JP2021106648A - Absorbent article - Google Patents

Abstract

To provide an absorbent article which includes an absorber that has a proper absorption speed function and is thinned.SOLUTION: An absorbent article 1 comprises: a polymer absorbent which includes a continuous skeleton and continuous holes; and a skin side sheet member which is provided on the skin side with respect to the polymer absorbent. The liquid adsorption after 30 seconds in the no-pressure DW method of the polymer absorbent is between 7.8 ml/g and 21.3 ml/g.SELECTED DRAWING: Figure 1

Description

The present invention relates to absorbent articles.

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 absorbent article using an absorber in which SAP having an excellent absorption amount and pulp fiber having an excellent absorption rate are combined is disclosed.

International Publication No. 2013-018571

It is desired that the thickness of the absorbent article be reduced from the viewpoints of distribution, storage, portability, wearing comfort, and the like. However, when SAP and pulp fibers are combined, there is a problem that the absorber becomes bulky (problem that the thickness is not reduced) due to the large amount of pulp in the pulp fibers.

On the other hand, if the pulp fibers are excluded and only SAP is used, the excellent absorption rate performance of the pulp fibers is not exhibited, and the absorber becomes an absorber with a slow absorption rate.

Therefore, an absorber that is thinner than when pulp fibers are used and has an absorption rate performance equal to or higher than that when pulp fibers are used is desired.

The present invention has been made in view of the above problems, and an object of the present invention is to realize an absorbent article having an appropriate absorption rate performance and having a thin absorber. be.

The main invention for achieving the above object is
An absorbent article comprising a polymer absorbent having a continuous skeleton and continuous pores, and a skin-side sheet member provided on the skin side of the polymer absorbent.
It is an absorbent article characterized in that the amount of the polymer absorbent after 30 seconds in the non-pressurized DW method is 7.8 ml / g or more and 21.3 ml / g or less.

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, it is possible to realize an absorbent article having an appropriate absorption rate performance and having a thin absorber.

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 schematic view showing a measuring device used in the non-pressurized DW method. FIG. 10 is a diagram showing the measurement results of measuring the amount of liquid absorbed after 30 seconds in the non-pressurized DW method. FIG. 11 is a schematic view showing a measuring device used in the volume increase rate measurement test. FIG. 12 is a diagram showing the test results of the volume increase rate measurement test. FIG. 13 is a schematic view showing a measuring device used in the volume reduction rate and water separation magnification measurement test. FIG. 14 is a diagram showing the test results of the volume reduction rate measurement test. FIG. 15 is a diagram showing the test results of the water separation magnification measurement test. FIG. 16A is an SEM photograph of the fracture surface of the absorbent A. FIG. 16B is a mapping diagram of the Na distribution in the same portion as in FIG. 16A.

The description of this specification and the accompanying drawings will clarify at least the following matters.

An absorbent article comprising a polymer absorbent having a continuous skeleton and continuous pores, and a skin-side sheet member provided on the skin side of the polymer absorbent.
An absorbent article characterized in that the amount of the polymer absorbent after 30 seconds in the non-pressurized DW method is 7.8 ml / g or more and 21.3 ml / g or less.

According to such an absorbent article, it is possible to realize an absorbent article having an appropriate absorption rate performance and having a thin absorber.

In such an absorbent article, it is desirable that the volume increase rate of the saturated liquid absorbing volume of the polymer absorbent with respect to the pre-absorbing volume is 233% or more and 567% or less.

According to such an absorbent article, it is possible to realize an absorbent article having a thinner absorber.

^{In such an absorbent article, the volume reduction rate of the volume after loading after applying a load of 30 g / cm 2} for 3 minutes to the polymer absorbent which has saturated liquid absorption is 34% or more with respect to the volume at the time of saturated liquid absorption. It is desirable that it is 48% or less.

According to such an absorbent article, even if the polymer absorbent once absorbs liquid and expands, it can be immediately separated from water by a load and returned to a thin state (compact state).

^{It is desirable that the water separation ratio of such an absorbent article after applying a load of 30 g / cm 2} for 3 minutes to the saturated liquid absorbing polymer absorbent is 65% or more and 72% or less.

