WO2020262343A1

WO2020262343A1 - Absorber and absorbent article

Info

Publication number: WO2020262343A1
Application number: PCT/JP2020/024503
Authority: WO
Inventors: 響菊池; 若菜岩井; 中下　将志; 裕樹合田
Original assignee: ユニ・チャーム株式会社
Priority date: 2019-06-28
Filing date: 2020-06-23
Publication date: 2020-12-30
Also published as: CN114080241A; CN117838442A; AU2020306265A1; JPWO2020262343A1; TW202116274A; KR20220027061A; BR112021020337A2

Abstract

The present invention pertains to an absorber (11) for absorbing bodily fluids, the absorber characterized by comprising a polymer absorbent provided with a continuous skeleton and continuous pores, the polymer absorbent being a hydrolysate of a crosslinked polymer of a (meth)acrylic acid ester and a compound containing two or more vinyl groups per molecule, and the polymer absorbent containing at least one —COONa group.

Description

Absorbents and absorbent articles

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

Conventionally, absorbent articles such as disposable diapers and sanitary napkins using a highly absorbent polymer (so-called "SAP") having a high absorption amount have been known. For example, as disclosed in Patent Document 1, an absorber in which an absorbent resin particle (highly absorbent polymer) 5 having an excellent absorption amount and a hydrophilic fiber 13 such as a pulp fiber having an excellent absorption rate are combined. The absorbent article 30 using 15 is disclosed.

International Publication No. 2013-018571

It is desired that the thickness of the absorbent article 30 be reduced from the viewpoint of distribution, storage, portability, and the like. However, for example, when only the absorbent resin particles 5 are used as the absorber 15, the absorption rate is inferior, so that when the body fluid or the like is vigorously excreted, the body fluid cannot be sufficiently absorbed. It was. On the other hand, when the absorbent resin particles 5 and the hydrophilic fibers 13 are combined, the absorber 15 may become bulky.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an absorber and an absorbent article that easily absorb body fluids.

The main invention for achieving the above object is an absorber for absorbing body fluid, which has a polymer absorbent having a continuous skeleton and continuous pores, and the polymer absorbent is (meth). An absorber which is a hydrolyzate of a crosslinked polymer of an acrylic acid ester and a compound containing two or more vinyl groups in one molecule, and also contains at least one -COONa group. Is.
Other features of the present invention will be clarified by the description in the present specification and the accompanying drawings.

According to the present invention, when the polymer absorbent absorbs the body fluid, the continuous skeleton is elongated, and the continuous skeleton is easily expanded, so that the body fluid is easily taken into the continuous pores by the capillary phenomenon. As an absorber, it becomes easier to absorb body fluids.

FIG. 1 is a schematic perspective view of a pants-type disposable diaper 1. FIG. 2A is a schematic plan view of the unfolded and stretched diaper 1 as viewed from the side surface of the skin. FIG. 2B is a schematic cross-sectional view taken along the line XX in FIG. 2A. FIG. 3 is a diagram illustrating a manufacturing process of the absorbent a. FIG. 4 is an SEM photograph of the absorbent a at a magnification of 50 times. FIG. 5 is an SEM photograph of the absorbent a at a magnification of 100 times. FIG. 6 is an SEM photograph of the absorbent a at a magnification of 500 times. FIG. 7 is an SEM photograph of the absorbent a at a magnification of 1000 times. FIG. 8 is an SEM photograph of the absorbent a at a magnification of 1500 times. FIG. 9 is a diagram showing each measurement result of the absorbent a. FIG. 10 is a graph showing the absorption rate and the absorption amount test result of the absorbent A. FIG. 11 is a graph showing the absorption rate and absorption amount test results of the highly absorbent polymer of the comparative example. FIG. 12A is an SEM photograph of the fracture surface of the absorbent A. FIG. 12B is a mapping diagram of the Na distribution of the same portion as that of FIG. 12A. FIG. 13 is a graph showing the relationship between the amount of absorption and the time of the absorbent a and the absorbent b when the liquid to be absorbed is pure water.

The description of the present specification and the accompanying drawings will clarify at least the following matters.
An absorber for absorbing body fluid, which has a polymer absorbent having a continuous skeleton and continuous pores, and the polymer absorbent is a (meth) acrylic acid ester and two in one molecule. It is a hydrolyzate of the crosslinked polymer of the above vinyl group-containing compound, and is an absorber characterized by containing at least one -COONa group.

According to such an absorber, when the polymer absorber absorbs the body fluid, the continuous skeleton is elongated, and the continuous pores are likely to expand as the continuous skeleton is elongated. Therefore, the continuous pores of the body fluid are caused by the capillary phenomenon. It becomes easier to take in the body fluid as an absorber.

It is desirable that the polymer absorbent is a monolith-like absorbent.

According to such an absorber, when the monolith-like absorber absorbs the body fluid, it becomes easier to take in the body fluid into the penetrating hole that widens with the elongation of the continuous skeleton, and it becomes easier to absorb the body fluid as an absorber.

In such an absorber, the first absorption weight in which the polymer absorbent per unit weight absorbs a NaCl aqueous solution having a concentration of 0.9 wt% and the polymer absorbent per unit weight have concentrations. With respect to the second absorption weight for absorbing 0 to 2.0 wt% NaCl aqueous solution, it is desirable that the first absorption weight is 0.5 to 1.9 times the second absorption weight.

According to such an absorber, it is possible to reduce the risk that the absorbed weight of the absorber will change depending on the components of the body fluid.

In such an absorber, a first polymer absorber that has absorbed a concentration of 0.9 wt% of a NaCl aqueous solution by the first absorption weight and a NaCl aqueous solution having a concentration of 0 to 2.0 wt% are absorbed by the second absorption weight. The second polymer absorbent was dehydrated for 90 seconds at 150 G at 850 rpm using a centrifuge for a predetermined time, and then the concentration of 0.9 wt% absorbed by the first polymer absorbent was 0.9 wt%. It is desirable that the weight of the NaCl aqueous solution is 0.5 to 1.6 times the weight of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% absorbed by the second polymer absorbent.

According to such an absorber, it is possible to reduce the risk that the water retention weight of the absorber will change depending on the components of the body fluid.

In such an absorber, the weight of the NaCl aqueous solution having a concentration of 0.9 wt% absorbed by the first polymer absorber after the dehydration is defined as the first water retention weight, and the weight after the dehydration is defined as the first water retention weight. The weight of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% absorbed by the second polymer absorbent is defined as the second water retention weight, and the first absorption weight and the first water retention of the first polymer absorbent. The value obtained by dividing the difference from the weight by the first absorption weight is 50 to 80%, and the difference between the second absorption weight and the second water retention weight of the second polymer absorbent is the above. It is desirable that the value divided by the second absorbed weight is 40 to 85%.

According to such an absorber, the polymer absorbent easily transfers the body fluid once absorbed to another substance, so that absorption and water separation can be repeated, and the body fluid can be removed from the polymer absorbent. After moving, it is possible to make the user less likely to feel wet.

It is desirable that the time for 2.0 g of the polymer absorbent to absorb 50 g of a 0.9 wt% NaCl aqueous solution by the vortex method is 1.0 to 10.0 seconds.

According to such an absorber, the polymer absorbent can absorb the liquid in a short time, so that the body fluid can be absorbed more quickly.

It is desirable that the absorption weight of the polymer absorbent for absorbing the CaCl2 aqueous solution having a concentration of 0.5 wt% is 13 times or more the weight of the polymer absorbent.

According to such an absorber, the absorber easily absorbs the body fluid even if the body fluid contains a large amount of divalent ions.

In such an absorber, after 1 minute has passed in a state where the lower end of 1.0 g of the polymer absorbent is in contact with the water surface of an aqueous NaCl solution having a concentration of 0.9 wt%, the concentration of the polymer absorbent is 0. It is desirable that the absorption amount of the 9.wt% NaCl aqueous solution is 15 ml or more.

According to such an absorber, the polymer absorber can quickly absorb a large amount of liquid even in the direction against gravity, so that the absorber can easily absorb the body fluid from various angles.

After 2 minutes have passed, the lower end of 2.0 g of the polymer absorbent in such an absorber under a load of 600 gw is in contact with the water surface of a 0.9 wt% NaCl aqueous solution. The amount of absorption of the aqueous NaCl solution having a concentration of 0.9 wt% by the polymer absorbent is 1.0 ml or more, and after 15 minutes, the amount of the aqueous solution of NaCl having a concentration of 0.9 wt% by the polymer absorbent is absorbed. , 5.0 ml or more is desirable.

According to such an absorber, even a loaded polymer absorber can absorb the liquid in a direction against gravity, so that the absorber can easily absorb the body fluid from various angles. Become.

It is desirable that the volume of the voids in the pores per unit volume of the polymer absorbent is 85% or more in such an absorber.

According to such an absorber, the capillary phenomenon makes it easier to take in the body fluid into the continuous pores, and makes it easier to absorb the body fluid as an absorber.

It is desirable that the polymer absorbent contains 0.1 to 30.0% of crosslinked polymerization residues.

