small holes are open in the polygon rarely, in such cases, the circumscribed circle of the cross-section of the polygon surrounding the small hole is measured.

[0067] Furthermore, it is preferable that the absorbent A has an average diameter of continuous pores of 1 μm to 1000 μm. When the average diameter of the continuous pores of the absorbent A is 1 μm or more, the space (pores) for taking in the liquid to be absorbed (body fluid) 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. Therefore, the composite absorber provided with such an absorbent A can stably exhibit excellent absorption performance. In particular, when the porosity per unit volume of the polymer absorbent described later is 85% or more and the average diameter of the continuous pores is 1 μm to 1000 μm, there is an advantage that more pores can absorb and modify the body fluid, so that more excellent ion exchange efficiency can be realized.

[0068] The average diameter (μm) of the continuous pores of the 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 for measuring the average diameter of the continuous pores, regardless of the ionic form of the absorbent A, a sample dried for 18 hours or more in a vacuum dryer set at a temperature of 50 ° C is used as the sample. The final pressure reached is set to 0 Torr.

[0069] Here, FIG. 3 is an SEM photograph of the absorbent A at a magnification of 50 times, FIG. 4 is an SEM photograph of the absorbent A at a magnification of 100 times, FIG. 5 is an SEM photograph of the absorbent A at a magnification of 500 times, FIG. 6 is an SEM photograph of the absorbent A at a magnification of 1000 times, and further, FIG. 7 is an SEM photograph of the absorbent A at a magnification of 1500 times. The absorbent A shown in FIGS. 3 to 7 is an example of an absorbent using butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, and each has a structure of a 2 mm square cube.

[0070] The absorbent A shown in FIGS. 3 to 7 has a large number of bubble-like macropores, and further has a portion where these bubble-like macropores overlap. The absorbent A has a continuous bubble structure in which the overlapping portions of these macropores become a common opening (mesopore), that is, a continuous bubble structure (continuous macropore structure).

[0071] The overlapping portion of these macropores becomes a common opening (mesopore) having 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 embrittle. The overlap of such macropores is about 1 to 12 per macropore, and many are about 3 to 10.

[0072] In addition, since the absorbent A has such a continuous bubble structure, it is possible to uniformly form macropore groups and mesopore groups, and there is an advantage that the pore volume and specific surface area can be significantly increased compared to the particle-aggregated porous bodies described in, for example, Japanese Patent Application Laid-Open No. 8-252579.

[0073] 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 to be absorbed (body fluid) of the porous body is less likely to collapse during absorption, and the 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.

[0074] 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.

[0075] Hereinafter, the state when the absorbent A comes into contact with a liquid such as body fluid (hereinafter simply referred to as "body fluid") will be described, but the same applies when the composite absorber 4 containing the absorbent A comes into contact with the body fluid.

[0076] First, the continuous pores provided in the absorbent A shown in FIGS. 3 to 7 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 body fluids such as urine come into contact with the absorbent A having such a large number of pores, first, the hydrophilic continuous skeleton instantaneously takes in a part of the body fluid by osmotic pressure and expands (i.e., swells). The expansion of this continuous skeleton occurs almost omnidirectionally. As the absorbent A expands in outer shape due to the expansion of the continuous skeleton during water absorption, 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 body fluid that can be retained in the pores also increases. The absorbent A that has absorbed a certain amount of body fluid and enlarged in this way can absorb a further predetermined amount of body fluid into the enlarged pores by capillary action.

[0077] In addition, the body fluid absorbed into the hydrophilic continuous skeleton of the absorbent A is difficult to be released from the continuous skeleton (i.e., difficult to separate from water), while the body fluid absorbed into the continuous pores is easy to separate from water. Therefore, in the composite absorbent body, the body fluid absorbed into the continuous pores separates from water and is transferred to the SAP with high water retention ability and is steadily retained in the SAP.

[0078] Also, more body fluid remains in the pores than in the hydrophilic continuous skeleton of the absorbent A. Since most of the absorption of body fluid by the absorbent A is carried out by retaining the body fluid in the pores by capillary action, the larger the porosity (i.e., the volume of the voids of the pores with respect to the unit volume of the absorbent A), which is the ratio of the volume of the voids of the pores (total pore volume), the more body fluid can be absorbed.

[0079] The porosity per unit volume of such a polymer absorbent is preferably 85% or more, more preferably 90% or more. When the porosity per unit volume of the polymer absorbent is 85% or more, more body fluid can be absorbed and gradually modified, so that the variation in the absorption performance of the SAP can be made less likely to occur. As a result, the composite absorbent containing such a polymer absorbent can exhibit the absorption performance as an absorbent more stably and favorably.

