Composite absorbent and sanitary article

Abstract

Provided is an absorbent having high absorbency that can instantaneously absorb a large amount of body fluid. A composite absorbent (4) according to the present invention is characterized by being a composite absorbent for absorbing body fluid, the composite absorbent comprising: a high-molecular absorbent having a continuous skeleton and a continuous void, the high-molecular absorbent introducing moisture into the continuous skeleton and then into the continuous void when absorbing moisture; and a superabsorbent polymer.

Description

Technical Field

[0001] This invention relates to composite absorbents and sanitary products having the same. Background Technology

[0002] For hygiene products such as disposable diapers and sanitary napkins, it is known that these products contain porous materials such as sponge materials and highly absorbent polymers (so-called "SAP") with high absorbency as absorbents.

[0003] For example, Patent Document 1 discloses an absorbent article comprising a polymer foam material (porous material) formed from a hydrophilic flexible structure of interconnected continuous air bubbles. Patent Document 2 discloses an absorbent article using an absorbent body composed of absorbent resin particles (highly absorbent polymer) with excellent absorption capacity and hydrophilic fibers such as pulp fibers with excellent absorption speed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 3231320

[0007] Patent Document 2: International Publication No. 2013 / 018571 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The absorbent raw materials used in these conventional absorbents have the following characteristics.

[0010] For example, the porous material disclosed in Patent Document 1 can absorb water instantly by introducing water into multiple pores with a defined space. However, the space that can absorb water is limited to the defined space formed by the multiple pores, so it is difficult to absorb a large amount of water.

[0011] On the other hand, the superabsorbent polymer (SAP) disclosed in Patent Document 2 can retain a large amount of water (i.e., high water retention capacity) by expanding the space of the volume fraction of the introduced water (i.e., expansion) and introducing water, but it is difficult to absorb water instantly due to its slow water absorption rate.

[0012] In addition, in order to compensate for the shortcomings of these absorbent materials, it was also considered that these absorbent materials were used at the same time. However, in cases such as when the wearer of sanitary products excretes a large amount of bodily fluids such as urine and menstrual blood, the amount that can be absorbed by the porous material may be exceeded in the initial stage of absorption (absorption limit). As a result, the bodily fluids that are not absorbed by the porous material cannot be absorbed immediately even by SAP, so the result may not be high absorption performance.

[0013] The present invention was made in view of this problem, and its purpose is to provide an absorbent with high absorption performance that can absorb large amounts of bodily fluids instantly.

[0014] Solution for solving the problem

[0015] One aspect (Aspect 1) of the present invention is a composite absorbent, characterized in that it is a composite absorbent for absorbing bodily fluids.

[0016] The aforementioned composite absorbent comprises: a polymeric absorbent with a hydrophilic continuous framework and continuous pores, and a highly absorbent polymer.

[0017] When absorbing moisture, the aforementioned polymeric absorbent introduces the moisture into the aforementioned continuous skeleton and then into the aforementioned continuous pores.

[0018] In this method 1, when the composite absorbent with a hydrophilic continuous skeleton and a continuous pore polymer absorbent absorbs body fluids such as urine and menstrual blood, the hydrophilic continuous skeleton expands by instantly introducing the body fluid through osmotic pressure, thereby increasing the volume of the continuous pores. This allows the body fluid to be introduced into the expanded continuous pores, thus instantly absorbing a large amount of body fluid. The absorbed body fluid can then be transported to the highly absorbent polymer (SAP) with high water retention capacity and firmly retained within the SAP.

[0019] Therefore, the composite absorber of this method can perform high absorption performance as an absorber.

[0020] In addition, another aspect of the present invention (aspect 2) is characterized in that, in the composite absorbent of aspect 1, when the aforementioned polymer absorbent absorbs water at its water retention limit, the volume of the expanded polymer absorbent is greater than the volume of the introduced water.

[0021] The composite absorbent of this method can achieve higher absorption performance because the polymer absorbent can introduce a larger amount of water into the continuous pores.

[0022] The present invention is further characterized in another aspect (mean 3) in that, in the composite absorbent of means 1 or 2, the water absorption capacity of the continuous pores of the aforementioned polymer absorbent is greater than the water absorption capacity of the aforementioned continuous skeleton.

[0023] The composite absorbent of this method can exhibit even higher absorption performance because the polymer absorbent can introduce a larger amount of water into the continuous pores.

[0024] The present invention is further characterized in that, in the composite absorbent of any one of the above embodiments 1 to 3, the mass ratio of the water absorption of the aforementioned continuous pores of the aforementioned polymer absorbent to the water absorption of the aforementioned continuous skeleton is 60:40 to 95:5.

[0025] In this composite absorbent, because the mass ratio of water absorption capacity of the continuous pores to the continuous skeleton of the polymer absorbent is within the specific range mentioned above, the polymer absorbent can more effectively introduce water into the continuous pores after introducing it into the continuous skeleton.

[0026] The further embodiment of the present invention (embodiment 5) is characterized in that, in the composite absorbent of any one of the embodiments 1 to 4 above, the absorption rate of the aforementioned polymer absorbent is relatively high from the moment it begins to absorb water until it reaches the water retention limit, and the absorption rate is relatively low after the water retention limit.

[0027] In this composite absorbent, the absorption rate of the polymeric absorbent is relatively high in the initial stage of water absorption, from the moment water absorption begins until the water retention limit is reached. This allows the body fluid to be instantly introduced into the continuous skeleton. On the other hand, in the later stage of water absorption after the water retention limit, the absorption rate of the polymeric absorbent is relatively low. This allows the body fluid to be firmly introduced into the continuous pores that have expanded due to the expansion of the continuous skeleton. Therefore, the high absorption performance of the absorbent can be more effectively utilized.

[0028] The further embodiment of the present invention (e.g., embodiment 6) is characterized in that, in the composite absorbent of any one of embodiments 1 to 5 above, the aforementioned polymeric absorbent is a monolithic absorbent.

[0029] Because the polymer absorbent in this composite absorbent is a monolithic columnar absorbent, it can rapidly absorb body fluids and more firmly deliver the body fluids temporarily held in the polymer absorbent to the SAP.

[0030] The further embodiment of the present invention (embodiment 7) is characterized in that, in the composite absorbent of any one of embodiments 1 to 6 above, the aforementioned polymer absorbent is a hydrolysate of a cross-linked polymer of (meth)acrylate and a compound containing two or more vinyl groups, and contains at least one -COONa group.

[0031] The composite absorbent of this method has the above-mentioned specific structure through the polymer absorbent. When absorbing body fluid, the hydrophilic continuous skeleton is easy to elongate (i.e., easy to expand) and the continuous pores are also easy to expand. Therefore, more body fluid can be introduced into the continuous pores more quickly, and as an absorbent, it can exert a further superior absorption performance.