According to such an absorber, when the body fluid is absorbed, the continuous skeleton is elongated, and as the continuous skeleton is elongated, the continuous pores can be easily expanded to be a polymer absorbent.

It is desirable that the average diameter of the continuous pores of such an absorber is 1 to 1000 μm.

It is desirable that the absorber has the polymer absorbent and a polymer compound having a higher water retention ratio than the polymer absorbent.

According to such an absorber, first, the polymer absorbent which easily absorbs the body fluid by the capillary phenomenon can absorb the body fluid, and the polymer compound can retain the body fluid. Therefore, as an absorber, the body fluid is quickly absorbed. And, it is possible to keep the body fluid in a water-retaining state.

It is desirable that the total ion exchange capacity of -COONa groups per unit weight of the polymer absorbent is 4.0 mg equivalent / g or more.

According to such an absorber, the polymer absorber is more likely to absorb body fluids than when the total ion exchange capacity of -COONa groups per unit weight is less than 4.0 mg equivalent / g, thus extending the continuous skeleton. As the continuous skeleton is elongated, the continuous pores are easily expanded, and the body fluid is easily taken into the continuous pores by the capillary phenomenon, so that the body fluid is easily absorbed as an absorber.

It is desirable that the article is an absorbent article having any of the above absorbers.

According to such an absorbent article, when the polymer absorbent of the absorber absorbs the body fluid, the continuous skeleton is elongated, and the continuous pores are easily expanded as the continuous skeleton is elongated. Therefore, the body fluid is caused by the capillary phenomenon. Can be easily taken into continuous pores, and can be made into an absorbent article that easily absorbs body fluids.

=== Embodiment ===
As an example of the absorbent article using the absorbent body according to the present embodiment, a so-called pants-type disposable diaper will be described as an example. The absorbent articles using the absorbent body are not limited to pants-type disposable diapers, but also include absorbent articles such as tape-type disposable diapers, sanitary napkins, absorbent pads, disposable diapers for pets, and absorbent pads for pets. It can be used as an absorber. Disposable diapers, absorbent pads and the like can be used for both infants and adults. The body fluid refers to a fluid discharged from living organisms including animals as well as humans. For example, sweat, urine, stool, menstrual blood, vaginal discharge, breast milk, blood, exudate and the like can be mentioned.

=== Basic configuration of pants-type disposable diaper 1 ===
FIG. 1 is a schematic perspective view of a pants-type disposable diaper 1. FIG. 2A is a schematic plan view of the unfolded and stretched diaper 1 as viewed from the side surface of the skin. FIG. 2B is a schematic cross-sectional view taken along the line XX in FIG. 2A. The "deployed state" means that the joints of the side portion 30a of the ventral member 30 and the side portion 40a of the dorsal member 40 on both sides of the diaper 1 are separated from each other and opened to expand the entire diaper 1 in a plane. It is in a state. The "extended state" refers to a state in which the elastic member included in the diaper 1 is extended to the extent that the wrinkles of the diaper 1 become invisible. Specifically, it shows a state in which the dimensions of each member (for example, the ventral member 30 described later) constituting the diaper 1 are extended until the dimensions match or are close to the dimensions of the member alone. The CC line in FIGS. 2A and 2B is the center line in the left-right direction. In FIG. 2B, the adhesive is omitted for convenience.

As shown in FIG. 1, the pants-type diaper 1 has a vertical direction, a horizontal direction, and a front-rear direction, and the diaper 1 is formed with a waist circumference opening BH and a pair of leg circumference openings LH. The vertical direction of the unfolded and extended diaper 1 in FIG. 2A is referred to as the "longitudinal direction", one side in the longitudinal direction is also referred to as the "ventral side", and the other side is also referred to as the "dorsal side". In the anterior-posterior direction, the ventral side of the wearer is the front side, and the dorsal side of the wearer is the rear side. Further, the diaper 1 has a thickness direction as shown in FIG. 2B, and the side in the thickness direction that comes into contact with the wearer is the skin side, and the opposite side is the non-skin side.

The diaper 1 is a so-called three-piece type, and has an absorbent main body 10, a ventral member 30, and a dorsal member 40. The ventral member 30 and the dorsal member 40 have a substantially rectangular shape in a plan view, and their longitudinal directions are along the left-right direction. The ventral member 30 covers the wearer's ventral side, and the dorsal member 40 covers the wearer's dorsal side. The absorbent body 10 has a substantially rectangular shape in a plan view. The ventral end 10ea and the dorsal end 10eb of the absorbent body 10 are overlapped with the skin side surface of the ventral member 30 and the dorsal member 40, respectively.

As shown in FIG. 2A, the unfolded and extended diaper 1 has a shape symmetrical with respect to the center line CC. The non-skin side surface of the ventral end 10ea and the dorsal end 10eb of the absorbent body 10 and the skin side surface of the ventral member 30 and the dorsal member 40 are joined with an adhesive or the like (not shown), and the ventral member is joined. The absorbent body 10 is folded in half so that the 30 and the dorsal member 40 face each other, and the left and right side portions 30a of the ventral member 30 and the left and right side portions 40a of the dorsal member 40 are side-welded portions. By welding and joining with SS, the diaper 1 becomes a pants type.

The ventral member 30 and the dorsal member 40 are provided with skin-

side sheets

31, 41 and non-skin-

side sheets

32, 42 made of a flexible non-woven fabric or the like, and a plurality of

thread rubbers

35, 45 that expand and contract in the left-right direction, respectively. The plurality of

rubber threads

35, 45 are arranged side by side with an interval in the vertical direction, and are fixed between the two sheets (31 and 32, 41 and 42) in a state of being extended in the horizontal direction. .. Therefore, the ventral member 30 and the dorsal member 40 can be expanded and contracted in the left-right direction to fit the wearer's waist circumference.

In the ventral member 30, the skin side sheet 31, the thread rubber 35, and the non-skin side sheet 32 are stacked in order from the skin side in the thickness direction, and are joined to each other by an adhesive such as hot melt. Similarly, in the dorsal member 40, the skin side sheet 41, the thread rubber 45, and the non-skin side sheet 42 are stacked in order from the skin side in the thickness direction, and are joined to each other by an adhesive such as hot melt. ..

The

skin side sheets

31, 41 and the

non-skin side sheets

32, 42 are sheets made of non-woven fabric, respectively, and specifically, spunbonded non-woven fabric. However, the present invention is not limited to this, and a non-woven fabric such as SMS (spun bond / melt blown / spun bond) non-woven fabric may be used. Further, in the present embodiment, a single fiber of polypropylene (PP), which is a thermoplastic resin, is used as a constituent fiber of the non-woven fabric, but the present invention is not limited to this. For example, a single fiber of another thermoplastic resin such as polyethylene (PE) may be used, or a composite fiber having a sheath core structure such as PE and PP may be used. Further, all of the skin-

side sheets

31, 41 and the non-skin-

side sheets

32, 42 do not have to be non-woven fabrics, and only one of the skin-

side sheets

31, 41 or the non-skin-

side sheets

32, 42 is other than the non-woven fabric. Other soft sheet materials may be used.

The absorbent main body 10 includes a top sheet 13, an absorber 11, and a back sheet 15, each of which is adhered with an adhesive such as hot melt. The top sheet 13 may be a liquid permeable sheet, and examples thereof include hydrophilic air-through non-woven fabrics and spunbonded non-woven fabrics. The back sheet 15 may be a liquid-impermeable sheet, and examples thereof include a polyethylene film, a polypropylene film, and a hydrophobic SMS non-woven fabric. The top sheet 13 and the back sheet 15 have a size that covers the entire absorber 11.

The absorbent body 10 has leg gathers LG provided at the ends in the left-right direction and expands and contracts in the longitudinal direction, and three-dimensional gathers provided on the skin side of the absorber 11 as a leak-proof wall portion for preventing lateral leakage. Has LSG. The leg gather LG and the three-dimensional gather LSG each include an elastic member 17 and an elastic member 18 that extend in the longitudinal direction (vertical direction).

The absorber 11 has a substantially rectangular shape in a plan view and includes an absorbent core 11c that absorbs a liquid. The absorbent core 11c is formed by wrapping a polymer absorbent (absorbent A) and a highly absorbent polymer (so-called SAP) with a tissue or the like to form a substantially hourglass shape. As the polymer absorbent (absorbent A) and the highly absorbent polymer (SAP), for example, granular ones can be used, and a sieve is used so that the particles each have a particle size within a predetermined range. Is preferable. In the following description, the particulate polymer absorbent (absorbent A) will be described, but the present invention is not limited to this. The polymer absorbent (absorbent A) used for an absorbent article such as diaper 1 can be appropriately used depending on the state of use, such as particulate, fine particle, block, sheet, and thread.

