CN114080241A

CN114080241A - Absorbent body and absorbent article

Info

Publication number: CN114080241A
Application number: CN202080046486.6A
Authority: CN
Inventors: 菊池响; 岩井若菜; 中下将志; 合田裕树
Original assignee: Unicharm Corp
Current assignee: Unicharm Corp
Priority date: 2019-06-28
Filing date: 2020-06-23
Publication date: 2022-02-22
Also published as: CN117838442A; TW202116274A; JPWO2020262343A1; BR112021020337A2; WO2020262343A1; KR20220027061A; AU2020306265A1

Abstract

The present invention relates to an absorbent (11) for absorbing bodily fluids, characterized by comprising a polymeric absorbent having a continuous skeleton and continuous pores, the polymeric absorbent being a hydrolysate of a crosslinked polymer of a (meth) acrylate and a compound containing 2 or more vinyl groups in 1 molecule, and the polymeric absorbent containing at least 1 or more-COONa groups.

Description

Absorbent body and absorbent article

Technical Field

The present invention relates to an absorbent body and an absorbent article.

Background

There are conventionally known absorbent articles such as disposable diapers and sanitary napkins that use superabsorbent polymers ("SAP") having a high absorption amount. For example, patent document 1 discloses an absorbent article 30 including an absorbent body 15, the absorbent body 15 having a combination of absorbent resin particles (super absorbent polymer) 5 excellent in absorption amount and hydrophilic fibers 13 (such as pulp fibers) excellent in absorption speed.

Reference list

Patent document

[ patent document 1] WO2013-018571

Disclosure of Invention

Problems to be solved by the invention

The absorbent article 30 is required to be thin from the viewpoint of commercial sale, storage, portability, and the like. However, if the absorbent body 15 includes only the absorbent resin particles 5, the absorption speed is poor, and there may be a case where the body fluid or the like that has been strongly discharged cannot be sufficiently absorbed. However, if the absorbent resin particles 5 and the hydrophilic fibers 13 are used in combination, there is a risk that the absorbent body 15 becomes bulky.

The present invention has been made in view of the above-described conventional problems, and an aspect of the present invention is to provide an absorbent body and an absorbent article that facilitate absorption of body fluid.

Means for solving the problems

A main aspect of the present invention for achieving the above-described aspect is an absorbent body for absorbing body fluid, comprising:

polymeric absorbents having a continuous framework and interconnected pores,

the polymeric absorbent is a hydrolysate of a crosslinked polymer of (meth) acrylate and a compound,

the compound contains 2 or more vinyl groups in 1 molecule,

the polymeric absorbent contains at least 1 or more-COONa groups.

Features of the present invention other than those described above will become apparent by reading the description of the present specification with reference to the accompanying drawings.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, when the polymeric absorbent absorbs body fluid, the continuous skeleton is elongated, and since the interconnected pores are also easily expanded as the continuous skeleton is elongated, the body fluid is easily taken into the interconnected pores by the capillary phenomenon, and the body fluid is easily absorbed by the absorbent body.

Drawings

Fig. 1 is a schematic perspective view of a pull-on disposable diaper 1.

Fig. 2A is a schematic plan view of the diaper 1 in a developed and stretched state as viewed from the skin-side surface. Fig. 2B is a schematic sectional view along arrow X-X in fig. 2A.

Fig. 3 is a view illustrating a manufacturing process of the absorbent a.

Fig. 4 is an SEM photograph of absorbent a at 50 × magnification.

Fig. 5 is an SEM photograph of absorbent a at 100 times magnification.

Fig. 6 is an SEM photograph of absorbent a at 500 times magnification.

Fig. 7 is an SEM photograph of absorbent a at 1000 × magnification.

Fig. 8 is an SEM photograph of absorbent a at 1500 times magnification.

Fig. 9 is a graph showing various measurement results with respect to the absorbent a.

Fig. 10 is a graph showing the results of an experiment on the absorption rate and the absorption amount of the absorbent a.

Fig. 11 is a graph showing the results of an experiment regarding the absorption rate and the absorption amount of the super absorbent polymer in the comparative example.

Fig. 12A is an SEM photograph of a fracture surface of the absorbent a.

Fig. 12B is a map of Na distribution in the same portion as in fig. 12A.

Fig. 13 is a graph showing the relationship between the absorption amounts of the absorbent a and the absorbent b and time when the liquid to be absorbed is pure water.

Detailed Description

At least the following matters will become clear from the description of the present specification and the accompanying drawings.

An absorbent body for absorbing bodily fluids, comprising:

polymeric absorbents having a continuous framework and interconnected pores,

the compound contains 2 or more vinyl groups in 1 molecule,

the polymeric absorbent contains at least 1 or more-COONa groups.

According to this absorbent body, when the polymeric absorbent absorbs body fluid, the continuous skeleton stretches, and since the interconnected pores easily expand as the continuous skeleton stretches, the body fluid easily enters into the interconnected pores by capillary phenomenon, and the body fluid is easily absorbed by the absorbent body.

In such an absorbent body, it is desirable that

The polymer absorbent is an integral absorbent.

According to this absorbent body, when the absorbent body in a bulk form absorbs body fluid, the body fluid easily enters the through holes that expand as the continuous chassis elongates, and the body fluid is easily absorbed by the absorbent body.

In such an absorbent body, it is desirable that

The weight of a 0.9 wt% NaCl aqueous solution absorbed per unit weight of the polymeric absorbent is defined as the 1 st absorption weight,

defining the weight of the 0-2.0 wt% NaCl aqueous solution absorbed by the polymer absorbent per unit weight as the 2 nd absorption weight, and

the 1 st absorption weight is 0.5 to 1.9 times of the 2 nd absorption weight.

According to this absorbent body, it is possible to suppress a situation in which the absorption weight of the absorbent body varies depending on the component of the body fluid.

In such an absorbent body, it is desirable that

The polymeric absorbent having absorbed the 1 st absorbed weight of a 0.9 wt% aqueous NaCl solution was defined as a 1 st polymeric absorbent,

the polymer absorbent having absorbed the 2 nd absorption weight of 0to 2.0 wt% NaCl aqueous solution is defined as a2 nd polymer absorbent, and

after the 1 st polymeric absorbent and the 2 nd polymeric absorbent have been dehydrated for a predetermined time of 90 seconds under the conditions of 150G and 850rpm using a centrifuge,

the weight of the 0.9 wt% NaCl aqueous solution absorbed by the 1 st polymer absorbent is 0.5-1.6 times of the weight of the 0-2.0 wt% NaCl aqueous solution absorbed by the 2 nd polymer absorbent.

According to the absorbent body, it is possible to suppress a situation in which the water retention weight of the absorbent body varies depending on the components of the body fluid.

In such an absorbent body, it is desirable that

Defining the weight of 0.9 wt% NaCl aqueous solution absorbed by the dehydrated 1 st polymeric absorbent as the 1 st water retention weight,

defining the weight of 0-2.0 wt% NaCl aqueous solution absorbed by the dehydrated 2 nd polymeric absorbent as the 2 nd water retention weight,

with respect to the 1 st polymeric absorbent, a value obtained by dividing a difference between the 1 st absorption weight and the 1 st water retention weight by the 1 st absorption weight is 50 to 80%, and

with respect to the 2 nd polymeric absorbent, a value obtained by dividing the difference between the 2 nd absorption weight and the 2 nd water retention weight by the 2 nd absorption weight is 40 to 85%.

According to the absorbent body, the polymeric absorbent easily allows absorbed body fluid to move to another substance, and therefore can easily repeat absorption and discharge of liquid, and the user is less likely to feel a wet feeling after the body fluid has moved outside the polymeric absorbent.

In such an absorbent body, it is desirable that

In the vortex method, 2.0g of the polymeric absorbent takes 1.0 to 10.0 seconds to absorb 50g of a 0.9 wt% NaCl aqueous solution.

According to the absorbent body, the polymeric absorbent can absorb liquid in a short time, and thus can absorb body fluid more quickly.

In such an absorbent body, it is desirable that

0.5 wt% CaCl absorbed by the polymer absorbent₂The absorption weight of the aqueous solution is 13 times or more of the weight of the polymer absorbent.

According to this absorbent, even a body fluid containing a large amount of divalent ions can be easily absorbed by the absorbent.

In such an absorbent body, it is desirable that

After 1.0g of the lower end portion of the polymeric absorbent had been in contact with the surface of a 0.9 wt% NaCl aqueous solution for 1 minute,

the absorption capacity of the 0.9 wt% NaCl aqueous solution absorbed by the high molecular absorbent is more than 15 ml.

According to this absorbent body, the polymeric absorbent can absorb a large amount of liquid in a short time even in the direction opposite to the gravitational force, and therefore the absorbent body easily absorbs body fluid from various angles.