[0080] For example, when determining the porosity of absorbent A shown in FIGS. 3 to 7 above, it is as follows. First, the specific surface area of 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 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, that is, the pore volume, is 15.5 mL, and the volume of 1 g of absorbent A is 1 mL. Then, the total volume (volume) of 1 g of absorbent A is 15.5 + 1 (mL). Since the ratio of the pore volume among them is the porosity, the porosity of absorbent A is 15.5 / (15.5 + 1)×100 ≒ 94%.

[0081] The absorbent A having such a hydrophilic continuous skeleton and continuous pores, that is, the polymer absorbent, is applied to a composite absorbent for absorbing body fluids such as urine, such as the composite absorbent 4 of the above-mentioned light incontinence pad 1, in the form of, for example, particles or sheets. And as described above, this polymer absorbent contains at least -COOH group and -COONa group as ion exchange groups, and has a specific ion exchange ability that the total ion exchange capacity of -COOH group and -COONa group per unit mass in the dry state is 4.0 meq / g or more. Therefore, when the polymer absorbent absorbs and temporarily holds body fluid, ions in the body fluid (especially, Ca 2+ 、Mg 2+Divalent ions such as) are ion-exchanged by -COOH groups and -COONa groups, and body fluids can be modified into body fluids that are less likely to adversely affect the absorption performance (particularly, water absorption amount, water retention amount, absorption rate) of the superabsorbent polymer (SAP). Therefore, since the composite absorber to which such a polymer absorbent is applied can transfer the body fluid to SAP after modifying the body fluid with the polymer absorbent, variations in the absorption performance of SAP are less likely to occur, and the absorption performance as an absorber can be stably exhibited.

[0082] Here, FIG. 8 is a graph showing the relationship between the monovalent and divalent ion concentrations in body fluid (urine) and the absorption performance (water absorption amount, water retention amount, and absorption rate) of SAP, and FIG. 9 is a graph showing the effect of Absorbent A, which is an example of a polymer absorbent, on the divalent ion concentration in body fluid (urine). As shown in FIG. 8, it can be seen that the water absorption amount, water retention amount, and absorption rate of SAP all decrease as the monovalent and divalent ion concentrations in body fluid (urine) increase. In particular, it can be seen that the divalent ion concentration has a great influence on the absorption performance of SAP, and even a small amount causes a significant decrease in the water absorption amount, water retention amount, and absorption rate of SAP. In this way, the ion concentration in body fluid (urine) has a great adverse effect on the absorption performance of SAP. However, such ion concentration varies depending on differences in diet (for example, components of ingested foods and drinks) and living environment (for example, frequency of sweating and urination), etc., for each body fluid (that is, differences in body fluid type and individual differences), so variations in the absorption performance of SAP also occur according to the variations. However, Absorbent A, which is an example of the present invention, contains at least -COOH groups and -COONa groups as ion exchange groups, and has a specific ion exchange ability that the total ion exchange capacity of -COOH groups and -COONa groups per unit mass in the dry state is 4.0 meq / g or more. Therefore, as shown in FIG. 9, ions (particularly divalent ions) in body fluid (urine) can be ion-exchanged by -COOH groups and -COONa groups to significantly reduce the ion concentration in body fluid (urine), that is, body fluid (urine) can be modified into body fluid that is less likely to adversely affect the absorption performance of SAP.

[0083] The graph shown in Fig. 9 shows the change rate of ion concentration (i.e., the ion exchange rate of absorbent A) before and after contact between absorbent A and the actual urine (actual urine A, B, and C) of three humans with different divalent ion concentrations, measured as follows. First, measure the divalent ion concentration (mEq / L) of each of the three actual urine samples A, B, and C using an ion meter (manufactured by Horiba Advanced Technology Co., Ltd., HORIBA Compact Calcium Ion Meter LAQUAtwin-Ca-11). The measured ion concentration is taken as the ion concentration "before contact with absorbent A". Next, place 0.2 g of the polymer absorbent (absorbent A) in a glass filter (Climbing Glass Filter, model number: 0777-01-101, outer diameter × leg length (mm): φ7 × 80, filter diameter: φ20 mm, capacity: 30 mL, material: borosilicate glass, pore diameter: 100 - 120 μm), pour 30 mL of the above actual urine, and measure the divalent ion concentration (mEq / L) of the resulting filtrate using the above ion meter. The measured ion concentration is taken as the ion concentration "after contact with absorbent A". Then, calculate the change amount of ion concentration (mEq / L) before and after contact with absorbent A by subtracting the ion concentration after contact with absorbent A from the ion concentration before contact with absorbent A. Further, divide this change amount of ion concentration before and after contact with absorbent A by the ion concentration before contact with absorbent A and multiply by 100 to calculate the change rate (%) of divalent ion concentration in each of the actual urine samples A, B, and C. Note that all of the above measurements are performed under the conditions of a temperature of 25°C and a humidity of 60%.