=== About polymer absorbents ===
The polymer absorbent is a hydrolyzate of a (meth) acrylic acid ester and a crosslinked polymer of a compound having two or more vinyl groups in one molecule, and is a polymer compound having at least -COONa group. The (meth) acrylic acid ester means an acrylic acid ester or a methacrylic acid ester. The polymer absorbent is a monolithic organic porous body having at least one -COONa group in one molecule. In addition, it may have a —COOH group. -COONa groups are distributed substantially uniformly in the skeleton of the porous body. "Monolith-like" refers to a porous body having penetrating pores and a skeleton and having a network-like co-continuous structure.

The polymer absorbent, which is a hydrolyzate of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene, has a continuous skeleton formed by an organic polymer having at least a -COONa group, and absorbs the liquid to be absorbed between the skeletons. It has a communication hole (continuous hole) that serves as a field. Further, since the hydrolysis treatment uses the -COOR group (carboxylic acid ester group) of the crosslinked polymer as the -COONa group or the -COOH group (FIG. 3), the polymer absorbent has a -COOR group. May be. The presence of -COOH group and -COONa group in the organic polymer forming a continuous skeleton can be confirmed by analysis by infrared spectrophotometric method or a method of quantifying weakly acidic ion exchange groups.

FIG. 3 is a diagram illustrating the manufacturing process of the absorbent A. In FIG. 3, the upper figure shows the constituent raw materials of the polymerization, the middle figure shows the monolith A as a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene, and the lower figure shows the monolith A in the middle figure. The absorbent A which has been decomposed and dried is shown.

Hereinafter, a hydrolyzate of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene (hereinafter, also referred to as “absorbent A”) as an example of a polymer absorbent will be described. The polymer absorbent is not limited to the absorbent A, and may be a hydrolyzate of a (meth) acrylic acid ester and a crosslinked polymer of a compound containing two or more vinyl groups in one molecule. Hereinafter, "monolith A" is an organic porous body composed of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene before being hydrolyzed, and is also referred to as "monolith-like organic porous body". .. "Absorbent A" is a hydrolyzate of a crosslinked polymer (monolith A) of (meth) acrylic acid ester and divinylbenzene after being hydrolyzed and dried. In the following description, the absorbent A refers to a dry state.

The structure of the absorbent A will be described. Absorbent A has a continuous skeleton and continuous pores. As shown in FIG. 3, the absorbent A, which is an organic polymer forming a continuous skeleton, is obtained by cross-linking polymerization using a (meth) acrylic acid ester which is a polymerization monomer and divinylbenzene which is a cross-linking monomer. It is obtained by hydrolyzing the crosslinked polymer (monomer A). The organic polymer forming a continuous skeleton has ethylene group polymerization residues (hereinafter, also referred to as “constituent unit X”) and crosslinked polymerization residues of divinylbenzene (hereinafter, also referred to as “constituent unit Y”) as constituent units. .) And. The polymerization residue (constituent unit X) of the ethylene group in the organic polymer forming the continuous skeleton has a -COONa group or -COOH group and -COONa group formed by hydrolysis of the carboxylic acid ester group. Since the polymerization monomer is a (meth) acrylic acid ester, the polymerization residue (constituent unit X) of the ethylene group has a —COONa group, a —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 cross-linking monomer will be described later.

In the absorbent A, the ratio of the crosslinked polymerization residue (constituent unit Y) of divinylbenzene in the organic polymer forming the continuous skeleton is 0.1 to 30 mol%, preferably 0.1 to 30 mol% with respect to all the structural units. It is 20 mol%. In the absorbent a using butyl methacrylate as the polymerization monomer and divinylbenzene as the cross-linking monomer, the ratio of the cross-linked polymerization residue (constituent unit Y) of divinylbenzene to the organic polymer forming the continuous skeleton is the total structural unit. On the other hand, it is about 3%, preferably 0.1 to 10 mol%, and more preferably 0.3 to 8 mol%. If the ratio of the crosslinked polymerized residue 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 amount of the liquid to be absorbed is absorbed. descend.

In the absorbent A, the ratio of the structural unit Y to the total number of moles of the structural unit X and the structural unit Y in the organic polymer forming the continuous skeleton is preferably 0.1 to 30 mol%, particularly preferably 0.5 to. It is 20 mol%. In the absorbent a using butyl methacrylate as a polymerized monomer and divinylbenzene as a crosslinked monomer, the ratio of the structural unit Y to the total number of moles of the structural unit X and the structural unit Y in the organic polymer forming the continuous skeleton is preferable. Is 0.1 to 10 mol%, particularly preferably 0.3 to 8 mol%. If the ratio of the structural unit Y to the total number of moles of the structural unit X and the structural 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, it is absorbed. The amount of the target liquid absorbed decreases.

In the absorbent A, the organic polymer forming the continuous skeleton may consist only of the structural unit X and the structural unit Y, or in addition to the structural unit X and the structural unit Y, the structural unit X and the constitution. It may have a structural unit other than the unit Y, that is, a polymer residue of a monomer other than (meth) acrylic acid ester and divinylbenzene. The structural units other than the structural unit X and the structural unit Y include styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth) acrylate, isobutene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, and the like. Polymerization residues of monomers such as vinylidene chloride, tetrafluoroethylene, (meth) acrylonitrile, vinyl acetate, ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, and trimethylpropantri (meth) acrylate can be mentioned. .. Further, the ratio of the structural units other than the structural unit X and the structural unit Y in the organic polymer forming the continuous skeleton is 0 to 50 mol%, preferably 0 to 30 mol% with respect to all the structural units. In the absorbent a using butyl methacrylate as the polymerization monomer and divinylbenzene as the cross-linking monomer, the ratio of the structural units other than the structural unit X and the structural unit Y in the organic polymer forming the continuous skeleton is relative to the total structural units. , 0 to 50 mol%, preferably 0 to 30 mol%.

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 space (vacancy) for taking in the porous water is likely to be crushed during absorption, and the absorption amount may decrease. On the other hand, if the thickness of the continuous skeleton is thicker than 100 μm, the absorption of the liquid may be delayed. Since the pore structure of the continuous skeleton of the absorbent A is an open cell structure, the thickness of the continuous skeleton is measured by using the skeleton cross section appearing on the test piece for electron microscope measurement as the evaluation point of the thickness. The skeleton is often polygonal because it is formed at intervals between water (water droplets) that are removed by dehydration / drying treatment after hydrolysis, which will be described later. Therefore, the thickness of the skeleton is the average value of the diameters of the circles circumscribing the polygonal cross section. In rare cases, there may be a small hole in the polygon, in which case the circumscribed circle of the cross section of the polygon surrounding the small hole is measured.

Absorbent A also has an average diameter of continuous pores of 1 to 1000 μm. If the average diameter of the continuous pores of the absorbent A is less than 1 μm, the space (vacancy) for taking in the porous water is likely to be crushed during absorption, and the absorption rate may decrease. On the other hand, if the average diameter of the continuous pores is thicker than 1000 μm, the absorption rate of the liquid may decrease. The average diameter of the continuous pores of the absorbent A can be measured by the mercury intrusion method, and is the maximum value of the pore distribution curve obtained by the mercury intrusion method. As a sample for measuring the average diameter of continuous pores, a sample dried at 50 ° C. for 18 hours or more by a vacuum dryer is used regardless of the ionic form of the absorbent A. The final ultimate pressure is 0TORR.

The absorbent A has a structure in which bubble-like macropores overlap each other (see FIGS. 4 to 8), and the overlapping portions have an average diameter of 1 to 1000 μm, preferably 10 to 200 μm, and particularly preferably 20 to 100 μm. It has an open cell structure that is an open cell structure (continuous macropore structure) that serves as a common opening (mesopore). Most of them have an open pore structure. The overlap of macropores is 1 to 12 for one macropore, and 3 to 10 for most macropores.

FIG. 4 is an SEM photograph of the absorbent a at a magnification of 50 times. FIG. 5 is an SEM photograph of the absorbent a at a magnification of 100 times. FIG. 6 is an SEM photograph of the absorbent a at a magnification of 500 times. FIG. 7 is an SEM photograph of the absorbent a at a magnification of 1000 times. FIG. 8 is an SEM photograph of the absorbent a at a magnification of 1500 times. The absorbent a is an example of the absorbent A in which butyl methacrylate is used as a polymerization monomer and divinylbenzene is used as a cross-linked monomer, and the absorbents a in FIGS. 4 to 8 are cubes of 2 mm square, respectively.

4 to 8 show scanning electron microscope (SEM) photographs of a morphological example of the absorbent a, which is a specific example of the absorbent A. The absorbent a shown in FIGS. 4 to 8 has a large number of bubbles. It has a shaped macropore, and the bubble-shaped macropores overlap each other, and this overlapping portion serves as a common opening (mesopore) to form an open cell structure. Most of them have an open pore structure. If the average diameter of the mesopore in the dry state is less than the above range, the absorption rate of the liquid to be absorbed becomes too slow, and if it exceeds the above range, the absorbent a (absorbent A) becomes brittle. When the absorbent A has such an open cell structure, a macropore group and a mesopore group can be uniformly formed, and compared with a particle-aggregated porous body as described in Japanese Patent Application Laid-Open No. 8-252579. , The pore volume and specific surface area can be significantly increased.