In such an absorbent body, it is desirable that

In a state where the lower end of 2.0g of the polymeric absorbent in a state of receiving a load of 600gw was in contact with the surface of a 0.9 wt% NaCl aqueous solution,

the polymeric absorbent absorbs 0.9 wt% NaCl aqueous solution in an amount of 1.0ml or more after 2 minutes, and

after 15 minutes, the amount of 0.9 wt% NaCl aqueous solution absorbed by the polymer absorbent was 5.0ml or more.

According to this absorbent body, even if the polymeric absorbent is subjected to a load, the polymeric absorbent can absorb liquid even in a direction opposite to the gravitational force, and therefore the absorbent body easily absorbs body fluid from various angles.

In such an absorbent body, it is desirable that

The polymeric absorbent has a void volume per unit volume of the interconnected pores of 85% or more.

According to this absorbent body, the body fluid easily enters the interconnected pores by the capillary phenomenon, and the body fluid is easily absorbed by the absorbent body.

In such an absorbent body, it is desirable that

The polymeric absorbent contains a crosslinked polymeric residue in an amount of 0.1 to 30.0%.

According to this absorbent, the following polymeric absorbents can be realized: when it absorbs body fluids, the continuous matrix elongates, and the interconnected pores also tend to expand as the continuous matrix elongates.

In such an absorbent body, it is desirable that

The average diameter of the interconnected pores is 1-1000 μm.

In such an absorbent body, it is desirable that

The absorbent body comprises

The polymeric absorbent and

a polymer compound having a higher water retention capacity than the polymer absorbent.

According to the absorbent, the polymeric absorbent absorbs body fluid more easily, and the body fluid can be retained by the polymeric compound while the body fluid is absorbed by the polymeric absorbent by capillary phenomenon. Therefore, the absorbent body can quickly absorb body fluid and then retain the body fluid.

In such an absorbent body, it is desirable that

The total ion exchange capacity of the-COONa groups per unit weight of the polymeric absorbent is 4.0mg equivalent/g or more.

According to this absorbent, the polymeric absorbent can absorb body fluid more easily than in the case where the total ion exchange capacity per unit weight of the-COONa groups is less than 4.0mg equivalent/g. Therefore, the continuous matrix is easily elongated, the interconnected pores are also easily expanded as the continuous matrix is elongated, and the body fluid is easily taken into the interconnected pores by the capillary phenomenon, and thus the body fluid is easily absorbed by the absorbent body.

An absorbent article including any of the above-described absorbers is desirable.

According to this absorbent article, when the polymeric absorbent of the absorbent body absorbs body fluid, the continuous skeleton stretches, and since the interconnected pores easily expand as the continuous skeleton stretches, the body fluid easily enters the interconnected pores by the capillary phenomenon. This makes it possible to obtain an absorbent article that easily absorbs body fluid.

Detailed description of the preferred embodiments

Taking a so-called pull-on disposable diaper as an example, an absorbent article having an absorbent body according to the present embodiment is described below. Note that the absorbent article having the absorber is not limited to a pull-on type disposable diaper, and the absorber may be used for an absorbent article such as a tape type disposable diaper, a sanitary napkin, an absorbent pad, a disposable diaper for pet, or an absorbent pad for pet. Disposable diapers or absorbent pads and the like may also be used by infants or adults. Note that the term "body fluid" refers to a liquid discharged from an organism (including not only humans but also animals). Examples of body fluids include sweat, urine, feces, menses, vaginal secretions, breast milk, blood, and exudates.

Basic constitution of pull-on disposable diaper 1

Fig. 1 is a schematic perspective view of a pull-on disposable diaper 1. Fig. 2A is a schematic plan view of the diaper 1 in a developed and stretched state as viewed from the skin-side surface. Fig. 2B is a schematic sectional view along arrow X-X in fig. 2A. The developed state is a state in which the side portion 30a of the abdominal-side member 30 and the side portion 40a of the back-side member 40, which are the side portions of the diaper 1, have been separated from each other and opened, so that the diaper 1 is fully developed into a planar shape. The stretched state is a state in which the elastic members of the diaper 1 have been stretched so that no wrinkles can be seen anymore in the diaper 1. Specifically, this is a state in which the diaper 1 has been stretched such that the dimensions of its constituent members (e.g., a ventral member 30 described later, etc.) match or are close to the dimensions of these members themselves. The line C-C in fig. 2A and 2B is the center line in the left-right direction. For convenience, the adhesive is not shown in fig. 2B.

As shown in fig. 1, the pull-on diaper 1 has an up-down direction, a left-right direction, and a front-back direction, and a waist opening BH and a pair of leg openings LH are formed in the diaper 1. When the diaper 1 is in the unfolded and stretched state in fig. 2A, the up-down direction will also be referred to as the "longitudinal direction", one side of the longitudinal direction will also be referred to as the "ventral side", and the other side of the longitudinal direction will also be referred to as the "dorsal side". With respect to the front-rear direction, a side corresponding to the abdomen of the wearer will also be referred to as a front side, and a side corresponding to the back of the wearer will also be referred to as a rear side. Further, the diaper 1 has a thickness direction as shown in fig. 2B, and with respect to the thickness direction, the side that contacts the wearer is also referred to as the skin side, and the opposite side is also referred to as the non-skin side.

The diaper 1 is a so-called three-piece diaper, and includes an absorbent main body 10, a stomach-side member 30, and a back-side member 40. The ventral-side member 30 and the dorsal-side member 40 are approximately rectangular in plan view, and the longitudinal direction thereof coincides with the left-right direction. The abdominal side member 30 covers the abdominal side of the wearer, and the back side member 40 covers the back side of the wearer. The absorbent main body 10 is approximately rectangular in plan view. The ventral end portion 10ea and the dorsal end portion 10eb of the absorbent body 10 overlap with the skin-side surfaces of the ventral member 30 and the dorsal member 40, respectively.

As shown in fig. 2A, the diaper 1 has a left-right symmetrical shape about the center line C-C in the unfolded and stretched state. The non-skin-side surfaces of the abdominal side end portion 10ea and the back side end portion 10eb of the absorbent main body 10 are joined to the skin-side surfaces of the abdominal side member 30 and the back side member 40 by using an adhesive or the like (not shown), the absorbent main body 10 is folded once so that the abdominal side member 30 and the back side member 40 face each other, and the two lateral side portions 30a of the abdominal side member 30 are joined at the side welded portions SS by being welded to the two lateral side portions 40a of the back side member 40, thereby obtaining the diaper 1 in a pants-type state.

The abdominal-side member 30 and the back-side member 40 respectively include

skin side sheets

31 and 41 and

non-skin side sheets

32 and 42 made of soft nonwoven fabric or the like, and

elastic cords

35 and 45 that stretch and contract in the left-right direction. The

elastic cords

35 and 45 are arranged side by side with a space in the up-down direction and fixed between the paired sheets (31 and 32, 41 and 42) in a state stretched in the left-right direction. Accordingly, the abdominal-side member 30 and the back-side member 40 can be expanded and contracted in the left-right direction, and thus fit to the waist of the wearer.

The skin side sheet 31, the elastic cord 35, and the non-skin side sheet 32 are stacked in this order in the thickness direction on the skin side of the abdominal-side member 30, and these members are joined to each other by using an adhesive such as a hot-melt adhesive. Similarly, the skin side sheet 41, the elastic cord 45, and the non-skin side sheet 42 are stacked in this order in the thickness direction on the skin side of the back-side member 40, and these members are joined to each other by using an adhesive such as a hot-melt adhesive.

The

skin side sheets

31 and 41 and the

non-skin side sheets

32 and 42 are each a sheet made of nonwoven fabric, and specifically a spunbonded nonwoven fabric sheet. However, there is no limitation thereto, and they may be nonwoven sheets made of SMS (spunbond/meltblown/spunbond) nonwoven. Further, in the present embodiment, a single fiber made of polypropylene (PP) as a thermoplastic resin is used as a constituent fiber of the nonwoven fabric sheet, but there is no limitation thereto. For example, a single fiber made of another thermoplastic resin such as Polyethylene (PE) may be used, or a composite fiber having a core-sheath structure including PE and PP may be used. Further, the

skin side sheets

31 and 41 and the

non-skin side sheets

32 and 42 need not both be nonwoven sheets, and the configuration in which the

skin side sheets

31 and 41 or the

non-skin side sheets

32 and 42 may be a sheet member other than those made of nonwoven fabric may be employed.

The absorbent main body 10 includes a top sheet 13, an absorbent body 11, and a back sheet 15 that are bonded using an adhesive such as a hot melt adhesive. The surface layer 13 only needs to be a liquid-permeable sheet, and examples thereof include a hydrophilic air-permeable nonwoven sheet and a spunbond nonwoven sheet. The bottom layer 15 only needs to be a liquid impermeable sheet, and examples thereof include a polyethylene film, a polypropylene film, and a hydrophobic SMS nonwoven fabric sheet. The top sheet 13 and the back sheet 15 are large enough to cover the entire absorbent body 11.

