Composite absorbent and sanitary article

Abstract

The present application provides an absorbent capable of stably exhibiting an absorption performance. A composite absorbent (4) of the present application is characterized by being a composite absorbent (4) for absorbing body fluids, the aforementioned composite absorbent comprising: a high-molecular absorbent having a continuous skeleton and a continuous void with hydrophilicity, and a superabsorbent polymer, the aforementioned high-molecular absorbent containing at least a -COOH group and a -COONa group as ion exchange groups, and the total ion exchange capacity of the aforementioned -COOH group and -COONa group per unit mass in a dry state being 4.0 mg equivalent / g or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite absorbent and a sanitary article having the same. BACKGROUND

[0002] For sanitary articles such as disposable diapers, sanitary napkins, and the like, it is known to use a high-absorbency polymer (so-called "SAP") having a high absorption capacity. For example, Patent Literature 1 discloses an absorbent article using an absorbent body in which absorbent resin particles (high-absorbency polymer) having an excellent absorption capacity, and hydrophilic fibers such as pulp fibers having an excellent absorption speed are combined.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2013 / 018571 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Such a high-absorbency polymer (SAP) can hold a large amount of moisture (i.e., has a high moisture-holding capacity), but on the other hand, has a slow water-absorption speed, and therefore in the conventional absorbent body, it is used in combination with pulp in a manner that can temporarily and quickly hold moisture. When the above-described conventional absorbent body is used, if a body fluid such as urine is discharged by a wearer of the sanitary article, the body fluid is quickly absorbed by the pulp in the absorbent body, is temporarily held in the pulp, and is then transported to the SAP having a high moisture-holding capacity, and is held in the SAP.

[0008] On the other hand, a body fluid such as urine, which is the absorption target of the absorbent body, greatly differs in the salt concentration in the body fluid depending on the dietary life (e.g., the components of the food taken, etc.), the living environment (e.g., the frequency of sweating or urination, etc.), and the like, and in particular, the 2-valent ions (e.g., Ca 2+ , Mg 2+ , etc.) in the body fluid, even in a small amount, greatly adversely affect the absorption performance (particularly, the water-absorption capacity, the moisture-holding capacity, the absorption speed) of the SAP.

[0009] However, the conventional absorbent body does not have a function of modifying the salt concentration in the body fluid such as urine, and therefore the body fluid temporarily held in the pulp is transported to the SAP in the original state, the absorption performance of the SAP is deviated due to the influence of the salt concentration (particularly, the 2-valent ion concentration) in the body fluid, and as a result, it can not be possible to stably exert the absorption performance of the absorbent body.

[0010] The present application has been made in view of such a problem, and an object thereof is to provide an absorbent body capable of stably exerting the absorption performance.

[0011] SOLUTION TO THE PROBLEM

[0012] One embodiment (Embodiment 1) of the present application is a composite absorbent, characterized by being a composite absorbent for absorbing body fluid,

[0013] The aforementioned composite absorbent includes a high-molecular absorbent having a continuous skeleton and a continuous void with hydrophilicity, and a superabsorbent polymer,

[0014] The aforementioned high-molecular absorbent contains at least a -COOH group and a -COONa group as ion exchange groups, and the total ion exchange capacity of the aforementioned -COOH group and -COONa group per unit mass in a dry state is 4.0 mg equivalent / g or more.

[0015] The composite absorbent of the present embodiment, by the high-molecular absorbent having a continuous skeleton and a continuous void with hydrophilicity, can rapidly absorb and temporarily hold body fluid such as urine, and furthermore, by containing the -COOH group and -COONa group as ion exchange groups in an amount of 4.0 mg equivalent / g or more, when the high-molecular absorbent absorbs and temporarily holds the body fluid, ion exchange of ions (particularly, Ca 2+ , Mg 2+ , and the like, which are divalent ions, by the -COOH group and -COONa group can modify the body fluid to a body fluid that does not easily cause adverse effects on the absorbency performance (particularly, water absorption amount, water retention amount, and absorption speed) of the superabsorbent polymer (SAP).

[0016] Thus, the composite absorbent of the present embodiment, since the body fluid is modified by the high-molecular absorbent and then delivered to the SAP, the absorbency performance of the SAP does not easily deviate, and the absorbency performance as an absorbent can be stably exhibited.

[0017] Further, another embodiment (Embodiment 2) of the present application is characterized in that, in the composite absorbent of the aforementioned Embodiment 1, the ion exchange rate of the polyvalent ions of the aforementioned high-molecular absorbent is 50% or more.

[0018] The composite absorbent of the present embodiment, since the ion exchange rate of the polyvalent ions (ions of 2 or more valences) of the high-molecular absorbent is 50% or more, the body fluid can be more surely modified, and thus the absorbency performance of the SAP can be more less deviated, and the absorbency performance as an absorbent can be further stably exhibited.

[0019] Further another embodiment (Embodiment 3) of the present application is characterized in that, in the composite absorbent of the aforementioned Embodiment 1 or 2, the water absorption amount per unit mass of the aforementioned high-molecular absorbent is 30 g / g or more.

[0020] The composite absorbent of the present embodiment, since the high-molecular absorbent has a water absorption amount of 1 or more, can absorb more body fluid, and is improved, can further stably exhibit the absorption performance as an absorbent, with less deviation in the absorption performance of the SAP.

[0021] The further other embodiment (Embodiment 4) of the present application is characterized in that, in the composite absorbent of any one of Embodiments 1 to 3 described above, the high-molecular absorbent has a porosity of 85% or more per unit volume.

[0022] The composite absorbent of the present embodiment, since the high-molecular absorbent has a porosity of 1 or more, can absorb more body fluid, and is improved, can further stably exhibit the absorption performance as an absorbent, with less deviation in the absorption performance of the SAP.

[0023] The further other embodiment (Embodiment 5) of the present application is characterized in that, in the composite absorbent of any one of Embodiments 1 to 4 described above, the high-molecular absorbent has an average diameter of the continuous voids of 1 μm to 1000 μm.

[0024] The composite absorbent of the present embodiment, since the average diameter of the continuous voids of the high-molecular absorbent is within the above specific range, not only the space (voids) for introducing the body fluid of the high-molecular absorbent is less likely to be crushed, but also can have a higher absorption speed, and can stably exhibit excellent absorption performance.

[0025] In particular, in the case where the high-molecular absorbent has a porosity of 85% or more per unit volume and an average diameter of the continuous voids of 1 μm to 1000 μm, since the body fluid can be absorbed and improved using more fine pores, it has the advantage that more excellent ion exchange efficiency can be achieved.

[0026] The further other embodiment (Embodiment 6) of the present application is characterized in that, in the composite absorbent of any one of Embodiments 1 to 5 described above, the high-molecular absorbent is a monolith-shaped absorbent.

[0027] The composite absorbent of the present embodiment, since the high-molecular absorbent is a monolith-shaped absorbent, not only can quickly absorb the body fluid, but also can more stably deliver the temporarily held liquid to the SAP, and thus can stably exhibit further excellent absorption performance.

[0028] The further other embodiment (Embodiment 7) of the present application is characterized in that, in the composite absorbent of any one of Embodiments 1 to 6 described above, the high-molecular absorbent is a hydrolyzate of a crosslinked polymer of a (meth)acrylate and a compound having 2 or more vinyl groups in one molecule.