According to such an absorbent article, even if the polymer absorbent once absorbs liquid and expands, it can be immediately separated from water by a load and returned to a thin state (compact state).

In such an absorbent article, the polymer absorbent is a hydrolyzate of a crosslinked polymer of two or more monomers containing at least (meth) acrylic acid ester, and has at least one hydrophilicity as a functional group. It is desirable to have a group.

According to such an absorbent article, the affinity with water is improved, and the absorption rate performance can be further improved.

In such an absorbent article, 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 It is desirable to contain at least one -COONa group.

According to such an absorbent article, a continuous skeleton and continuous pores can be easily formed, and a thin absorber (absorbable article) can be easily realized.

It is desirable that the absorbent article has a SAP that can be adjacent to the polymer absorbent.

According to such an absorbent article, it is possible to appropriately absorb the body fluid separated from the polymer absorbent into another agent (SAP) without hindering the thinning (compactness) of the absorber. Become.

In such an absorbent article, it is desirable that the volume of the voids of the pores per unit volume of the polymer absorbent is 85% or more.

According to such an absorbent article, the body fluid is easily taken into the continuous pores by the capillary phenomenon, and the body fluid is easily absorbed as an absorber.

In such an absorbent article, it is desirable that the polymer absorbent contains 0.1 to 30.0% of crosslinked polymerization residues.

According to such an absorbent article, 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.

In such an absorbent article, it is desirable that the average diameter of the continuous pores is 1 to 1000 μm.

According to such an absorbent article, the body fluid is easily taken into the continuous pores by the capillary phenomenon, and the body fluid is easily absorbed as an absorber.

=== 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 excreted not only from humans but also from living organisms including animals. 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 anterior side, and the dorsal side of the wearer is the posterior 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 each include 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. 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 back side member 40, the skin side sheet 41, the thread rubber 45, and the non-skin side sheet 42 are stacked in the order of thickness from the skin side, 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 a non-woven fabric, respectively, and specifically, a 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, and each of them 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 obtained by wrapping a polymer absorbent (absorbent A) and a highly absorbent polymer (so-called SAP) in a core wrap (specifically, a hydrophilic tissue) as an example of a skin-side sheet member, which is omitted. It is molded into an 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 crosslinked polymer of two or more monomers containing at least (meth) acrylic acid ester, and is a polymer compound having at least one hydrophilic group as a functional group. More specifically, it 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.

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 a -COONa group or a -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 a 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 water added to 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. Further, it may be a hydrolyzate of a crosslinked polymer of two or more monomers containing at least (meth) acrylic acid ester. Hereinafter, "monolith A" is an organic porous body composed of a crosslinked polymer of (meth) acrylic acid ester and divinylbenzene before hydrolysis treatment, 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 (Monolith A). The organic polymer forming a continuous skeleton has an ethylene group polymerization residue (hereinafter, also referred to as “constituent unit X”) and a crosslinked polymerization residue 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 produced 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 1 mol% with respect to all the constituent 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 polymerization 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 organic polymer forming the continuous skeleton may be composed of only 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 polymerization residue of a monomer other than the (meth) acrylic acid ester and divinylbenzene. The constituent units other than the constituent unit X and the constituent 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. .. The proportion 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%, based on the total structural units. In the absorbent A in which butyl methacrylate is used as a polymerization monomer and divinylbenzene is used as a 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. , 0-50 mol%, preferably 0-30 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 porous water is likely to be crushed during absorption, and the amount of absorption 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.

The 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 (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 having butyl methacrylate as a polymerization monomer and divinylbenzene as a cross-linking 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. The absorbent A shown in FIGS. 4 to 8 has a large number of bubble-like macropores. , Bubble-shaped macropores overlap each other, and this overlapping portion forms a common bubble structure (mesopore). 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 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. be. 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.

The absorbent A has a property that the continuous skeleton is elongated when the liquid is absorbed. 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, the body fluid retained in the pores is larger than the body fluid 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 intrusion 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%.