The absorbent main body 10 includes leg gathers LG provided at the lateral ends and extending and contracting in the longitudinal direction, and leg side gathers LSG provided on the skin side of the absorbent body 11 and serving as leakage preventing walls that prevent lateral leakage. The leg gathers LG and the leg side gathers LSG include

elastic members

17 and 18 stretched in the longitudinal direction (up-down direction), respectively.

The absorbent body 11 is approximately rectangular in plan view, and includes an absorbent core 11c for absorbing liquid. The absorbent core 11c includes a high molecular absorbent (absorbent a) and a super absorbent polymer (so-called "SAP") wrapped in tissue paper or the like, and is shaped into an approximately hourglass shape. The polymeric absorbent (absorbent a) and the Super Absorbent Polymer (SAP) may be, for example, in the form of particles, and it is preferable to use a sieve so that the particles all have a particle size within a predetermined range. Although the particulate polymer absorbent (absorbent a) is described below, there is no limitation thereto. The polymeric absorbent (absorbent a) used in the absorbent article such as the diaper 1 may be in the form of particles, fine particles, blocks, sheets, threads, or the like, and may be appropriately selected depending on the state of use.

Polymeric absorbent

The polymeric absorbent is a hydrolysate of a crosslinked polymer of a (meth) acrylate and a compound having 2 or more vinyl groups in 1 molecule, and is a polymeric compound having at least-COONa groups. The term "(meth) acrylate" means either acrylate or methacrylate. The polymer absorbent is a monolithic organic porous body having at least 1 or more-COONa groups in 1 molecule. The polymeric absorbent may further comprise-COOH groups. the-COONa groups are substantially uniformly distributed in the skeleton of the porous body. The term "monolithic porous body" means a porous body comprising through-holes and a skeleton and having a network-like co-continuous structure.

The polymeric absorbent, which is a hydrolysis product of a crosslinked polymer of a (meth) acrylate and divinylbenzene, has a continuous skeleton formed of an organic polymer having at least-COONa groups, and has communicating pores (interconnected pores) between portions of the skeleton, which serve as absorption spaces for absorption of an absorption object liquid. Further, the hydrolysis treatment includes converting the-COOR group (carboxylate group) of the crosslinked polymer into the-COONa group or the-COOH group (fig. 3), and thus the polymeric absorbent may have the-COOR group. The presence of-COOH groups and-COONa groups in the organic polymer forming a continuous skeleton can be confirmed by infrared spectrophotometry or by a method of quantifying weakly acidic ion exchange groups.

Fig. 3 is a view illustrating a manufacturing process of the absorbent a. In fig. 3, the upper diagram shows a polymer constituting raw material, the middle diagram shows an entirety a as a crosslinked polymer of (meth) acrylate and divinylbenzene, and the lower diagram shows an absorbent a obtained by hydrolyzing and drying the entirety a of the middle diagram.

The following describes a hydrolysate of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene (hereinafter, also referred to as "absorbent a") as an example of the polymeric absorbent. The polymeric absorbent is not limited to the absorbent a, and only needs to be a hydrolysate of a crosslinked polymer of a (meth) acrylate and a compound containing 2 or more vinyl groups in 1 molecule. Here, the "bulk a" is an organic porous material composed of a crosslinked polymer of (meth) acrylate and divinylbenzene before being subjected to hydrolysis, and will also be referred to as a "bulk organic porous material". The "absorbent A" is a hydrolysis product of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene (whole A) after undergoing hydrolysis and drying. Note that, in the following description, it is assumed that the absorbent a is in a dry state.

The structure of the absorbent a is described below. The absorbent A has a continuous framework and interconnected pores. The absorbent a, which is an organic polymer forming a continuous skeleton, is obtained by crosslinking polymerization using a (meth) acrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, and then hydrolyzing the obtained crosslinked polymer (whole a), as shown in fig. 3. The organic polymer forming the continuous skeleton has, as constituent units, polymerized residues of vinyl groups (hereinafter also referred to as "constituent units X") and crosslinked polymerized residues of divinylbenzene (hereinafter also referred to as "constituent units Y"). The polymerized residue of the vinyl group (constituent unit X) in the organic polymer forming the continuous skeleton has a-COONa group formed by hydrolysis of a carboxylate group, or the polymerized residue has a-COOH group and a-COONa group. Note that since the polymerized monomer is a (meth) acrylate, the polymerized residue of the vinyl group (constituent unit X) has a-COONa group, -COOH group, and an ester group. As a specific example, the production of the absorbent a using butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer is described below.

In the absorbent A, the proportion of the crosslinked polymeric residue of divinylbenzene (constituent unit Y) in the organic polymer forming the continuous skeleton to the whole constituent units is 0.1 to 30 mol%, and preferably 0.1 to 20 mol%. In the absorbent a comprising butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, the proportion of the crosslinked polymerization residue of divinylbenzene (constituent unit Y) in the organic polymer forming the continuous skeleton to the whole constituent units is about 3 mol%, preferably 0.1 to 10 mol%, and more preferably 0.3 to 8 mol%. If the ratio of the crosslinked polymeric residues of divinylbenzene in the organic polymer forming the continuous skeleton is less than the above range, the strength of the absorbent a decreases, and if it exceeds the above range, the absorption amount of the liquid to be absorbed decreases.

In the absorbent A, the proportion of the constituent unit Y in the organic polymer forming the continuous skeleton is preferably 0.1 to 30 mol%, and particularly preferably 0.5 to 20 mol%, with respect to the total number of moles of the constituent unit X and the constituent unit Y. In the absorbent a comprising butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, in the organic polymer forming the continuous skeleton, the proportion of the constituent unit Y to the total number of moles of the constituent unit X and the constituent unit Y is preferably 0.1 to 10 mol%, and particularly preferably 0.3 to 8 mol%. If the proportion of the constituent unit Y to the total number of moles of the constituent unit X and the constituent unit Y in the organic polymer forming the continuous skeleton is less than the above range, the strength of the absorbent a decreases, and if it exceeds the above range, the absorption amount of the liquid to be absorbed decreases.

In the absorbent a, the organic polymer forming the continuous skeleton may be composed of only the constituent unit X and the constituent unit Y, or may be composed of constituent units other than the constituent unit X and the constituent unit Y, such as polymerized residues of monomers other than (meth) acrylate and divinylbenzene. Examples of the constituent unit other than the constituent unit X and the constituent unit Y include polymerized residues of monomers such as styrene, α -methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth) acrylate, 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. Further, the proportion of the constituent unit other than the constituent unit X and the constituent unit Y in the organic polymer forming the continuous skeleton is 0to 50 mol% with respect to the whole constituent units, and preferably 0to 30 mol%. In the absorbent a comprising butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, the proportion of the constituent unit other than the constituent unit X and the constituent unit Y in the organic polymer forming the continuous skeleton is preferably 0to 50% by mol, and preferably 0to 30% by mol, with respect to the whole constituent units.

The thickness of the continuous skeleton of the absorbent A is 0.1 to 100 μm. If the thickness of the continuous skeleton of the absorbent a is less than 0.1 μm, the spaces (pores) in the porous structure for water intake collapse more easily during absorption, and there is a risk of a decrease in the amount of absorption. However, if the thickness of the continuous skeleton is greater than 100 μm, liquid absorption may be slowed. Note that, since the pore structure of the continuous skeleton of the absorbent a is an open pore structure, the thickness of the continuous skeleton is measured at a thickness evaluation point which is a cross section of the skeleton appearing in the test piece for electron microscope measurement. The skeleton is formed by gaps between water droplets removed by dehydration and drying after hydrolysis described later, and is therefore generally polygonal. The thickness of the skeleton is thus the average of the diameters of the circles circumscribing the polygonal cross-section. In rare cases, small holes may be present in the polygon, in which case the circumscribed circle of the cross-section of the polygon around the small hole is measured.

Furthermore, the average diameter of the interconnected pores in the absorbent A is 1 to 1000 μm. If the average diameter of the interconnected pores in the absorbent A is less than 1 μm, the spaces (pores) for water absorption in the porous structure are more likely to collapse during absorption, and there is a risk of a decrease in the absorption rate. However, if the average diameter of the interconnected pores is larger than 1000 μm, there is a risk that the liquid absorption rate is reduced. Note that the average diameter of the interconnected pores of the absorbent a is measured using mercury intrusion and is the maximum of the pore distribution curve obtained by mercury intrusion. The sample used for measurement of the average diameter of the interconnected pores was a sample obtained by drying at 50 ℃ for 18 hours or more by a vacuum dryer, regardless of the ionic form of the absorbent a. The final ultimate pressure is 0 TORR.