[0029] The composite absorbent of the present mode, by the high molecular absorbent having the above specific configuration, when absorbing the body fluid, the continuous skeleton of hydrophilicity easily elongates, and the continuous void also easily expands, so that more body fluid can be introduced to the continuous void more quickly, and as an absorbent, further high absorbency can be exhibited, and more body fluid can be modified solidly, and further, the deviation of the absorbency of the SAP can be prevented.

[0030] Further other mode (Mode 8) of the present application is characterized in that, in the composite absorbent of any one of the above Modes 1 to 7, the aforementioned high absorbency polymer is an acrylic high absorbency polymer having surface-located cations.

[0031] The acrylic high absorbency polymer (SAP) having surface-located cations is particularly susceptible to adverse effects on absorbency (particularly water absorption amount, water retention amount, and absorption speed) due to ions in the body fluid, but in the composite absorbent of the present mode, even if such SAP is contained, when the high molecular absorbent absorbs and temporarily retains the body fluid, the ions in the body fluid are ion-exchanged using -COOH groups and -COONa groups, and the body fluid is modified, so that the absorbency of the SAP is less likely to deviate, and the absorbency as an absorbent can be stably exhibited.

[0032] Further other mode (Mode 9) of the present application is a sanitary product characterized by having the composite absorbent of any one of the above Modes 1 to 8.

[0033] The sanitary product of the present mode, since it has the composite absorbent of any one of the above Modes 1 to 8, can exhibit high absorbency (e.g., less likely to cause backflow, fast absorption speed, and the like) as a sanitary product.

[0034] Effects of the Invention

[0035] The present application can provide an absorbent capable of stably exhibiting absorbency. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A schematic plan view of a light incontinence pad 1 in a developed state as viewed in the thickness direction from the skin-facing side.

[0037] Figure 2 A diagram for explaining a manufacturing process of an absorbent A as an example of a high molecular absorbent.

[0038] Figure 3 A SEM photograph of the absorbent A at a magnification of 50 times.

[0039] Figure 4 A SEM photograph of the absorbent A at a magnification of 100 times.

[0040] Figure 5 SEM photograph at a magnification of 500 times of the absorbent A.

[0041] Figure 6 SEM photograph at a magnification of 1000 times of the absorbent A.

[0042] Figure 7 SEM photograph at a magnification of 1500 times of the absorbent A.

[0043] Figure 8 A graph showing the relationship between the concentration of monovalent and divalent ions in a body fluid (urine) and the absorption performance (water absorption amount, water retention amount, and absorption speed) of SAP.

[0044] Figure 9 A graph showing the influence of the absorbent A, which is an example of a high-molecular absorbent, on the concentration of divalent ions in a body fluid (urine). DETAILED DESCRIPTION

[0045] The following describes a preferred embodiment of the composite absorbent of the present application in detail using a light incontinence pad 1, which is an example of a sanitary product to which the composite absorbent is applied.

[0046] Note that in the present specification, "viewing an object (e.g., a light incontinence pad, a composite absorbent, etc.) in a spread state placed on a horizontal plane from the upper side in the vertical direction (the surface sheet side when the object is a sanitary product)" is simply referred to as "plan view" unless otherwise specified.

[0047] Note that in the present specification, "lengthwise direction" refers to "the direction in which the length of an object (e.g., a light incontinence pad, a composite absorbent, etc.) in a spread state is long in plan view", "widthwise direction" refers to "the direction in which the length of the object is short in plan view", and "thicknesswise direction" refers to "the direction perpendicular to the object in a spread state placed on a horizontal plane", and these lengthwise, widthwise, and thicknesswise directions are in mutually orthogonal relationships, respectively.

[0048] In addition, in the present specification, "skin-facing side" refers to "the side relatively close to the skin of a wearer when the light incontinence pad 1 is worn" and "non-skin-facing side" refers to "the side relatively far from the skin of a wearer when the light incontinence pad 1 is worn" in the thicknesswise direction of the light incontinence pad 1 unless otherwise specified.

[0049] [Light Incontinence Pad]

[0050] Figure 1 A schematic plan view of a light incontinence pad 1 in a spread state of a composite absorbent 4 according to an embodiment of the present application.

[0051] As shown in Figure 1 the light incontinence pad 1 has a length direction L and a width direction W, and has an elongated outer shape in which both length direction end edges protrude in a circular arc shape toward the outer side in the length direction. Note that the outer shape of the light incontinence pad 1 is not limited to this manner, and any shape (for example, an oblong shape, a rectangular shape, an hourglass shape, etc.) can be adopted according to various uses, use methods, etc. if it is an elongated shape.

[0052] The light incontinence pad 1 has, as basic components in the thickness direction, a liquid permeable surface sheet 2 that forms the surface of the skin-facing side of the light incontinence pad 1, a back sheet 3 that forms the surface of the non-skin-facing side of the light incontinence pad 1, and a composite absorbent 4 that is positioned between these sheets.

[0053] In addition, the light incontinence pad 1 also has an adhesive portion (not shown) that is disposed on the surface of the non-skin-facing side of the back sheet 3 and adheres and fixes the inner surface of a garment such as an undergarment worn by the wearer.

[0054] Note that the light incontinence pad 1 is not limited to this configuration, and for example, can have a pair of side sheets for leak prevention that are disposed in a manner in which the positions on the skin-facing side compared to the surface sheet 2 are at both ends in the width direction W of the light incontinence pad 1 and extend in the length direction L, and a plurality of elastic members that are disposed in a manner in which each is along the length direction L of the pair of side sheets.

[0055] Furthermore, in the light incontinence pad 1, the composite absorbent 4 that is formed by a water-absorbing member that can absorb a body fluid such as urine that has passed through the surface sheet 2 excreted by the wearer is positioned between the surface sheet 2 and the back sheet 3, and the above-described composite absorbent 4 contains a high-molecular absorbent that has a continuous skeleton and a continuous void that are hydrophilic, and a superabsorbent polymer (SAP).

[0056] Furthermore, the above-described high-molecular absorbent contains at least a -COOH group and a -COONa group as ion exchange groups, and has a unique ion exchange capacity in which the total ion exchange capacity of the -COOH group and the -COONa group per unit mass in a dry state is 4.0 mg equivalent / g or more.

[0057] The composite absorbent 4, by the high-molecular absorbent having a continuous skeleton and a continuous void that are hydrophilic, can quickly absorb and temporarily hold a body fluid such as urine, and furthermore, by containing the -COOH group and the -COONa group as ion exchange groups in an amount of 4.0 mg equivalent / g or more, when the high-molecular absorbent absorbs and temporarily holds a body fluid, the ions (particularly, Ca 2+ , Mg 2+By exchanging divalent ions through -COOH and -COONa groups, body fluids can be modified into fluids that are less likely to have adverse effects on the absorption performance of SAP (especially water absorption, water retention, and absorption rate).

[0058] Therefore, since the composite absorbent 4 can transport body fluids to SAP after modification with a polymer absorbent, the absorption performance of SAP is not prone to deviation and can stably perform its absorption function as an absorbent.

[0059] Therefore, the incontinence pad 1 with this composite absorbent 4 can also be used as an incontinence pad to exert high absorption performance (such as low backflow and fast absorption speed).

[0060] The following describes in detail the various constituent components of sanitary products to which the composite absorbent of the present invention is applicable, using the above-described light incontinence pad 1.