[0032] In addition, another aspect (mean 8) of the present invention is a sanitary product characterized by having a composite absorbent of any one of the above-described means 1 to 7.

[0033] The sanitary products of this method, having a composite absorbent body of any one of the above methods 1 to 7, can exhibit excellent absorbency as sanitary products.

[0034] The effects of the invention

[0035] According to the present invention, an absorbent with high absorption performance that can instantly absorb large amounts of bodily fluids can be provided. Attached Figure Description

[0036] Figure 1 This is a schematic top view of the light incontinence pad 1 as seen from the side opposite the skin in the thickness direction.

[0037] Figure 2 The diagram illustrates the manufacturing process of absorbent A, an example of a polymeric absorbent.

[0038] Figure 3 This is a SEM image of absorbent A at 50x magnification.

[0039] Figure 4 This is a SEM image of absorbent A at 100x magnification.

[0040] Figure 5 This is a SEM image of absorbent A at 500x magnification.

[0041] Figure 6 This is a SEM image of absorbent A at 1000x magnification.

[0042] Figure 7 This is a SEM image of absorbent A at 1500x magnification.

[0043] Figure 8 Cross-sectional photographs obtained using a scanning electron microscope to show the appearance of absorbent A before and after water absorption.

[0044] Figure 9 CT images showing the absorption state of absorbent A at various amounts of distilled water added.

[0045] Figure 10CT images showing the absorption state of two SAPs at different amounts of distilled water added.

[0046] Figure 11 CT images showing the absorption state of Infinity particles at different amounts of distilled water added.

[0047] Figure 12 This is a graph showing the relationship between the water absorption ratio and volume change of absorbent A, an example of a polymeric absorbent. Detailed Implementation

[0048] The preferred embodiment of the composite absorbent of the present invention will be described in detail below using a light incontinence pad 1 as an example of a sanitary product to which the composite absorbent is applied.

[0049] It should be noted that, unless otherwise specified, in this instruction manual, "the view of an object placed horizontally in its unfolded state from the vertical top side (the surface side when the object is a sanitary product) in the thickness direction of the object (e.g., incontinence pads, composite absorbents, etc.)" will be referred to only as "top view".

[0050] It should be noted that in this specification, "length direction" refers to "the direction of the longer length of an object in a top view (such as a light incontinence pad, composite absorbent, etc. in an unfolded state)," "width direction" refers to "the direction of the shorter length of an object in a top view," and "thickness direction" refers to "the direction perpendicular to an object placed on a horizontal surface in an unfolded state." These length, width, and thickness directions are all orthogonal to each other.

[0051] In addition, unless otherwise specified in this instruction manual, in the thickness direction of the incontinence pad 1, the side "proximal to the wearer's skin when wearing the incontinence pad 1" is referred to as the "skin-opposing side", and the side "far from the wearer's skin when wearing the incontinence pad 1" is referred to as the "non-skin-opposing side".

[0052] [Minor Incontinence Pad]

[0053] Figure 1 A schematic top view of the light incontinence pad 1 in its unfolded state, according to an embodiment of the present invention, of the composite absorbent 4.

[0054] like Figure 1As shown, when viewed from above, the incontinence pad 1 has a longitudinally elongated shape with a length direction L and a width direction W, and two longitudinally elongated end edges protruding outward in an arc shape along the length direction. It should be noted that the shape of the incontinence pad 1 is not limited to this type. If it is longitudinally elongated, it can adopt any shape (e.g., oblong, rectangular, hourglass, etc.) depending on various uses and methods of use.

[0055] The incontinence pad 1 has a liquid-permeable surface sheet 2 forming the skin-facing side of the incontinence pad 1 in the thickness direction, a back sheet 3 forming the non-skin-facing side of the incontinence pad 1, and a composite absorbent body 4 located between these sheets as its basic components.

[0056] In addition, the incontinence pad 1 also has a surface disposed on the non-skin-facing side of the back panel 3, and an adhesive part (not shown) for adhering and fixing the incontinence pad 1 to the inner surface of the wearer's underwear or other clothing.

[0057] It should be noted that the incontinence pad 1 is not limited to this configuration. For example, it may have a pair of side sheets for forming a leak-proof wall, which are arranged at both ends of the incontinence pad 1 in the width direction W and extend in the length direction L, compared with the surface sheet 2 on the skin-opposing side; and multiple elastic members arranged in the length direction L of the pair of side sheets respectively.

[0058] Furthermore, in the incontinence pad 1, the composite absorbent 4 is located between the surface sheet 2 and the back sheet 3 and is formed by a water-absorbing component capable of absorbing bodily fluids such as urine and menstrual blood that are excreted by the wearer and pass through the surface sheet 2. The composite absorbent 4 includes: a polymer absorbent with a hydrophilic continuous skeleton and continuous pores, and a superabsorbent polymer (SAP).

[0059] Furthermore, this polymeric absorbent exhibits a unique water absorption behavior when absorbing moisture, which involves introducing moisture into the continuous skeleton and then into the continuous pores.

[0060] In the composite absorbent 4, when the aforementioned hydrophilic continuous skeleton and continuous pore polymer absorbent absorbs body fluids such as urine and menstrual blood, the hydrophilic continuous skeleton expands instantly by introducing body fluids through osmotic pressure, thereby increasing the volume of the continuous pores. This allows body fluids to be introduced into the enlarged continuous pores, thus enabling the instantaneous absorption of large amounts of body fluids. The absorbed body fluids can then be transported to the SAP with high water retention capacity and firmly retained within the SAP.

[0061] Therefore, composite absorber 4 can perform high absorption performance as an absorber.

[0062] Therefore, the incontinence pad 1, which also possesses this composite absorbent 4, can also perform excellent absorption as an incontinence pad.

[0063] 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.

[0064] (Surface sheet)

[0065] 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.

[0066] 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.

[0067] 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.

[0068] (Back panel)

[0069] In the aforementioned incontinence pad 1, the back panel 3 has an elongated shape, extending from one end edge in the length direction L of the incontinence pad 1 to the other end edge, and from one end edge in the width direction W of the incontinence pad 1 to the other end edge, when viewed from above. 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 and menstrual blood through the composite absorbent 4 to the outside of the incontinence pad 1.

[0070] 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.

[0071] (Complex absorber)

[0072] In the aforementioned mild incontinence pad 1, such as Figure 1As 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.

[0073] 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.

[0074] 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 and menstrual blood 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 a sheet such as thin paper for retaining it. In other words, the composite absorbent refers to an absorbent component composed of absorbent materials capable of absorbing and retaining bodily fluids, and a sheet for retaining them.

[0075] 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.