The total pore volume of the pores (vacancy) of the absorbent A is preferably 1 to 50 ml / g, preferably 2 to 30 ml / g. When the total pore volume of the absorbent A is less than 0.5 ml / g, the space (vacancy) for taking in the porous water is easily crushed at the time of absorption, and the absorption amount and the absorption rate are lowered. There is a fear. On the other hand, if it exceeds 50 ml / g, the strength of the absorbent A decreases. The total pore volume can be measured by the mercury press-fitting method. As the sample for measuring the total pore volume, the absorbent A which has been dried in a vacuum dryer at a temperature of 50 ° C. for 18 hours or more is used regardless of the ionic form of the absorbent A. The final ultimate pressure is 0TORR.

Hereinafter, the state of contact between the absorbent A and a liquid such as a body fluid (hereinafter, also referred to as “body fluid”) will be described, but the same applies to the case where the absorber 11 including the absorbent A and the body fluid come into contact with each other. is there. Further, since the weight of the absorbed body fluid is substantially proportional to the amount of body fluid, the weight of the body fluid is also referred to as "the amount of body fluid" below.

First, when the body fluid comes into contact with the absorbent A, it is absorbed into the pores (pores) of the absorbent A by the capillary phenomenon. As shown in FIGS. 4 to 8, the continuous pores included in the absorbent A are pores in which a plurality of pores (vacancy) communicate with each other, and many pores are provided from the appearance. You can see that. Due to the capillary phenomenon, a certain amount of body fluid enters the large number of pores, and the absorbent A absorbs the body fluid. A part of the fixed amount of body fluid absorbed by the absorbent A is absorbed by the continuous skeleton by osmotic pressure, and the continuous skeleton is elongated. Of the fixed amount of body fluid absorbed by the absorbent A, the body fluid not absorbed by the continuous skeleton is absorbed in a state of being retained in the pores.

Absorbent A has the property of extending the continuous skeleton when it absorbs a liquid. The extension of this continuous skeleton extends in almost all directions. As the outer shape of the absorbent A increases due to the extension of the continuous skeleton, the size of each pore also increases. As the size of the hole increases, the volume inside the hole increases, and the amount of body fluid that can be retained in the hole increases. That is, the absorbent A, which has grown by absorbing a certain amount of body fluid, can further absorb a predetermined amount of body fluid by the capillary phenomenon. Further, since the body fluid is absorbed by the capillary phenomenon, the absorbent A can quickly absorb the body fluid. Regarding the body fluid absorbed by the absorbent A, there are more body fluids retained in the pores than those absorbed by the continuous skeleton.

As described above, since most of the absorption of the body fluid of the absorbent A is performed by retaining the body fluid in the pores by the capillary phenomenon, the porosity (porosity) which is the ratio of the volume of the pores (total pore volume) The larger the volume of the voids in the pores relative to the volume of the absorbent A), the more body fluid can be absorbed. The porosity is preferably 85% or more.

The porosity of the absorbent a is determined. The specific surface area of the absorbent a obtained by the mercury injection method is 400 m ² / g, and the pore volume is 15.5 ml / g. The pore volume of 15.5 ml is the volume of the pores in 1 g of the absorbent A. Assuming that the specific gravity of the absorbent A is 1 g / ml, the volume occupied in 1 g of the absorbent A is 15.5 ml for the pore volume and 1 ml for the absorbent A, respectively. The total volume (volume) of 1 g of the absorbent A is 15.5 + 1 [ml], and the ratio of the pore volume is the porosity. As a result, the porosity is 15.5 / (15.5 + 1) × 100≈94%.

This absorbent A (absorbent a) has little change in the amount absorbed depending on the composition of the body fluid. The weight by which the absorbent A per unit weight absorbs the NaCl aqueous solution having a concentration of 0.9 wt% (first absorption weight) is the weight at which the NaCl aqueous solution having a concentration of 0 to 2.0 wt% is absorbed (second absorption weight). It is preferably 0.5 to 1.9 times that of. The NaCl aqueous solution having a concentration of 0.9 wt% is a saline solution having a concentration similar to that of a so-called physiological saline solution, which is said to have a composition close to that of a body fluid. The absorber 11 provided with the absorbent A having a first absorption weight of 0.5 to 1.9 times the second absorption weight is less likely to be affected by the concentration of electrolyte ions in the body fluid in terms of the amount of body fluid absorbed. The absorber 11 can more reliably absorb the body fluid.

The composition of body fluids, which are liquids discharged from living organisms such as sweat, urine, stool, menstrual blood, cages, breast milk, blood, and exudate, changes not only depending on the type of body fluid, but also on individual differences and health conditions. To do. For example, the concentration of electrolytes in the urine component of living organisms is different between humans and animals in terms of the concentration of ions such as Na ⁺ , K ⁺ , and Ca ²⁺ , and also in their health condition. Highly absorbent polymers (so-called SAP), which are widely used in absorbent articles, absorb body fluids by the principle of osmotic pressure, so that as the number of electrolyte ions increases (as the electrolyte concentration increases), the body fluids are absorbed. There was a risk that the weight that could be produced would decrease. On the other hand, the absorbent A (absorbent a) depends on the composition of the body fluid, particularly the electrolyte concentration, because the amount absorbed by the body fluid taken into the pores by the capillary phenomenon is larger than the amount absorbed by the body fluid based on the principle of osmotic pressure. The amount of absorption is unlikely to decrease.

FIG. 9 is a diagram showing each measurement result of the absorbent a. “Water absorption weight” and “water absorption rate” in FIG. 9 are synonymous with “absorption weight” and “absorption rate”. As shown in FIG. 9, the absorbent a having a particle size of 500 to 850 μm and the absorbent a having a particle size of 250 μm or less are measured a plurality of times. In addition, as a comparative example, the results of SAP (Aquakeep SA60S manufactured by Sumitomo Seika Chemical Co., Ltd.), which is a highly absorbent polymer, are also shown.

The absorption weight for absorbing the NaCl aqueous solution of each concentration can be measured by the following method.
First, a container containing 1000 ml of each is prepared for each concentration of NaCl aqueous solution.
Next, two nylon nets (255 mesh nylon net NBC Meshtec Inc. N-No. 255HD) cut to 200 mm x 200 mm are overlapped, and 1.0 g of absorbent A is sandwiched between the nylon nets. In this state, heat seal on all sides to make a bag containing the sample.
Subsequently, the bag containing the sample is immersed so as to touch the bottom surface of the container containing the NaCl aqueous solution of each concentration, and the upper side of the bag is fixed to the edge of the container with washing scissors and left for 1 hour.
Then, the bag is pulled up from the aqueous NaCl solution, and draining is performed for 15 minutes with the portion 5 mm from the upper end of the bag and 50 mm from both ends sandwiched between washing scissors.
Finally, the weight of the bag containing the absorbent A is measured, and the weight of the bag alone and 1.0 g (the weight of the absorbent A before absorbing the NaCl aqueous solution) are reduced from the measurement result to obtain the absorbent. The weight of the aqueous NaCl solution absorbed by A can be obtained.

As shown in FIG. 9, the weight (first) of an aqueous NaCl solution having a concentration of 0.9 wt% absorbed by 1.0 g of the absorbent a (first polymer absorbent, hereinafter also referred to as “first absorbent”). Absorption weight) is 37.71 to 62.09 g, and the concentration of 1.0 g of the absorbent a (second polymer absorbent, hereinafter also referred to as “second absorbent”) is 0 to 2. The weight of the 0 wt% NaCl aqueous solution (second absorption weight) is 34.40 to 68.61 g. From this measurement result, the lower limit of the ratio of the first absorbed weight to the second absorbed weight is (minimum value of the first absorbed weight / maximum value of the second absorbed weight), and the upper limit is (first absorbed weight). Maximum value / minimum value of the second absorbed weight). Therefore, the ratio of the first absorbed weight to the second absorbed weight is (37.71 / 68.61) to (62.09 / 34.40) ≈0.55 to 1.80, and the first absorbed weight is It is 0.55 to 1.80 times the second absorbed weight. The numerical value is calculated by using two significant figures after the decimal point.

Similarly, with respect to SAP, the weight of the NaCl aqueous solution having a concentration of 0.9 wt% absorbed by 1.0 g of SAP (first SAP) (first SAP absorbed weight) is 60.08 to 63.69 g, which is 1.0 g. The weight of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% absorbed by the SAP (second SAP) (second SAP absorption weight) is 45.74 to 311.12 g. The ratio of the first SAP absorption weight to the second SAP absorption weight is (minimum value of the first SAP absorption amount / maximum value of the second SAP absorption weight) to (maximum value of the first SAP absorption weight / minimum value of the second SAP absorption weight) = ( 60.08 / 311.12) to (63.69 / 45.74) ≈ 0.19 to 1.39. In SAP, the higher the concentration of the NaCl aqueous solution, the lower the absorption amount of the NaCl aqueous solution.