The absorbent A has a structure in which bubble-like macropores overlap each other (see FIGS. 4 to 8), and the overlapping portions each have an open pore structure of interconnected bubble structures (open pore structures) in which the average diameter of common openings (mesopores) is 1 to 1000 μm, preferably 10 to 200 μm, particularly preferably 20 to 100 μm. Most have an open cell structure. Each macro-hole overlaps 1-12 other macro-holes, and most overlap 3-10 macro-holes.

Fig. 4 is an SEM photograph of absorbent a at 50 × magnification. Fig. 5 is an SEM photograph of absorbent a at 100 times magnification. Fig. 6 is an SEM photograph of absorbent a at 500 times magnification. Fig. 7 is an SEM photograph of absorbent a at 1000 × magnification. Fig. 8 is an SEM photograph of absorbent a at 1500 times magnification. Absorbent a is an example of absorbent a comprising butyl methacrylate as a polymerized monomer and divinylbenzene as a crosslinking monomer, and absorbent a in fig. 4 to 8 is a cube having 2mm sides.

FIGS. 4 to 8 show Scanning Electron Microscope (SEM) photographs of examples of aspects of absorbent a as specific examples of absorbent A, and absorbent a shown in FIGS. 4 to 8 is an interconnected bubble-like structure having many bubble-like macropores which overlap each other so that the overlapping portions form a common opening (mesopore). Most have an open cell structure. If the average diameter of the mesopores in a dry state is less than the above range, the liquid absorption rate becomes too slow, and if it exceeds the above range, the absorbent a (absorbent a) becomes brittle. Since the absorbent a has such an open pore structure, large pore groups and mesoporous groups can be formed uniformly, and the pore volume and the specific surface area can be significantly increased as compared with the particle aggregation type porous body described in japanese patent application laid-open No. h8-252579 and the like.

The total pore volume of pores (holes) of the absorbent A is preferably 1 to 50ml/g, and more preferably 2 to 30 ml/g. If the total pore volume of the absorbent A is less than 0.5ml/g, the spaces (pores) for water intake in the porous structure are more likely to collapse during absorption, and there is a risk that the absorption amount and the absorption rate are reduced. Further, if the total pore volume exceeds 50ml/g, the strength of the absorbent A is lowered. Note that the total pore volume can be measured by mercury intrusion. The measurement sample of the total pore volume was absorbent a obtained by drying at a temperature of 50 ℃ for 18 hours or more by a vacuum dryer, regardless of the ionic form of the absorbent a. The final ultimate pressure (final ultimate pressure) is 0 TORR.

The following describes aspects of a case where the absorbent a is in contact with a liquid such as a body fluid (hereinafter, the term "body fluid" will be used), and these aspects are also similar in a case where contact is made between the body fluid and the absorbent body 11 including the absorbent a. Further, the weight of the absorbed body fluid is substantially proportional to the body fluid amount, and therefore the body fluid weight is also referred to as "body fluid amount" hereinafter.

First, when a body fluid comes into contact with the absorbent a, the body fluid is absorbed by pores (holes) of the absorbent a by a capillary phenomenon. As shown in fig. 4 to 8, the interconnected pores of the absorbent a are pores whose mesopores (holes) communicate with each other, and the fact that many pores are provided can also be seen from the outside. Due to the capillary phenomenon, a certain amount of body fluid enters the pores, and thus the absorbent a absorbs the body fluid. A part of the body fluid absorbed by the absorbent a is absorbed by the continuous matrix due to osmotic pressure, and thus the continuous matrix elongates. A portion of the bodily fluid not absorbed by the continuous matrix remains in the pores.

Absorbent a is characterized by a continuous matrix that elongates upon absorption of liquid. The continuous framework is elongated in substantially all directions. Due to this elongation of the continuous framework, as the size of the absorbent a increases, the size of the pores also increases. As the size of the pores increases, the volume of the pores also increases and a greater amount of bodily fluid can be stored in the pores. In other words, after absorbing a certain amount of body fluid and becoming larger, the absorbent a can further absorb a certain amount of body fluid by the capillary phenomenon. Since the body fluid is absorbed by the capillary phenomenon, the absorbent a can rapidly absorb the body fluid. Note that, in the absorbent a, the amount of the body fluid stored in the pores is larger than the amount of the body fluid absorbed by the continuous matrix.

In this way, most of the body fluid absorbed in the absorbent a is absorbed due to storage in the pores by the capillary phenomenon, and therefore the higher the porosity which is a proportion of the volume of the pores (total pore volume), that is, the higher the void volume of the pores relative to the volume of the absorbent a, the greater the amount of body fluid that can be absorbed. Preferably, the porosity is 85% or more.

The porosity of the absorbent a was obtained as described below. The specific surface area of the absorbent a as a result of the mercury intrusion method was 400m²The pore volume was 15.5 ml/g. The pore volume of 15.5ml is the volume of pores in 1g of absorbent A. If the specific gravity of the absorbent A is 1g/ml, the volume occupied in 1g of the absorbent A is 15.5ml for the pore volume and 1ml for the absorbent A. The total volume (cubic volume) of 1g of absorbent A was 15.5+1[ ml ]]And the ratio of the mesopore volume thereof is porosity. As a result, the porosity was 15.5/(15.5+ 1). times.100. apprxeq.94%.

The absorption amount of the absorbent a (absorbent a) hardly changes depending on the composition of the body fluid. Preferably, the absorption weight (1 st absorption weight) of the 0.9 wt% NaCl aqueous solution per unit weight of the absorbent A is 0to 2.0 wt% NaCl aqueous solution (2 nd absorption weight) 0.5 to 1.9 times. The 0.9 wt% aqueous NaCl solution is a saline solution similar to so-called normal saline, which is close to the composition of body fluid. If the absorber 11 includes the absorbent a having the 1 st absorption weight of 0.5 to 1.9 times the 2 nd absorption weight, the amount of body fluid that can be absorbed is less likely to be affected by the electrolyte ion concentration of the body fluid, and therefore the absorber 11 can absorb body fluid more reliably.

Body fluids are liquids discharged from organisms, such as sweat, urine, feces, menstrual blood, vaginal secretions, breast milk, blood, and exudates, and the composition of these body fluids varies not only according to the type of body fluid but also according to differences between individuals, health status, and the like. For example, in the case of electrolyte concentrations in the urine component of the organism, such as Na⁺、K⁺、Ca²⁺Plasma concentration differs between humans and animals, and also differs according to health conditions and the like. Superabsorbent polymers (so-called SAPs) widely used in absorbent articles are used to absorb body fluids by the principle of osmotic pressure, and therefore there is a risk that the weight of body fluids that can be absorbed decreases as the number of electrolyte ions increases (as the electrolyte concentration increases). However, with the absorbent a (absorbent a), the amount of body fluid absorbed by the pores by the capillary phenomenon is higher than the amount of body fluid absorbed by the osmotic pressure principle, and therefore the absorption amount is less likely to decrease according to the components of the body fluid, particularly the electrolyte concentration.

Fig. 9 is a graph showing various measurement results with respect to the absorbent a. The terms "absorbent weight" and "absorbent rate" in fig. 9 are synonymous with "absorbent weight" and "absorbent rate". As shown in FIG. 9, the absorbent a having a particle diameter of 500 to 850 μm and the absorbent a having a particle diameter of 250 μm or less were measured several times. As a comparative example, the figure also shows the results for "SAP" as a superabsorbent polymer ("AQUA KEEP" SA60S manufactured by SUMITOMO SEIKA CHEMICALS co.

The absorbed weight of the NaCl aqueous solution of various concentrations was measured as described below.

First, the containers were each filled with 1000ml of an aqueous NaCl solution of each concentration.

Next, two pieces of 200mm × 200mm nylon mesh (255 mesh nylon mesh N-No.255HD manufactured by NBC Meshtec inc., were overlapped with each other), 1.0g of absorbent a was disposed between the nylon meshes, and the four sides were heat-sealed to obtain a pouch having the sample inside.

Next, the sample bag was immersed and allowed to contact the bottom of the container with NaCl aqueous solution of different concentration, the upper side of the bag was fixed to the rim of the container using a clothes peg, and the sample bag was left in this state for 1 hour.

Thereafter, the pouch was taken out of the NaCl aqueous solution, the portions 5mm from the upper end and 50mm from both side ends of the pouch were clamped with a laundry clamp, and the pouch was drained for 15 minutes.

Finally, the weight of the pouch with the absorbent a inside was measured, and the weight of the NaCl aqueous solution absorbed by the absorbent a can be measured by subtracting the weight of the pouch itself and 1.0g (the weight of the absorbent a before absorbing the NaCl aqueous solution) from the measurement result.