Further, this polymer absorbent (absorbent A) has an absorption rate performance (initial liquid absorption speed) equal to or higher than that of pulp fiber. As a measuring method for evaluating the absorption rate of an absorbent, a non-pressurized DW (Demand Wettingity) method is generally well known. This non-pressurized DW method is described in, for example, Japanese Patent Application Laid-Open No. 2018-39944. The amount of the polymer absorbent after 30 seconds in the non-pressurized DW method (the amount of liquid absorbed after 30 seconds) is 7.8 ml / g or more and 21.3 ml / g or less, and the pulp fiber after the 30 seconds. It is equal to or higher than the amount of liquid absorbed (6.8 ml / g).

Hereinafter, a specific description will be given with reference to FIGS. 9 and 10. FIG. 9 is a schematic view showing a measuring device used in the non-pressurized DW method. FIG. 10 will be described later. Since the non-pressurized DW method is general as described above, the description of the non-pressurized DW method according to the present embodiment is based on the description of JP-A-2018-39944. However, since there are some differences, the non-pressurized DW method according to the present invention will be defined by clarifying the relevant parts.

The non-pressurized DW method is a measuring method performed using the non-pressurized DW method measuring device 50 shown in FIG. 9 in a room at 25 ° C. and 50% humidity. The non-pressurized DW method measuring device 50 shown in FIG. 9 includes a burette portion 52 (scale capacity 50 ml, length 86 cm, inner diameter 1.05 cm), a conduit (inner diameter 7 mm), and a measuring table 56. The burette portion 52 has a rubber stopper 51 at the upper part, an air introduction pipe 59 (tip inner diameter 3 mm) and a cock 57 at the lower part, and a cock 58 at the upper part of the air introduction pipe 59. A duct is attached from the burette portion 52 to the measuring table 56. In the central portion of the measuring table 56, a hole having a diameter of 3 mm is provided as a physiological saline supply portion, and a conduit is connected to the hole.

Using the non-pressurized DW method measuring device 50 having this configuration, first, the cock 57 of the burette portion 52 and the cock 58 of the air introduction pipe 59 are closed, and physiological saline having a sodium chloride concentration of 0.9% by weight adjusted to 25 ° C. Water 53 (NaCl aqueous solution) is put in from the upper part of the burette portion 52, the upper part of the burette is plugged with the rubber stopper 51, and then the cock 57 of the burette portion 52 and the cock 58 of the air introduction pipe 59 are opened. Next, after wiping off the physiological saline 53 overflowing on the measuring table 56, the upper surface of the measuring table 56 and the water surface of the physiological saline 53 coming out from the conduit port at the center of the measuring table 56 are at the same height. The height of the measuring table 56 is adjusted so as to be. While wiping the saline solution 53 from the saline solution supply section, the water surface of the saline solution 53 in the burette section 52 is adjusted to the top of the burette section 52 scale (0 ml line).

Subsequently, the cock 57 of the burette portion 52 and the cock 58 of the air introduction pipe 59 are closed, and the tissue 55 made of 100% wood pulp (grain 15 ± 1 gsm, non-woven fabric) is placed on the measuring table 56 so that the physiological saline supply portion is at the center. With a thickness gauge, a measurement pressure of 3 g / cm ^{(thickness at 2} o'clock is 0.1 ± 0.02 mm) is placed, and the test object (polymer) is placed on this tissue 55, centering on the physiological saline supply section of the measuring table 56. Put an absorbent). The test object is placed in a cylindrical container 54, and the circumference thereof is constrained by the container 54. After that, the cock 57 of the burette portion 52 and the cock 58 of the air introduction pipe 59 are opened.

When the test object begins to absorb liquid and the first bubble introduced from the air introduction pipe 59 reaches the water surface of the physiological saline 53 in the burette portion 52 (the water surface of the physiological saline 53 in the burette portion 52). The measurement start time is set as the measurement start time, and the decrease amount of the physiological saline 53 in the burette portion 52 (the amount of the physiological saline absorbed by the test object) M (ml) is continuously read. The amount of absorption of the test object after a lapse of a predetermined time from the start of liquid absorption (after 30 seconds in the present embodiment) is the amount absorbed by the DW method (ml / g) = M ÷ weight (g) of the test object. To be calculated by.