From this result, it can be seen that the absorbent A (absorbent a) enables absorption equal to or greater than that of SAP, and the absorption amount of the NaCl aqueous solution of the absorbent A does not change much depending on the concentration. Therefore, the absorber 11 using the absorbent A secures the same amount of body fluid as SAP, and reduces the possibility that the absorption capacity is lowered due to the concentration of electrolyte ions like SAP. Can be done.

Further, in the absorbent A, the change in the amount of the aqueous solution (water retention amount) held in the absorbent A is unlikely to change depending on the electrolyte ion concentration. Since the change in the amount of water retained in the aqueous solution due to the electrolyte ion concentration is small, it is possible to reduce the possibility that the amount of body fluid retained in the absorbent A will change depending on the composition of the body fluid.

The first absorbent (first polymer absorbent) that absorbed the first absorption amount of the NaCl aqueous solution having a concentration of 0.9 wt% and the concentration of 0 to 2.0 wt% by the same method as the above-mentioned measurement of the weight of the NaCl aqueous solution. A second absorbent (second polymer absorbent) that has absorbed the NaCl aqueous solution by the second absorption amount is prepared. The first absorbent and the second absorbent are dehydrated for 90 seconds at 150 G and 850 rpm using a centrifuge for each predetermined time. Then, when the weight of the NaCl aqueous solution absorbed by the first absorbent and the second absorbent is measured, the weight of the NaCl aqueous solution having a concentration of 0.9 wt% absorbed by the first absorbent (first water retention weight) is determined. , It is preferable that the weight is 0.5 to 1.6 times the weight of the NaCl aqueous solution (second water retention weight) having a concentration of 0 to 2.0 wt% absorbed by the second absorbent. The absorbent A, which has a first water retention weight of 0.5 to 1.6 times the second water retention weight, easily moves the body fluid once absorbed to the outside of the absorbent A and allows the body fluid to be absorbed by another substance. Become.

As shown in FIG. 9, the weight (first water retention weight) of the NaCl aqueous solution having a concentration of 0.9 wt% in a state where 1.0 g of the absorbent a retains water is 13.59 to 17.12 g, which is 1.0 g. The weight (second water retention weight) of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% in the state where the absorbent a is retained is 11.46 to 19.47 g. From this result, it can be seen that the difference in weight of the NaCl aqueous solution retained by the absorbent a due to the difference in the concentration of the NaCl aqueous solution is small.

For the absorbent a, the lower limit of the ratio of the first water retention weight to the second water retention weight is (minimum value of the first water retention weight / maximum value of the second water retention weight), and the upper limit is (first water retention weight). Maximum value / minimum value of the second water retention weight). Therefore, the ratio of the first water retention weight to the second water retention weight is (13.59 / 19.47) to (17.12 / 11.46) ≈0.70 to 1.49 times. The numerical value is calculated by using two significant figures after the decimal point.

Further, it can be seen that the water retention weight of the NaCl aqueous solution at each concentration is smaller for the absorbent a than for SAP as a whole. Regarding SAP, the weight of an aqueous NaCl solution having a concentration of 0.9 wt% (first SAP water retention weight) in a state where 1.0 g of SAP (first SAP) retains water is 39.98 to 40.41 g, which is 1.0 g. The weight (second SAP water retention weight) of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% in the state where the SAP (second SAP) retains water is 29.31 to 286.11 g. Therefore, the lower limit of the ratio of the first SAP water retention to the second SAP water retention is (minimum value of the first SAP water retention / maximum value of the second SAP water retention), and the upper limit is (maximum value of the first SAP water retention). / The minimum value of the second SAP water retention amount). Therefore, the ratio of the first SAP water retention amount to the second SAP water retention amount is (39.98 / 286.11) to (40.41 / 9.31) ≈0.14 to 1.38 times.

The difference between the above-mentioned absorption weight and water retention weight is the weight of the liquid (hereinafter, also referred to as "water separation weight") that releases (separates) the liquid once absorbed by the absorbent A or SAP to the outside. Further, the value obtained by dividing the water separation weight by the absorption weight is the ratio of the water separation weight to the amount of the liquid once absorbed, and is also referred to as the water separation ratio. For the absorbent A, the value obtained by dividing the difference between the first absorption weight and the first water retention weight by the first absorption weight of the first absorbent is preferably 50 to 80%. Similarly, for the second absorbent, the value obtained by dividing the difference between the second absorption weight and the second water retention weight by the second absorption weight is preferably 40 to 85%. The absorbent A, which has the above-mentioned numerical water separation rate, easily moves the body fluid once absorbed to another substance. That is, it is easy to repeatedly absorb and separate water. By moving the body fluid once absorbed to the outside of the absorbent A, it becomes easy to reduce the wet feeling given to the wearer by the absorber 11 provided with the absorbent A.

For the absorbent a, the lower limit of the first water separation rate, which is the value obtained by dividing the water separation weight of the NaCl aqueous solution having a concentration of 0.9 wt% by the first absorbent by the first absorption weight, is {(the minimum value of the first absorption weight). -Maximum value of first water retention weight) / Minimum value of first absorption weight} x 100, and the upper limit of the first water separation rate is {(Maximum value of first absorption weight-Minimum value of first water retention weight) / Maximum value of first absorbed weight} × 100. The lower limit of the second water separation rate, which is the value obtained by dividing the water separation weight of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% by the second absorbent by the second absorption weight, is {(minimum value of the second absorption weight-second). Maximum value of water retention weight) / minimum value of second absorption weight} × 100, and the upper limit of the second water separation rate is {(minimum value of second absorption weight-maximum value of second water retention weight) / second Minimum value of absorbed weight} × 100. As shown in FIG. 9, the first water separation rate of the absorbent a is {(37.71-17.12) /37.71} × 100 to {(62.09-13.59) /62.09}. × 100 ≈ 54.60 to 78.11. The second water separation rate of the absorbent a is {(34.40-19.47) /34.40} × 100 to {(68.61-11.46) /68.61} × 100≈43.40 to It becomes 83.30. The numerical value is calculated by using two significant figures after the decimal point.

As shown in FIG. 9, when the water retention weights of the absorbent a and the SAP are compared, it is difficult to make a simple comparison because the values of the absorption weights are different from each other, but the water retention weight of the absorbent a is larger than the water retention weight of the SAP. There are fewer overall. That is, the absorbent a has a lower water retention than SAP.

Further, it is preferable that 2.0 g of the absorbent A absorbs 50 g of a 0.9 wt% NaCl aqueous solution by the vortex method for 1.0 to 10.0 seconds. Since the absorbent A capable of absorbing the aqueous NaCl solution within this time can absorb the liquid in a short time, the absorber 11 provided with the absorbent A can quickly absorb the body fluid.

The absorption time is measured by the vortex method as follows.
A rotor having a size of 30 × 8 mm is placed in a container, and a 50 g concentration of 0.9 wt% NaCl aqueous solution adjusted to a liquid temperature of 25 ° C ± 1 ° C is placed therein.
Adjust the rotor to a rotation speed of 600 ± 30 rpm with a magnetic stirrer (MITAMURA RIKEN KOGYO INC. MAGMIX STIRRER (AC100W)) and stir the aqueous NaCl solution.
2.00 g of the absorbent A is charged into the stirring container, and the time measurement is started at the same time as the charging.
Then, the time when the surface of the solution in the solution becomes flat is measured. The flattening of the solution surface is determined by observing the disappearance of the light reflected on the liquid surface of the vortex, assuming that the slope of the violently rotating liquid vortex approaches a flat surface.

As shown in FIG. 9, the time for 2.0 g of the absorbent a to absorb 50 g of a 0.9 wt% NaCl aqueous solution is 1.69 to 1.93 seconds. With respect to 2.0 g of the absorbent a, the time for absorbing the aqueous solution of NaCl having a lower concentration of 0.3 wt% is 1.56 to 2.01 seconds, and the concentration of 2.0 wt% is higher. Since the time for absorbing the NaCl aqueous solution is 1.36 to 2.29 seconds, the time for 2.0 g of the absorbent a to absorb 50 g of the NaCl aqueous solution having a concentration of 0 to 2.0 wt% is 1.34. It is ~ 2.29 seconds, and it can be seen that the change in absorption time depending on the concentration of the NaCl aqueous solution is small.

As described above, since the absorbent A has a high water separation rate and a high absorption rate, the absorber 11 of the absorbent article such as the diaper 1 has a higher water retention ratio than the absorbent A together with the absorbent A. It is more preferable to include a polymer compound. Examples of the polymer compound having a higher water retention ratio than the absorbent A include so-called SAP such as sodium polyacrylate. Since SAP has high water retention and low water release, it can continue to retain the body fluid once absorbed. However, the absorption rate is slow (see FIG. 9), and it takes time to absorb the body fluid. In this respect, since the absorber 11 is provided with the absorbent A and SAP, when the body fluid comes into contact with the absorber 11, the absorbent A having a high absorption rate first absorbs the body fluid. Then, the absorbent A having a high water separation rate releases the body fluid into the absorber 11. The body fluid is retained in the SAP as the SAP absorbs the released body fluid over time. As a result, the absorber 11 moves the body fluid once absorbed by the absorbent A to the SAP so that the amount of the body fluid retained in the absorbent A is small, so that the body fluid remains on the surface of the absorber 11. It reduces the risk of getting wet and reduces the feeling of wetness that the wearer feels. Further, as the absorber 11, the excrement is easily kept in the internal SAP, so that the possibility of the excrement leaking from the absorbent article such as the diaper 1 can be reduced.