As shown in FIG. 9, 1.0g of the absorbent a (1 st polymer absorbent, hereinafter also referred to as "1 st absorbent") had an absorbent weight (1 st absorbent weight) of 37.71 to 62.09g of a 0.9 wt% NaCl aqueous solution, and 1.0g of the absorbent a (2 nd polymer absorbent, hereinafter also referred to as "2 nd absorbent") had an absorbent weight (2 nd absorbent weight) of 34.40 to 68.61g of a 0to 2.0 wt% NaCl aqueous solution. From these measurement results, the lower limit value of the ratio of the 1 st absorbed weight to the 2 nd absorbed weight is [ minimum value of the 1 st absorbed weight/maximum value of the 2 nd absorbed weight ], and the upper limit value is [ maximum value of the 1 st absorbed weight/minimum value of the 2 nd absorbed weight ]. Therefore, the ratio of the 1 st absorption weight to the 2 nd absorption weight is [37.71/68.61] - [62.09/34.40 ]. apprxeq.0.55 to 1.80, and the 1 st absorption weight is 0.55 to 1.80 times the 2 nd absorption weight. Note that these values are calculated as the remainder of two significant digits.

Similarly, in the case of the SAP, 1.0g of the SAP (1 st SAP) has an absorbent weight (1 st SAP absorbent weight) of 60.08 to 63.69g of a 0.9 wt% aqueous NaCl solution, and 1.0g of the SAP (2 nd SAP) has an absorbent weight (1 st SAP absorbent weight) of 45.74 to 311.12g of a 0to 2.0 wt% aqueous NaCl solution. The ratio of the 1 st SAP absorption weight to the 2 nd SAP absorption weight is in the range of [ minimum value of the 1 st SAP absorption weight/maximum value of the 2 nd SAP absorption weight ] - [ maximum value of the 1 st SAP absorption weight/minimum value of the 2 nd SAP absorption weight ] - [60.08/311.12] - [63.69/45.74] - [ 0.19-1.39 ]. In the case of the SAP, the absorption amount of the NaCl aqueous solution decreases as the concentration of the NaCl aqueous solution increases.

It is understood from these results that the absorbent a (absorbent a) can absorb as much or more amount as the SAP, and the amount of the NaCl aqueous solution absorbed by the absorbent a hardly varies depending on the concentration. Therefore, with the absorbent body 11 including the absorbent a, it is possible to suppress the risk of a decrease in absorption capacity according to the electrolyte ion concentration like SAP, while also maintaining the same amount of body fluid as SAP.

Further, the amount of the aqueous solution held in the absorbent a (water holding amount) does not easily vary depending on the electrolyte ion concentration. Since the water retention amount of the aqueous solution does not change so much depending on the electrolyte ion concentration, the risk of the amount of the body fluid stored in the absorbent a changing depending on the composition of the body fluid can be reduced.

The same method as the above-mentioned measurement of the weight of the NaCl aqueous solution was used to prepare the 1 st absorbent (the 1 st polymeric absorbent) having absorbed the 0.9 wt% NaCl aqueous solution of the 1 st absorption amount and the 2 nd absorbent (the 2 nd polymeric absorbent) having absorbed the 0to 2.0 wt% NaCl aqueous solution of the 2 nd absorption amount. The 1 st absorbent and the 2 nd absorbent were dehydrated for a predetermined time of 90 seconds under the conditions of 150G and 850rpm using a centrifuge. In measuring the weight of the aqueous NaCl solution absorbed by the 1 st absorbent and the 2 nd absorbent, it is preferable that the weight of the 0.9 wt% aqueous NaCl solution absorbed by the 1 st absorbent (1 st water retention weight) is 0.5 to 1.6 times the weight of the 0to 2.0 wt% aqueous NaCl solution absorbed by the 2 nd absorbent (2 nd water retention weight). The absorbent A having a 1 st water retention weight of 0.5 to 1.6 times the 2 nd water retention weight readily absorbs body fluid and moves the body fluid outward from the absorbent A so as to be absorbed by another substance.

As shown in FIG. 9, the weight (1 st water retention weight) of the 0.9 wt% NaCl aqueous solution held in 1.0g of absorbent a was 13.59 to 17.12g, and the weight (2 nd water retention weight) of the 0to 2.0 wt% NaCl aqueous solution held in 1.0g of absorbent a was 11.46 to 19.47 g. From these results, it can be understood that the weight of the NaCl aqueous solution held by the absorbent a varies little depending on the difference in the concentration of the NaCl aqueous solution.

In the case of the absorbent a, the lower limit value of the ratio of the 1 st water retention weight to the 2 nd water retention weight is [ minimum value of the 1 st water retention weight/maximum value of the 2 nd water retention weight ], and the upper limit value is [ maximum value of the 1 st water retention weight/minimum value of the 2 nd water retention weight ]. Therefore, the ratio of the 1 st water retention weight to the 2 nd water retention weight is (13.59/19.47) - (17.12/11.46) ≈ 0.70-1.49. Note that these values are calculated as the remainder of two significant digits.

Further, it is understood that the water holding weight of the NaCl aqueous solution at each concentration of the absorbent a is generally lower than that of the SAP. In the case of SAP, the weight of 0.9 wt% NaCl aqueous solution (1 st SAP water retention weight) held in 1.0g of SAP (1 st SAP) is 39.98 to 40.41g, and the weight of 0to 2.0 wt% NaCl aqueous solution (2 nd SAP water retention weight) held in 1.0g of SAP (2 nd SAP) is 29.31 to 286.11 g. Thus, the lower limit of the ratio of 1 st SAP water retention to 2 nd SAP water retention is [ 1 st SAP minimum/2 nd SAP maximum ] and the upper limit is [ 1 st SAP maximum/2 nd SAP minimum ]. Therefore, the ratio of the water retention capacity of the 1 st SAP to the water retention capacity of the 2 nd SAP is (39.98/286.11) - (40.41/29.31) ≈ 0.14-1.38.

The difference between the absorption weight and the water retention weight is the weight of the liquid discharged (separated) to the outside after being absorbed by the absorbent a or the SAP (hereinafter also referred to as "free water weight"). Further, a value obtained by dividing the weight of the separated water by the absorbed weight is a ratio of the amount of the absorbed liquid to the weight of the separated water, and will also be referred to as a separated weight factor. In the case of the absorbent A, it is preferable that the 1 st absorbent has a value of 50 to 80% when the 1 st absorbent is divided by the 1 st absorbent. Similarly, for the 2 nd absorbent, it is preferable that when the difference between the 2 nd absorbent weight and the 2 nd water retention weight is divided by the 2 nd absorbent weight, the result is 40 to 85%. If the absorbent A has the above-mentioned hydrox value, such absorbent A easily allows the absorbed body fluid to move to another substance. In other words, the absorbent a can easily repeat absorption and discharge of liquid. Since the absorbed body fluid is allowed to move to the outside of the absorbent a, the wearer is less likely to feel that the absorbent body 11 containing the absorbent a is wet.

In the case of the absorbent a, the 1 st water-leaving ratio of the 1 st absorbent is a result of dividing the water-leaving weight of a 0.9 wt% NaCl aqueous solution by the 1 st absorbed weight, and the lower limit value of the 1 st water-leaving ratio is { (minimum value of 1 st absorbed weight-maximum value of 1 st retained weight)/minimum value of 1 st absorbed weight }. times.100. The upper limit value of the 1 st water-separating ratio is { (maximum value of 1 st absorbed weight-minimum value of 1 st water-holding weight)/maximum value of 1 st absorbed weight } × 100. The 2 nd water-leaving ratio of the 2 nd absorbent is a result of dividing a water-leaving weight of a 0to 2.0 wt% NaCl aqueous solution by the 2 nd absorbed weight, and its lower limit value is { (minimum value of 2 nd absorbed weight-maximum value of 2 nd retained weight)/minimum value of 2 nd absorbed weight }. times.100. The upper limit value of the 2 nd water-separating ratio is { (maximum value of 2 nd absorbed weight-minimum value of 2 nd water-holding weight)/maximum value of 2 nd absorbed weight }. times.100. As shown in FIG. 9, the 1 st water separation ratio of the absorbent a is { (37.71-17.12)/37.71 } x 100 { (62.09-13.59)/62.09 } x 100 ≈ 54.60-78.11. The 2 nd water separation rate of the absorbent a is { (34.40-19.47)/34.40 } multiplied by 100 { (68.61-11.46)/68.61 } multiplied by 100 ≈ 43.40-83.30. Note that these values are calculated as the remainder of two significant digits.

Note that, as shown in fig. 9, when comparing the water retention weights between the absorbent a and the SAP, the values of the absorbed weights thereof are different, and thus a simple comparison is difficult, but the water retention weight of the absorbent a is generally lower than that of the SAP. In other words, the absorbent a has a lower water retention than the SAP.