[0061] (Surface sheet)

[0062] In the aforementioned mild incontinence pad 1, such as Figure 1 As shown, the surface sheet 2 has a longitudinally elongated shape, extending from one end edge in the length direction L of the incontinence pad 1 to the other end edge, and from near one end edge in the width direction W of the incontinence pad 1 to near the other end edge, when viewed from above. The surface sheet 2 is a liquid-permeable sheet-like member formed by being positioned in the thickness direction of the incontinence pad 1 on the skin-facing side, creating a contact surface that can abut against the wearer's skin, i.e., the skin-facing side surface of the incontinence pad 1.

[0063] In addition, such as Figure 1 As shown, the surface sheet 2 has a slightly larger size in the length direction L and width direction W compared to the composite absorber 4 disposed on the non-skin-facing side of the surface sheet 2, and is joined to the back sheet 3 located on the non-skin-facing side in the periphery.

[0064] In this invention, there are no particular restrictions on the shape, size, weight, etc. of the surface sheet, as long as it can be used as a surface sheet for hygiene products. Any shape, size, weight, etc. can be adopted that corresponds to the desired liquid permeability, skin feel, softness, strength, etc.

[0065] (Back panel)

[0066] In the aforementioned incontinence pad 1, the back panel 3 has an elongated shape that, when viewed from above, extends from one end edge in the length direction L of the incontinence pad 1 to the other end edge, and also extends from one end edge in the width direction W of the incontinence pad 1 to the other end edge. The back panel 3 is a non-permeable sheet member disposed in the thickness direction of the incontinence pad 1 on the non-skin-facing side, forming the non-skin-facing surface of the incontinence pad 1, and preventing leakage of bodily fluids such as urine through the composite absorbent 4 to the outside of the incontinence pad 1.

[0067] In this invention, there are no particular restrictions on the shape, size, weight, etc. of the back sheet, as long as it can be used as the back sheet of a sanitary product. Any shape, size, weight, etc. can be adopted that corresponds to the desired leak-proof performance, breathability, strength, etc.

[0068] (Complex absorber)

[0069] In the aforementioned mild incontinence pad 1, such as Figure 1 As shown, the composite absorbent 4 has the following longitudinal shape when viewed from above: it extends in a wide region along the length direction L from near one end edge to near the other end edge, with the center portion of the light incontinence pad 1 in the length direction L as the center, and also extends in a wide region along the width direction W from near one end edge to near the other end edge, and the two ends in the length direction protrude outward in an arc shape.

[0070] More specifically, when viewed from above, the composite absorber 4 has a tapered portion in the middle of its length direction that is relatively smaller in the width direction compared to other parts, and further includes a minimum width portion in which the composite absorber 4 has the minimum width in the tapered portion, and a maximum width portion in which the composite absorber 4 has the maximum width on the outer side of the tapered portion in the length direction.

[0071] The composite absorbent 4 is formed by a defined absorbent component disposed between the surface sheet 2 and the back sheet 3 in the thickness direction of the light incontinence pad 1, capable of absorbing and retaining bodily fluids such as urine that permeate through the surface sheet 2. This absorbent component is composed of absorbent materials such as polymeric absorbents, hydrophilic fibers, and highly absorbent polymers (described later), and sheets such as thin paper that hold it in place. In other words, the composite absorbent refers to an absorbent component composed of absorbent materials capable of absorbing and retaining bodily fluids, and sheets that hold them in place.

[0072] It should be noted that in the light incontinence pad 1, the composite absorbent 4 is bonded to the surface sheet 2 and the back sheet 3 using any adhesive such as a hot melt adhesive.

[0073] Further, the composite absorbent 4 contains, as essential constituent components, the high molecular absorbent having the above-described unique ion exchange capacity with the continuous skeleton and the continuous voids having the hydrophilicity as described above, and a super absorbent polymer. The high molecular absorbent is as described later, and the super absorbent polymer is a powder or a granular substance formed of a super absorbent polymer such as a sodium acrylate copolymer, which is known in the field as SAP (Super Absorbent Polymer).

[0074] Note that the specific kind of the super absorbent polymer (SAP) is not particularly limited, and for example, an acrylic SAP in which cations exist on the surface can be appropriately used. Such an acrylic SAP in which cations exist on the surface is particularly susceptible to adverse effects on the absorbency (particularly, the water absorption amount, the water retention amount, and the absorption speed) due to ions in the body fluid, but even in the case where the composite absorbent 4 contains such a SAP, when the high molecular absorbent absorbs and temporarily retains the body fluid, the ions in the body fluid are ion-exchanged using the -COOH group and the -COONa group, and the body fluid is modified, so the absorbency of the SAP is not easily deviated, and the absorbency as an absorbent can be stably exhibited.

[0075] Note that the composite absorbent 4 can contain only the above-described high molecular absorbent and the SAP as the water-absorbing material, or can contain a water-absorbing material known in the field in addition to them. As such a water-absorbing material, for example, a hydrophilic fiber or the like can be cited, and more specifically, pulp fibers (for example, pulverized pulp or the like), cotton, rayon, cellulose-based fibers such as acetate, or the like can be cited.

[0076] Note that the composite absorbent 4 can have a structure in which such a high molecular absorbent, a SAP, and an arbitrary water-absorbing material are covered with a sheet of tissue paper or the like having a hydrophilicity.

[0077] In the present application, the outer shape, the various dimensions, the basis weight, and the like of the composite absorbent are not particularly limited as long as the effects of the present application are not hindered, and any outer shape, various dimensions, basis weight, and the like corresponding to the desired water-absorbing property, softness, strength, and the like can be adopted.

[0078] The high molecular absorbent used in the composite absorbent of the present application is described in more detail below.

[0079] [High Molecular Absorbent]

[0080] In the present application, the high molecular absorbent, if having a continuous hydrophilic skeleton and continuous pores, contains at least -COOH group and -COONa group as ion exchange groups, and has a total ion exchange capacity of -COOH group and -COONa group per unit mass in a dry state of 4.0 mg equivalent / g or more, is not particularly limited. As such a high molecular absorbent, for example, a hydrolyzate of a cross-linked polymer of at least two or more monomers containing a (meth) acrylate ester, a high molecular compound having at least one or more hydrophilic groups in a functional group can be exemplified. More specifically, a hydrolyzate of a cross-linked polymer of a (meth) acrylate ester and a compound containing two or more vinyl groups in one molecule, a high molecular compound having at least -COOH group and -COONa group can be exemplified. The above high molecular absorbent is an organic porous body having at least one or more -COONa groups in one molecule, and further having -COOH group. The -COONa group is substantially uniformly distributed in the skeleton of the porous body.

[0081] If the high molecular absorbent is a hydrolyzate of a cross-linked polymer of a (meth) acrylate ester and a compound containing two or more vinyl groups in one molecule, as described later, the continuous skeleton is easily elongated (i.e., easily expanded) when absorbing a body fluid such as urine, and the continuous pores are also easily expanded, so that more body fluid can be introduced into the continuous pores more quickly. Thus, the composite absorbent containing such a high molecular absorbent can exhibit further high absorption performance as an absorbent, and can solidly modify more body fluid, and can further less likely cause a deviation in the absorption performance of the SAP.

[0082] Note that, in the present specification, the (meth) acrylate ester refers to an acrylate ester or a methacrylate ester.