[0076] Furthermore, the composite absorbent 4 comprises a polymeric absorbent exhibiting the aforementioned unique water-absorbing behavior, possessing a hydrophilic continuous skeleton and continuous pores, as described above, and a highly absorbent polymer. As described later, the polymeric absorbent is a powder or granular material formed from highly absorbent polymers such as sodium acrylate copolymers, known in the art, and is referred to as SAP (Super Absorbent Polymer).

[0077] It should be noted that the composite absorbent 4, as a water-absorbing material, may only contain the aforementioned polymeric absorbent and highly absorbent polymer, or it may contain water-absorbing materials known in the field in addition to these. Examples of such water-absorbing materials include, for example, hydrophilic fibers, and more specifically, pulp fibers (e.g., crushed pulp), cotton, rayon, cellulose fibers such as acetate, etc.

[0078] It should be noted that the composite absorbent 4 can have a structure in which such a polymer absorbent, highly absorbent polymer, or any water-absorbing material is covered by a coating sheet such as hydrophilic paper.

[0079] In this invention, the shape, size, and weight of the composite absorbent are not particularly limited as long as they do not hinder the effect of the invention. Any shape, size, and weight corresponding to the desired absorbency, softness, strength, etc., can be adopted.

[0080] The polymeric absorbent used in the composite absorbent of the present invention will be described in more detail below.

[0081] [Polymer absorbent]

[0082] In this invention, the polymeric absorbent is not particularly limited if it possesses a hydrophilic continuous framework and continuous pores, and exhibits a unique water-absorbing behavior in which water is introduced into the continuous framework and then into the continuous pores during water absorption. Examples of such polymeric absorbents include hydrolysates of cross-linked polymers containing at least two monomers of (meth)acrylate, and examples of polymeric compounds having at least one hydrophilic group in their functional groups. More specifically, examples of hydrolysates are hydrolysates of cross-linked polymers containing (meth)acrylate and compounds containing two or more vinyl groups per molecule, and examples of polymeric compounds having at least a -COONa group. The aforementioned polymeric absorbent is an organic porous body having at least one -COONa group per molecule, and may further have -COOH groups. The -COONa groups are distributed substantially uniformly in the framework of the porous body.

[0083] If the polymeric absorbent is a hydrolysate of a cross-linked polymer of (meth)acrylate and a compound containing two or more vinyl groups in one molecule, and contains at least one -COONa group, then as described later, when absorbing bodily fluids such as urine and menstrual blood, the hydrophilic continuous skeleton is easy to elongate (i.e., easy to expand), and the continuous pores are also easy to enlarge. Therefore, more bodily fluids can be introduced into the continuous pores more quickly, and it can play a further excellent absorption role as an absorbent.

[0084] It should be noted that in this specification, (meth)acrylate refers to acrylate or methacrylate.

[0085] In the polymeric absorbent formed by the hydrolysis of this crosslinked polymer of (meth)acrylate and divinylbenzene, a hydrophilic continuous skeleton is formed by an organic polymer having at least -COONa groups, and there are connecting pores (continuous pores) between the skeletons that serve as absorption sites for the target fluid (i.e., urine, menstrual blood, etc.).

[0086] It should be noted that hydrolysis treatment causes the -COOR groups (i.e., carboxylic acid ester groups) of the cross-linked polymer to form -COONa groups or -COOH groups (see reference). Figure 2 Therefore, polymeric absorbents can have -COOR groups.

[0087] The presence of -COOH and -COONa groups in organic polymers that form a hydrophilic continuous backbone can be confirmed by analysis using infrared spectrophotometry and quantitative methods for weakly acidic ion-exchange groups.

[0088] Here, Figure 2 This diagram illustrates the manufacturing process of absorbent A, an example of a polymeric absorbent. Figure 2 In the diagram, the top figure shows the constituent raw materials of the polymerization, the middle figure shows the monolithic column A as a crosslinked polymer of (meth)acrylate and divinylbenzene, and the bottom figure shows the absorbent A obtained by hydrolyzing and drying the monolithic column A in the middle figure.

[0089] The following description uses absorbent A, formed from the hydrolysate of a crosslinked polymer of (meth)acrylate and divinylbenzene, as an example of a polymer absorbent.

[0090] It should be noted that the polymer absorbent is not limited to absorbent A, but can also be a hydrolysate of a cross-linked polymer of (meth)acrylate and a compound having two or more vinyl groups in one molecule, or a hydrolysate of a cross-linked polymer containing at least two monomers of (meth)acrylate, etc.

[0091] However, if the polymeric absorbent is a monolithic columnar absorbent, it can rapidly absorb body fluids and has the advantage of being able to deliver the body fluids temporarily held in the polymeric absorbent more firmly to the SAP.

[0092] It should be noted that in the following description, "monolithic column A" refers to an organic porous body formed by a cross-linked polymer of (meth)acrylate and divinylbenzene before hydrolysis treatment, sometimes referred to as "monolithic columnar organic porous body".

[0093] Additionally, "Absorbent A" is a hydrolysate of a cross-linked polymer (monolithic column A) of (meth)acrylate and divinylbenzene that has undergone hydrolysis and drying treatment. It should be noted that in the following description, Absorbent A refers to the absorbent in its dried state.

[0094] First, the structure of absorbent A will be explained.

[0095] As described above, absorbent A has a hydrophilic continuous backbone and continuous pores. Absorbent A is an organic polymer with a hydrophilic continuous backbone, such as... Figure 2 As shown, the cross-linked polymer (monolithic column A) is obtained by cross-linking (meth)acrylate as a polymerizing monomer and divinylbenzene as a cross-linking monomer, and then further hydrolyzing the resulting cross-linked polymer.

[0096] Organic polymers that form a hydrophilic continuous backbone, as structural units, have vinyl polymeric residues (hereinafter referred to as "structural unit X") and divinylbenzene crosslinked polymeric residues (hereinafter referred to as "structural unit Y").

[0097] Furthermore, the vinyl polymeric residues (structural unit X) in the organic polymer forming the hydrophilic continuous backbone have two types of groups: -COONa group, or -COOH group and -COONa group, generated by the hydrolysis of the carboxylic acid ester group. It should be noted that when the polymeric monomer is (meth)acrylate, the vinyl polymeric residues (structural unit X) have -COONa group, -COOH group and ester group.

[0098] In absorbent A, the ratio of cross-linked polymeric residues (structural unit Y) of divinylbenzene in the organic polymer forming a hydrophilic continuous backbone is, for example, 0.1 to 30 mol%, preferably 0.1 to 20 mol%, relative to all structural units. For example, in absorbent A where butyl methacrylate is used as the polymeric monomer and divinylbenzene is used as the cross-linking monomer, the ratio of cross-linked polymeric residues (structural unit Y) of divinylbenzene in the organic polymer forming a hydrophilic continuous backbone is, for example, about 3%, preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%, relative to all structural units.