[0084] As described above, absorbent A of the present invention example has the above-mentioned unique ion exchange ability that conventional water-absorbing materials do not have. It can quickly absorb body fluids such as urine and temporarily hold them. Moreover, it can ion-exchange ions (especially divalent ions) in the body fluid to modify the body fluid into a body fluid that is less likely to adversely affect the absorption performance of SAP. As a result, such a composite absorber containing the absorbent A (polymer absorbent) can transfer the body fluid to the SAP after modifying it, so that the absorption performance of the SAP is less likely to vary, and the absorption performance as an absorber can be stably exhibited.

[0085] In the present invention, the total ion exchange capacity of -COOH groups and -COONa groups per unit mass of the polymer absorbent in the dry state is preferably 6.0 meq / g or more, and more preferably 8.0 meq / g or more.

[0086] In the present invention, the polymer absorbent preferably has an ion exchange rate of polyvalent ions (that is, ions with a valence of 2 or more) of 50% or more. When the ion exchange rate of polyvalent ions of the polymer absorbent is 50% or more, the body fluid can be more reliably modified, so that the variation in the absorption performance of the SAP can be made less likely to occur. Therefore, such a composite absorber containing the polymer absorbent can more stably exhibit the absorption performance as an absorber. In addition, the ion exchange rate of polyvalent ions of the polymer absorbent is more preferably 60% or more, and still more preferably 70% or more. Here, the ion exchange rate of polyvalent ions of the polymer absorbent can be measured by any measurement method such as ICP emission spectrometry, IC analysis, atomic absorption spectrometry, etc. For example, the ion exchange rate of divalent ions can be measured as follows.

[0087] <Measurement method for ion exchange rate of divalent ions of polymer absorbent> (1) Prepare artificial urine by dissolving 200 g of urea, 80 g of sodium chloride, 8 g of magnesium sulfate, 3 g of calcium chloride, and about 1 g of dye: Blue No. 1 in 10 L of ion-exchanged water. (2) Measure the divalent ion concentration (mEq / L) of the prepared artificial urine using an ion meter (manufactured by Horiba Advanced Technology Co., Ltd., HORIBA Compact Calcium Ion Meter LAQUAtwin-Ca-11). The measured ion concentration is defined as the "ion concentration before contact with the polymer absorbent". (3) Place 0.2 g of the polymer absorbent, which is the sample for measurement, into a glass filter (Climbing glass filter, model number: 0777 - 01 - 101, outer diameter × leg length (mm): φ7 × 80, filter diameter: φ20 mm, capacity: 30 mL, material: borosilicate glass, pore diameter: 100 - 120 μm), pour 30 mL of the above artificial urine, and measure the divalent ion concentration (mEq / L) of the resulting filtrate using the above ion meter. The measured ion concentration is defined as the "ion concentration after contact with the polymer absorbent". (4) Calculate the change in ion concentration (mEq / L) before and after contact with the polymer absorbent by subtracting the ion concentration after contact with the polymer absorbent from the ion concentration before contact with the polymer absorbent. Further, divide this change in ion concentration (mEq / L) before and after contact with the polymer absorbent by the ion concentration before contact with the polymer absorbent and multiply by 100 to calculate the change rate (%) of the divalent ion concentration. And in this specification, this "change rate (%) of the divalent ion concentration" is defined as the "divalent ion exchange rate of the polymer absorbent". Note that all of the above measurements are performed under the conditions of a temperature of 25°C and a humidity of 60%.

[0088] Also, when the sample for measurement (polymer absorbent) is recovered from a hygiene product and used, it can be obtained according to the following <Method for recovering the sample for measurement (polymer absorbent)>.