As also shown in Japanese Patent Application Laid-Open No. 2018-39944, in the non-pressurized DW method, a mesh is usually placed on a measuring table 56, and a test object is placed on the mesh. On the other hand, in the present embodiment, the above-mentioned tissue 55 is placed instead of the mesh in order to carry out the test in a situation close to the actual absorbent article (diaper 1). That is, in the non-pressurized DW method according to the present invention, the mesh size is 15 ± 1 gsm between the measuring table 56 and the test object (polymer absorbent), and the measuring pressure is 3 g / cm ² o'clock with a non-woven fabric thickness gauge. This is a test method carried out by sandwiching a tissue 55 having a thickness of 0.1 ± 0.02 mm and 100% wood pulp.

FIG. 10 is a diagram showing the measurement results of measuring the amount of liquid absorbed after 30 seconds in the non-pressurized DW method. Four polymer absorbents, pulp fibers as a comparative example, and Infinity particles as a reference example were prepared as polymer absorbents, and each of them was used as a test object, and the amount of liquid absorbed after 30 seconds in the non-pressurized DW method. Was measured. Here, the Infinity particle body is an absorbent manufactured by P & G, and has a structure (foamed structure) similar to that of the polymer absorbent. However, unlike polymer absorbents, it does not have the function of absorbing liquid and expanding.

The amount of the polymer absorbent after 30 seconds in the non-pressurized DW method is 7.8 ml / g or more and 21.3 ml / g or less, and the amount of the pulp fiber after 30 seconds (6.8 ml / g). It is equal to or higher than g), and considerably larger (good) than the liquid absorption amount (2.3 ml / g) of the Infinity particle body after 30 seconds.

Then, as described above, since the polymer absorbent is applied to the absorbent article (absorbent 11), the absorbent article (diaper 1) according to the present embodiment is specified as follows. That is, the absorbent article (diaper 1) has a polymer absorbent having a continuous skeleton and continuous pores, and a tissue provided on the skin side of the polymer absorbent, and is a polymer absorbent. The amount of liquid absorbed after 30 seconds in the non-pressurized DW method is 7.8 ml / g or more and 21.3 ml / g or less. Therefore, as described below, it is possible to realize an absorbent article having an appropriate absorption rate performance and having a thin absorber 11.

Conventionally, an absorbent article using an absorber in which SAP having an excellent absorption amount and pulp fiber having an excellent absorption rate are combined has been known.

However, when SAP and pulp fibers are combined, there is a problem that the absorber becomes bulky (problem that the thickness is not reduced) due to the large amount of pulp in the pulp fibers. In such a case, it is not preferable from the viewpoints of distribution, storage, portability, wearing comfort (wearing discomfort, poor breathability) and the like.

On the other hand, if the pulp fibers are excluded and only SAP is used, the excellent absorption rate performance of the pulp fibers is not exhibited, and the absorber becomes an absorber with a slow absorption rate. Further, if the absorption surface is enlarged to compensate for the slow absorption rate, other problems such as leakage, wearing discomfort, and an increase in skin load may occur.

On the other hand, in the absorbent article (diaper 1) according to the present embodiment, a polymer absorbent having a continuous skeleton and continuous pores is used instead of the pulp fiber, so that the absorber 11 has such a structure. (By extension, the absorbent article) can be made thinner (in particular, the absorber 11 before absorbing liquid (before expansion) can be made thinner). Further, instead of the pulp fiber, a polymer absorbent having a liquid absorption amount of 7.8 ml / g or more and 21.3 ml / g or less after 30 seconds in the non-pressurized DW method was used, so the pulp fiber was used. It is possible to obtain absorption rate performance equal to or higher than that of the case (quickly draw body fluid from the tissue).

Therefore, according to the present embodiment, it is possible to realize an absorbent article having an appropriate absorption rate performance and having a thin absorber 11.

Further, as described above, the polymer absorbent according to the present embodiment is a hydrolyzate of a crosslinked polymer of two or more monomers containing at least (meth) acrylic acid ester, and at least one functional group. It has the above hydrophilic groups.

Therefore, the affinity with water is improved, and the absorption rate performance can be further improved.

Further, the polymer absorbent according to the present embodiment 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. Contains one or more -COONa groups.

Therefore, it becomes easy to form a continuous skeleton and continuous pores, and it becomes possible to easily realize a thin absorber 11 (absorbable article).