[0099] It should be noted that if the ratio of cross-linked polymer residues of divinylbenzene in the organic polymer forming the hydrophilic continuous backbone is 0.1 mol% or more, the strength of absorbent A is not easily reduced. In addition, if the ratio of cross-linked polymer residues of divinylbenzene is 30 mol% or less, the absorption amount of the target liquid is not easily reduced.

[0100] In addition, the organic polymer forming the hydrophilic continuous backbone in absorbent A may contain only structural units X and Y, or may contain polymer residues of monomers other than structural units X and Y, namely (meth)acrylate and divinylbenzene.

[0101] As structural units other than structural units X and Y, examples include polymer residues of monomers such as styrene, α-methylstyrene, vinyltoluene, vinyl benzyl chloride, glycidyl methacrylate, isobutylene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate.

[0102] It should be noted that the ratio of structural units other than structural units X and Y in the organic polymer forming the hydrophilic continuous backbone is, for example, 0 to 50 mol%, preferably 0 to 30 mol%, relative to all structural units.

[0103] Furthermore, absorbent A preferably has a hydrophilic continuous framework with a thickness of 0.1 to 100 μm. If the thickness of the hydrophilic continuous framework of absorbent A is 0.1 μm or more, the spaces (pores) in the porous body used to introduce the target fluid (body fluid) are less likely to be damaged during absorption, and the absorption capacity is less likely to decrease. On the other hand, if the thickness of the hydrophilic continuous framework is 100 μm or less, an excellent absorption rate can be easily obtained.

[0104] It should be noted that the hydrophilic continuous framework of absorbent A has a continuous bubble structure, therefore the thickness of the continuous framework is measured at the cross-section of the framework appearing on the test piece used for electron microscopy. Since the continuous framework is formed by the spacing of water (droplets) removed through dehydration / drying after hydrolysis, it is mostly polygonal in shape. Therefore, the thickness of the continuous framework is set as the average value of the diameter (μm) of the circumcircle of the polygonal cross-section. In rare cases, small holes are formed within the polygon; in such cases, the circumcircle of the polygonal cross-section surrounding the small hole is measured.

[0105] Furthermore, absorbent A preferably has an average diameter of continuous pores of 1 to 1000 μm. If the average diameter of continuous pores in absorbent A is 1 μm or more, the spaces (pores) in the porous body used to introduce the target fluid (body fluid) are less likely to be damaged during absorption, and the absorption rate is less likely to decrease. On the other hand, if the average diameter of continuous pores is 1000 μm or less, an excellent absorption rate is easily obtained.

[0106] It should be noted that the average diameter (μm) of the continuous pores in absorbent A can be determined using mercury intrusion porosimetry, employing the maximum value of the pore distribution curve obtained using this method. For the sample used to determine the average diameter of the continuous pores, regardless of the ionic form of absorbent A, the sample is prepared by drying in a vacuum desiccator at a temperature set to 50°C for at least 18 hours. It should be noted that the ultimate limiting pressure is set to 0 Torr.

[0107] Here, Figure 3 This is a SEM image of absorbent A at 50x magnification. Figure 4 This is a SEM image of absorbent A at 100x magnification. Figure 5 This is a SEM image of absorbent A at 500x magnification. Figure 6 A SEM image of absorbent A at 1000x magnification, and then... Figure 7This is a SEM image of absorbent A at 1500x magnification.

[0108] These Figures 3-7 The absorbent A shown is an example of an absorbent in which butyl methacrylate is used as a polymer monomer and divinylbenzene is used as a crosslinking monomer, and each has a cubic structure of 2 mm square.

[0109] Figures 3-7 The absorbent A shown has numerous bubble-like macropores, and these bubble-like macropores overlap with each other. The overlapping portions of these macropores in absorbent A form a continuous bubble structure with common openings (mesopores), that is, a continuous bubble structure (continuous macroporous structure).

[0110] The overlapping portions of these macropores form common openings (mesopores) with an average diameter of 1–1000 μm, preferably 10–200 μm, and particularly preferably 20–100 μm in the dry state, and most of them form an open-pore structure. If the average diameter of the mesopores in the dry state is 1 μm or more, the absorption rate of the target liquid is better. On the other hand, if the average diameter of the mesopores in the dry state is 1000 μm or less, the absorbent A is less likely to become brittle.

[0111] It should be noted that the overlap of these large holes is about 1 to 12 for a single large hole, and mostly about 3 to 10.

[0112] Furthermore, since absorbent A has this continuous bubble structure, it has the advantage of being able to uniformly form macropore groups and mesopore groups, and compared with the particle-aggregated porous bodies described in Japanese Patent Application Publication No. 8-252579, it can significantly increase the pore volume and specific surface area.

[0113] It should be noted that the total pore volume of absorbent A is preferably 0.5–50 mL / g, more preferably 2–30 mL / g. If the total pore volume of absorbent A is 0.5 mL / g or more, the spaces (pores) in the porous body used to introduce the target fluid (body fluid) are less likely to be damaged during absorption, and the absorption capacity and absorption rate are less likely to decrease. On the other hand, if the total pore volume of absorbent A is 50 mL / g or less, the strength of absorbent A is less likely to decrease.

[0114] It should be noted that the total pore volume can be determined using mercury porosimetry. For the sample used in the determination of the total pore volume, regardless of the ionic form of absorbent A, the sample is dried in a vacuum desiccator at a temperature set to 50°C for at least 18 hours. It should be noted that the ultimate limiting pressure is set to 0 Torr.

[0115] The following describes the appearance of absorbent A in contact with bodily fluids (hereinafter referred to as "bodily fluids"). The same applies to the contact between the composite absorbent 4 containing absorbent A and bodily fluids. Furthermore, the mass of the absorbed bodily fluid is approximately proportional to the volume of the bodily fluid; therefore, in the following description, the mass of the bodily fluid will sometimes be referred to simply as the "volume of the bodily fluid."

[0116] first, Figures 3-7 The absorbent A shown has a continuous porous structure consisting of multiple interconnected micropores (voids), which can be visually confirmed by the presence of numerous pores. When bodily fluids such as urine or menstrual blood come into contact with this porous absorbent A, the hydrophilic continuous framework instantly introduces a portion of the fluid through osmotic pressure, causing it to elongate (i.e., swell). This elongation of the continuous framework occurs in virtually all directions.

[0117] Here, Figure 8 Cross-sectional images obtained using scanning electron microscopy (SEM) show the appearance of absorbent A before and after water absorption. Figure 8 In the image, the SEM image on the left (a) shows absorbent A before water absorption, and the SEM image on the right (b) shows absorbent A after water absorption.