[0089] <Method for recovering the sample for measurement (polymer absorbent)> (1) Peel off the surface sheet etc. from the hygiene product to expose the absorbent body. (2) Drop the measurement object (polymer absorbent) from the exposed absorbent body, and remove things other than the measurement object (in particle form) (for example, pulp, synthetic resin fibers, etc.) using tweezers or the like. (3) Using a microscope or a simple magnifying glass as the magnifying observation means, observe at a magnification at which the difference from SAP can be recognized or at a magnification at which the pores of the porous body can be visually recognized, and recover the measurement object using tweezers or the like. Note that the magnification of the simple magnifying glass is not particularly limited as long as it is a magnification at which the pores of the porous body can be visually recognized, and for example, magnifications of 25 times to 50 times can be mentioned. (4) The measurement object collected in this way is used as a sample for measurement in various measurement methods.

[0090] Furthermore, in the present invention, the polymer absorbent preferably has a water absorption per unit mass of 30 g / g or more. When the polymer absorbent has a water absorption of a certain level or more in this way, more body fluid can be absorbed and gradually modified, so that variations in the absorption performance of the SAP can be made less likely to occur. Therefore, the composite absorbent containing such a polymer absorbent can more stably exhibit the absorption performance as an absorbent. In addition, the water absorption per unit mass of the polymer absorbent is more preferably 40 g / g or more, and even more preferably 50 g / g or more. Here, the water absorption per unit mass of the polymer absorbent can be measured as follows.

[0091] <Method for Measuring Water Absorption per Unit Mass of Polymer Absorbent> (1) Enclose 1 g of the sample for measurement (polymer absorbent) in a mesh bag (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)) cut into a 10 cm square. The mass (g) of the mesh bag should be measured in advance. When the sample for measurement (polymer absorbent) is recovered from a hygiene product and used, it can be obtained according to the aforementioned <Method for Recovering Sample for Measurement (Polymer Absorbent)>. (2) Immerse the mesh bag containing the sample in physiological saline (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 water absorption (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 water absorption by the mass of the sample (=1 g) to obtain the water absorption per unit mass (g / g) of the sample (polymer absorbent). All of the above measurement methods are performed under the conditions of a temperature of 25°C and a humidity of 60%.

[0092] Next, the manufacturing method of such a polymer absorbent will be described in detail using the above absorbent A as an example.

[0093] [Manufacturing Method of Polymer Absorbent] As shown in Fig. 2, the above absorbent A can be obtained through a crosslinking polymerization step and a hydrolysis step. Each of these steps will be described below.

[0094] (Crosslinking Polymerization Step) First, an oil-soluble monomer for crosslinking polymerization, a crosslinkable monomer, a surfactant, water, and, if necessary, a polymerization initiator are mixed 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.

[0095] In the above absorbent A, as shown in the upper figure of Fig. 2, 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.

[0096] Specifically, in absorbent A, as shown in the upper figure of Fig. 2, first, 9.2 g of t-butyl methacrylate as the oil-soluble monomer, 0.28 g of divinylbenzene as the crosslinkable monomer, 1.0 g of sorbitan monooleate (hereinafter abbreviated as "SMO") as the surfactant, and 0.4 g of 2,2'-azobis(isobutyronitrile) as the 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 defoaming mixer (manufactured by EMI Co., Ltd.), which is a planetary stirring device, to obtain a water-in-oil emulsion.

[0097] Furthermore, transfer this emulsion promptly to a reaction vessel, seal it, and polymerize it under static conditions at 60°C for 24 hours. After the polymerization is complete, take out the content, extract it with methanol, and then dry it 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 had a continuous bubble structure, and the thickness of the continuous skeleton was 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.

[0098] In addition, 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 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%.

[0099] 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 it is preferably in the range of about 2 to 70% with respect to the total amount of the oil-soluble monomer and the surfactant.

[0100] In addition, in order to control the bubble shape, size, etc. of 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.

[0101] Also, the mixing method when forming the water-in-oil emulsion is not particularly limited, and for example, any mixing method can be adopted, such as a method of mixing all components at once, or a method of separately and uniformly dissolving the oil-soluble components, which are the oil-soluble monomer, the surfactant, and the oil-soluble polymerization initiator, and the water-soluble components, which are water and the water-soluble polymerization initiator, and then mixing the respective components.

[0102] Furthermore, the mixing device for forming the emulsion is not particularly limited, and any device such as a normal mixer, a homogenizer, a high-pressure homogenizer, etc. can be adopted according to the desired emulsion particle size. Furthermore, the object to be treated can be put into a mixing container, and the object to be treated can be stirred and mixed by rotating it around the rotation axis while revolving around the rotation axis in a state where the mixing container is tilted, and a so-called planetary stirring device can also be used.