As described above, when the body fluid enters the continuous pores due to the capillary phenomenon, the continuous skeleton of the polymer absorbent partially absorbs the body fluid by osmotic pressure and extends. Then, the pores are enlarged by such elongation, and the body fluid is further taken in. That is, the polymer absorbent absorbs body fluid while expanding (increasing volume) (in other words, it can expand to increase the amount of liquid retained). Therefore, the polymer absorbent (absorber 11) before body fluid absorption (before expansion) can be thinned. In order to consider such matters, the following test (hereinafter referred to as a volume increase rate measurement test) for measuring the volume increase rate of the saturated liquid absorption volume of the polymer absorbent with respect to the volume before the liquid absorption was performed.

Hereinafter, a specific description will be given with reference to FIGS. 11 and 12. FIG. 11 is a schematic view showing a measuring device used in the volume increase rate measurement test. FIG. 12 will be described later.

The volume increase rate measuring device 60 shown in FIG. 11 includes a test object storage container 61 and a petri dish 62. The test object storage container 61 has a nylon mesh (not shown) attached to the lower end of an acrylic tubular member having openings at the upper and lower ends.

The tubular member has an inner diameter of 26 mm, a length of 80 mm, an outer diameter of 38 mm, and a weight of 57 g. As the nylon mesh, N-N0255HD 115 manufactured by NBC Meshtec is used. The petri dish 62 is a container having an inner diameter of 97 mm and a weight of 58 g.

Then, the test object 63 is put into the test object storage container 61 from the upper end (opening), and the height of the put test object 63 is measured. Then, the volume of the test object 63 is obtained by the calculation formula (volume = bottom area (3.14 × (inner diameter (26 mm) / 2) ² ) × height), and this is used as the volume before liquid absorption. The upper end of the test object 63 may be slightly curved, but in this case, the height of the uppermost portion is measured. Further, the weight of the test object storage container 61 containing the test object 63 is measured for the water separation magnification measurement test described later.

Next, 60 cc of physiological saline (NaCl aqueous solution) having a salt concentration of 0.9% by weight was placed in the petri dish 62, and the test object 63 (the volume of which had been measured before absorption) was contained in the petri dish 62. Place the containment container 61 (see FIG. 11). Then, the test object 63 begins to absorb the physiological saline through the nylon mesh, and the height (volume) of the test object 63 changes. The height (volume) change is continuously visually observed, and the height of the test object 63 is measured when the height is stable (that is, when the liquid is absorbed to saturation). Then, the volume of the test object 63 is obtained by the above calculation formula, and this is used as the volume at the time of saturated liquid absorption. In the present embodiment, since it has been confirmed that the height of the test object 63 stabilizes in two and a half minutes after the start of absorbing the liquid, the height is measured two and a half minutes later. .. Further, the point of measuring the height of the uppermost portion when the upper end portion of the test object 63 is slightly curved is the same as the measurement before the liquid absorption. Further, for the water separation magnification measurement test described later, the weight of the test object storage container 61 containing the test object 63 that has absorbed the liquid to saturation is measured.

FIG. 12 is a diagram showing the test results of the volume increase rate measurement test. Three polymer absorbents were prepared as polymer absorbents, pulp fibers as a comparative example, and Infinity particles as a reference example, and each of them was used as a test object 63 to set the volume before liquid absorption and the volume during saturated liquid absorption. Measured (tested 3 times for each test object 63). Then, the volume increase rate of the saturated liquid absorbing volume with respect to the pre-absorbing volume (as will be described later, in the comparative example and the reference example, since the volume has decreased, the volume decrease rate is obtained. The rate of change in volume) was calculated. That is, the volume change rate is obtained by dividing the volume during saturated liquid absorption ÷ the volume before liquid absorption. For example, in the case of the first pulp fiber in FIG. 12, it is 13.3 ÷ 15.9 = 0.83. , 83%.

The volume change rate of the polymer absorbent is 233% or more and 567% or less, and the volume change rate of the pulp fiber and the Infinity particle body is 83% or more and 85% or less and 60% or more and 66% or less, respectively. That is, the volume of the pulp fiber and the Infinity particle body is reduced (reduced) due to the liquid absorption, while the volume of the polymer absorbent is increased (expanded).