[0083] In the high molecular absorbent formed by a hydrolyzate of a cross-linked polymer of such a (meth) acrylate ester and divinylbenzene, a continuous hydrophilic skeleton is formed by an organic polymer having at least -COONa group and -COOH group, and a communication hole (continuous pore) serving as an absorption site for an absorption target liquid (i.e., a body fluid such as urine) is provided between the skeletons.

[0084] Note that, the hydrolysis treatment causes the -COOR group (i.e., carboxylate group) of the cross-linked polymer to form -COONa group or -COOH group (see Figure 2 ), so that the high molecular absorbent can have -COOR group.

[0085] The presence of -COOH groups and -COONa groups in the organic polymer forming the continuous skeleton of hydrophilicity, 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 quantitative method for weakly acidic ion exchange groups.

[0086] Here, Figure 2 is a diagram for explaining the manufacturing process of the absorbent A, which is an example of a high-molecular absorbent. The Figure 2 Here, the upper drawing shows the polymerized constituent raw material, the middle drawing shows the entire column A, which is a cross-linked polymer of (meth)acrylate and divinylbenzene, and the lower drawing shows the absorbent A obtained by subjecting the entire column A of the middle drawing to hydrolysis and drying treatment.

[0087] Hereinafter, the absorbent A formed by the hydrolyzate of a cross-linked polymer of (meth)acrylate and divinylbenzene, which is an example of a high-molecular absorbent, will be explained.

[0088] Note that, as a high-molecular absorbent, the absorbent A is not limited thereto, and can be a hydrolyzate of a cross-linked polymer of (meth)acrylate and a compound having two or more vinyl groups in one molecule, or a hydrolyzate of a cross-linked polymer of two or more kinds of monomers containing at least (meth)acrylate, and the like.

[0089] Here, if the high-molecular absorbent is an entire columnar absorbent, not only can the body fluid be quickly absorbed, but also the body fluid temporarily held in the high-molecular absorbent can be more firmly delivered to the SAP, and thus the composite absorbent containing such a high-molecular absorbent can stably exhibit further excellent absorbent performance.

[0090] Note that, in the following explanation, "the entire column A" refers to an organic porous body formed of a cross-linked polymer of (meth)acrylate and divinylbenzene before hydrolysis treatment, and is sometimes referred to as "an entire columnar organic porous body".

[0091] In addition, the "absorbent A" is a hydrolyzate of a cross-linked polymer of (meth)acrylate and divinylbenzene (the entire column A) after hydrolysis treatment and drying treatment. Note that, in the following explanation, the absorbent A refers to the absorbent in the dry state.

[0092] First, the structure of the absorbent A will be explained.

[0093] The absorbent A has a continuous skeleton of hydrophilicity and a continuous void as described above. The absorbent A, which is an organic polymer having a continuous skeleton of hydrophilicity, has a continuous skeleton of hydrophilicity and a continuous void as described above. Figure 2The cross-linked polymer obtained (whole column A) is further hydrolyzed to obtain, as shown in the formula.

[0094] The organic polymer forming the continuous skeleton of hydrophilicity has, as a structural unit, a polymerized residue of a vinyl group (hereinafter referred to as "structural unit X") and a cross-linked polymerized residue of divinylbenzene (hereinafter referred to as "structural unit Y").

[0095] Further, the polymerized residue of a vinyl group (structural unit X) in the organic polymer forming the continuous skeleton of hydrophilicity has both a -COOH group and a -COONa group generated by hydrolysis of a carboxylate group. Note that in the case where the polymerizable monomer is a (meth)acrylate, the polymerized residue of a vinyl group (structural unit X) has a -COONa group, a -COOH group, and an ester group.

[0096] In the absorbent A, the ratio of the cross-linked polymerized residue of divinylbenzene (structural unit Y) in the organic polymer forming the continuous skeleton of hydrophilicity is, for example, 0.1 to 30 mol%, preferably 0.1 to 20 mol%, with respect to the total structural units. For example, in the absorbent A in which butyl methacrylate is set as the polymerizable monomer and divinylbenzene is set as the cross-linking monomer, the ratio of the cross-linked polymerized residue of divinylbenzene (structural unit Y) in the organic polymer forming the continuous skeleton of hydrophilicity is, for example, about 3%, preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%, with respect to the total structural units.

[0097] Note that if the ratio of the cross-linked polymerized residue of divinylbenzene in the organic polymer forming the continuous skeleton of hydrophilicity is 0.1 mol% or more, the strength of the absorbent A does not easily decrease, and if the ratio of the cross-linked polymerized residue of divinylbenzene is 30 mol% or less, the absorption amount of the absorption target liquid does not easily decrease.

[0098] In addition, in the absorbent A, the organic polymer forming the continuous skeleton of hydrophilicity can contain only the structural unit X and the structural unit Y, or in addition to the structural unit X and the structural unit Y, can have a structural unit other than the structural unit X and the structural unit Y, that is, a polymerized residue of a monomer other than the (meth)acrylate and the divinylbenzene.

[0099] As the structural unit other than the structural unit X and the structural unit Y, for example, a polymerization residue of a monomer such as styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, isobutylene, butadiene, isoprene, chlorobutadiene, chloroethylene, bromoethylene, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and the like can be exemplified.

[0100] Note that the ratio of the structural unit other than the structural unit X and the structural unit Y in the organic polymer forming the continuous hydrophilic skeleton is, for example, 0 to 50 mol%, preferably 0 to 30 mol%, relative to the total structural units.

[0101] In addition, the thickness of the continuous hydrophilic skeleton of the absorbent A is preferably 0.1 to 100 μm. If the thickness of the continuous hydrophilic skeleton of the absorbent A is 0.1 μm or more, the space (pore) in the porous body for introducing the absorption target liquid (body fluid) is not easily crushed at the time of absorption, and the absorption amount is not easily reduced. On the other hand, if the thickness of the continuous hydrophilic skeleton is 100 μm or less, an excellent absorption speed is easily obtained.

[0102] Note that the fine pore structure of the continuous hydrophilic skeleton of the absorbent A is a continuous bubble structure, and thus the thickness of the continuous skeleton is evaluated as the diameter (μm) of the circle circumscribed to the skeleton cross section of the test piece for electron microscope measurement. The continuous skeleton is formed with the spacing between water droplets removed by dehydration / drying treatment after hydrolysis, and thus is mostly in the shape of a polygon. Therefore, the thickness of the continuous skeleton is evaluated as the average of the diameters of the circles circumscribed to the polygonal cross sections. In addition, there are rare cases in which a small hole is formed in the polygon, and in this case, the circle circumscribed to the cross section of the polygon surrounding the small hole is measured.

[0103] Further, the average diameter of the continuous pores of the absorbent A is preferably 1 μm to 1000 μm. If the average diameter of the continuous pores of the absorbent A is 1 μm or more, the space (pore) in the porous body for introducing the absorption target liquid (body fluid) is not easily crushed at the time of absorption, and the absorption speed is not easily reduced. On the other hand, if the average diameter of the continuous pores is 1000 μm or less, an excellent absorption speed is easily obtained. Therefore, the composite absorbent having such an absorbent A can stably exhibit excellent absorption performance.