Further, absorption of the 0.9 wt% NaCl aqueous solution by the absorbent A after 1 minute has passed in a state where the lower end of 1.0 g of the absorbent A is in contact with the water surface of the 0.9 wt% NaCl aqueous solution. The amount is preferably 15 ml or more. The state in which the lower end portion of the absorbent A is in contact with the water surface of the NaCl aqueous solution is a state in which the absorbent A absorbs the NaCl aqueous solution in the direction against gravity. Even in the direction against gravity, the absorbent A, which can absorb 15 ml or more of a 0.9 wt% NaCl aqueous solution in a time of 1 minute, enables quick absorption of a larger amount of the NaCl aqueous solution. The absorber 11 including the agent A can absorb the body fluid from various angles.

As shown in FIG. 9, the amount of the aqueous NaCl solution having a concentration of 0.9 wt% absorbed by the absorbent a after 1 minute is 20.2 to 26.5 ml. In this way, the absorbent a can be well absorbed in the direction against gravity. For SAP, the amount of the 0.9 wt% NaCl aqueous solution absorbed after 1 minute is 14.0 to 18.0 ml. From this result, it can be seen that the absorbent A can absorb the body fluid more quickly than the SAP even in the direction against gravity.

Further, the concentration absorbed by the absorbent A after 2 minutes has passed in a state where the lower end of 2.0 g of the absorbent A under a load of 600 gw is in contact with the water surface of the NaCl aqueous solution having a concentration of 0.9 wt%. More preferably, the 0.9 wt% NaCl aqueous solution is 1.0 ml or more, and the 0.9 wt% NaCl aqueous solution absorbed by the absorbent A after 15 minutes is 5.0 ml or more. When the absorbent A is used for the absorber 11, the absorber 11 once absorbed the excrement may be crushed in the thickness direction depending on the weight of the wearer, or crushed in the left-right direction by both legs of the wearer. To do. In this respect, even when a predetermined load is applied to the absorbent A, the absorbent A can absorb the NaCl aqueous solution, and can also absorb the NaCl aqueous solution in the direction against gravity. By providing the absorber A, the body 11 can absorb the body fluid from various angles even when a load is applied to the absorber 11 (absorbent A).

As shown in FIG. 9, with respect to the absorbent a, the amount of the 0.9 wt% NaCl aqueous solution absorbed by 2.0 g of the absorbent A after 2 minutes was 2.6 to 5.6 ml, and 15 minutes had passed. The concentration of 0.9 wt% NaCl aqueous solution that was later absorbed by the absorbent A is 13.2 to 25.2 ml. Regarding SAP, the concentration of 0.9 wt% NaCl aqueous solution absorbed by 2.0 g of SAP after 2 minutes was 0.8 to 1.0 ml, and the concentration of 0.9 wt% absorbed by the absorbent A after 15 minutes. % NaCl aqueous solution is 4.0 ml. From this result, it can be seen that the absorbent A has better absorbency than SAP even in the state of being pressurized and in the direction against gravity.

Further, it is preferable that the absorbent A per unit weight absorbs the CaCl ₂ aqueous solution having a concentration of 0.5 wt% at least 13 times the weight of the absorbent A. Even in an aqueous solution of Ca2 + having more electrolyte ions than Na +, a solution 13 times or more the weight of the absorbent A can be absorbed. Therefore, the absorber 11 provided with the absorbent A has a body fluid composition. Regardless, it is possible to easily absorb body fluids.

FIG. 9 shows the weight at which 1 g of the absorbent a absorbed the CaCl ₂ aqueous solution having a concentration of 0.5 wt%. The absorption weight of the CaCl ₂ aqueous solution is measured by the same method as the measurement of the weight of the NaCl aqueous solution. As shown in FIG. 9, the measurement result of the absorption weight for absorbing the CaCl ₂ aqueous solution having a concentration of 0.5 wt% of the absorbent a is 16.29 to 27.69 g, and 1 g of the absorbent a has a concentration of 0.5 wt%. % CaCl ₂ aqueous solution absorbs 16.29 times or more the weight of the absorbent a.

As shown in FIG. 9, the absorption weight of a CaCl ₂ aqueous solution having a concentration of 0.5 wt% with 1 g of SAP is 6.71 to 7.43 g. Comparing the weight of 1 g of the absorbent a absorbing the 0.5 wt% CaCl ₂ aqueous solution with the weight of 1 g of SAP absorbing the 0.5 wt% CaCl ₂ aqueous solution, the absorbent a clearly absorbs. The weight is heavier. Further, the weight of 1 g of SAP absorbed by the CaCl ₂ aqueous solution having a concentration of 0.5 wt% is less than the weight of 1 g of SAP absorbed by the NaCl aqueous solution having a concentration of 0.9 wt%. That is, the absorption amount of SAP decreases as the number of electrolyte ions increases, whereas the absorption amount of the absorbent a decreases due to the number of electrolyte ions, unlike SAP. Therefore, by using the absorbent a (absorbent A), it is possible to reduce the risk that the amount of absorption will decrease depending on the composition of the body fluid.

The following absorption rate test and absorption amount test were performed on the absorbent A. FIG. 10 is a graph showing the absorption rate and the absorption amount test result of the absorbent A. FIG. 11 is a graph showing the absorption rate and absorption amount test results of the highly absorbent polymer of the comparative example.

As shown in FIG. 10, in the absorption rate test, the liquid to be absorbed was tested with pure water and a 0.9% sodium chloride aqueous solution, and the immersion time was 5 to reach the absorption amount of 90% of the saturated absorption amount in both cases. It was within seconds. Further, the absorption amount test of the absorbent A was carried out using 0.9% sodium chloride aqueous solution, 4% NaOH aqueous solution, 35% hydrochloric acid and 29% ammonia water as test water. As a result, the absorption amount of 0.9% sodium chloride aqueous solution was 67 g / g-resin, the absorption amount of 4% NaOH aqueous solution was 78 g / g-resin, the absorption amount of 35% hydrochloric acid was 28 g / g-resin, and 29% ammonia. The amount of water absorbed was 105 g / g-resin.

(Absorption rate test method)
A sample tube is a tube having a length of 100 mm and an inner diameter of 10 mm in which one end is sealed with a non-woven fabric and a dry absorbent A is put therein. The weight of the tube before and after putting the absorbent A is measured, and the weight of the absorbent A in the tube is calculated in advance. Next, the tube is pulled up from the solution after a predetermined time has elapsed with the non-woven fabric side of the sample tube immersed in the solution to be absorbed having a known concentration. Then, after holding for 1 minute, the weight of the tube is measured. This immersion and measurement are repeated until there is no weight change. The amount of absorption when the weight change disappears is defined as the saturated absorption amount.

(Absorption test method)
Perform according to the JIS method. A tea bag containing the absorbent A is used as a sample, and the absorption amount of the absorption target liquid is determined from the weights before and after the absorption before and after the sample is immersed in the absorption target liquid for 24 hours.

(Comparison example)
Super-absorbent polymer manufactured by Wako Pure Chemical Industries, Ltd. Trade name: Absorption rate test and absorption amount test are performed using a highly absorbent polymer (acrylic acid salt type). As shown in FIG. 11, as a result of the absorption amount test, in the absorption rate test, the immersion time required to reach 90% of the saturated absorption amount in pure water is 12 minutes, which is 0.9. In the% sodium chloride aqueous solution, the immersion time required to reach 90% of the saturated absorption amount is 3.5 minutes. The absorption amount of the 0.9% sodium chloride aqueous solution was 52 g / g-resin, the absorption amount of the 4% NaOH aqueous solution was unmeasurable because it was dissolved during immersion, and the absorption amount of 35% hydrochloric acid was 2 g. It was / g-resin, and the absorption amount of 29% aqueous ammonia was 128 g / g-resin.