[0103] Also, the mixing conditions are not particularly limited, and the stirring rotation speed, the 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 its average diameter can be arbitrarily set within a wide range.

[0104] The polymerization conditions of the water-in-oil 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.

[0105] 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 Fig. 2 can be obtained.

[0106] (Hydrolysis step) Subsequently, the step of hydrolyzing the monolith A (crosslinked polymer) to obtain the absorbent A (hydrolysis step) will be described.

[0107] First, immerse monolith A in dichloroethane added with zinc bromide and stir at 40°C for 24 hours. After contacting with methanol, 4% hydrochloric acid, 4% sodium hydroxide aqueous solution, and water in this order for hydrolysis, dry it to obtain block-shaped absorbent A. Further, crush this block-shaped absorbent A into a predetermined size to obtain particulate absorbent A. Note that the form of this absorbent A is not limited to particulate form, and for example, it may be formed into a sheet shape during or after drying.

[0108] Also, the method for hydrolyzing 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 a 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.

[0109] Among the polymerization raw materials of the organic polymer that forms the hydrophilic continuous skeleton of absorbent A, the (meth)acrylate ester is not particularly limited, but an alkyl ester of C1 - C10 (that is, having 1 to 10 carbon atoms) of (meth)acrylic acid is preferred, and an alkyl ester of C4 (that is, having 4 carbon atoms) of (meth)acrylic acid is particularly preferred. Note that examples of the C4 alkyl ester of (meth)acrylic acid include t-butyl (meth)acrylate, n-butyl (meth)acrylate, and iso-butyl (meth)acrylate.

[0110] In addition, the monomers used for crosslinking polymerization may consist only of (meth)acrylate and divinylbenzene, or may contain other monomers in addition to (meth)acrylate and divinylbenzene. In the latter case, the 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, isobutylene, 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 other monomers other than (meth)acrylate and divinylbenzene in all the monomers used for crosslinking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

[0111] In addition, the surfactant is not limited to the above-mentioned sorbitan monooleate, and any surfactant can 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.

[0112] 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, and tetramethylthiuram disulfide. 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.

[0113] In addition to the light incontinence pad of the above-described embodiment, the composite absorber of the present invention can be applied to various sanitary products such as panty-type disposable diapers, tape-type disposable diapers, sanitary napkins, absorption liners, absorption pads (for example, pressure ulcer pads, maternity pads, etc.), absorption sheets, breast pads, disposable diapers for pets, absorption pads for pets, excrement treatment sheets for pets, wet sheets, wet tissues, cosmetic wiping sheets, masks, and the like. Therefore, the body fluid that is the liquid to be absorbed by the composite absorber is a liquid discharged from the wearer of the sanitary product, and examples thereof include urine, sweat, feces, menstrual blood, lochia, breast milk, blood, and exudate.

[0114] In addition, the present invention is not limited to the above-described embodiments and the like, and appropriate combinations, substitutions, changes, and the like are possible within a range not departing from the object and gist of the present invention.

Explanation of Reference Numerals

[0115] 1 Light incontinence pad 2 Surface sheet 3 Back sheet 4 Composite absorber

Claims

1. A composite absorber for absorbing body fluids, The composite absorber includes a hydrophilic continuous skeleton and a polymer absorbent having continuous pores, and a superabsorbent polymer, The polymer absorbent contains at least -COOH groups and -COONa groups as ion exchange groups, and the total ion exchange capacity of the -COOH groups and -COONa groups per unit mass in the dry state is 6.0 meq / g or more, and the water absorption per unit mass is 30 g / g or more. The composite absorber is characterized by this.

2. The composite absorber according to claim 1, wherein the polymer absorbent has an ion exchange rate of polyvalent ions of 50% or more.

3. The composite absorber according to claim 1 or 2, wherein the polymer absorbent has a porosity of 85% or more per unit volume of the polymer absorbent.

4. The composite absorber according to any one of claims 1 to 3, wherein the polymer absorbent has an average diameter of the continuous pores of 1 μm to 1000 μm.

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

6. The composite absorber according to any one of claims 1 to 5, wherein 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.

7. The composite absorber according to any one of claims 1 to 6, wherein the superabsorbent polymer is an acrylic acid-based superabsorbent polymer having cations on its surface.

8. A sanitary product characterized by having the composite absorber according to any one of claims 1 to 7.

Images