[0104] In particular, in the case where the porosity per unit volume of the high molecular absorbent described later is 85% or more and the average diameter of the continuous pores is 1 μm to 1000 μm, the body fluid can be absorbed and modified using more fine pores, and thus has the advantage that more excellent ion exchange efficiency can be achieved.

[0105] Note that the average diameter (μm) of the continuous pores of the absorbent A can be measured by the mercury intrusion method using the maximum value of the pore distribution curve obtained by the mercury intrusion method described above. For the sample for measuring the average diameter of the continuous pores, a substance obtained by drying for 18 hours or more using a reduced-pressure drier set at a temperature of 50°C is used as the sample regardless of the ionic form of the absorbent A. Note that the final limit pressure is set to 0 Torr.

[0106] Here, Figure 3 is a SEM photograph at a magnification of 50 times of the absorbent A, Figure 4 is a SEM photograph at a magnification of 100 times of the absorbent A, Figure 5 is a SEM photograph at a magnification of 500 times of the absorbent A, Figure 6 is a SEM photograph at a magnification of 1000 times of the absorbent A, and Figure 7 is a SEM photograph at a magnification of 1500 times of the absorbent A.

[0107] These Figures 3 to 7 The absorbent A shown in the drawing is an example of an absorbent in which butyl methacrylate is used as the polymerization monomer and divinylbenzene is used as the cross-linking monomer, and has a structure of a cube of 2 mm on each side.

[0108] Figures 3 to 7 The absorbent A shown in the drawing has many bubble-shaped large pores, and further has portions in which these bubble-shaped large pores overlap each other. The absorbent A has a continuous bubble structure in which the portions in which the large pores overlap each other form a common opening (mesopore), that is, a continuous bubble structure body (continuous large pore structure body).

[0109] The portions in which the large pores overlap each other form a common opening (mesopore) having an average diameter of 1 to 1000 μm, preferably 10 to 200 μm, and particularly preferably 20 to 100 μm in the dried state, and most of them form an opening structure. If the average diameter of the mesopore in the dried state is 1 μm or more, the absorption speed of the absorption target liquid is more excellent. On the other hand, if the average diameter of the mesopore in the dried state is 1000 μm or less, the absorbent A is less likely to be brittle.

[0110] Note that the number of the large pores overlapping each other is about 1 to 12 for one large pore, and most of them are about 3 to 10.

[0111] In addition, by the absorbent A having such a continuous bubble structure, it is possible to uniformly form a large pore group and a mesopore group, and it is possible to further increase the pore volume and the specific surface area compared to a particle aggregation type porous body described in Japanese Patent Application Publication No. 8-252579 and the like.

[0112] Note that the total pore volume of the fine pores (voids) of the absorbent A is preferably 0.5 to 50 mL / g, more preferably 2 to 30 mL / g. If the total pore volume of the absorbent A is 0.5 mL / g or more, the space (voids) of the porous body for introducing the absorption target liquid (body fluid) is not easily crushed at the time of absorption, and the absorption amount and the absorption speed are not easily reduced. On the other hand, if the total pore volume of the absorbent A is 50 mL / g or less, the strength of the absorbent A is not easily reduced.

[0113] Note that the total pore volume can be measured by a mercury porosimetry. For the measurement of the total pore volume, a material obtained by drying for 18 hours or more using a reduced-pressure drier set at a temperature of 50°C is used regardless of the ionic form of the absorbent A. Note that the final limit pressure is set to 0 Torr.

[0114] The following describes the appearance of the absorbent A when it comes into contact with a liquid such as a body fluid (hereinafter simply referred to as "body fluid"), and the same applies to the case where the composite absorbent 4 containing the absorbent A comes into contact with a body fluid.

[0115] First, Figures 3 to 7 The continuous voids of the absorbent A shown in the drawing are voids in which a plurality of fine pores (voids) are connected to each other, and a large number of voids can be confirmed with the naked eye from the appearance. If a body fluid such as urine comes into contact with the absorbent A provided with such a large number of voids, first, the continuous skeleton of the hydrophilic material is elongated (i.e., swells) by introducing a part of the body fluid instantaneously using osmotic pressure. The elongation of the continuous skeleton occurs in substantially all directions. For the absorbent A, the outer shape of the absorbent A is increased by the elongation of the continuous skeleton at the time of water absorption, and the size of each void is also increased accordingly. If the size of the void is increased in this way, the volume inside the void is increased, and thus the amount of the body fluid that can stay inside the void is also increased. The absorbent A that has absorbed a certain amount of the body fluid in this way can further absorb a predetermined amount of the body fluid into the enlarged voids by capillary phenomenon.

[0116] Note that the body fluid absorbed into the continuous skeleton of the hydrophilic material of the absorbent A is not easily released from the continuous skeleton (i.e., water is not easily released), and on the other hand, the body fluid absorbed into the continuous voids is easily released, and thus in the composite absorbent, the body fluid absorbed into the continuous voids is released and transported to the SAP having a high water-retaining capacity, and is firmly held in the SAP.

[0117] In addition, the body fluid absorbed by the absorbent A is increased compared to the body fluid absorbed into the continuous skeleton of the hydrophilic material, and stays inside the voids. Most of the absorption of the body fluid by the absorbent A is performed by staying the body fluid inside the voids using capillary phenomenon, and thus the porosity (i.e., the volume of the voids per unit volume of the absorbent A) is larger, and thus more body fluid can be absorbed.

[0118] The porosity of the high molecular absorbent per unit volume is preferably 85% or more, and more preferably 90% or more. If the porosity of the high molecular absorbent per unit volume is 85% or more, more body fluid can be absorbed, and the quality can be improved, and thus the absorbency of the SAP can be less likely to be deviated. Thus, the composite absorbent containing the high molecular absorbent can further stably and favorably exhibit the absorbency as an absorbent.

[0119] For example, if the porosity of the absorbent A described above is calculated, it is as follows. Figures 3 to 7

[0120] First, the specific surface area of the absorbent A obtained by the mercury porosimetry is 400 m 2 / g, and the pore volume is 15.5 mL / g. The 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.

[0121] Here, if the specific gravity of the absorbent A is assumed to be 1 g / mL, the volume of the pores in 1 g of the absorbent A, that is, the pore volume is 15.5 mL, and in addition, the volume of 1 g of the absorbent A is 1 mL.

[0122] Thus, the total volume (volume) of 1 g of the absorbent A is 15.5 + 1 (mL), and the ratio of the pore volume in this is the porosity, and thus the porosity of the absorbent A is 15.5 / (15.5 + 1) x 100 = 94%.

[0123] The absorbent A having such a continuous skeleton and continuous pores with hydrophilicity, that is, the high molecular absorbent, is, for example, in the form of particles, tablets, or the like, and is used in a composite absorbent for absorbing body fluid such as urine, such as the composite absorbent 4 of the light incontinence pad 1 described above.

[0124] Further, the high molecular absorbent contains at least the -COOH group and the -COONa group as the ion exchange groups as described above, and has a unique ion exchange capacity in which the total ion exchange capacity of the -COOH group and the -COONa group per unit mass in the dry state is 4.0 mg equivalent / g or more, and thus when the high molecular absorbent absorbs and temporarily retains the body fluid, the ions (particularly, Ca 2+ , Mg 2+ ​The ion exchange of the ions (particularly, the divalent ions) in the body fluid (urine) by the -COOH group and the -COONa group can greatly reduce the ion concentration in the body fluid (urine), i.e., can change the body fluid (urine) to a body fluid that is less likely to adversely affect the absorption performance of the SAP. Therefore, the composite absorbent using such a high molecular weight absorbent can stably exhibit the absorption performance as an absorbent because the body fluid can be changed by the high molecular weight absorbent and then supplied to the SAP, and the absorption performance of the SAP is less likely to be deviated.