[0118] like Figure 8 As shown, for absorbent A, the shape of absorbent A increases due to the elongation of the continuous skeleton during water absorption, and the size of each pore also increases accordingly. If the size of the pores increases, the volume within the pores increases, and therefore the amount of body fluid that can remain within the pores also increases. That is, absorbent A, having absorbed a certain amount of body fluid and increased in size, can further absorb a predetermined amount of body fluid into the enlarged pores through capillary action.

[0119] Thus, absorbent A exhibits a unique water-absorbing behavior when absorbing water (body fluids), which involves introducing water into the hydrophilic continuous framework and then absorbing it into the continuous pores.

[0120] It should be noted that the body fluid absorbed into the hydrophilic continuous skeleton of absorbent A is not easily released from the continuous skeleton (i.e., it is not easy to release water), while the body fluid absorbed into the continuous pores is easy to release water. Therefore, in the composite absorbent, the body fluid absorbed into the continuous pores releases water and is transported to the superabsorbent polymer (SAP) with high water retention capacity, and is firmly retained in the SAP.

[0121] Here, regarding the amount of body fluid absorbed into the continuous skeleton of absorbent A and the amount of body fluid absorbed into the continuous pores, of the total amount of body fluid absorbed by absorbent A, the amount of body fluid released by absorbent A through centrifugation (150G / 90 seconds) is the amount of body fluid absorbed into the continuous pores, and the other amount of body fluid (i.e., the amount of body fluid that was not released by absorbent A through centrifugation) is the amount of body fluid absorbed into the continuous skeleton.

[0122] Furthermore, compared to body fluid absorbed into the hydrophilic continuous framework, more body fluid remains within the pores when absorbed by absorbent A. Since most of the body fluid absorption achieved using absorbent A occurs through capillary action, retaining the body fluid within the pores, a higher porosity (the volume of pores relative to the volume of absorbent A) allows for the absorption of more body fluid. It should be noted that this porosity is preferably 85% or higher.

[0123] For example, if the above is obtained... Figures 3-7 The porosity of absorbent A shown is as follows.

[0124] Firstly, absorbent A, obtained using the mercury intrusion porosimetry method, has a specific surface area of ​​400 m². 2 / g, pore volume is 15.5mL / g. This pore volume of 15.5mL / g means that the volume of the pores in 1g of absorbent A is 15.5mL.

[0125] Here, if the specific gravity of absorbent A is assumed to be 1 g / mL, then the volume occupied by the micropores in 1 g of absorbent A, i.e., the micropore volume, is 15.5 mL. In addition, the volume of 1 g of absorbent A is 1 mL.

[0126] Therefore, the total volume of 1g of absorbent A is 15.5+1 (mL), and the ratio of the pore volume is the porosity. Thus, the porosity of absorbent A is 15.5 / (15.5+1)×100≒94%.

[0127] The absorbent A, i.e., the polymer absorbent, which has this hydrophilic continuous skeleton and continuous pores, is used in composite absorbent bodies such as the composite absorbent body 4 of the aforementioned incontinence pad 1 for absorbing bodily fluids such as urine and menstrual blood, for example in the form of granules or flakes.

[0128] Furthermore, as described above, this polymeric absorbent exhibits a unique water-absorbing behavior when absorbing moisture: it introduces water into a hydrophilic continuous framework and then into continuous pores. Therefore, it can instantly absorb large amounts of body fluid, and then transport this absorbed body fluid (mainly the fluid absorbed into the continuous pores) to the high-water-retention SAP (Superabsorbent Polymer), where it is firmly retained. Thus, composite absorbents using this polymeric absorbent can exhibit high absorption performance.

[0129] Here, we prepared a polymeric absorbent as an example of the present invention, two highly absorbent polymers (SAP(A) and SAP(B)) as comparative examples, and Infinity particles as a comparative example. The absorption states of each sample when a predetermined amount of distilled water was added were observed using a 3D micro-X-ray CT device (CosmoScan FX (manufactured by Rigaku Corporation)). During the imaging, the polymeric absorbent and other samples were fixed to the base of the device using double-sided tape, and distilled water was added from above. The imaging conditions were: tube voltage: 90 kV, tube current: 88 μA, irradiation time: 2 minutes, resolution: 20 μm, matrix: 512 × 512 × 512. The observation results are as follows: Figures 9-11 As shown.

[0130] It should be noted that, Figure 9 CT images showing the absorption state of absorbent A at different amounts of distilled water added. Figure 10 CT images showing the absorption states of two SAPs at different amounts of distilled water added. Figure 11 CT images showing the absorption state of Infinity particles at various amounts of distilled water added. Figures 9-11 In the CT images, the white areas correspond to the water-absorbing areas. The amount of distilled water added is expressed by the water absorption capacity per unit mass of absorbents such as polymer absorbents, i.e., the water absorption ratio (g / g).

[0131] It should be noted that the Infinity particles mentioned above refer to the absorbent manufactured by P&G, which has a structure similar to that of polymer absorbents (foamed structure), but unlike polymer absorbents, it does not have the function of absorbing water and swelling.

[0132] like Figure 9 As shown, in this example of the invention, the absorbent A absorbs water from its hydrophilic continuous framework as the amount of distilled water added (water absorption ratio) increases, and the continuous framework elongates, thus increasing the size of the absorbent A. The water absorption ratio reaches the water retention limit L of the absorbent A. HAfter absorbing 10g / g (i.e., 25% water), continuous pore absorption can absorb even more water. It should be noted that the water absorption rate reaches the water absorption limit L of absorbent A. A After reaching 60g / g, such as Figure 9 As shown, it does not easily absorb water, and water overflows when the water absorption rate is 90g / g.

[0133] On the other hand, for the comparative example SAP, such as Figure 10 As shown, both SAPs absorbed water evenly while the amount of distilled water added (water absorption ratio) increased, without exhibiting the staged water absorption behavior of absorbent A in this invention example.

[0134] Furthermore, for the comparative example of Infinity particles, such as Figure 11 As shown, as the amount of distilled water added increases, water is absorbed from the upper side of the Infinity particles. Furthermore, the Infinity particles do not exhibit the phased water absorption behavior of absorbent A in this embodiment of the invention.

[0135] As can be seen from the above, the absorbent A of the present invention exhibits the unique water absorption behavior not found in conventional SAP and Infinity particles, and can exert excellent absorption performance by instantly absorbing a large amount of body fluid and then delivering the absorbed body fluid to the SAP with high water retention capacity.