Further, it is preferable that in the vortex method, 2.0g of the absorbent A takes 1.0 to 10.0 seconds to absorb 50g of the 0.9 wt% NaCl aqueous solution. With the absorbent a that can absorb the NaCl aqueous solution in this time, the absorbent a can absorb the liquid in a short time, and therefore the absorbent body 11 containing the absorbent a can rapidly absorb the body fluid.

The absorption time in the vortex method was measured as follows.

A30X 8mm rotator and 50g of a 0.9 wt% NaCl aqueous solution set to a liquid temperature of 25. + -. 1 ℃ were placed in the vessel.

Then, the aqueous NaCl solution was stirred with a rotator set to a rotation speed of 600. + -.30 rpm using a magnetic STIRRER (MITAMURA RIKEN KOGYO INC. MAGMIX STIRRER, AC 100W).

Then, 2.00g of absorbent a was introduced into the vessel during stirring, and time measurement was started simultaneously with the introduction.

Then, the time when the solution surface was flattened was measured. The fact that the surface of the solution is flattened is determined based on the point at which the slope of the vortex in the rapidly rotating liquid has approached the plane, and by observing the loss of light reflected by the surface of the liquid of the vortex.

As shown in FIG. 9, 2.0g of absorbent a required 1.69 to 1.93 seconds to absorb 50g of 0.9 wt% NaCl aqueous solution. Note that 2.0g of the absorbent a requires 1.56 to 2.01 seconds to absorb a lower 0.3 wt% NaCl aqueous solution and 1.36 to 2.29 seconds to absorb a higher 2.0 wt% NaCl aqueous solution, and thus 2.0g of the absorbent a requires 1.34 to 2.29 seconds to absorb 50g of a 0to 2.0 wt% NaCl aqueous solution, and it can be understood that the absorption time hardly varies depending on the concentration of the NaCl aqueous solution.

As described above, the absorbent a has a high water separation rate and a high absorption speed, and therefore it is further preferable that the absorbent body 11 of the absorbent article such as the diaper 1 includes the absorbent a and a high molecular compound having a higher water retention capacity than the absorbent a. One example of the high molecular compound having a higher water retention capacity than the absorbent a is a so-called SAP such as sodium polyacrylate. The SAP has high water retention and lower water-leaving property, and thus body fluid that has been absorbed can be continuously retained therein. However, the absorption rate is low (see fig. 9), and the absorption of body fluid takes time. In view of this, if the absorbent body 11 includes the absorbent a and the SAP, when the body fluid comes into contact with the absorbent body 11, the body fluid is first absorbed by the absorbent a having a high absorption speed. Then, the absorbent a having a high water-leaving rate releases the body fluid into the absorbent body 11. Then, the released body fluid is slowly absorbed by the SAP, and the body fluid is stored in the SAP. Therefore, in the absorbent body 11, the body fluid absorbed by the absorbent body a moves to the SAP, so that little body fluid remains in the absorbent body a, thereby suppressing a situation in which the body fluid remains on the surface of the absorbent body 11 so that the wearer feels wetness. Further, in the absorbent body 11, excrement is easily stored in the SAP, and thus leakage of excrement from an absorbent article such as the diaper 1 can be suppressed.

Further, it is preferable that the amount of 0.9 wt% NaCl aqueous solution absorbed by the absorbent A is 15ml or more after 1.0g of the lower end portion of the absorbent A has been in contact with the surface of the 0.9 wt% NaCl aqueous solution for 1 minute. The lower end portion of the absorbent a in contact with the surface of the NaCl aqueous solution is a state in which the absorbent a absorbs the NaCl aqueous solution in the direction opposite to the gravity. Even in this direction opposite to the gravitational force, the absorbent A can absorb 15ml or more of the 0.9 wt% NaCl aqueous solution in 1 minute, and therefore can rapidly absorb a large amount of the NaCl aqueous solution, and therefore the absorbent body 11 containing the absorbent A can absorb body fluid from various angles.

As shown in FIG. 9, the absorbent A had absorbed 20.2 to 26.5ml of a 0.9 wt% NaCl aqueous solution after 1 minute. In this way, the absorbent a has good absorption capacity even in the direction opposite to the gravitational force. The SAP has absorbed 14.0-18.0 ml of a 0.9 wt.% NaCl aqueous solution after 1 minute. From these results, it can be understood that the absorbent a can absorb body fluid faster even in the direction opposite to the gravity force, compared to the SAP.

Further, it is further preferable that, when the lower end portion of 2.0g of the absorbent a subjected to a load of 600gw is in contact with the surface of the 0.9 wt% NaCl aqueous solution, the absorbent a has absorbed 1.0ml or more of the 0.9 wt% NaCl aqueous solution after 2 minutes, and has absorbed 5.0ml or more of the 0.9 wt% NaCl aqueous solution after 15 minutes. In the case where the absorbent body 11 contains the absorbent a, after the absorbent body 11 has absorbed excrement, the absorbent body 11 is flattened in the thickness direction by the weight of the wearer, or is flattened in the left-right direction by the legs of the wearer. In view of this, even while a predetermined load is applied to the absorbent a, the absorbent a can absorb the NaCl aqueous solution, and furthermore can absorb the NaCl aqueous solution even in the direction opposite to the gravity, and therefore, since the absorbent body 11 contains the absorbent a, the absorbent body 11 can absorb body fluid from various angles even when a load is applied to the absorbent body 11 (absorbent a).

As shown in FIG. 9, in the case of absorbent a, 2.0g of absorbent a has absorbed 2.6 to 5.6ml of 0.9 wt% NaCl aqueous solution after 2 minutes, and 13.2 to 25.2ml of 0.9 wt% NaCl aqueous solution after 15 minutes. In the case of SAP, 2.0g of SAP had absorbed 0.8-1.0 ml of 0.9 wt% NaCl solution after 2 minutes, and 4.0ml of 0.9 wt% NaCl solution after 15 minutes. From these results, it can be understood that the absorbent a has better absorbency than the SAP even when it is pressed and also absorbs liquid in the direction opposite to the gravity.

Furthermore, it is preferred that 0.5 wt% CaCl be absorbed per unit weight of absorbent A₂The absorption weight of the aqueous solution is 13 times or more of the weight of the absorbent A. Even in the case of Ca2+ solution having more electrolyte ions than Na +, the absorbent a can absorb a weight 13 times or more the weight of the absorbent a, and therefore the absorbent body 11 containing the absorbent a can easily absorb body fluid regardless of the composition of the body fluid.

FIG. 9 shows 0.5% by weight CaCl absorbed by 1g of absorbent a₂Weight of aqueous solution. Note that CaCl was measured similarly to the measurement of the absorbed weight of the NaCl aqueous solution₂The absorbed weight of the aqueous solution. As shown in FIG. 9, it was found that 0.5 wt% CaCl was absorbed by the absorbent a₂The absorption weight of the aqueous solution is 16.29-27.69 g, and 1g of absorbent a absorbs 0.5 wt% of CaCl₂The weight of the aqueous solution is 16.29 times or more of the weight of the absorbent a.

As shown in FIG. 9, 1g of SAP absorbed 0.5 wt% CaCl₂The absorption weight of the aqueous solution is 6.71 to 7.43 g. 0.5% by weight CaCl absorbed in comparative 1g of absorbent a₂Weight of aqueous solution and 0.5 wt% CaCl absorbed by 1g SAP₂The absorbent a absorbs significantly more weight of the aqueous solution. Furthermore, 1g SAP absorbed 0.5 wt% CaCl₂SAP absorption of less than 1g of aqueous solution0.9 wt% aqueous NaCl solution. In other words, the higher the number of electrolyte ions, the smaller the absorption amount of SAP, and the absorption amount of the absorbent a is hardly reduced according to the number of electrolyte ions unlike SAP. For this reason, the use of the absorbent a (absorbent a) makes it possible to suppress a decrease in absorption amount according to the composition of the body fluid.

The absorption rate test and the absorption amount test carried out with respect to the absorbent A are described below. Fig. 10 is a graph showing the results of an experiment on the absorption rate and the absorption amount of the absorbent a. Fig. 11 is a graph showing the results of an experiment regarding the absorption rate and the absorption amount of the super absorbent polymer in the comparative example.

As shown in fig. 10, in the absorption rate test, pure water and a 0.9% sodium chloride aqueous solution were used as the liquid to be absorbed, and the immersion time required for the absorption amount to reach 90% of the saturated absorption amount was 5 seconds or less in both cases. In addition, in the absorption amount test of the absorbent a, a 0.9% aqueous sodium chloride solution, a 4% aqueous NaOH solution, 35% hydrochloric acid, and 29% aqueous ammonia were used as test solutions. As a result, the absorption amount of the 0.9% aqueous sodium chloride solution was 67 g/g-resin, the absorption amount of the 4% aqueous NaOH solution was 78 g/g-resin, the absorption amount of the 35% hydrochloric acid was 28 g/g-resin, and the absorption amount of the 29% aqueous ammonia was 105 g/g-resin.