[0125] Here, Figure 8 the graph showing the relationship between the ion concentration of the monovalent and divalent ions in the body fluid (urine) and the absorption performance (water absorption amount, water retention amount, and absorption speed) of the SAP, Figure 9 the graph showing the influence of the absorbent A as an example of the high molecular weight absorbent on the ion concentration of the divalent ions in the body fluid (urine).

[0126] As Figure 8 shown, if the ion concentration of the monovalent and divalent ions in the body fluid (urine) increases, the water absorption amount, the water retention amount, and the absorption speed of the SAP all decrease. In particular, it is known that the influence of the ion concentration of the divalent ions on the absorption performance of the SAP is large, and even a small amount of the divalent ions greatly reduces the water absorption amount, the water retention amount, and the absorption speed of the SAP.

[0127] Thus, the ion concentration in the body fluid (urine) greatly adversely affects the absorption performance of the SAP, and the ion concentration is deviated depending on the difference in the dietary life (e.g., the components of the food taken, etc.), the living environment (e.g., the frequency of sweating or urination, etc.), and the like, and thus the kind of the body fluid (i.e., the kind of the body fluid, the individual difference, etc.) is deviated, and accordingly, the absorption performance of the SAP is deviated.

[0128] However, the absorbent A as an example of the present application contains at least the -COOH group and the -COONa group as the ion exchange groups, and has a unique ion exchange capacity in which the total ion exchange capacity of the -COOH group and the -COONa group per unit mass in the dry state is 4.0 mg equivalent / g or more, and thus, as Figure 9 shown, the ion exchange of the ions (particularly, the divalent ions) in the body fluid (urine) by the -COOH group and the -COONa group can greatly reduce the ion concentration in the body fluid (urine), i.e., can change the body fluid (urine) to a body fluid that is less likely to adversely affect the absorption performance of the SAP.

[0129] Note that, Figure 9 the graph shown in FIG. 1 is obtained by measuring the change rate of the ion concentration (i.e., the ion exchange rate of the absorbent A) of the actual urine (actual urine A, B, and C) of three people having different ion concentrations of the divalent ions before and after the contact with the absorbent A as follows.

[0130] First, the ion concentration (mEq / L) of each of the divalent ions of the actual urine A, B, and C was measured using an ion meter (HORIBA Advanced Techno, Co., Ltd., HORIBA Compact Calcium Ion Meter LAQUAtwin-Ca-11). The measured ion concentration was set as the ion concentration "before contact with the absorbent A".

[0131] Next, 0.2 g of the high-molecular absorbent (absorbent A) was added to a glass filter (a climbing glass filter, Model No. 0777-01-101, outer diameter x leg length (mm): φ7 x 80, filter diameter: φ20 mm, capacity: 30 mL, material: borosilicate glass, pore diameter: 100 to 120 μm), 30 mL of the above actual urine was injected, and the divalent ion concentration (mEq / L) of the obtained filtrate was measured using the above ion meter. The measured ion concentration was set as the ion concentration "after contact with the absorbent A".

[0132] Next, the ion concentration change amount (mEq / L) before and after contact with the absorbent A was calculated by subtracting the ion concentration after contact with the absorbent A from the ion concentration before contact with the absorbent A. Further, the change rate (%) of the divalent ion concentration of each of the actual urine A, B, and C was calculated by dividing the ion concentration change amount (mEq / L) before and after contact with the absorbent A by the ion concentration before contact with the absorbent A and multiplying by 100.

[0133] Note that the above measurement was performed under the conditions of a temperature of 25°C and a humidity of 60%.

[0134] As described above, the absorbent A of the present application example has the above unique ion exchange capacity that the conventional water-absorbing material does not have, and can not only quickly absorb and temporarily hold a body fluid such as urine but also perform ion exchange of ions (particularly, divalent ions) in the body fluid and modify the body fluid into a body fluid that is less likely to adversely affect the absorption performance of the SAP.

[0135] Thus, the composite absorbent containing the absorbent A (high-molecular absorbent) can modify the body fluid and deliver the modified body fluid to the SAP, and therefore the absorption performance of the SAP is less likely to be deviated, and the absorption performance as an absorbent can be stably exhibited.

[0136] Note that in the present application, the total ion exchange capacity of the -COOH group and the -COONa group per unit mass of the high-molecular absorbent in the dry state is preferably 6.0 mg equivalent / g or more, and more preferably 8.0 mg equivalent / g or more.

[0137] Note that in the present application, the ion exchange rate of the polyvalent ions (i.e., ions of 2 valence or more) of the high molecular absorbent is preferably 50% or more. If the ion exchange rate of the polyvalent ions of the high molecular absorbent is 50% or more, the body fluid can be modified more reliably, and thus the deviation in the absorbency of the SAP can be less likely to occur. Therefore, the composite absorbent containing such a high molecular absorbent can further stably exhibit the absorbency as an absorbent.

[0138] Note that the ion exchange rate of the polyvalent ions of the high molecular absorbent is more preferably 60% or more, and further preferably 70% or more.

[0139] Here, the ion exchange rate of the polyvalent ions of the high molecular absorbent can be measured by any of ICP emission spectrometry, IC analysis, atomic absorbance analysis, and the like, and for example, the ion exchange rate of the ions of 2 valence can be measured as follows.

[0140] <Measurement method of ion exchange rate of ions of 2 valence of high molecular absorbent>

[0141] (1) Urea 200 g, sodium chloride 80 g, magnesium sulfate 8 g, calcium chloride 3 g, and a colorant: blue No. 1 about 1 g were dissolved in ion exchange water 10 L, thereby producing artificial urine.

[0142] (2) The concentration (mEq / L) of the ions of 2 valence of the produced artificial urine was measured using an ion meter (manufactured by HORIBA Advanced Techno, Co., Ltd., HORIBA small calcium ion meter LAQUAtwin-Ca-11). The measured ion concentration was set as the "ion concentration before contact with the high molecular absorbent".

[0143] (3) The high molecular absorbent 0.2 g as a sample for measurement was added to a glass filter (climbing type glass filter, model number: 0777-01-101, outer diameter x leg length (mm): φ7 x 80, filter diameter: φ20 mm, capacity: 30 mL, material: borosilicate glass, pore diameter: 100 to 120 μm), and the above artificial urine 30 mL was injected, and the concentration (mEq / L) of the ions of 2 valence of the obtained filtrate was measured using the above ion meter. The measured ion concentration was set as the "ion concentration after contact with the high molecular absorbent".

[0144] (4) The ion concentration before contact with the polymer absorbent is subtracted from the ion concentration after contact with the polymer absorbent, and thus the ion concentration change amount (mEq / L) before and after contact with the polymer absorbent is calculated, and further the ion concentration change amount (mEq / L) before and after contact with the polymer absorbent is divided by the ion concentration before contact with the polymer absorbent and multiplied by 100, and thus the change rate (%) of the ion concentration of 2 valence is calculated. In the present specification, this "change rate (%) of the ion concentration of 2 valence" is set as "ion exchange rate of 2 valence of the polymer absorbent".