[0136] It should be noted that, in this invention, the polymeric absorbent is preferably at a water retention limit of L. H When absorbing water, the volume of the swelling polymeric absorbent is greater than the volume of the introduced water. Because this polymeric absorbent can introduce a larger amount of water into the continuous pores, composite absorbents containing this polymeric absorbent can exhibit higher absorption performance. It should be noted that the properties of this polymeric absorbent can be achieved, for example, by appropriately adjusting the total micropore volume of the continuous pores and the porosity of the polymeric absorbent.

[0137] Here, the water retention limit L H The volume of the polymer absorbent that swells upon absorbing water, and its water retention limit L. H The volume of water introduced by the polymer absorbent during water absorption can be measured as follows.

[0138] <Water retention limit L H Methods for determining the volume of polymeric absorbent that swells upon water absorption >

[0139] (1) Seal 1g of the sample (polymer absorbent) for testing into a mesh bag cut into 10cm squares (manufactured by NBCMeshtec Inc., N-No.255HD 115). It should be noted that the mass (g) of the mesh bag is determined in advance.

[0140] (2) Immerse the mesh bag containing the sample in physiological saline (0.9% sodium chloride aqueous solution) for 1 hour.

[0141] (3) Determine the mass (g) of the mesh bag after it has been suspended for 5 minutes to drain water.

[0142] (4) After water control, the mesh bag was centrifuged at 150g for 90 seconds, and the mass (g) of the mesh bag after centrifugation was determined.

[0143] (5) Subtract the mass of the sample (=1g) and the total mass of the mesh bag from the mass of the centrifuged mesh bag to calculate the water retention capacity (g) of the sample. Then divide this water retention capacity by the mass of the sample (=1g) to obtain the water retention capacity per unit mass of the sample (polymer absorbent) (g / g). This water retention capacity per unit mass is the water retention limit L. H (g / g).

[0144] (6) In addition, take out 30 test samples (polymer absorbent) and measure their mass, then divide the mass by the number of samples (30 samples) to calculate the average mass (g) of each sample.

[0145] (7) Select the one sample that best matches the average mass value from the 30 samples, and fix the one sample to the base of the 3D micro X-ray CT device (CosmoScan FX, Rigaku Corporation) using double-sided tape.

[0146] (8) Add water equivalent to the water retention limit L obtained in (5) above the fixed 1 sample. H Add a certain amount (g) of distilled water to make the above 1 sample contain distilled water.

[0147] (9) A single sample containing distilled water was observed using the aforementioned 3D micro X-ray CT device (tube voltage: 90kV, tube current: 88μA, irradiation time: 2 minutes, resolution: 20μm, matrix: 512×512×512). The water retention limit L was calculated from the obtained CT image. H The volume (cm³) of an expanded sample. 3 ).

[0148] It should be noted that, regarding the water retention limit L... H The volume of water introduced by the superabsorbent during water absorption, with distilled water as 1g = 1cm³.3 Calculate the water retention limit L mentioned above. H Amount (g) Volume (cm³) 3 ).

[0149] In addition, if the test sample (polymer absorbent) is recycled from the sanitary product, it can be obtained according to the following <Recycling Method of Test Sample (Polymer Absorbent)>.

[0150] <Method for recovering the sample (polymer absorbent) used in the determination>

[0151] (1) Peel off the surface sheet or other parts of the sanitary product to expose the absorbent.

[0152] (2) Allow the analyte (polymer absorbent) to fall from the exposed absorber, and use tweezers or the like to remove the (particulate) analyte other substances (such as pulp, synthetic resin fibers, etc.).

[0153] (3) As a means of magnified observation, a microscope or a simple magnifying glass is used to observe the sample at a magnification that allows for the recognition of the difference from SAP or to visually confirm the pores of the porous body. At the same time, tweezers or similar tools are used to retrieve the sample. It should be noted that the magnification of the simple magnifying glass is not particularly limited if it is a magnification that allows for visual confirmation of the pores of the porous body. For example, magnifications of 25x to 50x can be listed.

[0154] (4) The analytes recovered in this way are used as test samples in various test methods.

[0155] Furthermore, the absorbent polymer preferably has a continuous pore structure with a greater water absorption capacity than the continuous framework. Because this absorbent polymer can introduce a larger amount of water into the continuous pores, the composite absorbent containing this absorbent can exhibit even higher absorption performance. It should be noted that the properties of this absorbent polymer can be achieved, for example, by appropriately adjusting the total micropore volume of the continuous pores and the porosity of the absorbent polymer.

[0156] Here, the water absorption capacity of the continuous pores and the water absorption capacity of the continuous skeleton of the polymer absorbent can be measured as follows.

[0157] <Methods for determining the water absorption capacity of continuous pores and continuous skeletons in polymeric absorbents>

[0158] (1) Seal 1g of the sample (polymer absorbent) for testing into a mesh bag cut into 10cm squares (manufactured by NBCMeshtec Inc., N-No.255HD 115). It should be noted that the mass (g) of the mesh bag is determined in advance.

[0159] (2) Immerse the mesh bag containing the sample in physiological saline (0.9% sodium chloride aqueous solution) for 1 hour.

[0160] (3) Determine the mass (g) of the mesh bag after it has been suspended for 5 minutes to drain water.

[0161] (4) Subtract the mass of the sample (=1g) and the total mass of the mesh bag from the mass of the mesh bag after water control determined in (3) above to calculate the water absorption capacity (g) of the sample. Then divide the water absorption capacity by the mass of the sample (=1g) to obtain the water absorption capacity per unit mass (g / g) of the sample (polymer absorbent). This water absorption capacity per unit mass is set as the water absorption limit L. A (g / g).

[0162] (5) Then, the mesh bag after water control in (3) above was centrifuged at 150g for 90 seconds, and the mass (g) of the mesh bag after centrifugation was measured.

[0163] (6) Subtract the mass of the sample (=1g) and the total mass of the mesh bag from the mass of the centrifuged mesh bag determined in (5) above to calculate the water retention capacity (g) of the sample. Then divide this water retention capacity by the mass of the sample (=1g) to obtain the water retention capacity per unit mass of the sample (polymer absorbent) (g / g). This water retention capacity per unit mass is the water retention limit L. H (g / g), the water retention limit L H Set it to "Water absorption of continuous skeleton".

[0164] (7) Next, the water absorption limit L obtained from (4) above is... A Subtract the water retention limit L H The obtained amount (g / g) is set as "water absorption of continuous pores".

[0165] It should be noted that the preferred mass ratio of water absorption capacity of the continuous pores to that of the continuous skeleton in the polymeric absorbent is 60:40 to 95:5. If this mass ratio is within this specific range, the absorbent can more effectively introduce water into the continuous skeleton and then into the continuous pores. It should also be noted that this characteristic of the polymeric absorbent can be achieved by appropriately adjusting the total micropore volume of the continuous pores and the porosity of the polymeric absorbent.