Absorption rate test method

The sample tube was obtained by placing dry absorbent A in a nonwoven tube having a length of 100mm, an inner diameter of 10mm and a sealed end. The weight of the tube was measured before and after placing the absorbent a in the tube, thereby calculating the weight of the absorbent a in the tube in advance. Next, the nonwoven fabric side of the sample tube is immersed in an absorption object liquid having a known concentration, and then the tube is lifted from the solution after a predetermined time. The weight of the tube was then measured after 1 minute. This dipping and measurement were repeated until there was no change in weight. The absorption amount when the weight no longer changes is considered to be the saturated absorption amount.

Absorption capacity test method

The test was carried out according to the JIS method. The sample is a tea bag in which the absorbent a is placed, and the absorption amount of the liquid to be absorbed is obtained based on the weight of the sample before and after immersion in the liquid to be absorbed for 24 hours.

Comparative example

The absorption rate test and the absorption amount test were performed using a superabsorbent polymer called "high absorbent polymer (acrylate based)" manufactured by Wako Chemicals inc. As shown in fig. 11, as a result of the absorption amount test, in the absorption rate test, an immersion time of 12 minutes was required until the absorption amount reached 90% of the saturated absorption amount in pure water, and an immersion time of 3.5 minutes was required until the absorption amount reached 90% of the saturated absorption amount in a 0.9% sodium chloride aqueous solution. Further, the absorption amount of the 0.9% aqueous sodium chloride solution was 52 g/g-resin, the absorption amount of the 4% aqueous NaOH solution could not be measured due to dissolution during impregnation, the absorption amount of the 35% hydrochloric acid was 2 g/g-resin, and the absorption amount of the 29% aqueous ammonia was 128 g/g-resin.

The absorbent a may also be used as a monolith ion exchanger, and the absorbent a may also be referred to as a "monolith organic porous ion exchanger". The total ion exchange capacity of the absorbent A per unit weight of the-COONa groups and-COOH groups is 5mg equivalent/g or more, and preferably 6mg equivalent/g or more. If the total ion exchange capacity of the-COOH groups and the-COONa groups of the whole ion exchanger in a dry state is less than the above range, the absorption amount of the liquid to be absorbed decreases and the absorption rate also decreases. The upper limit of the total ion exchange capacity of the-COOH groups and the-COONa groups of the whole ion exchanger in the dry state is not particularly limited, but is, for example, 14.0mg equivalent/g or less, or 13.0mg equivalent/g or less. The total ion exchange capacity per unit weight of the-COONa groups and-COOH groups of the absorbent A having butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer is 4.0mg equivalent/g or more, and preferably 6mg equivalent/g or more. Further, the upper limit value of the total ion exchange capacity of the-COOH groups and-COONa groups of the whole ion exchanger of the absorbent a in a dry state is not particularly limited, but is, for example, 11mg equivalent/g or less, or 14mg equivalent/g or less. It is desirable that the total ion exchange capacity per unit weight of the-COONa groups of the absorbent A is 4.0mg equivalent/g or more. As long as the total ion exchange capacity per unit weight of the-COONa groups in the absorbent a is 4.0mg equivalent/g or more, the polymeric absorbent is more likely to absorb body fluid and therefore the continuous skeleton is easily elongated, the interconnected pores are also easily expanded as the continuous skeleton is elongated, and body fluid is easily taken into the interconnected pores by capillary phenomenon and therefore the body fluid is easily absorbed by the absorbent body, as compared to the case where the total ion exchange capacity per unit weight of the-COONa groups is less than 4.0mg equivalent/g.

Note that, in the present invention, the total ion exchange capacity of the-COOH group and the-COONa group means the ion exchange capacity of the-COOH group if the whole ion exchanger of the present invention has only the-COOH group; refers to the ion exchange capacity of the-COONa groups if the integral ion exchanger of the invention has only-COONa groups; and refers to the sum of the ion exchange capacities of the-COOH groups and the-COONa groups if the overall ion exchanger of the present invention has both-COOH groups and-COONa groups. Further, the total ion exchange capacity per unit weight of the-COOH groups and-COONa groups of the whole ion exchanger in a dry state is measured by: the amount of-COOH groups was quantified by neutralization titration with a sufficient amount of an acid for ion exchange groups of the whole ion exchanger using a sample having all-COOH groups, and all of the whole ion exchanger used at that time was recovered, and then a dry weight was obtained. Further, the total ion exchange capacity per unit weight of-COONa groups can be obtained from the amount of acid added in order to set all the ion exchange groups of the entire ion exchanger to-COOH groups.

In the monolithic ion exchanger, the introduced ion exchange groups are not only uniformly distributed on the surface of the whole but also uniformly distributed in the skeleton of the whole. The expression "uniform distribution of ion exchange groups" as used herein refers to a state in which the distribution of ion exchange groups is uniform at the surface and at least in the order of μm in the framework. The distribution state of the ion exchange groups can be easily checked using EPMA.

Examples of the structure of the monolithic ion exchanger include an open pore structure (JP 2002-.

The ion exchange capacity of the absorbent a as the whole cation exchanger of the absorbent a was 8mg equivalent/g in a dry state, and it was confirmed that carboxyl groups were quantitatively introduced. Further, as a result of measurement using the mercury intrusion method, the average diameter of three-dimensional continuous pores of the absorbent A in a dry state was 49.1 μm, and the total pore volume in a dry state was 13.5 ml/g. The thickness of the continuous skeleton obtained by SEM observation was 9.5 μm.

Fig. 12A and 12B show the distribution state of sodium obtained by EPMA to determine the distribution state of carboxyl groups in a as a whole. Fig. 12A is an SEM photograph of a fracture surface of the absorbent a. Fig. 12B is a map of Na distribution in the same portion as in fig. 12A. In fig. 12A and 12B, it can be confirmed that, with respect to the distribution state of the carboxyl groups in the framework cross section, the carboxyl groups are uniformly distributed not only on the framework surface of the entire cation exchanger but also inside the framework, and the carboxyl groups have been uniformly introduced into the entire ion exchanger.

Further, one example of the structure of the absorbent a is a bulk ion structure such as an open pore structure disclosed in JP 2002-.

Process for producing absorbent A

As shown in fig. 3, the absorbent a may be obtained by a cross-linking polymerization step and a hydrolysis step. The following describes a method for producing the absorbent a.

First, an oil-soluble monomer for crosslinking polymerization and a crosslinkable monomer, a surfactant, water and optionally a polymerization initiator are mixed to obtain a water-in-oil emulsion. Water-in-oil emulsions are emulsions in which the oil phase is the continuous phase and in which water droplets are dispersed.

As shown in the upper part of fig. 3, in the absorbent a, the whole a is formed by performing crosslinking using butyl methacrylate as the (meth) acrylate as the oil-soluble monomer, divinylbenzene as the crosslinkable monomer, sorbitan monooleate as the surfactant, and isobutyronitrile as the polymerization initiator.

In the absorbent a, as shown in the upper part of fig. 3, first, 9.2g of t-butyl methacrylate as an oil-soluble monomer, 0.28g of divinylbenzene as a crosslinkable 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 were mixed and uniformly dissolved.

Next, a mixture of tert-butyl methacrylate, divinylbenzene, SMO, and 2,2' -azobis (isobutyronitrile) was added to 180g of pure water, and stirred under reduced pressure using a vacuum stirring defoaming mixer (manufactured by EME corp., ltd.) as a planetary motion stirring device to obtain a water-in-oil emulsion.

Thereafter, the emulsion was quickly transferred to a reaction vessel, sealed, left to stand and polymerized at 60 ℃ for 24 hours. After completion of the polymerization, the content was taken out, extracted with methanol, and dried under reduced pressure to obtain a monolith a having a continuous macroporous structure. The internal structure of the monolith a was observed using SEM. Fig. 10A is an SEM photograph of a fracture surface of the absorbent a. Fig. 10B is a map of Na distribution in the same portion as in fig. 10A. The whole A had an open cell structure and the thickness of the continuous skeleton was 5.4. mu.m. The average diameter, measured by mercury intrusion, was 36.2 μm and the total pore volume was 15.5 ml/g.

Note that the content of divinylbenzene is preferably 0.3 to 10 mol%, and more preferably 0.3 to 5 mol% with respect to the whole monomers. Further, the proportion of divinylbenzene to the total of butyl methacrylate and divinylbenzene is preferably 0.1 to 10 mol%, and more preferably 0.3 to 8 mol%. In the absorbent A, the ratio of butyl methacrylate to the total of butyl methacrylate and divinylbenzene and the ratio of divinylbenzene to the total of butyl methacrylate and divinylbenzene were 97.0 mol% and 3.0 mol%, respectively.