The absorbent A can also be used as a monolith ion exchanger, and the absorbent A is also referred to as a "monolith-like organic porous ion exchanger". The total ion exchange capacity of the -COONa group and the -COOH group per unit weight of the absorbent A is 5 mg equivalent / g or more, preferably 6 mg equivalent / g or more. If the total ion exchange capacity of the -COOH group and the -COONa group in the dry state of the monolith ion exchanger is less than the above range, the absorption amount of the liquid to be absorbed decreases and the absorption rate also slows down. The upper limit of the total ion exchange capacity of the -COOH group and the -COONa group in the dry state of the monolith ion exchanger is not particularly limited, but is, for example, 14.0 mg equivalent / g or less, or 13.0 mg equivalent /. g or less can be mentioned. The total ion exchange capacity of -COONa group and -COOH group per unit weight of the absorbent a using butyl methacrylate as a polymerization monomer and divinylbenzene as a cross-linking monomer is 4.0 mg equivalent / g or more, preferably 6 mg equivalent / g. It is g or more. The upper limit of the total ion exchange capacity of the -COOH group and the -COONa group in the dry state of the monolith ion exchanger of the absorbent a is not particularly limited, but is, for example, 11 mg equivalent / g or less, or 14 mg equivalent /. g or less can be mentioned. It is desirable that the total ion exchange capacity of the −COONa group per unit weight of the absorbent A is 4.0 mg equivalent / g or more. By using an absorbent A having a total ion exchange capacity of −COONa groups of 4.0 mg equivalent / g or more per unit weight, the total ion exchange capacity of −COONa groups per unit weight is 4.0 mg equivalent / g. Since the polymer absorber absorbs the body fluid more easily than when the amount is less, the continuous skeleton is more likely to be elongated, and the continuous skeleton is more likely to expand as the continuous skeleton is elongated. By facilitating uptake, it becomes easier to absorb body fluid as an absorber.

In the present invention, the total ion exchange capacity of -COOH group and -COONa group is defined as-when the monolith ion exchanger of the present invention has only -COOH group among -COOH group and -COONa group. It refers to the ion exchange capacity of the COOH group, and when the monolith ion exchanger of the present invention has only the -COONa group among the -COOH group and the -COONa group, it refers to the ion exchange capacity of the -COONa group. When the monolith ion exchanger of the present invention has both -COOH group and -COONa group among -COOH group and -COONa group, it means the total ion exchange capacity of -COOH group and -COONa group. In addition, the total ion exchange capacity of -COOH groups and -COONa groups per weight of the monolith ion exchanger in the dry state was set to all -COOH groups by using a sufficient amount of acid for the ion exchange groups of the monolith ion exchanger. It is measured by quantifying the amount of -COOH groups by neutralization titration using a sample, recovering the entire amount of the monolith ion exchanger used at this time, and determining the value of dry weight. Further, the total ion exchange capacity of -COONa groups per unit weight can be obtained from the amount of acid added to convert all the ion exchange groups of the monolith ion exchanger into -COOH groups.

In the monolith ion exchanger, the introduced ion exchange groups are uniformly distributed not only on the surface of the monolith but also inside the skeleton of the monolith. The term "uniformly distributed ion-exchange groups" as used herein means that the distribution of ion-exchange groups is uniformly distributed on the surface and inside the skeleton on the order of at least μm. The distribution of ion-exchange groups can be easily confirmed by using EPMA.

Examples of the structure of the monolith ion exchanger include an open cell structure (Japanese Patent Laid-Open No. 2002-306976, JP-A-2009-62512), a co-continuous structure (Japanese Patent Laid-Open No. 2009-67982), and a particle-aggregated structure (Japanese Patent Laid-Open No. 2009-67982). Japanese Patent Application Laid-Open No. 2009-7550), particle composite structure (Japanese Patent Laid-Open No. 2009-108294) and the like can be mentioned.

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

FIGS. 12A and 12B show the distribution state of sodium by EPMA in order to confirm the distribution state of the carboxyl group in the monolith A. FIG. 12A is an SEM photograph of the fracture surface of the absorbent A. FIG. 12B is a mapping diagram of the Na distribution of the same portion as that of FIG. 12A. According to FIGS. 12A and 12B, the distribution of carboxyl groups in the skeleton cross section is such that the carboxyl groups are uniformly distributed not only on the skeleton surface of the monolithic cation exchanger but also inside the skeleton, and the carboxyl groups are uniformly distributed in the monolith ion exchanger. It can be confirmed that it is uniformly introduced in.

Further, as an example of the structure of the absorbent A, the open cell structure disclosed in JP-A-2002-306976 and JP-A-2009-62512 and the co-continuous structure disclosed in JP-A-2009-67982. Further, there are monolith ion structures listed as a particle-aggregated structure disclosed in JP-A-2009-7550, a particle-composite structure disclosed in JP-A-2009-108294, and the like.

=== About the manufacturing method of absorbent A ===
As shown in FIG. 3, the absorbent A can be obtained through a cross-linking polymerization step and a hydrolysis step. Hereinafter, a method for producing the absorbent A will be described.

First, an oil-soluble monomer for cross-linking polymerization, a cross-linking monomer, a surfactant, water, and a polymerization initiator, if necessary, are mixed to obtain a water-in-oil emulsion. The water-in-oil emulsion is an emulsion in which the oil phase is a continuous phase and water droplets are dispersed therein.

In the absorbent A, as shown in the upper part of FIG. 3, butyl methacrylate is used as the (meth) acrylic acid ester as the oil-soluble monomer, divinylbenzene is used as the crosslinkable monomer, and sorbitanmono is used as the surfactant. Monolith A is cross-linked and polymerized using oleate and isobutyronitrile as a polymerization initiator.

In the absorbent A, as shown in the upper part of FIG. 3, first, 9.2 g of t-butyl methacrylate as an oil-soluble monomer, 0.28 g of divinylbenzene as a crosslinkable monomer, and sorbitan monooleate as a surfactant (sorbitan monooleate). 1.0 g (hereinafter abbreviated as SMO) and 0.4 g of 2,2'-azobis (isobutyronitrile) as a polymerization initiator are mixed and uniformly dissolved.

Next, a mixture of t-butyl methacrylate / divinylbenzene / SMO / 2,2'-azobis (isobutyronitrile) was added to 180 g of pure water, and a vacuum stirring defoaming mixer (EME), which is a planetary stirring device, was added. Stir under reduced pressure using (manufactured by the same company) to obtain a water-in-oil emulsion.

After that, this emulsion is immediately transferred to a reaction vessel, sealed, and polymerized at 60 ° C. for 24 hours under standing. After completion of the polymerization, the contents are taken out, extracted with methanol, and dried under reduced pressure to obtain a monolith A having a continuous macropore structure. The internal structure of this monolith A was observed by SEM. FIG. 10A is an SEM photograph of the fracture surface of the absorbent A. FIG. 10B is a mapping diagram of the Na distribution of the same portion as that of FIG. 10A. The monolith A had an open cell structure, and the thickness of the continuous skeleton was 5.4 μm. The average diameter measured by the mercury intrusion method was 36.2 μm, and the total pore volume was 15.5 mL / g.

The content of divinylbenzene with respect to all the monomers is preferably 0.3 to 10 mol%, more preferably 0.3 to 5 mol%. Further, the ratio 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 is 97.0 mol%, and the ratio of divinylbenzene is 3.0 mol%.

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

Further, in order to control the bubble shape and size of monolith 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 are used in the system. May coexist in.

There is no particular limitation on the mixing method for forming the water-in-oil emulsion. A method in which each component is mixed at once, an oil-soluble component which is an oil-soluble monomer, a surfactant and an oil-soluble polymerization initiator, and a water-soluble component which is water or a water-soluble polymerization initiator are uniformly dissolved separately. After that, a mixing method such as a method of mixing each component can be adopted. The mixing device for forming the emulsion is also not particularly limited, and in order to obtain the desired emulsion particle size, a normal mixer, a homogenizer, a high-pressure homogenizer, or an object to be treated is placed in a mixing container, and the mixing container is tilted. An appropriate device can be selected from a so-called planetary stirrer or the like that stirs and mixes the object to be processed by rotating the object to be processed while revolving around the revolution axis in the state of being revolved. Further, the mixing conditions are not particularly limited, and the stirring rotation speed and the stirring time can be arbitrarily set in order to obtain the desired emulsion particle size. Among these mixing devices, the planetary stirrer can uniformly generate water droplets in the W / O emulsion, and the average diameter thereof can be arbitrarily set in a wide range.

Various conditions can be selected for the polymerization conditions for polymerizing the water-in-oil emulsion depending on the type of monomer and the initiator system. For example, when azobisisobutyronitrile, benzoyl peroxide, potassium persulfate or the like is used as the polymerization initiator, it is subjected to heat polymerization at 30 to 100 ° C. for 1 to 48 hours in a sealed container under an inert atmosphere. Just do it. When hydrogen peroxide-ferrous chloride, sodium persulfite-sodium bisulfite, etc. are used as the polymerization initiator, the polymerization may be carried out at 0 to 30 ° C. for 1 to 48 hours in a sealed container in an inert atmosphere. .. After completion of the polymerization, the contents are taken out and soxhlet extracted with a solvent such as isopropanol to remove the unreacted monomer and the residual surfactant to obtain the monolith A shown in the middle figure of FIG.

Subsequently, the monolith A (crosslinked polymer) is hydrolyzed to obtain an absorbent A. Monolith A is immersed in dichloroethane containing zinc bromide, stirred at 40 ° C. for 24 hours, and then contacted with methanol, 4% hydrochloric acid, 4% sodium hydroxide aqueous solution, and water in this order to hydrolyze and dry. After that, the block-shaped absorbent A is pulverized to a predetermined size to obtain a particulate absorbent A.