[0166] In addition, the absorption rate of the polymer absorbent is preferably relatively high from the moment it begins to absorb water until it reaches the water retention limit, and relatively low after the water retention limit.

[0167] Here, Figure 12This is a graph showing the relationship between the water absorption ratio and the volume change of absorbent A, which is an example of the polymeric absorbent of the present invention.

[0168] like Figure 12 As shown, after absorbent A begins to absorb water, the volume change increases rapidly with the increase of the water absorption ratio (i.e., the water absorption rate R1 is large), but the water absorption ratio reaches the water retention limit L of absorbent A. H After reaching 10g / g, the volume change increases slowly (i.e., the water absorption rate R2 is small).

[0169] Thus, absorbent A, from the moment it begins to absorb water until it reaches its water retention limit L, H In the initial stage of water absorption, the absorption rate is relatively high, thus allowing body fluids to be instantly introduced into the continuous skeleton. On the other hand, at the water retention limit L... H In the later stages of water absorption, the absorption rate is relatively low, allowing the body fluid to be effectively drawn into the continuous pores that expand through the expansion of the continuous framework. This enables absorbent A to more effectively exert its high absorption performance as an absorbent.

[0170] It should be noted that the volume change of the polymeric absorbent can be determined based on the aforementioned <water retention limit L>. H Method for determining the volume of the polymer absorbent that expands during water absorption: Measure the volume of the polymer absorbent that expands at each water absorption ratio, divide it by the volume of the polymer absorbent before water absorption, and multiply by 100 to obtain the volume.

[0171] The manufacturing method of this polymeric absorbent will be described in detail below, using absorbent A as an example.

[0172] [Manufacturing method of polymeric absorbent]

[0173] The above-mentioned absorbent A can be as follows: Figure 2 As shown, it is obtained through a cross-linking polymerization process and a hydrolysis process. These processes are explained below.

[0174] (Cross-linking polymerization process)

[0175] First, oil-soluble monomers for crosslinking polymerization, crosslinking monomers, surfactants, water, and a polymerization initiator as needed are mixed to obtain a water-in-oil droplet emulsion. This water-in-oil droplet emulsion is an emulsion in which the oil phase forms a continuous phase and water droplets are dispersed therein.

[0176] Next, regarding the absorbent A mentioned above, such as Figure 2As shown in the figure above, butyl methacrylate, an oil-soluble monomer, is used as a (meth)acrylate; divinylbenzene is used as a crosslinking monomer; sorbitol monooleate is used as a surfactant; and isobutyronitrile is used as a polymerization initiator to carry out crosslinking polymerization to obtain the monolithic column A.

[0177] Specifically, for absorbent A, such as Figure 2 As shown in the figure above, first mix 9.2g of tert-butyl methacrylate as an oil-soluble monomer, 0.28g of divinylbenzene as a crosslinking monomer, 1.0g of sorbitan monooleate (hereinafter referred to as "SMO") as a surfactant, and 0.4g of 2,2'-azobis(isobutyronitrile) as a polymerization initiator and dissolve them evenly.

[0178] Next, the mixture of tert-butyl methacrylate / divinylbenzene / SMO / 2,2'-azobis(isobutyronitrile) was added to 180g of pure water and stirred under reduced pressure using a vacuum stirring degassing mixer (manufactured by EME, Inc.) as a planetary stirring device to obtain a water-in-oil droplet emulsion.

[0179] The emulsion was then rapidly transferred to a reaction vessel and sealed, and polymerized at 60°C for 24 hours. After polymerization, the contents were removed, extracted with methanol, and dried under reduced pressure to obtain a monolithic column A with a continuous macroporous structure. It should be noted that SEM observation of the internal structure of monolithic column A revealed a continuous bubble structure with a continuous framework thickness of 5.4 μm. Furthermore, mercury porosimetry determined the average diameter of the continuous pores to be 36.2 μm and the total micropore volume to be 15.5 mL / g.

[0180] It should be noted that the content of divinylbenzene relative to all monomers is preferably 0.3 to 10 mol%, more preferably 0.3 to 5 mol%. Furthermore, 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%. It should be noted that in the above-mentioned absorbent A, the ratio of butyl methacrylate to the total of butyl methacrylate and divinylbenzene is 97.0 mol%, and the ratio of divinylbenzene is 3.0 mol%.

[0181] The amount of surfactant added can be set according to the type of oil-soluble monomer and the desired size of emulsion particles (macropores), and is preferably in the range of about 2% to 70% relative to the total amount of oil-soluble monomer and surfactant.

[0182] It should be noted that, in order to control the shape and size of the bubbles in column A, alcohols such as methanol and stearyl alcohol; carboxylic acids such as stearic acid; hydrocarbons such as octane, dodecane, and toluene; and cyclic ethers such as tetrahydrofuran and dioxane can coexist in the polymerization system.

[0183] Furthermore, there are no particular restrictions on the mixing method when forming water-in-oil droplet emulsions. For example, any mixing method can be used, such as mixing all components together at once, or dissolving the oil-soluble components (which are oil-soluble monomers, surfactants, and oil-soluble polymerization initiators) and the water-soluble components (which are water-soluble polymerization initiators) uniformly separately and then mixing the components.

[0184] Furthermore, there are no particular limitations on the mixing device used to form the emulsion. Any device such as a conventional mixer, homogenizer, or high-pressure homogenizer can be used depending on the desired emulsion particle size. Alternatively, a so-called planetary mixing device can be used, in which the material to be treated is added to a mixing container, and the mixing container rotates on its own axis while being tilted, thereby stirring and mixing the material to be treated.

[0185] Furthermore, there are no particular restrictions on mixing conditions; the stirring speed and stirring time can be set arbitrarily according to the desired emulsion particle size. It should be noted that when using the aforementioned planetary stirring device, water droplets in the W / O emulsion can be generated uniformly, and their average diameter can be set arbitrarily within a wide range.

[0186] The polymerization conditions for water-in-oil droplet emulsions can vary depending on the type of monomer and initiator. For example, when using azobisisobutyronitrile, benzoyl peroxide, or potassium persulfate as polymerization initiators, polymerization can be carried out in a sealed container under an inert atmosphere at a temperature of 30–100°C for 1–48 hours. When using hydrogen peroxide-ferrous chloride or sodium persulfate-sodium acid sulfite as polymerization initiators, polymerization can be carried out in a sealed container under an inert atmosphere at a temperature of 0–30°C for 1–48 hours.

[0187] It should be noted that after polymerization, the contents are removed and subjected to Soxhlet extraction using solvents such as isopropanol. This removes unreacted monomers and residual surfactants, yielding the desired product. Figure 2 The overall column A is shown in the middle figure.