As described above, in the absorbent article (diaper 1) in the present embodiment, the polymer absorbent having a volume increase rate of the saturated liquid absorbing volume with respect to the pre-absorbing volume is 233% or more and 567% or less is used. ing. That is, since a polymer absorbent that absorbs body fluid while significantly expanding (increasing volume) is used, the polymer absorbent (absorber 11) before absorbing body fluid (before expansion) can be thinned. It becomes possible to realize a thinner absorbent article (diaper 1).

As described above, the polymer absorbent (absorbent A) absorbs body fluid (expands to increase the amount of liquid retained) while expanding (increasing volume), but a load (pressure) is applied to the polymer absorbent. When (for example, when the wearer wearing the diaper 1 moves and pressure is applied by the wearer), the body fluid is discharged to the outside while shrinking (volume reduction) (hereinafter, for convenience, water separation). Call). For example, SAP, which can be used for the absorber 11 together with the polymer absorbent, hardly separates water even when pressure is applied once it absorbs the body fluid, but the polymer absorbent releases water while shrinking (volume reduction). It has an easy property. In order to consider such matters, the following test for measuring the volume reduction rate and the water separation ratio when a load is applied to the polymer absorbent (hereinafter referred to as the volume reduction rate and the water separation ratio measurement test) is referred to as the above-mentioned volume. The rate of increase measurement test was followed.

Hereinafter, a specific description will be given with reference to FIGS. 13 to 15. FIG. 13 is a schematic view showing a measuring device (hereinafter, referred to as a volume reduction rate and the like measuring device 70) used in the volume reduction rate and water separation magnification measurement test. 14 and 15 will be described later.

The volume reduction rate measuring device 70 shown in FIG. 13 includes a pressure member 71 and an underlay filter paper 74 in addition to the test object storage container 61 described above.

The pressurizing member 71 includes a pressing member 72 that contacts and presses against the test object 63 (polymer absorbent) and a weighting weight 73 that is placed on the pressing member 72. Similar to the test object storage container 61, the pressing member 72 is formed by attaching a nylon mesh to the lower end portion of an acrylic tubular member having openings at the upper end portion and the lower end portion. The tubular member has an inner diameter of 19.5 mm, a length of 120 mm, an outer diameter of 25.5 mm, and a weight of 28 g. As for the nylon mesh, N-N0255HD 115 manufactured by NBC Meshtec is used as in the test object storage container 61.

The weighting weight 73 is formed by attaching an acrylic columnar member (diameter 25 mm, length 8 mm) and a weighting filter paper to the bottom of the weight, and the weight is 124 g.

Then, by placing the weighting weight 73 on the pressing member 72, a total of 152 g (30 g / cm ² ) of the pressing member 71 is formed. The value of 30 g / cm ² assumes the pressure applied when the wearer wearing the diaper 1 moves.

The underlay filter paper 74 is located at the lowermost part and is where the test object storage container 61 is placed. For the underlay filter paper 74, FILTERPAPER manufactured by ADVANTEC is used.

The volume reduction rate and water separation ratio measurement test is performed following the volume increase rate measurement test described above. The test object storage container 61 containing the test object 63 sucked to saturation is taken out from the petri dish 62, and the test object storage container 61 is placed on the underlay filter paper 74. Before placing the test object storage container 61 on the underlay filter paper 74, the weight of the underlay filter paper 74 is measured.

Then, the pressure member 71 is placed on the test object 63. That is, the pressing member 72 is inserted into the test object storage container 61 so that the nylon mesh is on the lower side. Then, the pressing member 72 is located on the test object 63 with the nylon mesh in contact with the test object 63. Then, when the weighting weight 73 is placed on the pressing member 72, the weight of the pressing member 72 and the weighting weight 73 is finally applied to the test object 63.

Then, the physiological saline absorbed in the test object 63 begins to separate from the underlay filter paper 74 via the nylon mesh of the test object storage container 61, and the height (volume) of the test object 63 changes. (Decrease). Then, the height is measured 3 minutes after the load is applied. From the height, the volume of the test object 63 is calculated by the above formula, and this is used as the post-load volume (after ^{applying a 30 g / cm 2 load to the saturated liquid-absorbed test object 63 for 3 minutes).} The point of measuring the height of the uppermost portion when the upper end portion of the test object 63 is slightly curved is the same as the measurement before liquid absorption and the like.