The amount of the surfactant added varies significantly depending on the kind of the oil-soluble monomer and the size of the intended emulsion particles (macropores). The amount of the surfactant added is preferably in the range of about 2 to 70% with respect to the total amount of the oil-soluble monomer and the surfactant.

Further, in order to control the shape and size of the bubbles of the whole 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 may be co-present in the system.

The mixing method used in forming the water-in-oil emulsion is not particularly limited. A method of mixing all the components together at once, or a method in which an oil-soluble component including an oil-soluble monomer, a surfactant, and an oil-soluble polymerization initiator is uniformly mixed, then water and a water-soluble component as a water-soluble polymerization initiator are uniformly mixed, and then the components are mixed together may be employed. The mixing device for forming the emulsion is also not particularly limited, and in order to obtain a desired emulsion particle diameter, an appropriate device may be selected from, for example, a general mixer, a homogenizer, a high-pressure homogenizer, or a so-called planetary stirring device, in which case the target substance is placed in a mixing vessel, and stirred and mixed by rotating the mixing vessel around a revolution axis in an inclined state. Further, the mixing conditions are not particularly limited, and the stirring speed and the stirring time may be set as desired to obtain a desired particle diameter of the emulsion. Among these mixing devices, the planetary stirring device can uniformly generate water droplets in the W/O emulsion, and the average diameter thereof can be set as desired within a wide range.

The various polymerization conditions for polymerizing the water-in-oil emulsion may be selected depending on the kind of the monomer and the initiator system. For example, when azobisisobutyronitrile, benzoyl peroxide, potassium persulfate or the like is used as the polymerization initiator, thermal polymerization is sufficiently allowed at 30 to 100 ℃ for 1 to 48 hours in a sealed container under an inert atmosphere. When hydrogen peroxide-ferrous chloride or sodium persulfate-sodium bisulfite or the like is used as a polymerization initiator, thermal polymerization is sufficiently allowed at 0to 30 ℃ for 1 to 48 hours in a sealed vessel under an inert atmosphere. After the polymerization is completed, the content is taken out and subjected to Soxhlet extraction (Soxhlet extraction) with a solvent such as isopropyl alcohol to remove unreacted monomers and residual surfactant, thereby obtaining a whole a shown in the middle portion of fig. 3.

Subsequently, the whole a (crosslinked polymer) is hydrolyzed to obtain an absorbent a. The whole a was immersed in dichloroethane containing zinc bromide and stirred at 40 ℃ for 24 hours, then contacted with methanol, 4% hydrochloric acid, 4% aqueous sodium hydroxide solution, and water in this order to perform hydrolysis, and then dried, and then the bulk absorbent a was pulverized into a predetermined size to obtain a particulate absorbent a.

The hydrolysis method of the whole a is not particularly limited, and various methods can be used. For example, any of various solvents including 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 is used, and there is a method of contacting the solvent with a strong base such as sodium hydroxide, or a method of contacting the solvent with a hydrohalogen acid such as hydrochloric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, or a bronsted acid such as zinc bromide, aluminum chloride, aluminum bromide, titanium (IV) chloride, cerium chloride/sodium iodide, or magnesium iodide.

Among the polymerization raw materials of the organic polymer forming the continuous skeleton of the absorbent a, the (meth) acrylic acid ester is not particularly limited, but is preferably a C1 to C10 alkyl ester of (meth) acrylic acid, and particularly preferably a C4 alkyl ester of (meth) acrylic acid. Examples of the C4 alkyl ester of (meth) acrylic acid include t-butyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate.

The monomers used for the cross-linking polymerization may be only (meth) acrylate and divinylbenzene, or may comprise (meth) acrylate and divinylbenzene and further monomers other than (meth) acrylate and divinylbenzene. Examples of other monomers include styrene, alpha-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobutylene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, (meth) acrylonitrile, vinyl acetate, ethylene glycol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate. Note that, among all monomers used for the crosslinking polymerization, the proportion of the monomers other than the (meth) acrylate and the divinylbenzene is preferably 0to 80 mol%, and more preferably 0to 50 mol%.

The surfactant is not limited to sorbitan monooleate. It may be any surfactant that can form a water-in-oil (W/O) emulsion when the cross-linking polymerized monomer and water are mixed. Examples include nonionic surfactants such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether and polyoxyethylene sorbitan monooleate; anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate and sodium dioctyl sulfosuccinate; cationic surfactants such as distearyldimethylammonium chloride; and amphoteric surfactants such as lauryl dimethyl betaine. These surfactants may be used alone or in combination of two or more thereof.

It is preferable to use a compound that generates radicals by heat and light irradiation as a polymerization initiator. The polymerization initiator may be water-soluble or oil-soluble, and examples thereof include azobis (4-methoxy-2, 4-dimethylvaleronitrile), azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanecarbonitrile, azobis (2-methylpropionamidine) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-sodium bisulfite, and tetramethylthiuram disulfide. However, in some cases, even if a polymerization initiator is not added, there are systems in which polymerization is performed only by heating or only by irradiation with light, and in such systems, the addition of a polymerization initiator is unnecessary.

As another example of the absorbent A, an absorbent b comprising 6.4g of t-butyl methacrylate and 2.8g of 2-ethylhexyl methacrylate may be used instead of 9.2g of t-butyl methacrylate as the absorbent a. Absorbent b was the same as absorbent a except that the oil-soluble monomers were 6.4g of t-butyl methacrylate and 2.8g of 2-ethylhexyl methacrylate. The ion exchange capacity of the absorbent b in a dry state was 5.0mg equivalent/g.

The absorbent b was subjected to an absorption rate test using pure water as the liquid to be absorbed in a manner similar to the absorbent a described above. Fig. 13 is a graph showing the relationship between the absorption amounts of the absorbent a and the absorbent b and time when the liquid to be absorbed is pure water. As shown in FIG. 13, the saturated absorption amount was 18 g/g-resin, and it took 5 seconds or less of immersion time until the absorption amount reached 90% of the saturated absorption amount.

Other embodiments

Although the embodiments of the present invention have been described above, the above-described embodiments of the present invention are merely to facilitate understanding of the present invention and are not to be construed as limiting the present invention in any way. Various changes or modifications may be made to the invention and equivalents may be covered without departing from the spirit thereof.

Although the absorbent body 11 includes the absorbent a (absorbent a) and the SAP in the above-described embodiment, there is no limitation thereto. The absorbent body 11 may be constituted only by the absorbent a. Further, the substance used together with the absorbent a is not limited to the SAP. For example, the absorber 11 may include the absorbent a and pulp fibers, and the absorber 11 may include the absorbent A, SAP and pulp fibers.

Description of the reference numerals

1 diaper (pull-on disposable diaper, absorbent article), 10 absorbent body, 10ea end, 10eb end, 11 absorber, 11c absorbent core, 13 top sheet, 15 back sheet, 30 ventral member, 30a side portion, 31 skin side sheet, 32 non-skin side sheet, 35 elastic cord, 40 back side member, 40a side portion, 41 skin side sheet, 42 non-skin side sheet, 45 elastic cord, SS welded portion, LH leg opening, BH waist opening

Claims

1. An absorbent body for absorbing bodily fluids, comprising:

polymeric absorbents having a continuous framework and interconnected pores,

the compound contains 2 or more vinyl groups in 1 molecule,

the polymeric absorbent contains at least 1 or more-COONa groups.

2. The absorbent body according to claim 1, wherein

The polymer absorbent is an integral absorbent.

3. The absorbent body according to claim 1 or 2, wherein

the 1 st absorption weight is 0.5 to 1.9 times of the 2 nd absorption weight.

4. An absorbent body according to claim 3 wherein

5. The absorbent body according to claim 4, wherein

6. The absorbent body according to any one of claims 1 to 5, wherein

7. The absorbent body according to any one of claims 1 to 6, wherein

8. The absorbent body according to any one of claims 1 to 7, wherein

9. The absorbent body according to any one of claims 1 to 8, wherein

In a state where the lower end of 2.0g of the polymeric absorbent, which was subjected to a load of 600gw, was brought into contact with the surface of a 0.9 wt% NaCl aqueous solution,

10. The absorbent body according to any one of claims 1 to 9, wherein

11. The absorbent body according to any one of claims 1 to 10, wherein

12. The absorbent body according to any one of claims 1 to 11, wherein

The average diameter of the interconnected pores is 1-1000 μm.

13. The absorbent body according to any one of claims 1 to 12, wherein

The absorbent body comprises

The polymeric absorbent and

14. The absorbent body according to any one of claims 1 to 13, wherein

15. An absorbent article comprising the absorbent body according to any one of claims 1 to 14.