[0188] (Hydrolysis process)

[0189] Next, the process of hydrolyzing the monolithic column A (crosslinked polymer) to obtain absorbent A (hydrolysis process) will be described.

[0190] First, the monolithic column A is immersed in dichloroethane containing zinc bromide and stirred at 40°C for 24 hours. It is then hydrolyzed by sequential contact with methanol, 4% hydrochloric acid, 4% sodium hydroxide aqueous solution, and water, followed by drying to obtain a block-shaped absorbent A. Next, the block-shaped absorbent A is pulverized into a specified size to obtain granular absorbent A. It should be noted that the form of absorbent A is not limited to granules; for example, it can be formed into flakes during or after drying.

[0191] Furthermore, there are no particular restrictions on the method of hydrolyzing the monolithic column A; various methods can be used. Examples include contacting strong bases such as sodium hydroxide with aromatic solvents such as toluene and xylene, halogen solvents such as chloroform and dichloroethane, ether solvents such as tetrahydrofuran and isopropyl ether, amide solvents such as dimethylformamide and dimethylacetamide, alcohol solvents such as methanol and ethanol, carboxylic acid solvents such as acetic acid and propionic acid, or water; or contacting hydrohalic acids such as hydrochloric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, and p-toluenesulfonic acid, or Lewis acids such as zinc bromide, aluminum chloride, aluminum bromide, titanium chloride (IV), cerium chloride / sodium iodide, and magnesium iodide.

[0192] In addition, among the polymer raw materials of the organic polymer that forms the hydrophilic continuous skeleton of absorbent A, there are no particular limitations on (meth)acrylates, but C1 to C10 (i.e., carbon number 1 to 10) alkyl esters of (meth)acrylates are preferred, and C4 (i.e., carbon number 4) alkyl esters of (meth)acrylates are particularly preferred.

[0193] It should be noted that, as C4 alkyl esters of (meth)acrylic acid, examples include tert-butyl (meth)acrylic acid, n-butyl (meth)acrylic acid, and isobutyl (meth)acrylic acid.

[0194] In addition, the monomers used in crosslinking polymerization can be only (meth)acrylate and divinylbenzene, or they can contain other monomers besides (meth)acrylate and divinylbenzene.

[0195] In the latter case, other monomers are not particularly limited, and examples include styrene, α-methylstyrene, vinyltoluene, vinyl benzyl chloride, glycidyl methacrylate, 2-ethylhexyl methacrylate, isobutylene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, methacrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.

[0196] It should be noted that the ratio of monomers other than (meth)acrylate and divinylbenzene in the total monomers used in the crosslinking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

[0197] Furthermore, the surfactant is not limited to the aforementioned sorbitol monooleate; any surfactant that can form a water-in-oil (W / O) emulsion when the monomer for crosslinking polymerization is mixed with water is acceptable. Examples of such surfactants include nonionic surfactants such as sorbitol monolaurate, sorbitol monopalmitate, sorbitol monostearate, sorbitol trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, and polyoxyethylene sorbitol monooleate; anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, and sodium dioctyl sulfosuccinate; cationic surfactants such as distearate dimethyl ammonium chloride; and amphoteric surfactants such as lauryl dimethyl betaine. These surfactants can be used alone or in combination of two or more.

[0198] Furthermore, polymerization initiators are suitably compounds that generate free radicals through heat and light irradiation. Moreover, polymerization initiators can be water-soluble or oil-soluble, and examples include azobis(4-methoxy-2,4-dimethylpentanonitrile), azobisisobutyronitrile, azobisdimethylpentanonitrile, azobiscyclohexanenitrile, azobiscyclohexaneformitrile, azobis(2-methylpropanediamine) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-sodium acid sulfite, tetramethylthiuram disulfide, etc. However, depending on the need, there are also systems where polymerization occurs even without the addition of a polymerization initiator, only through heating and light irradiation; therefore, when using such systems, it is not necessary to add a polymerization initiator.

[0199] It should be noted that, in addition to the light incontinence pad described in the above embodiments, the composite absorbent of the present invention can also be applied to various hygiene products such as shorts-type disposable diapers, band-type disposable diapers, sanitary napkins, absorbent linings, absorbent pads (e.g., pressure ulcer pads, maternity pads, etc.), absorbent sheets, breast pads, disposable diapers for pets, absorbent pads for pets, pet waste disposal sheets, wet wipes, wet wipes, cosmetic wipes, and masks. Therefore, the bodily fluids that the composite absorbent is intended to absorb are liquids excreted by the wearer of the hygiene products, such as urine, sweat, feces, menstrual blood, vaginal discharge, breast milk, blood, and exudate.

[0200] Furthermore, the present invention is not limited to the above-described embodiments, and can be appropriately combined, substituted, or modified without departing from the purpose and spirit of the present invention.

[0201] Explanation of reference numerals in the attached figures

[0202] 1. Light incontinence pad

[0203] 2 Surface sheet

[0204] 3. Back side

[0205] 4. Complex Absorber

Claims

1. A composite absorbent body, characterized by, A composite absorbent for absorbing body fluids, The composite absorbent comprises a high-molecular absorbent having a continuous skeleton and a continuous void, and a superabsorbent polymer, The high-molecular absorbent introduces water into the continuous skeleton and then into the continuous void when absorbing water, The high-molecular absorbent is a hydrolyzed product of a cross-linked polymer of (meth)acrylate and divinylbenzene which is a compound having two or more vinyl groups in one molecule, The ratio of the cross-linked polymer residue of divinylbenzene in the organic polymer forming the continuous skeleton having hydrophilicity is 0.1 to 30 mol% with respect to the total structural units.

2. The composite absorbent according to claim 1, wherein, The volume of the high-molecular absorbent expanded when absorbing water at the water retention limit is greater than the volume of the water introduced.

3. The composite absorbent according to claim 1 or 2, characterized in that, The amount of water absorbed by the continuous void of the high-molecular absorbent is greater than the amount of water absorbed by the continuous skeleton.

4. The composite absorbent according to claim 1 or 2, characterized in that, The mass ratio of the amount of water absorbed by the continuous void to the amount of water absorbed by the continuous skeleton of the high-molecular absorbent is 60:40 to 95:

5.

5. The composite absorbent according to claim 1 or 2, wherein The absorption speed of the high-molecular absorbent is relatively large from the start of water absorption until the water retention limit is reached, and the absorption speed after the water retention limit is relatively small.

6. The composite absorbent according to claim 1 or 2, wherein The high-molecular absorbent is a monolithic columnar absorbent.

7. The composite absorbent according to claim 1 or 2, wherein The high-molecular absorbent contains at least one or more -COONa groups.

8. A sanitary article, characterized in that It has the composite absorbent of any one of claims 1 to 7.

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