In addition, the weight of the underlay filter paper 74 is measured together with the height 3 minutes after the load is applied. Then, the value obtained by subtracting the weight of the underlay filter paper 74 before applying the weight from the measured weight (after applying a 30 g / cm ² load to the saturated liquid-absorbed test object 63 for 3 minutes). ) The amount of water separation.

FIG. 14 is a diagram showing the test results of the volume reduction rate measurement test. The same three polymer absorbents as in the volume increase rate measurement test were used as test objects 63, and the volume after loading was measured (each test object 63 was tested three times). Then, the volume reduction rate of the volume after loading with respect to the saturated liquid absorption volume (obtained in the volume increase rate test, see FIG. 12) was determined. As shown in FIG. 14, the volume reduction rate of the polymer absorbent is 34% or more and 48% or less, and the volume of the polymer absorbent is half or less (significantly reduced).

FIG. 15 is a diagram showing the test results of the water separation magnification measurement test. Similar to the volume reduction rate measurement test, the amount of water separation was measured using three polymer absorbents as test objects 63 (tests were performed three times for each test object 63). Then, the water separation ratio, which is the ratio of the water separation amount to the absorption amount, was obtained. Regarding the amount of absorption, as described above, the weight of the test object storage container 61 containing the test object 63 was measured before and after the liquid absorption during the volume increase rate measurement test, so the difference between the two is taken. Obtained by As shown in FIG. 15, the water separation ratio is 65% or more and 72% or less, and water is separated at a rate of more than half (significant water separation. The SAP water separation ratio is 40% at the highest. It is said to be a degree).

As described above, in the absorbent article (diaper 1) according to the present embodiment, at the time of saturated liquid absorption, the volume after loading after applying a load ^{of 30 g / cm 2 for 3 minutes to the saturated liquid-absorbed polymer absorbent.} A polymer absorbent having a volume reduction rate of 34% or more and 48% or less with respect to volume is used. Further, a polymer absorbent having a water separation ratio of 65% or more and 72% or less after applying a load ^{of 30 g / cm 2 for 3 minutes to the saturated liquid absorbing polymer absorbent is used.} That is, since a polymer absorbent whose volume is significantly reduced while significantly separating water when a load is applied is used, even if the polymer absorbent (absorber 11) once absorbs liquid and expands, the load is applied. It is possible to immediately separate the water and return to the thin state (compact state) (when the thin state is reached, the liquid can be absorbed again).

Further, as described above, the absorbent article (diaper 1) according to the present embodiment has SAP that can be adjacent to the polymer absorbent. That is, the absorber 11 includes a polymer absorbent and SAP, and SAP has a higher liquid retention capacity (liquid retention) than the polymer absorbent and has a property of being hard to expand, so that water is separated from the polymer absorbent. The body fluid can be appropriately absorbed (passed) to another agent (SAP) without hindering the thinning (compactness) of the absorber 11.

=== 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, if necessary, a polymerization initiator 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 formed by cross-linking polymerization 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.

Then, 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. 16A is an SEM photograph of the fracture surface of the absorbent A. FIG. 16B is a mapping diagram of the Na distribution in the same portion as in FIG. 16A. 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%. The ratio of divinylbenzene to the total of butyl methacrylate and divinylbenzene is preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%. In the 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.

The mixing method for forming the water-in-oil emulsion is not particularly limited. A method of mixing each component at once, an oil-soluble monomer, a surfactant, and an oil-soluble polymerization initiator, and a water-soluble component that 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 while revolving around the revolution axis in the state of being 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 heat-polymerized 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 under 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.

The method for hydrolyzing the monolith A is not particularly limited, 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, and alcohol solvents such as methanol and ethanol. , A carboxylic acid solvent such as acetic acid or propionic acid, or a method of contacting with a strong base such as sodium hydroxide using water as a solvent, hydrohalogen acid such as hydrochloric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid. , Brenstead acid such as p-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, and polyoxyethylene group sorbitan monooleate. Agents, anionic surfactants such as potassium oleate, sodium dodecylbenzene sulfonate, sodium dioctyl sulfosuccinate, cationic surfactants such as distearyldimethylammonium chloride, and amphoteric surfactants such as lauryldimethylbetaine may be used. 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.