There are no particular restrictions on the method of hydrolysis of Monolith A, and various methods can be used. For example, 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 solvent such as acetic acid and propionic acid, or water as a solvent and contact with strong base such as sodium hydroxide, hydrohalogen acid such as hydrochloric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid , P-solvented acid such as toluene sulfonic acid, or Lewis acid such as zinc bromide, aluminum chloride, aluminum bromide, titanium (IV) chloride, cerium chloride / sodium iodide, magnesium iodide, etc. Can be mentioned.

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 the alkyl esters of C1 to C10 of the (meth) acrylic acid are preferable, and the (meth) acrylic acid is preferable. C4 alkyl esters of acids are particularly preferred. Examples of the C4 alkyl ester of (meth) acrylic acid include (meth) acrylic acid t-butyl ester, (meth) acrylic acid n-butyl ester, and (meth) acrylic acid iso-butyl ester.

The monomer used for the cross-linking polymerization may be only (meth) acrylic acid ester and divinylbenzene, and in addition to (meth) acrylic acid ester and divinylbenzene, other than (meth) acrylic acid ester and divinylbenzene. It may contain a monomer. Other monomers include styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth) acrylate, diethylhexyl (meth) acrylate, isobutene, butadiene, isobrene, chloroprene, vinyl chloride, vinyl bromide, Examples thereof include vinylidene chloride, tetrafluoroethylene, (meth) acrylonitrile, vinyl acetate, ethylene glycol di (meth) acrylate, and trimethylpropantri (meth) acrylate. The proportion of the monomers other than the (meth) acrylic acid ester and divinylbenzene in all the monomers used for the cross-linking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

Surfactants are not limited to sorbitan monooleate. Any material may be used as long as it can form a water-in-oil (W / O) emulsion when the cross-linking polymerization monomer and water are mixed. For example, nonionic surfactants such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene group nonylphenyl ether, polyoxyethylene group stearyl ether, polyoxyethylene group sorbitan monooleate, etc. Agents, anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, sodium dioctyl sulfosuccinate, cationic surfactants such as distearyldimethylammonium chloride, and amphoteric surfactants such as lauryldimethylbetaine may be used. it can. These surfactants may be used alone or in combination of two or more.

As the polymerization initiator, a compound that generates radicals by heat and light irradiation is preferably used. The polymerization initiator may be water-soluble or oil-soluble, and may be, for example, azobis (4-methoxy-2,4-dimethylvaleronitrile), azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, azobiscyclohexane. Examples thereof include carbonitrile, azobis (2-methylpropionamidine) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-sodium acid sulfite, tetramethylthium disulfide and the like. .. However, in some cases, the polymerization proceeds only by heating or light irradiation without adding the polymerization initiator, so that it is not necessary to add the polymerization initiator in such a system.

As another example of the absorbent A, instead of the absorbent a, t-butyl methacrylate (9.2 g), an absorbent b containing 6.4 g of t-butyl methacrylate and 2.8 g of diethylhexyl methacrylate may be used. it can. It is the same as the absorbent a except that the oil-soluble monomer is 6.4 g of t-butyl methacrylate and 2.8 g of 2 ethylhexyl methacrylate. The ion exchange capacity of the absorbent b in the dry state is 5.0 mg equivalent / g.

For the absorbent b, an absorption rate test was conducted using pure water as the absorption target liquid in the same manner as the above-mentioned absorbent a. FIG. 13 is a graph showing the relationship between the amount of absorption and the time of the absorbent a and the absorbent b when the liquid to be absorbed is pure water. As shown in FIG. 13, the saturated absorption amount was 18 g / g-resin, and the immersion time was within 5 seconds to reach the absorption amount of 90% of the saturated absorption amount.

=== Other embodiments ===
The above-described embodiment is for facilitating the understanding of the present invention, and is not for limiting the interpretation of the present invention. It goes without saying that the present invention can be modified or improved without departing from the spirit thereof, and the present invention includes an equivalent thereof.

In the above-described embodiment, the absorber 11 includes the absorbent A (absorbent a) and SAP, but the present invention is not limited to this. The absorber 11 may be composed of only the absorbent A. Further, the substance used together with the absorbent A is not limited to SAP. For example, the absorber 11 including the absorbent A and the pulp fiber may be used, or the absorber 11 including the absorbent A, SAP and the pulp fiber may be used.

1 diaper (pants type disposable diaper, absorbent article), 10 absorbent body, 10ea end, 10eb end, 11 absorber, 11c absorbent core, 13 topsheet, 15 backsheet, 30 ventral member, 30a side Part, 31 skin side sheet, 32 non-skin side sheet, 35 thread rubber, 40 back side member, 40a side part, 41 skin side sheet, 42 non-skin side sheet, 45 thread rubber, SS welded part, LH leg circumference opening , BH waist opening

Claims

An absorber for absorbing body fluids
It has a polymer absorbent with a continuous skeleton and continuous pores,
The polymer absorbent is a hydrolyzate of a (meth) acrylic acid ester and a crosslinked polymer of a compound containing two or more vinyl groups in one molecule, and at least one -COONa group. An absorber characterized by containing.
The absorber according to claim 1.
The polymer absorbent is an absorber characterized by being a monolith-like absorbent.
The absorber according to claim 1 or 2.
The first absorption weight of the polymer absorbent per unit weight for absorbing an aqueous NaCl solution having a concentration of 0.9 wt% and
Regarding the second absorption weight at which the polymer absorbent per unit weight absorbs a NaCl aqueous solution having a concentration of 0 to 2.0 wt%.
An absorber characterized in that the first absorbed weight is 0.5 to 1.9 times the second absorbed weight.
The absorber according to claim 3.
A first polymer absorbent that absorbs a concentration of 0.9 wt% NaCl aqueous solution by the first absorption weight, and a second polymer absorbent that absorbs a concentration of 0 to 2.0 wt% NaCl aqueous solution by the second absorption weight. about,
The weight of the 0.9 wt% NaCl aqueous solution absorbed by the first polymer absorbent after dehydration at 150 G for 90 seconds under the condition of 850 rpm using a centrifuge for a predetermined time is the second. An absorber characterized by being 0.5 to 1.6 times the weight of an aqueous NaCl solution having a concentration of 0 to 2.0 wt% absorbed by the polymer absorbent.
The absorber according to claim 4.
The weight of the 0.9 wt% NaCl aqueous solution absorbed by the first polymer absorbent after the dehydration was defined as the first water retention weight.
The weight of the aqueous NaCl solution having a concentration of 0 to 2.0 wt% absorbed by the second polymer absorbent after the dehydration was defined as the second water retention weight.
The value obtained by dividing the difference between the first absorption weight and the first water retention weight of the first polymer absorbent by the first absorption weight is 50 to 80%.
An absorber characterized in that the value obtained by dividing the difference between the second absorption weight and the second water retention weight of the second polymer absorbent by the second absorption weight is 40 to 85%.
The absorber according to any one of claims 1 to 5.
An absorber according to a vortex method, wherein 2.0 g of the polymer absorbent absorbs 50 g of a 0.9 wt% NaCl aqueous solution for 1.0 to 10.0 seconds.
The absorber according to any one of claims 1 to 6.
An absorber characterized in that the absorption weight of the polymer absorbent for absorbing a CaCl2 aqueous solution having a concentration of 0.5 wt% is 13 times or more the weight of the polymer absorbent.
The absorber according to any one of claims 1 to 7.
After 1 minute has passed in a state where the lower end of 1.0 g of the polymer absorbent is in contact with the water surface of the NaCl aqueous solution having a concentration of 0.9 wt%, the NaCl aqueous solution having a concentration of 0.9 wt% due to the polymer absorbent is added. An absorber characterized in that the amount of absorption is 15 ml or more.
The absorber according to any one of claims 1 to 8.
With the lower end of 2.0 g of the polymer absorbent under a load of 600 gw in contact with the water surface of an aqueous NaCl solution having a concentration of 0.9 wt%,
After 2 minutes, the amount of the NaCl aqueous solution having a concentration of 0.9 wt% absorbed by the polymer absorbent was 1.0 ml or more.
An absorber characterized in that after 15 minutes, the amount of the NaCl aqueous solution having a concentration of 0.9 wt% absorbed by the polymer absorbent is 5.0 ml or more.
The absorber according to any one of claims 1 to 9.
An absorber characterized in that the volume of voids in the pores per unit volume of the polymer absorbent is 85% or more.
The absorber according to any one of claims 1 to 10.
The polymer absorbent is an absorber containing 0.1 to 30.0% of crosslinked polymerization residues.
The absorber according to any one of claims 1 to 11.
An absorber characterized in that the average diameter of the continuous pores is 1 to 1000 μm.
The absorber according to any one of claims 1 to 12.
The absorber is characterized by having the polymer absorbent and a polymer compound having a higher water retention ratio than the polymer absorbent.
The absorber according to any one of claims 1 to 13.
An absorber characterized in that the total ion exchange capacity of -COONa groups per unit weight of the polymer absorbent is 4.0 mg equivalent / g or more.
An absorbent article comprising the absorber according to any one of claims 1 to 14.