[0145] Note that the above measurement is all performed under the conditions of temperature 25°C and humidity 60%.

[0146] In addition, in the case where the sample for measurement (polymer absorbent) is used by being recovered from the product of the sanitary product, it can be obtained according to the following "Recovery method of sample for measurement (polymer absorbent)".

[0147] "Recovery method of sample for measurement (polymer absorbent)"

[0148] (1) The surface sheet or the like is peeled from the product of the sanitary product, and the absorbent is exposed.

[0149] (2) The sample for measurement (polymer absorbent) is caused to fall from the exposed absorbent, and a substance other than the sample for measurement (for example, pulp, synthetic resin fiber, or the like) is removed using tweezers or the like.

[0150] (3) As a magnifying observation means, a microscope or a simple magnifying glass is used, and at the same time, the sample for measurement is recovered using tweezers or the like, 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 confirmed. 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 confirmed, and for example, a magnification of 25 to 50 times can be cited.

[0151] (4) The sample for measurement thus recovered is used as a sample for measurement in various measurement methods.

[0152] Further, in the present application, the water absorption amount per unit mass of the polymer absorbent is preferably 30 g / g or more. If the polymer absorbent has a water absorption amount of 30 g / g or more, more body fluid can be absorbed, and the quality can be improved firmly, and thus the deviation of the absorption performance of SAP can be less likely to occur. Therefore, the composite absorbent containing such a polymer absorbent can further stably exert the absorption performance as an absorbent.

[0153] Note that the water absorption amount per unit mass of the polymer absorbent is more preferably 40 g / g or more, and further preferably 50 g / g or more.

[0154] Here, the water absorption amount per unit mass of the high molecular absorbent can be measured as follows.

[0155] <Method for measuring water absorption amount per unit mass of high molecular absorbent>

[0156] (1) 1 g of a sample (high molecular absorbent) for measurement was enclosed in a mesh bag (NBC Meshtec Inc. product, N-NO255HD 115 (standard width: 115 cm, 255 meshes / 2.54 cm, opening: 57 μm, wire diameter: 43 μm, thickness: 75 μm)) cut to 10 cm square. Note that the mesh bag was previously measured for mass (g). In addition, in the case where the sample (high molecular absorbent) for measurement is recovered from a product of a sanitary product, it can be obtained according to the aforementioned <Method for recovering sample (high molecular absorbent) for measurement>.

[0157] (2) The mesh bag with the sample enclosed was immersed in physiological saline (0.9% aqueous sodium chloride solution) for 1 hour.

[0158] (3) The mass (g) of the mesh bag after water control for 5 minutes was measured.

[0159] (4) The water absorption amount (g) of the sample was calculated by subtracting the mass of the sample (= 1 g) and the total mass of the mesh bag from the mass of the mesh bag after water control measured in the aforementioned (3), and further dividing the water absorption amount by the mass of the sample (= 1 g), thereby obtaining the water absorption amount per unit mass (g / g) of the sample (high molecular absorbent).

[0160] Note that the above measurement was performed under conditions of temperature 25°C and humidity 60%.

[0161] The production method of such a high molecular absorbent will be described in detail below, taking the aforementioned absorbent A as an example.

[0162] [Production method of high molecular absorbent]

[0163] The aforementioned absorbent A can be obtained by passing through a crosslinking polymerization step and a hydrolysis step as shown in Figure 2 . These steps will be described below.

[0164] (Crosslinking polymerization step)

[0165] First, an oil-soluble monomer, a crosslinkable monomer, a surfactant, water, and a polymerization initiator as needed were mixed to obtain a water-in-oil droplet type emulsion. The water-in-oil droplet type emulsion is an emulsion in which water droplets are dispersed in an oil phase forming a continuous phase.

[0166] Next, for the aforementioned absorbent A, as shown in Figure 2As an oil-soluble monomer, butyl methacrylate as a (meth)acrylate ester was used, as a cross-linkable monomer, divinylbenzene was used, as a surfactant, sorbitan monooleate was used, and further, as a polymerization initiator, isobutyronitrile was used, and cross-linking polymerization was performed to obtain the monolith column A.

[0167] Specifically, for the absorbent A, as shown in the above diagram, 9.2 g of t-butyl methacrylate as an oil-soluble monomer, 0.28 g of divinylbenzene as a cross-linkable monomer, 1.0 g of sorbitan monooleate (hereinafter referred to as "SMO") as a surfactant, and 0.4 g of 2,2'-azobis(isobutyronitrile) as a polymerization initiator were mixed and uniformly dissolved. Figure 2

[0168] Next, the mixture of t-butyl methacrylate / divinylbenzene / SMO / 2,2'-azobis(isobutyronitrile) was added to 180 g of pure water, and stirring was performed under reduced pressure using a vacuum stirring defoaming mixer (manufactured by EME, Inc.) as a planetary stirring device to obtain a water-in-oil droplet type emulsion.

[0169] Further, the emulsion was quickly transferred to a reaction vessel and sealed, and polymerization was performed under the conditions of 60°C for 24 hours. After the completion of polymerization, the contents were taken out, extracted with methanol, and dried under reduced pressure to obtain the monolith column A having a continuous macroporous structure. Note that as a result of observing the internal structure of the monolith column A using SEM, the monolith column A had a continuous bubble structure, and the thickness of the continuous skeleton was 5.4 μm. In addition, the average diameter of the continuous pores was 36.2 μm, and the total pore volume was 15.5 mL / g as measured using a mercury porosimeter.

[0170] Note that the content of divinylbenzene with respect to the total monomers is preferably 0.3 to 10 mol%, and more preferably 0.3 to 5 mol%. In addition, the ratio of divinylbenzene with respect to the total of butyl methacrylate and divinylbenzene is preferably 0.1 to 10 mol%, and more preferably 0.3 to 8 mol%. Note that in the above absorbent A, the ratio of butyl methacrylate with respect to the total of butyl methacrylate and divinylbenzene was 97.0 mol%, and the ratio of divinylbenzene was 3.0 mol%.

[0171] The amount of the surfactant to be added 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.

[0172] ​Note that, in order to control the bubble shape, size, etc. of the monolithic column A, methanol, stearyl alcohol, and the like can be co-presented in the polymerization system; carboxylic acids such as stearic acid; hydrocarbons such as octane, dodecane, and toluene; cyclic ethers such as tetrahydrofuran and dioxane; and the like.

[0173] Further, the mixing method when forming the water-in-oil droplet type emulsion is not particularly limited, and for example, a method in which the components are gathered and mixed at once, a method in which oil-soluble components such as the oil-soluble monomer, the surfactant, and the oil-soluble polymerization initiator, and water-soluble components such as water and the water-soluble polymerization initiator are separately and uniformly dissolved, and then the components are mixed, and the like can be employed.

[0174] Further, the mixing device for forming the emulsion is also not particularly limited, and a general mixing machine, a homogenizer, a high-pressure homogenizer, and the like can be employed according to the desired emulsion particle diameter, and further, a so-called planetary stirring device in which the processed material is added to a mixing container, and the mixing container is rotated around a revolution axis while being revolved, thereby stirring and mixing the processed material, and the like can be used.