=== Other embodiments ===
Although the embodiments of the present invention have been described above, the above-described embodiments are for facilitating the understanding of the present invention, and are not for limiting the interpretation of the present invention. Further, it is needless to say that the present invention can be modified or improved without departing from the spirit thereof, and the present invention includes an equivalent thereof. For example, the following modifications are possible.

In the above embodiment, a tissue has been described as an example as a skin-side sheet member provided on the skin side of the polymer absorbent, but the present invention is not limited to this. For example, it may be a hydrophilic non-woven fabric.

Further, in the above embodiment, the skin-side sheet member wraps the polymer absorbent (absorbent A) and SAP to form the absorber 11 together with the polymer absorbent (absorbent A) and SAP. However, it is not limited to this. For example, there may be a case where there is no core wrap that wraps the polymer absorbent (absorbent A) and SAP (in such a case, the top sheet 13 corresponds to the skin-side sheet member).

That is, the skin-side sheet member may have a function of once receiving the liquid and delivering it to the polymer absorbent (absorbent A).

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

1 Diapers (pants-type disposable diapers, absorbent items),
10 Absorbent body, 10ea end, 10eb end,
11 absorber, 11c absorbent core,
13 top sheet, 15 back sheet, 17 elastic member, 18 elastic member,
30 ventral member, 30a side,
31 skin side sheet, 32 non-skin side sheet, 35 thread rubber,
40 dorsal member, 40a side,
41 skin side sheet, 42 non-skin side sheet, 45 thread rubber,
50 non-pressurized DW method measuring device, 51 rubber stopper, 52 burette part,
53 Saline, 54 Containers, 55 Tissues, 56 Measuring Tables,
57 cocks, 58 cocks, 59 air introduction pipes,
60 Volume increase rate measuring device, 61 Test object storage container,
62 Petri dish, 63 test object,
70 Volume reduction rate measuring device, 71 Pressurizing member, 72 Pressing member,
73 Weighted weight, 74 Filter paper for underlay,
SS welding part, LH leg circumference opening, BH waist circumference opening,

Claims (10)

An absorbent article comprising a polymer absorbent having a continuous skeleton and continuous pores, and a skin-side sheet member provided on the skin side of the polymer absorbent.
An absorbent article characterized in that the amount of the polymer absorbent after 30 seconds in the non-pressurized DW method is 7.8 ml / g or more and 21.3 ml / g or less. The absorbent article according to claim 1.
An absorbent article characterized in that the volume increase rate of the saturated liquid absorbing volume of the polymer absorbent with respect to the pre-absorbing volume is 233% or more and 567% or less. The absorbent article according to claim 2.
^{The volume reduction rate of the volume after loading after applying a 30 g / cm 2} load to the saturated liquid-absorbed polymer absorbent for 3 minutes with respect to the saturated liquid-absorbing volume is 34% or more and 48% or less. Absorbent article. The absorbent article according to claim 2 and 3.
An absorbent article characterized in that the water separation ratio after applying a ² load of 30 g / cm for 3 minutes to the saturated liquid-absorbing polymer absorbent is 65% or more and 72% or less. The absorbent article according to any one of claims 1 to 4.
The polymer absorbent is a hydrolyzate of a crosslinked polymer of two or more monomers containing at least (meth) acrylic acid ester, and is characterized by having at least one hydrophilic group as a functional group. Absorbent article. The absorbent article according to claim 5.
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 absorbent article characterized by containing. The absorbent article according to any one of claims 1 to 6.
An absorbent article characterized by having a SAP that can be adjacent to the polymer absorbent. The absorbent article according to any one of claims 1 to 7.
An absorbent article characterized in that the volume of the voids of the pores per unit volume of the polymer absorbent is 85% or more. The absorbent article according to any one of claims 1 to 7.
The polymer absorbent is an absorbent article characterized by containing 0.1 to 30.0% of crosslinked polymerization residues. The absorbent article according to any one of claims 1 to 7.
An absorbent article characterized in that the average diameter of the continuous pores is 1 to 1000 μm.

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