[0175] Further, the mixing conditions are also not particularly limited, and the stirring rotation speed, the stirring time, and the like can be arbitrarily set according to the desired emulsion particle diameter. Note that, when the above planetary stirring device is used, water droplets in the W / O emulsion can be uniformly generated, and the average diameter thereof can be arbitrarily set in a wide range.

[0176] The polymerization conditions of the water-in-oil droplet type emulsion can be various conditions according to the types of the monomer, the initiator, and the like. For example, in the case where azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and the like are used as the polymerization initiator, the polymerization can be performed in a sealed container under an inactive atmosphere at a temperature of 30 to 100°C for 1 to 48 hours, and in the case where hydrogen peroxide-ferrous chloride, sodium persulfate-sodium sulfite, and the like are used as the polymerization initiator, the polymerization can be performed in a sealed container under an inactive atmosphere at a temperature of 0 to 30°C for 1 to 48 hours.

[0177] Note that, after the polymerization is completed, the content is taken out, and Soxhlet extraction is performed using a solvent such as isopropyl alcohol, thereby removing the unreacted monomer and the residual surfactant, and the monolithic column A shown in FIG. 2 can be obtained. Figure 2

[0178] (Hydrolysis Step)

[0179] Next, the step (hydrolysis step) in which the monolithic column A (crosslinked polymer) is hydrolyzed to obtain the absorbent A will be described.

[0180] ​First, the monolith column A is impregnated with zinc bromide in dichloroethane, stirred at 40°C for 24 hours, and then hydrolyzed by sequentially contacting with methanol, 4% hydrochloric acid, 4% aqueous sodium hydroxide, and water, and dried to obtain the absorbent A in a block shape. Further, the absorbent A in a block shape is pulverized to a predetermined size to obtain the absorbent A in a granular shape. Note that the form of the absorbent A is not limited to a granular shape, and for example, the absorbent A can be formed into a sheet shape at the time of drying or after drying.

[0181] In addition, the method of hydrolyzing the monolith column A is not particularly limited, and various methods can be employed. For example, a method of contacting a strong base such as sodium hydroxide with a solvent such as toluene, xylene, chloroform, dichloroethane, tetrahydrofuran, isopropyl ether, dimethylformamide, dimethylacetamide, methanol, ethanol, carboxylic acid such as acetic acid, propionic acid, or water; or a method of contacting a hydrogen halide such as 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, or a Bronsted acid such as can be employed.

[0182] In addition, among the polymerization raw materials of the organic polymer that forms the continuous hydrophilic skeleton of the absorbent A, the (meth)acrylic acid ester is not particularly limited, and a C1 to C10 (i.e., carbon number 1 to 10) alkyl ester of (meth)acrylic acid is preferred, and a C4 (i.e., carbon number 4) alkyl ester of (meth)acrylic acid is particularly preferred.

[0183] Note that the C4 alkyl ester of (meth)acrylic acid includes, for example, t-butyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate.

[0184] In addition, the monomer used in the cross-linking polymerization can be only the (meth)acrylic acid ester and the divinylbenzene, or can contain other monomers in addition to the (meth)acrylic acid ester and the divinylbenzene.

[0185] In the latter case, the other monomers are not particularly limited, and for example, styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobutylene, butadiene, isoprene, chlorobutadiene, chloroethylene, bromoethylene, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate can be mentioned.

[0186] Note that the ratio of other monomers than the (meth)acrylate and divinylbenzene in all the monomers used in the cross-linking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

[0187] In addition, the surfactant is not limited to the above-described sorbitan monooleate, and any surfactant can be used as long as it can form a water-in-oil droplet (W / O) emulsion when the monomers for cross-linking polymerization and water are mixed. As such a surfactant, nonionic surfactants such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, and polyoxyethylene sorbitan monooleate; anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, and dioctyl sodium sulfosuccinate; cationic surfactants such as distearyl dimethyl ammonium chloride; and amphoteric surfactants such as lauryl dimethyl betaine can be used. These surfactants can be used alone or in combination.

[0188] In addition, the polymerization initiator is suitably a compound that generates radicals by heat and light irradiation. Further, the polymerization initiator can be water-soluble or oil-soluble, and examples thereof include azobis(4-methoxy-2,4-dimethylvaleronitrile), azobis(isobutyronitrile), azobisdimethylvaleronitrile, azobiscyclohexanecarbonitrile, azobiscyclohexanemethylnitrile, azobis(2-methylpropionamidine) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-sodium bisulfite, and tetramethylthiuram disulfide. However, depending on the system, polymerization can proceed even without the addition of a polymerization initiator by heating or light irradiation alone, and thus the addition of a polymerization initiator is not necessary when using such a system.

[0189] Note that the composite absorbent of the present application can be applied to various sanitary products other than the light incontinence pad of the above-described embodiments, such as a pant-type disposable diaper, a belt-type disposable diaper, a sanitary napkin for use in menstruation, an absorbent liner, an absorbent pad (e.g., a decubitus pad, a lying-in pad, and the like), an absorbent sheet, a breast pad, a disposable diaper for pets, an absorbent pad for pets, a feces disposal sheet for pets, a wet sheet, a wet wipe, a cosmetic wipe, a mask, and the like. Thus, the body fluid to be absorbed by the composite absorbent is a liquid discharged from a wearer of the sanitary product, and examples thereof include urine, sweat, feces, menstrual blood, leucorrhea, breast milk, blood, and exudate.

[0190] In addition, the present application is not limited to the above-described embodiments, and the like, and can be appropriately combined, substituted, changed, and the like, within a range that does not depart from the object and the gist of the present application.

[0191] Explanation of Reference Signs

[0192] 1 Light incontinence pad

[0193] 2 surface sheet

[0194] 3 backsheet

[0195] 4 composite absorbent

Claims

1. A composite absorber, characterized in that, It is a composite absorbent used to absorb bodily fluids. The composite absorbent comprises: a polymeric absorbent with a hydrophilic continuous framework and continuous pores, and a highly absorbent polymer. The polymeric absorbent is a hydrolysate of a cross-linked polymer of (meth)acrylate and divinylbenzene, which is a compound containing two or more vinyl groups in one molecule. The ratio of the crosslinked polymer residues of the divinylbenzene in the organic polymer forming the hydrophilic continuous backbone is 0.1 to 20 mol% relative to all structural units. The polymeric absorbent contains at least -COOH and -COONa groups as ion exchange groups, and the total ion exchange capacity of the -COOH and -COONa groups per unit mass in the dry state is 6.0 mg equivalents / g or more, and the water absorption capacity per unit mass of the polymeric absorbent is 30 g / g or more.

2. The composite absorber according to claim 1, characterized in that, The ion exchange rate of the multivalent ions in the polymer absorbent is over 50%.

3. The composite absorber according to claim 1 or 2, characterized in that, For the polymeric absorbent, the porosity per unit volume of the polymeric absorbent is 85% or more.

4. The composite absorber according to claim 1 or 2, characterized in that, The average diameter of the continuous pores in the polymer absorbent is 1 μm to 1000 μm.

5. The composite absorber according to claim 1 or 2, characterized in that, The polymeric absorbent is a monolithic columnar absorbent.

6. The composite absorber according to claim 1 or 2, characterized in that, The highly absorbent polymer is an acrylic-based highly absorbent polymer with cations present on its surface.

7. A hygiene product, characterized in that, It has the composite absorber as described in any one of claims 1 to 6.

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